ArticlePDF AvailableLiterature Review

A Systematic Review on the Health Effects of Plums ( Prunus domestica and Prunus salicina )

March 2016
Phytotherapy Research 30(5):n/a-n/a

DOI:10.1002/ptr.5581

Authors:

Ezinne Igwe

University of Wollongong

Karen Charlton

University of Wollongong

In recent times, plums have been described as foods with health‐promoting properties. Research on the health effects of plum continue to show promising results on its antiinflammatory, antioxidant and memory‐improving characteristics. The increased interest in plum research has been attributed to its high phenolic content, mostly the anthocyanins, which are known to be natural antioxidants. A systematic review of literature was carried out to summarize the available evidence on the impact of plums ( Prunus species; domestica and salicina) on disease risk factors and health outcomes. A number of databases were searched according to the Preferred Reporting Items for Systematic Reviews and Meta‐Analyses guidelines for relevant studies on plum health effects in vitro , animal studies and clinical trials. A total of 73 relevant peer‐reviewed journal articles were included in this review. The level of evidence remains low. Of the 25 human studies, 6 were confirmatory studies of moderate quality, while 19 were exploratory. Plums have been shown to possess antioxidant and antiallergic properties, and consumption is associated with improved cognitive function, bone health parameters and cardiovascular risk factors. Most of the human trials used the dried version of plums rather than fresh fruit, thus limiting translation to dietary messages of the positioning of plums in a healthy diet. Evidence on the health effect of plums has not been extensively studied, and the available evidence needs further confirmation. Copyright © 2016 John Wiley & Sons, Ltd.

. Evidence on the effect of plums and its associated products on bone health

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REVIEW

A Systematic Review on the Health Effects of

Plums (Prunus domestica and Prunus salicina)

Ezinne O. Igwe*and Karen E. Charlton

School of Medicine, University of Wollongong, Northfields Avenue, Wollongong, New South Wales 2522, Australia

In recent times, plums have been described as foods with health-promoting properties. Research on the health

effects of plum continue to show promising results on its antiinflammatory, antioxidant and memory-

improving characteristics. The increased interest in plum research has been attributed to its high phenolic

content, mostly the anthocyanins, which are known to be natural antioxidants.

A systematic review of literature was carried out to summarize the available evidence on the impact of plums

(Prunus species; domestica and salicina) on disease risk factors and health outcomes.

A number of databases were searched according to the Preferred Reporting Items for Systematic Reviews and

Meta-Analyses guidelines for relevant studies on plum health effects in vitro, animal studies and clinical trials.

A total of 73 relevant peer-reviewed journal articles were included in this review. The level of evidence re-

mains low. Of the 25 human studies, 6 were confirmatory studies of moderate quality, while 19 were exploratory.

Plums have been shown to possess antioxidant and antiallergic properties, and consumption is associated with

improved cognitive function, bone health parameters and cardiovascular risk factors. Most of the human trials

used the dried version of plums rather than fresh fruit, thus limiting translation to dietary messages of the

positioning of plums in a healthy diet.

Evidence on the health effect of plums has not been extensively studied, and the available evidence needs

Keywords: plums; Prunus domestica;Prunus salcina; health effects; systematic review.

INTRODUCTION

The plum is a drupe fruit which belongs to the subgenus

Prunus (Family Rosaceae). The subgenus can be differ-

entiated from other subgenera (peaches, cherries, etc.)

as the shoots have a terminal bud and unclustered single

side buds, the flowers combine in groups of one to five

on short stems, and the fruit have a crease running down

one side and a smooth seed. Between 19 and 40 differ-

ent species of plum exist. Of these, only 2, the hexaploid

European plum (Prunus domestica) and the diploid

Japanese plum (Prunus salicina and hybrids), are of

commercial significance across the globe (Topp et al.,

2012). The nutritional composition of the two species

is considered similar (Table 1).

The European plum is believed to have been discov-

ered about 2000 years ago, with its origin somewhere

near the Caspian Sea. The fruit was introduced into

the USA in the 17th century by pilgrims, while the

Japanese plum has its origin in China but derived its

name from the country where it was mostly cultivated

and developed, Japan. The Japanese plum was intro-

duced into the USA in the late 19th century. Today,

the main producers of commercially grown plums are

the United States, Serbia, China and Romania. (UN

Food and Agriculture Organization, 2011).

Prunes are the dried version of plums and are known

for their laxative effect, which is commonly attributed to

its high fibre content (Tinker et al., 1991). Earlier studies

attributed the laxative effect of prunes to the presence

of phenolics (chlorogenic acid) (Chok and Lang, 1961)

and sorbitol (Reele and Chodos, 1985) that are in the

fruit, together with its high fibre content (Stacewicz-

Sapuntzakis et al., 2001). In the USA, prunes are re-

ferred to as dried plums. This name change was effected

in a bid to promote prunes as a health food instead of

being associated with old age (Zasky, 2008). Prunes

are produced industrially by drying plums at 85–90°C

for 18 h. This process is believed to have originated

thousands of years ago also near the Caspian Sea, the

same region where the European plums were discov-

ered. With migration and civilization, prunes spread

throughout Europe. Today, California, USA is the

leading producer of prunes (dried plums) worldwide

(Norton, 2009).

In classifying whole and natural foods based on their

unique nutritional composition, flavonoid content is

one of the most important methods of classification

(Stadlmayr et al., 2011). The high levels of phenolic com-

pounds, including flavonoids and particularly the sub-

class of anthocyanins observed in the plum, have

resulted in a dramatically increased interest in plum-

based research since the 1990s (Nakatani et al., 2000;

Walle et al., 2003). A number of health benefits have

been associated to the plum fruit and these include im-

proved bone health, cognition and memory, antioxidant

anti-inflammatory effects and easement of constipation.

* Correspondence to: Ezinne Oyidia Igwe, School of Medicine, Univer-

sity of Wollongong, Northfields Avenue, Wollongong, New South Wales

2522, Australia.

E-mail: eok167@uowmail.edu.au

PHYTOTHERAPY RESEARCH

Phytother. Res. (2016)

Published online in Wiley Online Library

(wileyonlinelibrary.com) DOI: 10.1002/ptr.5581

Received 23 July 2015

Revised 30 November 2015

Accepted 09 January 2016

These health-promoting properties have been attrib-

uted to the plum’s antioxidant capacity as a result of

the high phenolic content (Yu et al., 2009a; Noratto

et al., 2009; Franklin et al., 2006; Pawlowski et al., 2014;

Shukitt-Hale et al., 2009).

These observed health effects have been reported

from studies that have used different research designs

(in vitro, animal studies and clinical studies) and have in-

vestigated both plums, and related products and extracts

(Stacewicz-Sapuntzakis, 2013).

The aim of this systematic literature review is to de-

termine the level of current evidence on the beneficial

health effects of plum and its associated products.

MATERIALS AND METHODS

A number of electronic databases were searched:

Scopus, Web of Science, Cochrane library, CINAHL,

MedLine and ScienceDirect up to June 2015 with a com-

bination of search terms, including plum or prunes or

Prunus domestica or Prunus salicina and health effects

used as keywords (see Appendix 1 for Medline search

strategy).

Inclusion criteria for journal articles include

1. Studies carried out in vitro, on animal and clinical

studies.

2. Studies that utilized the fresh, dried, juice version or

extracts of the plum species P. domestica or P.

salicina.

3. All studies assessing any health outcome associated

with plum consumption.

4. Studies reported in English. Only studies reported in

English were included due to language barrier, rea-

sons of time efficiency and cost of translation not be-

ing feasible.

Exclusion criteria for journal articles include

1. Studies on the quantification of the nutritional com-

position and antioxidant properties of plums.

2. Studies that utilize different species of plums, for

example, the Japanese apricot, also known as

Japanese plums in the Prunus mume specie.

3. Studies assessing properties related to plum cultiva-

tion, harvest and the commercial aspects of the plum

fruit.

Articles were assessed for peer-reviewed status using

Ulrich’s Web (available at: http://ulrichsweb.

serialssolutions.com.ezproxy.uow.edu.au/). A hand

search yielded one additional article, which was relevant

to this review.

For the clinical trials, all the relevant studies retrieved

were classified as either confirmatory or exploratory

studies. They were rated for their quality using relevant

criteria from the Delphi list, Cochrane Back Review

Group and the CONSORT Statement (Table 9), and

strength of evidence of study design assessed using the

Australian National Health and Medical Research

Council hierarchy levels of evidence with rankings from

level I–IV.

The National Health and Medical Research Council ev-

idence hierarchy has six levels according to type of

research question with systematic review of level II studies

classified as levels I, randomized controlled trials, classified

as level II. Studies ranging from a pseudorandomised

Table 1. Major nutritional composition of European (Prunus

domestica) and Japanese (Prunus salicina) plums, per 100 g

weight (data from (USDA, 2014); data are a mix of Japanese

and European plums)

Component

European plum (P. domestica) and

Japanese plums (P. salicina)

Fresh

plums

Dried

prunes

Plum

juice

Water/moisture (g) 87.23 30.92 84.02

Energy (kj) 192 1006 243

Carbohydrate (g) 11.42 63.88 15.15

Protein (g) 0.70 2.18 0.51

Fat (g) 0.28 0.38 0.02

Sugars, total 14.22

Glucose (g) 5.07 25.46 23.3

Fructose (g) 3.07 12.45 11.8

Sucrose (g) 1.57 0.15 3.7

Total dietary fibre 1.4 7.1 0.9

Minerals

Calcium (mg) 6 43 10

Iron (mg) 0.17 0.93 0.34

Magnesium (mg) 7 41 8

Phosphorus (mg) 16 69 15

Potassium (mg) 157 732 154

Sodium (mg) 0 2 1

Zinc (mg) 0.10 0.44 0.11

Copper (mg) 0.057 0.281 0.054

Manganese (mg) 0.052 0.299 0.033

Fluoride (μg) 2.0 4.0

—

Vitamins

Ascorbic acid (C) (mg) 9.5 0.6 2.8

Thiamine (B

) (mg) 0.028 0.051 0.023

Riboflavin (B

) (mg) 0.026 0.186 0.059

Niacin (B

) (mg) 0.417 1.882 0.473

Pantothenic acid (B

) (mg) 0.135 0.422 0.072

Pyridoxine (B

) (mg) 0.029 0.205 0.027

Total Folate (μg) 5 4 3

Vitamin A, RAE (μg) 17 39 50

Vitamin E (mg) 0.26 0.43 0.18

Vitamin K

(μg) 6.4 59.5 4.3

Carotenoids

Carotene, beta (μg) 190 394 554

Carotene, alpha (μg) 0 57 0

Cryptoxanthin, beta (μg) 35 93 102

Lutein + zeaxanthin (μg) 73 148 49

Phenolic compounds

Total (mg) 111 184 121

Neochlorogenic acid (mg) 81 131 198.5

Chlorogenic acid (mg) 14.4 44 46.5

Anthocyanins (mg) 7.6

—

0.172

Catechins (mg) 5.4

—

Table adapted from (Stacewicz-Sapuntzakis, 2013) and (Netzel

et al., 2012)

(Stacewicz-Sapuntzakis, 2013) (plum juice concentrate)

(Mangels et al., 1993)

(Shukitt-Hale et al., 2009)

—

No available data.

E. O. IGWE AND K. CHARLTON

controlled trial to a comparative study without concurrent

controls classified as levels III-1 to III-3 and case series with

either post-test or pre-test/post-test outcomes classified as

level IV (NHMRC, 2000).

RESULTS

A total of 73 studies were eligible for inclusion in this

review (Fig.1). Of these, 18 investigated bone health

(2 in vitro, 12 animal studies and 4 clinical trials), and

20 investigated its anticancer and antiinflammatory

properties (13 in vitro studies, 6 animal studies and 1 clin-

ical trial). Eleven studies reported on plums’antioxidant

properties and their effect on cognition (2 in vitro

studies, 5 animal studies and 4 clinical trials) while nine

studies investigated the effect of plums on different com-

ponents of the metabolic syndrome (cholesterol, high

blood pressure and anti-thrombosis; 3 animal studies

and 6 clinical trials). For its commonly known laxative ef-

fect and satiety, 8 clinical studies were carried out. Five

studies examined its anti-allergic, anti-microbial and

immune-enhancing properties (2 in vitro studies and 3

animal studies), and 2 clinical studies examined its ef-

fects on liver function and risk factors for kidney stone

formation. Some of the findings reported from the

in vitro studies like improved bone health and anti-

inflammatory properties have also been confirmed in an-

imal and human studies. Tables 2–8 summarize the ex-

perimental and clinical studies, and Table 9 summarizes

the quality of the clinical studies included in this review.

Figure 1. PRISMA flow diagram for study selection process.

HEALTH EFFECTS OF PLUMS (Prunus domestica AND Prunus salicina)

Table 2. Evidence on the effect of plums and its associated products on bone health

Reference Location Plum product investigated Sample/method Level of evidence* Effects observed

In vitro studies

(Bu et al., 2008) USA Dried plum extract

(Prunus domestica)

RAW 264.7 murine macrophage cells Inhibition of osteoclastogenesis under

inflammatory and oxidative stress

conditions possibly by polyphenol content

(Bu et al., 2009) USA Polyphenols extracted from

dried plum (P. domestica)

MC3T3-E1 cells pre-treated with dried plum

polyphenols (0, 2.5, 5, 10 and 20 μg/mL) and

24 h later stimulated with TNF-α(0 or 1.0 ng/mL).

Improvement of osteoblast activity and

function by up-regulating Runx2, Osterix and

IGF-I and increasing lysyl oxidase expression,

and reduction in osteoclastogenesis signalling

Animal studies

(Smith et al., 2014a) USA Dried plum (P. domestica) Six weeks dietary supplementation of dried plum

(5%, 15% or 25%) in adult, osteopenic

ovariectomized rats

Restoration of bone mineral density by two

higher doses and bone turnover suppression

(Deyhim et al., 2005) USA Dried plum (P. domestica) Dietary supplementation of dried plum (5%, 15%

and 25%) in adult, osteopenic ovariectomized rats

for 40 days

Bone quality improvement (restoring bone

density) with all doses

(Franklin et al., 2006) USA Dried plum (P. domestica) Dietary supplementation of dried plum (5%, 15%

and 25%) in orchidectomized rats for 90 days

Prevention of osteopenia in androgen deficient

male rats

(Bu et al., 2007) USA Dried plum (P. domestica) Dietary supplementation of dried plum (25%) in

osteopenic orchidectomized rats for 90 days

Reversion of bone loss due to orchidectomy

(Smith et al., 2014b) USA Dried plum (P. domestica) Dietary supplementation of dried plum (25%) in

adult mice for 4 or 12 weeks

Improvement in bone mass and structure

(Rendina et al., 2013) USA Dried plum (P. domestica) Eight weeks dietary supplementation of dried plum

(25%) in adult, osteopenic ovariectomized mice

Bone loss prevention with anabolic effect

(Halloran et al., 2010) USA Dried plum (P. domestica) Dietary supplementation of dried plum (15% or

25%) in adult and aged (old) male mice for 6 months

Restoration of lost bone and increase in bone

volume

(Rendina et al., 2012) USA Dried plum (P. domestica) Dietary supplementation of dried plum (5%, 15% or

25%) in ovariectomized adult mice for 4 weeks

Improvement of bone structure and

biomechanical properties and suppression of

lymphocyte TNF-αproduction by higher doses

(Pawlowski et al., 2014) USA Dried plum powder extract

(P. domestica)

Dietary supplementation of plum extract (9% or

20%) in ovariectomized rats for six intervention

(10 days) and washout (10 days) cycles

Improvement in bone calcium retention

(Monsefi et al., 2013) Iran Plum extract (P. domestica) Oral administration of plum extract (1.6 g/kg) in

distilled water in pregnant mice for 30 days

Increased osteogenesis index in fetuses of

mice treated with plum extract

(Arjmandi et al., 2010) USA Dried plum (P. domestica) One hundred eighty 3-month-old female

Sprague–Dawley rats assigned to 15 groups (n= 12)

and either ovariectomized (14 groups) or

sham-operated (Sham, one group) then placed on

different dietary treatments including one

supplemented with 5% fructooligosaccharides and

7.5% dried plum for 60 days.

Diets supplemented with 5%

fructooligosaccharides and 7.5% dried plum

was most effective in reversing both right

femur and fourth lumbar bone mineral density

and fourth lumbar calcium loss while significantly

decreasing trabecular separation.

(Continues)

E. O. IGWE AND K. CHARLTON

Table 2. (Continued)

Reference Location Plum product investigated Sample/method Level of evidence* Effects observed

(Johnson et al., 2011) USA Dried plum

(P. domestica)

Seventy two 3-month-old female Sprague–Dawley

rats assigned to six groups (n= 12/group) and either

ovariectomized (five groups) or sham-operated

(Sham, one group) then placed on a semi purified,

powdered casein-based diet for 45 days to induce

bone loss. Thereafter, the groups were placed on

different dietary treatments, including one

supplemented with 5% fructooligosaccharides and

7.5% dried plum for 60 days.

In combination with soy protein, dried plum and

fructooligosaccharides had the most pronounced

effect in increasing lumbar bone mineral density.

Clinical trials

(Hooshmand et al., 2011) USA Dried plum

(P. domestica)

Hypothesis: dried plums reverses bone loss in

osteopenic postmenopausal women.

n= 160 osteopenic postmenopausal women

Study design/methods: randomized controlled

trial. Postmenopausal women randomly assigned

to treatment groups of dried plum (100 g/d) or

dried apple (75 g) daily for 1 year. Blood and urine

samples collected.

Sample size power: not stated

Dose: 100 g/day.

Duration: 1 year.

II Confirmatory Statistically significant increase in bone mineral

density of ulna and spine with decreased serum

levels in bone turnover markers (bone-specific

alkaline phosphatase and tartrate-resistant acid

phosphatase-5b) observed

(Arjmandi et al., 2002) USA Dried plum

(P. domestica)

Hypothesis: addition of dried plums to the diets

of postmenopausal women would positively

influence markers of bone turnover.

n= 58 postmenopausal women

Study design/methods: randomized controlled

trial. Postmenopausal women randomly assigned

to treatment groups of dried plum (100 g/d) or

dried apple (75 g) daily for 3 months. Blood and

urine samples collected.

Sample size power: not stated

Dose: 100 g/day.

Duration: 3 months.

II Exploratory Statistically significant increase in serum levels

of insulin-like growth factor-1 and bone-specific

alkaline phosphatase associated with increased

rates of bone formation

(Hooshmand et al., 2014) USA Dried plum

(P. domestica)

Hypothesis: dried plum has an effect on circulating

levels of sclerostin and bone metabolism measured

in serum levels of receptor activator of NF-

B ligand

and osteopotegerin.

n= 160 women with mild bone loss.

Study design/methods: randomised controlled trial.

Subjects randomly assigned to one of two groups

of dried plum or dried apple and provided with

II Exploratory Increase in bone mineral density of the ulna and

spine and also the receptor activator of NF-

ligand and osteopotegerin levels. A reduction in

serum sclerostin was also observed.

(Continues)

HEALTH EFFECTS OF PLUMS (Prunus domestica AND Prunus salicina)

Table 2. (Continued)

Reference Location Plum product investigated Sample/method Level of evidence* Effects observed

500 mg Caplus 400 IU (10 μg) vitamin D.

Sample size power: not stated Dose: 100 g

dried plum per day Duration: 1 year

(Simonavice et al., 2014) USA Dried plum

(P. domestica)

Hypothesis: 6-month intervention with resistance

training and a combination of resistance training

and dried plum would improve total and regional

(lumbar spine, femur and forearm) BMD. Increase

lean body mass, skeletal muscular strength and

decrease fat body mass. Additionally, it was

hypothesized that the biochemical analyses for

both groups would reveal increased levels of bone

formation markers, decreased levels of bone

resorption markers, and decreased levels of

inflammation markers, with the RT + DP group

having the most improvements in these areas in

breast cancer survivors.

n= 23 female breast cancer survivors.

Study design/methods: case–control. Subjects

stratified into 1(RT) or 2(RT + DP) treatment groups.

Sample size power: not stated

Dose: 90 g dried plum per day

Duration: 6 months

II Exploratory No difference between groups or any

group-by-time interaction observed for any of

the variables.

RT, resistance training; DP, dried plum.

*Clinical trials ranked using (NHMRC, 2000) Levels of Evidence Hierarchy where I is a systematic review (highest rating) and IV is a case series or cross-sectional study (lowest rating) and also classified

as exploratory or confirmatory studies.

E. O. IGWE AND K. CHARLTON

Table 3. Evidence on the anti-cancerous and antiinflammatory properties of plums and its associated products

Reference Location Plum product investigated Sample/method

Level of

evidence* Effects observed

In vitro studies

(Yu et al., 2009a) Korea Immature plum extract

(IPE)

(Prunus salicina)

Human hepatocellular carcinoma HepG2 cells,

Kato III gastric cancer cells, HeLa human

cervical carcinoma cells, U937 leukaemia

cells and MCF 7 hormone-dependent breast

cancer cells

Cell growth inhibition by IPE, that is, induction of

cancerous cell apoptosis

(Noratto et al., 2009) USA Mature red-fleshed plum

extract

(Prunus domestica)

MCF-7; the oestrogen-positive human breast

cancer cell line, MDA-MB-453; the oestrogen

negative human breast cancer cell line, and

MCF-10A; the breast epithelial cells

Inhibition of breast cancer cell proliferation and

significantly reduced toxicity on the normal cells

(Lee et al., 2009) USA Plum extract

(P. salicina)

Chicken spleen, RP9 tumour cells and HD11

macrophages

Stimulation of spleen lymphocyte proliferation

and NO production by cultured macrophages and

inhibition of tumour cell growth

(Fujii et al., 2006) Japan Prune extract

(P. domestica)

Caco-2 human colon carcinoma cell line,

KATO III human stomach carcinoma cell line

and CCD-18Co normal human colon fibroblast

cell line

Induction of cell apoptosis of cancer cells but not

normal cells

(Lea et al., 2008) USA Plum extract

(P. domestica)

SW1116, HT29, Caco-2 human colon cancer

cells and NCM460 human colon cells.

Growth inhibition and induction of differentiation

on colon cancer cells

(Hooshmand et al., 2015) USA Dried plum polyphenol

extract

(P. domestica)

Stimulation of macrophage RAW 264.7 cells

with either 1 μgmL

1

(for measurement of NO

production) or 1 ng mL

1

(for measurement of

COX-2 expression) of lipopolysaccharide to

induce inflammation and treated with different

doses of dried plum polyphenols.

Reduction in Nitric oxide and malondialdehyde

production with highest dose treatment

(1000 μgmL

1

). Reduction in lipopolysaccharide-

induced expression of COX-2 by the 100 and

1000 μgmL

1

dose.

(Kim et al., 2003) USA Plum polyphenol extract

(P. domestica)

Treatment of two cancer cell lines (HepG2

human liver cancer cells and DLD1 human

colon cancer cells) with polyphenol extract

of plum.

Antiproliferative activities on both cancer cell

lines in a dose dependent manner.

(Nishida et al., 2014) Japan Plum pectin extract

(P. domestica)

Incubation of heparan sulfate in differentiated

Caco-2 cells with pectin extracted from plums.

There was an obvious change in the sulphated

structures of HS following pectin

administration. Also, pectin upregulated human

HS 6-O-endosulfatase-2 (HSulf-2) expression

and inhibited HSulf-1 expression.

(Nishida et al., 2015) Japan Plum pectin extract

(P. domestica)

Incubation of differentiated Caco-2 cells

(cultured in 6-well plates at a cell density of

1.0 × 10

cells/well), with pectin, extracted

from plums.

Pectin-treated differentiated Caco-2 cells

promoted growth of IEC-6 cells and also an

upregulation of relative mRNA and protein

expression levels of Wnt3a protein.

(Continues)

HEALTH EFFECTS OF PLUMS (Prunus domestica AND Prunus salicina)

Table 3. (Continued)

Reference Location Plum product investigated Sample/method

Level of

evidence* Effects observed

(Popov et al., 2014) Russia Plum pectic polysaccharide

extract

(P. domestica)

0.05 mL of plum pectic polysaccharide added

to peritoneal cell suspension and incubated in

a 96-well

flat-bottom tissue culture plate in the absence

or presence of phorbol-12-myristate-13-acetate

at 37°C for 15 mins.

Reduction in the adhesion of peritoneal

leukocytes. Inhibition of the production of

superoxide anion radicals by reducing xanthine

oxidase activity.

(Vizzotto et al., 2014) USA Plum polyphenol extract

(P. domestica)

Oestrogen independent MDA-MB-435,

oestrogen dependent MCF-7 breast cancer

cell lines and one non-cancerous breast line

MCF-10A exposed to varying concentrations

of plum extracts for 24 h.

Dose-dependent cytotoxic effect against MDA-

MB-435, weak activity against MCF-7 and small

or no activity against MCF-10A observed.

(Yu et al., 2007) Korea Immature, mid-mature and

mature plum extract

(P. salicina)

Six human cell cancer lines (Hep G2 human

hepatocellular carcinoma cells and Kato 111

human gastric carcinoma cells, Hela human

cervical carcinoma cells, U937 human

leukaemia cells, MCF 7 hormone-dependent

human breast cancer cells, and MDA-MB-231

hormone-independent human breast cancer

cells) incubated with varying concentration of

plum extract.

Cytotoxic effects observed and apoptosis

observed in MDA-MB-231 cells mediated by the

immature plum extract.

(Yu et al., 2009b) Korea Immature plum extract

(P. salicina)

Incubation of PMA-induced HepG2 human

hepatocellular carcinoma cells with Immature

plum extract.

Antimigrative property in (phorbol 12-myristate

13-acetate) PMA-induced HepG2 cells observed.

A strong inhibitory effect on the PMA-induced

MMP-9 secretion through suppression of the

transcriptional activity of the MMP-9 gene

independently of the TIMP gene in HepG2 cells

was also observed.

Animal studies

(Kim et al., 2008) Korea Immature plum extract IPE

(P. salicina)

Intraperitoneal injection of IPE (2.5 or 5 g/kg

bw/day) dissolved in phosphate buffered

saline for 5 days in male mice with

benzo(α)pyrene induced liver toxicity

Chemopreventive efficacy by inhibiting the

induction of CYP1A1 expression and reducing

the activity of glutathione peroxidase, superoxide

dismutase and catalase

(Cantu-Jungles et al., 2014) Brazil Polysaccharides from prunes

(P. domestica)

Inducement of acute gastric ulcer in rats using

intragastric administration of ethanol P.A. after

four different oral treatments including

polysaccharides from prunes fraction (3 and

10 mg/kg).

Reduction and inhibition of gastric lesion area

by prune polysaccharides fractions.

(Noratto et al., 2015) USA Plum juice

(P. salicina)

Administration of plum juice in drinking water

to obese Zucker rats ad libitum for 11 weeks

Antiadipogenic and anti-inflammatory effects.

Reduction in blood glucose, triglycerides and HDL

cholesterol levels

(Continues)

E. O. IGWE AND K. CHARLTON

Table 3. (Continued)

Reference Location Plum product investigated Sample/method

Level of

evidence* Effects observed

(Mishra et al., 2012) India Plum extract

(P. domestica)

Inducement of peptic ulcer by pyloric ligation

in Wistar albino rats after administration of

plum extract (100, 150 or 200 mg kg

1

) for

7 days

Antioxidant and anti-ulcerogenic activity

(Yang and Gallaher, 2005) USA Dried plum

(P. domestica)

Dietary supplementation of dried plum (4.75 or

9.5%) in male Wistar rats for 10 days followed

by administration of two doses (1 week apart)

of azoxymethane and dietary supplementation

for 9 more weeks

Inhibition of risk factors associated with colon

carcinogenesis (reduction in faecal total and

secondary bile acids concentration, reduction in

colonic β-glucuronidase and 7α-dehydroxylase

activities and increased antioxidant activity)

(Gallaher and Gallaher, 2009) USA Dried plum

(P. domestica)

Dietary supplementation of dried plum (4.75 or

9.5%) and cholesterol in apolipoprotein

E-deficient mice for 5 months.

Development of atherosclerosis Impeded

Clinical trial

(Kasim-Karakas et al., 2002) USA Dried plum

(P. domestica)

Hypothesis: prune intake may alter the

metabolism of estrogens because prunes are a

rich source of both soluble and insoluble fibre

and cinnamates and decrease intestinal transit

time.

III-2 Exploratory Decrease in the independent excretion of 2OHE1

and 16αOHE1 observed but no statistically

significant change in the 2OHE1 - 16αOHE1

ratio following prune supplementation

n= 19 healthy premenopausal women

Study design/methods: crossover study.

After consuming habitual diets for three

menstrual cycles (control

run-in period), participants replaced dietary

simple sugars with prunes for another three

menstrual cycles (intervention period).

Sample size power: not stated

Dose: 100 g dried plum per day

Duration: 6 months.

as exploratory or confirmatory studies.

HEALTH EFFECTS OF PLUMS (Prunus domestica AND Prunus salicina)

Table 4. Evidence on the antioxidant property and effect on cognition of plums and its associated products

Reference Location

Plum product

investigated Sample/method

Level of

evidence Effects observed

In vitro studies

(Bouayed et al., 2009) France Phenolics from

plums

(P. domestica)

Polyphenolics extracted from seven varieties of

plum and quantified. Their antiradical activities

and protection against oxidative stress

evaluated in peripheral blood granulocytes.

Antioxidant activity and protection of blood

granulocytes from H

-induced oxidative

stress by preventing granulocytes from

intracellular ROS accumulation.

(Donovan et al., 1998) USA Prune/prune

juice extract

(P domestica)

Human LDL from plasma prepared from blood

collected from healthy volunteers.

Inhibition of LDL oxidation.

Animal studies

(Shukitt-Hale et al.,

2009)

USA Plum juice/dried

plum powder

(P. domestica)

Two groups of aged rats with either

consumption of a mixture of water and plum

juice (100%) (Group 1) or dietary

supplementation with dried plum powder (2%)

(group 2) for 8 weeks

Improved cognitive function assessed by

Morris Water Maze

(Shahidi et al., 2013) Iran Plum extract

(P. domestica)

Plum extracts (75, 100, 150 mg/kg)

administration by oral gavage to male mice

once a day for 7 days

Improvement in learning and memory in

mice assessed by the passive avoidance

test

(Kao-Ting et al., 2013) Taiwan Dried plum

powder (Prunus

salicina)

Dietary supplementation of dried plum powder

(2%) in nicotinamide/streptozotocin-induced

diabetic rats for 2 months

Improvement in cognitive performance,

antioxidant activity and improvement in

insulin sensitivity

(Sharma and Sisodia,

2013)

India Plum extract

(P. domestica)

Administration of optimum dose of plum

extract in distilled water to mice for 15 days

pre/post whole body exposure to 10 Gy

gamma-radiations

Antioxidant capabilities and improved

spatial learning

(Bouayed et al., 2007) France Chlorogenic

acid from P.

domestica

Administration of chlorogenic acid (20 mg/kg)

to mice and antioxidant effect on peripheral

blood granulocytes.

Decrease in anxiety related behaviours

(anxiolytic-like effect) and protection of

granulocytes from oxidative stress by

chlorogenic acid in vitro.

Clinical trials

(Prior et al., 2007) USA Dried plum/

dried plum

juice

(P. domestica)

Hypothesis: changes in antioxidant capacity

following consumption of plum juice may be

used to assess its potential to alter in vivo

antioxidant status and provide estimates of

dietary antioxidants necessary to prevent

postprandial oxidative stress.

II Exploratory No effect on plasma hydrophilic (H-) or

lipophilic (L-) antioxidant capacity measured

as Oxygen Radical Absorbance Capacity

(ORAC

)

n= 6 healthy volunteers.

Study design/methods: randomized cross-over

study. Fasting blood sample collected and

participants fed test juices and blood samples

(Continues)

E. O. IGWE AND K. CHARLTON

Table 4. (Continued)

Reference Location

Plum product

investigated Sample/method

Level of

evidence Effects observed

collected at 1, 2 and 4 h post juice

consumption.

Sample size power: not stated

Dose: 315 mL of dried plum juice; or dried

plums (131 g blended in 315 mL water

Duration: 2 weeks (with 2 weeks washout

period)

(Ko et al., 2005) Korea Plum juice

(P. salicina)

Hypothesis: Consumption of fruit juices

could scavenge ROS generated in

human plasma.

IV Exploratory Improved antioxidant activity in human

plasma measured by dichlorofluorescein

fluorescence

n= 10 healthy men.

Study design/methods: cross-over study.

Consumption of single dose of 150 mL of

plum juice. Blood samples collected at 0,

30, 60, 90 and 120 min after consumption

Sample size power: not stated

Dose: a single dose of 150 mL

Duration: 1 day (with 1 day washout period)

(González-Flores et al.,

2011)

Spain Plum

(P. salicina)

Hypothesis: there is a possible antioxidant

effect associated with diets enriched with

Japanese plums (P. salicina Lindl. cv.

Crimson Globe) in young, middle-aged and

elderly individuals.

IV Exploratory Statistically significant increase in

antioxidant capacity and urinary

6-sulfatoxymelatonin (aMT6-s)

n= 18 (6 per young, middle aged and older

group).

Study design/methods: Consumption of 390 g

plums without seeds per day divided into two

portions: 195 g as the lunch dessert and

195 g as the dinner dessert for 5 days. First-

void morning urines were collected before

treatment (basal values), the immediate day

after the last ingestion of plums (assay) and

1 day afterwards (post-assay).

Sample size power: not stated

Dose: 2 portions 390 g (195 g each) daily.

Duration: 5 days.

(Continues)

HEALTH EFFECTS OF PLUMS (Prunus domestica AND Prunus salicina)

Table 4. (Continued)

Reference Location

Plum product

investigated Sample/method

Level of

evidence Effects observed

(Netzel et al., 2012) Australia Plum juice

(P. salicina)

Hypothesis: there is a possible antioxidant

effect associated with Queen Garnet Plum

Juice ingestion on the urinary antioxidant

capacity and the concentration of

malondialdehyde, a biomarker for oxidative

stress.

IV Exploratory Increase in urinary antioxidant capacity

and decrease in malondialdehyde

excretion (biomarker for oxidative

stress)

n=2 healthy male subjects

Study design/methods: crossover study.

Consumption of 400 mL of Queen Garnet

Plum Juice or 400 mL of water as an

antioxidant-free control beverage separated

by a 1-week washout phase.

Sample size power: not stated

Dose: single dose of 400 mL.

LDL, low-density lipoprotein; ROS, reactive oxygen species.

E. O. IGWE AND K. CHARLTON

Table 5. Evidence on the effect of plums and its associated products on the different components of metabolic syndrome

Reference Location Plum product investigated Sample/method

Level of

evidence* Effects observed/conclusion

Animal studies

(Negishi et al., 2007) Japan Prune extract

(Prunus domestica)

Dietary supplementation of prune extract

(25%) in stroke-prone spontaneously

hypertensive rats for 5 weeks

Suppression of high (systolic) blood pressure

(Kuo et al., 2015) Taiwan Plum powder

(Prunus salicina)

Dietary supplementation of plum powder

(2% or 5%) in high cholesterol diet in mice

for 5 months

Amelioration of some symptoms of neurodegenerative

conditions like increased cholesterol and β-amyloid

(Aβ) concentration in the brain by both doses

(Lucas et al., 2000) USA Dried plums

(P. domestica)

Dietary supplementation (5% or 25% dried

plum) with dried plum in 48 ovariectomized

(ovx) 90-day old female Sprague–Dawley

rats for 45 days.

With elevated serum total cholesterol brought about by

ovariectomy, 25% prune diet prevented this increase

without affecting HDL cholesterol concentration and also

reduction in liver total lipids was observed.

Clinical trials

(Tinker et al., 1991) USA Dried plums

(P. domestica)

Hypothesis: (a) prunes as a source of fibre can

lower plasma cholesterol in men with mild to

moderate hypercholesterolemia (5.2–7.5 mmol

cholesterol/L). (b) faecal bile acid excretion is

increased in response to the ingestion of prunes

as a source of fibre, which may help explain the

cholesterol lowering effect of fibre.

II Confirmatory Plasma LDL cholesterol was statistically significantly

reduced after the prune period than the control, faecal

bile acid conc. of lithocholic acid was also statistically

significantly lower with prune consumption and both

faecal wet and dry weights were statistically

significantly higher with prune consumption.

n=41 free living men with mild

hypercholesterolemia.

Study design/methods: crossover study. 8 weeks

period split into two experimental diet periods,

each lasting 4 weeks. Subjects randomly

assigned a diet sequence, starting with either

consumption of a grape juice-control

supplement (GJ control) or a prune supplement.

Sample size power: not stated

Dose: 12 prunes (~100 g/d)

Duration: 8 weeks.

(Chai et al., 2012) USA Dried plums

(P. domestica)

Hypothesis: regular intake of apple favourably

improves lipid profiles, reduces atherogenic

risk ratios, lowers C-reactive protein levels,

and decreases levels of oxidative stress

marker in postmenopausal women

II Exploratory No statistically significant difference between treatment

groups in altering serum levels of atherogenic cholesterols

observed. For the dried apple group, total cholesterol was

statistically significantly reduced at 6 months.

n= 160 postmenopausal women

Study design/methods: case–control study.

Subjects randomly assigned to treatment

groups of dried apple (75 g) or dried plum

(100 g/d)

(Continues)

HEALTH EFFECTS OF PLUMS (Prunus domestica AND Prunus salicina)

Table 5. (Continued)

Reference Location Plum product investigated Sample/method

Level of

evidence* Effects observed/conclusion

Sample size power: 95%

Dose: 100 g/day

Duration: 1 year.

(Afaghi et al., 2009) Iran Prunes Hypothesis: 8 fruits (Golab apples, green

apples, fresh apricots, prunes, cherries,

blueberries, golden no-seed grapes, and red

sultanas) are low glycemic index and

recommendable for diabetics and weight loss.

II Exploratory Serving size of prunes was low glycemic load fruit. Prunes

among other tested fruits were low glycemic index and can

be recommended for diabetics and weight loss management.

n=8

Study design/methods: crossover study. Eight

subjects (healthy, young men aged 20–28,

normal weight with body mass index: 20–25

kg/m

) randomly assigned to one of eight

fruits and blood glucose measured at 0, 15,

30, 45,60, 90 and 120 mins after consumption.

Sample size power: 95%

Dose: 143 g

Duration: not stated —different occasions

after overnight fasting.

(Ahmed et al., 2010a) Pakistan Prunes

(P. domestica)

Hypothesis: use of prunes is useful in

cardiovascular disorders to bring about changes

in blood pressure or prevention of atherosclerosis.

II Confirmatory Reduction of blood pressure by single dose of prunes daily

group and the controls with the double dose of prunes

showing a reduction in just systolic blood pressure. There was

an increase in serum HDL of the control group whereas test

groups had significantly reduced serum cholesterol and LDL.

The data predicts cardiovascular protective effects of prunes.

n= 259 pre-hypertensive patients (systolic

BP = 120–139 mmHg, diastolic BP = 80–89 mmHg)

Study design/methods: randomised controlled trial.

Patients randomly assigned to three groups of

A-single dose, B-double dose or C-control group.

Blood pressure was recorded fortnightly, and

blood samples were taken at 0 and 8 weeks.

Sample size power: not stated.

Dose: group A-11.5 gm. Group B-23 gm.

Control-glass of water.

Duration: 8 weeks.

(Santhakumar et al.,

2015a)

Australia Plum juice

(P. salicina)

Hypothesis: anthocyanin-rich Queen Garnet

Plum Juice may ameliorate platelet activation-

related thrombogenesis and maintain

haemostatic function by (1) reducing platelet

aggregation and activation through blocking/

inhibiting various platelet activation pathways;

(2) prolonging clotting time and reducing

II Exploratory Queen Garnet Plum Juice supplementation inhibited platelet

aggregation induced by adenosine diphosphate, collagen and

arachidonic acid. There was reduction in platelet activation-

dependent surface-marker P-selectin expression

of activated de-granulated platelets. Increase in activated

partial thromboplastin clotting time and reduction in plasma-

(Continues)

E. O. IGWE AND K. CHARLTON

Table 5. (Continued)

Reference Location Plum product investigated Sample/method

Level of

evidence* Effects observed/conclusion

fibrinogen concentration; and (3) exhibiting

favourable effects on lipid profile and

inflammation.

fibrinogen and malondialdehyde levels, a plasma biomarker

of oxidative stress.

n=21

Study design/methods: randomized, double

blind, placebo crossover trial. Healthy

volunteers randomly assigned to three

supplement groups of A-Queen Garnet

plum juice, B-prune juice or C-colour

matched placebo. Blood samples were

collected at least 8 h pre-prandial and mid-

stream fasting urine samples collected.

Sample size power: not stated.

Dose: 200 mL/day of each juice.

Duration: 28 days with 2 weeks washout

period.

(Santhakumar et al.,

2015b)

Australia Plum juice

(P. salicina)

Hypothesis: anthocyanin-rich Queen Garnet

Plum Juice may impart anti-thrombotic

effects via (a) inhibition of platelet

aggregation by simultaneously targeting

different platelet activation pathways

(adenosine diphosphate: ADP-P2Y12/

P2Y1; collagen: GPVI/α2β1 and arachidonic

acid: cyclooxygenase-1–COX-1), (b)

reducing platelet hyper-activation and de-

granulation by blocking surface receptors

responsible for activation, and (c) favourably

altering coagulation parameters and lipid profile.

II Exploratory Inhibition of adenosine diphosphate-induced platelet

aggregation both without and under exercise induced

oxidative stress, inhibition of arachidonic acid-induced

aggregation under oxidative stress. Also, there was

reduced platelet activation-dependant

P-selectin expression both without and under

oxidative stress. Favourable effects on

coagulation parameters both with and without

oxidative stress were also observed.

n=13

Study design/methods: randomized, double

blind, placebo crossover trial. Healthy

volunteers randomly assigned to two

supplement groups of A-Queen Garnet

plum juice or B-a flavoured and coloured

formulated cordial placebo. Oxidative

stress was induced by constant load

exercise bout for 1 h at 70% of their

2PEAK

Blood samples were collected at

fasting state and at least 8–12 h pre-

prandial on day 1 and day 29.

(Continues)

HEALTH EFFECTS OF PLUMS (Prunus domestica AND Prunus salicina)

The quality of the clinical studies included is, at best,

of moderate quality. There were 6 confirmatory studies

of moderate quality (1 on bone health, 2 on different

components of metabolic syndrome, and 3 on satiety

and laxative effect) and 19 exploratory studies. Evi-

dence on the health effect of plums has not been exten-

sively studied, and the available evidence needs further

confirmation.

BONE HEALTH

Based on results from 18 studies (2 in vitro, 12 animal

studies and 4 clinical trials) reported in this review,

promising evidence exists on the effect of plum on bone

health. This body of evidence has mostly been in agree-

ment and also confirmed in human trials. Bu et al. (2008)

in their in vitro study involving two groups investigated

the effect of dried plum polyphenols on osteoclastogen-

esis in which one group was stimulated with lipopolysac-

charide (LPS) to induce inflammation and the other

group stimulated with hydrogen peroxide (H

)to

induce lipid peroxidation. It was observed that the

LPS-stimulated sample produced NO (nitric oxide)

detectable at 8 h, which further increased at 16 h, while

the H

stimulated cells did not produce NO. This in-

crease in NO associated with LPS was downregulated

by different doses (10, 20, 30 μg/mL) of plum polyphe-

nol at both 8 h and 16 h. The authors concluded

that dried plum polyphenols directly inhibit osteoclasto-

genesis, which leads to reduced osteoclast activity by

downregulation of Nuclear factor of activated T-cells,

cytoplasmic 1 (NFATc1) and inflammatory mediators.

The results from this in vitro experiment by Bu et al.

(2008) has also been confirmed in animal studies

(Deyhim et al., 2005; Franklin et al., 2006; Bu et al.,

2007; Smith et al., 2014a). Among these, the study by

Smith et al. (2014a) is slightly different in that unlike

the other studies that studied longer term effects of

dried plum on systemic biochemical markers of bone

metabolism and alteration in gene expression as the

main outcome measure, their main objective was to un-

derstand the mechanism of action by which dried plum

altered bone metabolism. Regulators of osteoblast and

osteoclast differentiation and osteoblast activity were

studied over a period of 6 weeks. Compared with the an-

abolic therapy using parathyroid hormone that signifi-

cantly increased systemic and local indicators of bone

formation with no effect on systemic marker of bone re-

sorption, dried plum supplementation suppressed bone

turnover with no effect on the indices of bone formation

at the endocortical surface. In another study by the

same research team, dried plum supplementation ini-

tially suppressed cancellous bone turnover but demon-

strated a biphasic response over time, exerting positive

effects on bone mass and bone structure (Smith et al.,

2014b). Plum extract has also been shown to be effective

in increasing bone calcium retention by 20%

(Pawlowski et al., 2014).

Rendina et al. (2013) compared the dried plum with

other dried fruits (apple, apricot, grape and mango)

and observed that only the dried plum had an anabolic

effect on trabecular bone in the vertebra and prevented

bone loss in the tibia. This demonstrates a potentially

unique effect of plum that was absent in the other fruits

Table 5. (Continued)

Reference Location Plum product investigated Sample/method

Level of

evidence* Effects observed/conclusion

Sample size power: not stated.

Dose: 200 mL/day of each juice.

Duration: 28 days with 2 weeks washout

period.

LDL, low-density lipoprotein; HDL, high-density lipoprotein.

as exploratory or confirmatory studies.

E. O. IGWE AND K. CHARLTON

Table 6. Evidence on the satiety and laxative effect of plums and its associated products

Reference Location

Plum product

investigated Sample/method

Level of

evidence* Effects observed

Clinical trials

(Piirainen et al.,

2007)

Finland Prune juice (prepared from

plum juice concentrate,

prune puree, water and

7% fructose)

(Prunus domestica)

Hypothesis: prune juice alone may have a

laxative effect on the bowel function of those

adults with certain gastrointestinal symptoms

but are otherwise healthy.

IV Confirmatory Laxative effect with increased flatulence.

n= 54 volunteers with mild GIT symptoms.

Study design/methods: 1 week baseline

period, 2 week prune juice (consumption)

period followed by 1 week follow-up period

with daily record of bowel habit

Sample size power: not stated.

Dose: 125 mL twice a day.

Duration: 4 weeks.

(Cheskin et al.,

2009)

USA Plum juice

(P. domestica)

Hypothesis: plum juice supplementation diet

would induce significant improvements in

bowel frequency, and consistency, and

possibly decrease appetite compared with

baseline as well as placebo and psyllium

treatments.

II Confirmatory Constipation relief and stool softening

evident with consumption of plum juice.

n= 36 adults with chronic constipation

symptoms.

Study design/methods: randomized

controlled crossover trial. Consumption of a

daily portion of plum juice in comparison with

psyllium and apple juice in adults with chronic

constipation symptoms.

Sample size power: not stated.

Dose: 8 oz (237 mL) per day.

Duration: 14 days.

(Attaluri et al.,

2011)

USA Dried plum

(P. domestica)

Hypothesis: dried plums are as effective as

psyllium in the treatment of adults with

chronic constipation.

II Confirmatory Effective treatment with dried plum on

mild to moderate constipation observed.

n= 40 patients with chronic constipation.

Study design/methods: single blind,

randomized cross-over study. Consumption of

a daily portion of dried plums or psyllium for a

treatment period of 3 weeks after which

participants continued on their usual remedies

for constipation for another 6 weeks. For the

(Continues)

HEALTH EFFECTS OF PLUMS (Prunus domestica AND Prunus salicina)

Table 6. (Continued)

Reference Location

Plum product

investigated Sample/method

Level of

evidence* Effects observed

duration of the study, subjects maintained

daily symptom and stool diaries.

Sample size power: 80%.

Dose: 50 g twice a day with meals.

Duration: 14 weeks (with 1 week washout

period between treatments).

(Farajian et al.,

2010)

Greece Prunes

(P. domestica)

Hypothesis: a preload including dried prunes

consumed as a snack before a meal,

compared with an isoenergetic bread product

preload, would reduce (a) meal time energy intake,

(b) appetite for dessert offered after lunch and,

II Exploratory Reduced consumption of dessert with

lower energy intake observed. An increased

satiety at all time points between snack and

meal was also observed.

n= 45 normal weight subjects.

Study design/methods: randomized cross-

over study. Fasting participants offered a

standardized breakfast followed by a preload

of either dried prunes or bread product after

2 h. Three hours after the preload, a

standardized lunch and desert was provided.

Subjects also rated their hunger, thirst, desire

to eat, motivation to eat and satiety on 100 mm

line visual analogue scales just before and right

after the preload consumption, every 45 min up

till the 180th minute On completion of the test

day, detailed record of all foods and beverages

intake for the next 24 h was collected.

Sample size power: not stated.

Dose: five prunes (40 g) before meals on each

testing day.

Duration: 2 days (with 1 week washout period).

(Furchner-Evanson

et al., 2010)

USA Dried plum

(P. domestica)

Hypothesis: snack choices similar in fat,

protein, carbohydrate and sugar contents

while differing in fibre content have an effect

on satiety, subsequent food intake and plasma

glucose, insulin and ghrelin responses.

II Exploratory Satiety index area under the curve greater

for dried plum trial. Consumption of the dried

plum elicited lower plasma glucose and insulin

area under the curve and tended to promote

a greater plasma ghrelin antioxidant capacity.

n= 19 healthy female subjects

Study design/methods: randomized crossover

study with at least 1 day washout. Subjects

randomly assigned to receive four different test

foods including dried plums. Blood samples

(Continues)

E. O. IGWE AND K. CHARLTON

Table 6. (Continued)

Reference Location

Plum product

investigated Sample/method

Level of

evidence* Effects observed

collected at baseline and every 15 mins in 1 h

then 90 and 120 mins.

Sample size power: not stated.

Dose: served in a 238 kcal (1000 kj) portion.

Duration: not stated.

(Howarth et al.,

2010)

USA Dried plum

(P. domestica)

Hypothesis: snack selection (dried plums vs

common carbohydrate-rich low-fat cookies)

influences daily energy consumption, nutrient

intake and metabolic responses.

II Exploratory No change observed with energy intake or

weight. In comparison with cookie, dried

plum promoted greater intake of fibre,

potassium, riboflavin, niacin and calcium.

There was an observed reduction in total fat

as well as cholesterol intake with dried plum

snacks. Dried plum did not alter plasma

triglyceride concentration but softer stool

consistency was observed with dried plum

consumption.

n= 26 healthy female subjects

Study design/methods: randomized crossover

study with 2 weeks washout. Subjects

randomly assigned to receive either dried

plums or low-fat cookies for two separate

2-week feeding. A 7 day bowel habit

questionnaire was completed.

Sample size power: 80%

Dose: served in a 100 kcal portion

twice a day.

Duration: 4 weeks.

(Lucas et al., 2004) USA Dried plum

(P. domestica)

Hypothesis: dradual incorporation of 100 g of

dried plum into the daily diet of healthy

postmenopausal women would not cause

significant changes in self-reported bowel

habits including frequency of defecation,

faecal bulk and stool consistency.

II Exploratory With both dried plum and apples, there was no

statistically significant differences observed

for any of the parameters used to assess

bowel function.

This indicates the absence of any negative side

effects associated with prune consumption.

n=58

Study design/methods: randomized

controlled trial. Postmenopausal women

randomly assigned to treatment groups of

dried plum (100 g/d) or dried apple (75 g)

daily for 3 months. A 7 day bowel habit

questionnaire was completed.

Sample size power: not stated

Dose: 100 g/day.

Duration: 3 months.

(Pasalar et al.,

2013)

Iran Prunes

(P. Domestica)

Hypothesis: prunes and flixweed are effective

in the prevention of constipation among

Iranian pilgrims who attended the Hajj

ceremony in 2010 in the kingdom of Saudi Arabia.

II Exploratory Using Rome III criteria to define constipation

(less than three times of defecation/week,

with straining, difficulty in defecation,

unproductive urges, feeling

(Continues)

HEALTH EFFECTS OF PLUMS (Prunus domestica AND Prunus salicina)

Table 6. (Continued)

Reference Location

Plum product

investigated Sample/method

Level of

evidence* Effects observed

of anorectal obstruction, hand manoeuver to

facilitate stool extraction and feeling of

incomplete evacuation), a statistically

significant difference was observed

between the groups with the case group

less constipated.

Study design/methods: randomised controlled

trial. 170 Iranian Hajj pilgrims randomly assigned

to two groups of case and control. Case group

received measured doses of prunes and flixweed

daily before lunch and dinner and control group

had their meals with no intervention.

Sample size power: not stated

Dose: 40–50 g/day with 10–15 g of flixweed.

Duration: 3 weeks.

as exploratory or confirmatory studies.

E. O. IGWE AND K. CHARLTON

Table 7. Evidence on the anti-allergic, anti-microbial and immune-enhancing property of plums and its associated products

Reference Location

Plum product

investigated Sample/method

Level of

evidence* Effects observed

In vitro studies

(Cevallos-Casals et al.,

2006)

USA Plum extract

(Prunus salicina)

Plum extract placed in a well with diluted

bacteria inoculum.

Inhibitory effects against Escherichia coli

0157:H7 and Samonella enteritidis.

(Yaqeen et al., 2013) Pakistan Prune extract

(Prunus domestica)

Ethanol extracts of prunes tested against nine

bacteria; five gram-positive bacteria

(Staphylococcus aureus,Streptococcuc

intermedias,Bacillus cereus, and Bacillus pumilus)

and four gram-negative bacteria (Eschrichia coli,

Proteus mirabilis,Shigella flexneri,Salmonella

typhi and Klebsiela pneumoniae).

Antibacterial activity observed.

Animal studies

(Karasawa et al., 2012) Japan Prune extract

(P. salicina)

Dietary supplementation with 25% ovalbumin

and 1% prune extract over 6 weeks in rats

injected 20 L of distilled water containing 20 g

of mite allergen between the 3rd to 6th week

Reduction in allergic response in comparison

with control group

(Lee et al., 2008) USA Plum powder

(P. salicina)

Dietary supplementation with 0.5% or 1.0%

plum in 1-day old chickens and oral

inoculation with 5000 sporulated oocysts of

Eimeria acervulina at day 12 post-hatch.

Increase in body weight gain, levels of

MRNAs for interferon-ϒand interleukin-15.

There was a reduction in faecal oocyst

shedding and chickens fed the plum

supplemented diets exhibited greater spleen

cell proliferation

(Noratto et al., 2014) USA Plum juice

(P. domestica)

Administration of plum juice in obese Zucker

rats for 11 weeks. Body weight recorded once

a week.

Several bacteria groups (e.g. Lactobacillus

and members of Ruminococcacea) were

found to be more abundant in the plum

group. There was also a distinct contrast

between the microbiota of control and

treatment groups.

as exploratory or confirmatory studies.

HEALTH EFFECTS OF PLUMS (Prunus domestica AND Prunus salicina)

Table 8. Evidence on the effect of plum and its associated products on liver function and kidney stone risk factors

Reference Location

Plum product

investigated Sample/method Level of evidence* Effects observed

Clinical trials

(Ahmed et al., 2010b) Pakistan Prune juice

(Prunus domestica)

Hypothesis: prune juice does not alter liver function. II Exploratory Liver function test showed significant

reduction of serum alanine transaminase

and serum alkaline phosphatase but no

effect on serum aspartate transaminase

and bilirubin

n=107 healthy volunteers

Study design/methods: case–control study.

Participants randomly assigned to three different

groups of A (single dose of 1 pack of prunes =

11.43 kg, i.e. three prunes), B (control; a glass of

water) and C (double dose of group A) consumed

daily. Blood samples were taken on week zero and

week 8 for liver function tests, that is, serum

alkaline phosphatase, bilirubin, aspartate

transaminase and alanine transaminase.

Sample size power: not stated

Dose: three prunes (~11.43 g) or a double dose

of six prunes (~22.86 g) per day.

Duration: 8 weeks.

(Keßler et al., 2002) Germany Plum juice

(P. domestica)

Hypothesis: plum, cranberry- and blackcurrant

juice may have an influence on the urinary

composition and therefore on multiple risk

factors of kidney stone formation.

II Exploratory No significant effect on urinary biochemical

or physiochemical parameters

n=12 healthy male subjects.

Study design/methods: Participants control-

fed a standardized diet daily with plum juice.

Twenty four-hour urine sample collected.

Sample size power: not stated

Dose: 330 mL of plum juice.

Duration: 5 days

as exploratory or confirmatory studies.

E. O. IGWE AND K. CHARLTON

Table 9. Quality rating of included clinical studies using relevant criteria from the Delphi List, Cochrane Back Review Group and the CONSORT Statement (Verhagen et al., 1998; Van Tulder et al.,

2003; Schulz et al., 2010)

J Nutr (2011) 106:

923–930

J Wom Health

Gend-B (2002) 11:

61–68

Br J Nutr (2014)

112: 55–60

Appl Physiol Nutr

Metab (2014) 39:

730–739

Am J Clin Nutr

(2002) 76:

1422–1427.

J Am Coll Nutr

(2007) 26:

170–181.

J Med Food (2005)

8(1): 41–46.

J Food Nutr Res

(2011) 50:

229–236.

n= 160 dried plum

(Prunus domestica)

100 g/day versus

dried apple Parallel

12 months

n= 58 dried plum

(P. domestica)

100 g/day versus

dried apple Parallel

3 months

n= 160 dried plum

(P. domestica)

100 g/day versus

dried apple Parallel

1 year

n= 23 dried plum

(P. domestica)

90 g/day + resistance

training versus

resistance training

case–control 6 months

n= 19 dried plum

(P. domestica)

100 g/day versus

habitual dietary

simple sugars

Cross-over 6 months

n= 6 dried

plum/dried plum

juice (P. domestica)

131 g versus

selected fruits

Cross-over 2 weeks

n= 10 plum juice

(P. salicina) Single

dose of 150 mL

versus selected

fruit juices Cross-over

18 days

n= 18 dried plum

(P. salicina)

2 × 195 g/day Case

series 5 days

A Postmenopausal

women (Osteopenic)

Postmenopausal

women

Women with

mild bone loss

Female breast cancer

survivors

Postmenopausal

women (Healthy)

Healthy volunteers Healthy volunteers Healthy volunteers

B Yes Yes Yes Yes No Yes No Not applicable

C No (not feasible) No (not feasible) No (not feasible) No (not feasible) No (not feasible) No No Not applicable

D Yes Yes Yes Yes Yes Yes Yes Yes

E Yes Yes Yes Yes Yes Yes Yes Yes

F Yes Yes Yes Yes Do not know Yes Yes Not applicable

G Yes Yes Yes Yes Yes Yes Yes Yes

H Yes Yes Yes Yes Yes Yes Yes Yes

I Yes Yes Yes Yes Yes Probably no Probably no Probably no

JNo No No No No No No No

K Yes Yes Yes Yes Yes Yes Yes Yes

L Yes Yes Yes Yes Yes Yes Yes Yes

TS 10 10 10 9 8 9 8 7

J Food Biochem

(2012) 36: 159–170.

Am J Clin Nutr

(1991) 53 (5):

1259–1265

J Acad Nutr Diet

(2012) 112:

1158–1168.

Curr Top Nutraceut

R (2009) 7:

157–160

J Ayub Med Coll

Abbottabad (2010a)

22(1): 38–31

J Funct Foods

(2015a) 12:

11–22

J Funct Foods

(2015b) 14:

747–757

Nutr Res

(2007) 27:

511–513.

Internet J Nutr

Wellness (2009)

7: 1-1

n= 2 plum juice

(Prunus. salicina)

Single dose of

400 mL versus

400 mL water

Cross-over 1 week

n= 41 prunes

(P. domestica)

100 g/day versus

360 mL grape juice

Cross-over 8 weeks

n= 160 dried plum

(P. domestica)

100 g/day versus

dried apple Parallel

12 months

n= 8 prunes

143 g/day versus

eight different fruits

Cross-over

n= 259 prunes

(P. domestica)

11.5 g or 23 g/day

versus water Parallel

8 weeks

n= 21 plum juice

(P. salicina)

200 mL/day versus

prune juice/placebo

Cross-over 28 days

n= 13 plum juice

(P. salicina)

200 mL/day versus

placebo Cross-over

28 days

n= 54 prune juice

(P. domestica)

2 × 125mL/day

Case-series 4 weeks

n= 36 Plum juice

(p. dometica)

8 ounces/day vs

psyllium and apple

juice Cross-over

6 weeks

A Healthy volunteers Free living men

with mild

hypercholesterlemia

Postmenopausal

women

Healthy young men Pre-hypertensive

patients

Healthy volunteers Healthy volunteers Adults with mild

GIT symptoms

Adults with chronic

constipation

symptoms

B No Not stated Not stated No Not stated Yes Yes Not applicable Yes

C No (not feasible) No (not feasible) No (not feasible) No (not feasible) No (not feasible) Yes Yes Not applicable no (not feasible)

D Yes Yes Yes Yes Yes Yes Yes Yes Yes

(Continues)

HEALTH EFFECTS OF PLUMS (Prunus domestica AND Prunus salicina)

Table 9. (Continued)

E Yes Yes Yes Yes Yes Yes Yes Yes Yes

F Yes Yes Yes Yes Yes Yes Yes Not applicable Yes

G Yes Yes Yes Yes Yes Yes Yes Yes Yes

H Probably no Probably no Yes Yes Yes No No Yes Yes

I Yes Yes Yes Yes Yes Yes No Probably no Yes

JNo No No No No No No No No

K Yes Yes Yes Yes Yes Yes Yes Yes Yes

L Yes Yes Yes Yes Yes Yes Yes Yes Yes

TS 8 8 9 8 8 9 8 7 10

Aliment Pharm Ther

(2011) 33: 822–828

Eat Behav (2010)

11(3): 201–203

Appetite (2010)

3: 564–569

J Am Diet Assoc

(2010) 9:

1322–1327

J Appl Res

(2004) 4: 37–43

Res J Pharm Biol

Chem Sci (2013)

2: 1195–1204

J Pharm Sci

(2010b) 23:

463–466.

n= 40 dried plum

(P. domestica)

2 × 50 g/day versus

psyllium Cross-over

14 weeks

n= 45 prunes

(P. domestica) 40 g

prune pre-load

versus bread

product Cross-over

over 1 week

n= 19 dried plum

(P. domestica)

238 kcal portion

versus baked foods

and water Cross-over

n= 26 Dried plum

(P. domestica)

100 kcal portion

versus low fat

cookies Cross-over

4 weeks

n= 58 dried plum

(P. domestica)

100 g/day versus

dried apple Parallel

3 months

n= 170 dried

plum and flixweed

(P. domestica)

40–50 g/day Parallel

3 weeks

n= 107 prunes

(P. domestica) three

groups of either

single dose, double

dose or control

case–control 8 weeks

A Patients with

chronic constipation

Normal weight

individuals

Healthy female

subjects

Healthy female

subjects

Postmenopausal

women

Iranian Hajj pilgrims Healthy volunteers

B yes Yes Yes Yes Yes Yes Yes

C No (not feasible) No (not feasible) No (not feasible) No (not feasible) No (not feasible) No (not feasible) No (not feasible)

D Yes Yes Yes Yes Yes Yes Yes

E Yes Yes Yes Yes Yes Yes Yes

F Yes Yes Yes Yes Yes No Yes

G Yes Yes Yes Yes Yes Yes Yes

H Yes Yes No No Yes Yes Yes

I Probably no Probably no Yes Yes Yes Yes Yes

J no No No Yes No No No

K yes Yes Yes Yes Yes Yes Yes

L yes Yes Yes Yes Yes Yes Yes

TS 9 9 8 9 9 8 10

An eligibility criteria specified, B randomization appropriate, C treatment allocation concealed, D similarity at baseline, E outcome measures and control intervention explicitly described, F co-intervention

comparable, G outcome measures relevant, H adverse events and I drop-outs fully described, J sample size based on a priori power calculation, K point estimates and measures of variability presented for

the primary outcome measure, L appropriate timing giving a total score (TS) of 12.

E. O. IGWE AND K. CHARLTON

studied. This anabolic effect of dried plum supplementa-

tion has also been observed by others (Halloran et al.,

2010) in animal models. Prevention of age-associated

bone loss was evident because of this anabolic effect,

while bone volume increased and already lost bone

was restored.

Investigating further, Monsefi et al. (2013) observed

the effect of plum extract on bone parameters in the off-

spring of pregnant mice as well as in non-pregnant mice.

Plum extract was orally administered to the sample pop-

ulation, and results showed that in the non-pregnant

mice, there was an increase in the femoral and tibial

lengths and serum calcium content, while the foetuses

and new-borns of the pregnant mice had higher osteo-

genesis index, which was calculated by dividing the ossi-

fied length by the total length of each bone.

Ovarian hormone deficiency, which is evident in post-

menopausal women, is a known major risk factor for os-

teoporosis (Baron, 1993). For this reason, effect of plum

consumption on bone health in human trials has been

carried out mostly on postmenopausal women. A die-

tary supplementation trial compared the effects of con-

sumption of dried plum (100 g) with dried apple (75 g)

for 3 months on markers of bone turnover in postmeno-

pausal women (Arjmandi et al., 2002). The difference in

the amount of dried plum and dried apple compared

was related to comparable quantities of energy, carbo-

hydrates, fat and fibre, obtainable from 100 g of dried

plum. Baseline and post-treatment values of serum and

urinary biochemical markers of bone status showed that

only dried plums significantly increased serum levels of

insulin-like growth factor-1 and bone-specific alkaline

phosphatase activity.

A similar longer-term randomized controlled study

compared the effects of dried plum and dried apple

on osteopenic postmenopausal women for 1 year

(Hooshmand et al., 2011). In addition to similar results

of Arjmandi et al. (2002), the authors observed that

dried plum significantly increased bone mineral density

of the ulna and spine.

In a slightly different study, Simonavice et al. (2014)

examined the effects of resistance training and dried

plum consumption on strength, body composition,

blood markers of bone and inflammation in breast can-

cer survivors. They observed that even though the

breast cancer survivors increased upper and lower body

strength, no improvements were observed in their body

composition and bone mineral density.

ANTIOXIDANT AND ANTIINFLAMMATORY

ACTIVITY

The antioxidant property of plums has mostly been at-

tributed to its high phenolic content (Ko et al., 2005;

Lea et al., 2008). Research on this health effect has

mostly been carried out with the ripe plum fruit or its

products. Yu et al. (2009a) on the other hand studied

the antioxidant effect of immature plum extract (IPE)

on selected cancer cells in vitro. The authors observed

that even though the IPE was effective in inhibiting

growth of the cancer cells (human hepatocellular carci-

noma HepG2 cells, Kato III gastric cancer cells, HeLa

human cervical carcinoma cells, U937 leukaemia cells

and MCF 7 hormone-dependent breast cancer cells),

this inhibitory effect was not observed in the hormone-

dependent breast cancer cells, and as the fruit ripened,

there was a reduction in its inhibitory effect. In a similar

study, Noratto et al. (2009) aimed to identify the pheno-

lic fraction responsible for the potential chemopreven-

tive and/or chemotherapeutic action in plum. They

observed that all extract fractions were effective in

exerting antioxidant effect on studied cancer cell lines

with the flavonols and procyanidins more effective than

the phenolic acids and anthocyanins. This result was

also confirmed by Lea et al. (2008) who, in addition,

observed that the synergic effect of the total phenolic

content of the plum extract significantly increased its an-

tioxidant activity.

Investigating this antioxidant effect on human colon

cancer cells, Fujii et al. (2006) and Lea et al. (2008), in

similar studies with prune and plum extract, respec-

tively, observed that the extracts did not reduce the via-

ble cell number of the human normal colon fibroblast

cells while inducing apoptosis of cancer cells. Noratto

et al. (2009), among other studies, also observed similar

results in their study with breast cancer cell lines.

These results have also been confirmed in animal

studies. Kim et al. (2008) observed that IPE inhibited

the growth of hepatoma HepG2 cells and had a protec-

tive effect against benzo(α)pyrene induced liver toxicity

by decreasing serum aminotransferase and hepatic con-

tents of lipid peroxide. In addition to studying the anti-

oxidant capabilities in animal studies, Mishra et al.

(2012) also observed an anti-ulcer effect after feeding

Wistar albino rats for 7days with 100, 150 or 200 mg

1

of plum extract and inducing peptic ulcer by pylo-

ric ligation. Gastric ulcerative index was estimated,

which showed that the group pre-treated with plum

extract had a significantly reduced gastric volume and

a significantly lower ulcerative index. This anti-ulcer

effect was also observed by (Cantu-Jungles et al., 2014)

in which acute gastric ulcer was induced by administra-

tion of ethanol P.A. after different oral treatments,

including prune polysaccharides, which showed a reduc-

tion and inhibition of the gastric lesion area. Yang and

Gallaher (2005) further investigated the effect of plum

on colon cancer risk factors whereby they observed that

even though dietary supplementation with dried plum

showed no inhibitory effect on aberrant crypt foci for-

mation at the initiation stage of cancer and early pro-

gression, it was able to inhibit several risk factors

associated with colon carcinogenesis. These include

reduction in faecal total and secondary bile acid

concentration, decrease in colonic β-glucuronidase and

7α-dehydroxylase activities and increased antioxidant

activities.

Contrary to observing similar results with in vitro and

animal studies, results from human trials have not been

in agreement. A study that investigated the plasma anti-

oxidant capacity changes after a meal observed that con-

sumption of a meal containing dried plum or dried plum

juice did not alter plasma antioxidant capacity (hydro-

philic and lipophilic ORAC

) (Prior et al., 2007). This

result was contradicted by the findings of Ko et al.

(2005) that demonstrated that nine different fruit juices,

including plum juice, exhibited significant antioxidant

effects in human plasma within 30 mins of consumption

by suppressing reactive oxygen species generation. Sim-

ilarly, González-Flores et al. (2011) confirmed the

HEALTH EFFECTS OF PLUMS (Prunus domestica AND Prunus salicina)

antioxidant capability of plums in young, middle-aged

and elderly adults. After consumption of 195 g of plum

twice a day for 5 days, there was a significant increase

from baseline in urinary 6-sulfatoxymelatonin (an anti-

oxidant) and total antioxidant capacity levels measured

by colorimetric assay. Similarly, Netzel et al. (2012) ob-

served that following consumption of the Queen Garnet

plum juice, there was a threefold increase in hippuric

acid excretion (a potential biomarker for total polyphe-

nols intake and metabolite), an increase in urinary anti-

oxidant capacity and a reduction in malondialdehyde

excretion, which is a biomarker for oxidative stress.

COGNITIVE IMPROVEMENT

Cognitive improvement associated with consumption of

plum has not been extensively studied in humans. Most

of the available evidence is from animal studies. This

effect on cognition has mainly been attributed to the an-

tioxidant property of plums as a result its high polyphe-

nolic content. In a study in which four groups of mice

were fed a high-cholesterol diet, with either 2% or 5%

plum powder supplementation, a significant difference

was observed in the time taken to complete the Morris

water maze task between the group fed just the high-

cholesterol diet and the control group, as well as the

5% and 2% plum powder supplementation group

(Kuo et al., 2015). In a similar study but slightly contra-

dictory results, Shukitt-Hale et al. (2009) compared the

effects of 100% plum juice and 2% dried plum powder

supplementation to modify age-related deficits in cogni-

tive function in aged rats. It was observed that there was

an improvement in cognition with the plum juice, but

not with the dried plum powder.

Using plum extract, Shahidi et al. (2013) supple-

mented the diets of three groups of mice with different

doses (75, 100, 150 mg/kg). There was a statistically sig-

nificant difference in the number of trials to acquisition

in the passive avoidance test that evaluates learning

and memory between the control group and the plum

extract treated groups. The retention test also showed

that the treated groups had increased step through

latency in the retention in comparison with the control

group. These results are in line with similar studies

(Sharma and Sisodia, 2013; Kao-Ting et al., 2013) that

demonstrate a beneficial health effect of plum on

cognition.

Bouayed et al. (2007) examined the effect of

chlorogenic acid from plums on anxiety-related behav-

iours in mice using the light/dark test, the elevated plus

maze and the free exploratory test. Results showed a

decrease in anxiety-related behaviours (anxiolytic-like ef-

fect) and protection of granulocytes from oxidative stress.

Plum consumption protected against oxidative stress

induced by radiation with special attention to spatial

learning. Sharma and Sisodia (2013) observed that plum

possesses prophylactic ability against radiation-induced

metabolic disorders and also improved spatial learning.

Exposed mice that had received plum performed better

by taking less time to reach the coloured platform in the

circular water tank apparatus (proxy for spatial learning

and memory). Similarly, Kao-Ting et al. (2013) studied

the effect of plum consumption for 2 months on

cognitive performance and expression of cerebral

neurodegeneration-related protein in streptozotocin-

induced diabetic rats. Cognitive performance, assessed

using the Morris water maze, showed that the plum sup-

plemented diet had a significant beneficial effect on spa-

tial memory and learning. There was also a significant

reduction in expression of cerebral beta-amyloid, which

is evident in Alzheimer’s disease. Significant decreases

in hyperglycaemia, insulin resistance and oxidative

stress in the sample of rats were also observed.

CARDIOVASCULAR DISEASE RISK FACTORS

Insulin resistance, a major risk factor for metabolic syn-

drome and selected cancers, presents a major public

health concern (Tsugane and Inoue, 2010). Studying

the beneficial health effects of plums on cardiovascular

disease risk factors, Noratto et al. (2015) compared the

effect of plum juice with peach juice and a placebo

group, which received the same amount of sugar in

either peach or plum juice in obese Zucker rats. Their

results showed that the plum juice group had the lowest

weight gain and also that plum polyphenols exerted the

highest anti-adipogenic and antiinflammatory effects in

fat tissues. This provides evidence of the reduction of

mRNA levels of peroxisome proliferator-activated

receptor associated with plum intake.

Negishi et al. (2007) studied the effect of prune extract

on blood pressure elevation in stroke-prone spontane-

ously hypertensive rats for 5 weeks. They observed that

prune extract supplementation in diet suppressed the el-

evation of systolic blood pressure but not diastolic blood

pressure. A study by Gallaher and Gallaher (2009) on

apoE-deficient mice, known to be susceptible to rapid

development of atherosclerotic lesions when fed choles-

terol, investigated the ability of dried plum supplemen-

tation to reduce atherosclerosis. The percentage

arterial tree atherosclerotic lesion area was significantly

lower in groups fed the dried plum supplemented diet

(4.75%), either with or without cholesterol, compared

with the group fed cholesterol without dried plum

supplementation.

In human trials, results have been inconclusive. Chai

et al. (2012) studied the effect of daily dried plum con-

sumption in comparison with dried apple on cardiovas-

cular disease risk factors in postmenopausal women

over a 1-year period. Results showed that serum total

cholesterol levels were significantly lower in the dried

apple group in comparison with the dried plum group

only at 6 months. There was also a cholesterol-lowering

effect for serum total and low-density lipoprotein cho-

lesterol at 12 months, but this was not significant.

Neither dried apple nor dried plum had a significant

effect on the serum levels of atherogenic cholesterol.

Contrary to this observation, Tinker et al. (1991) ob-

served that in adult men with mild hypercholesterol-

emia, supplementation with prunes significantly

lowered plasma low-density lipoprotein cholesterol

compared with a grape juice control group. A signifi-

cantly lower faecal bile acid concentration of lithocholic

acid was also reported.

Regarding the effect of prunes on high blood pres-

sure, Ahmed et al. (2010a) conducted a study with three

groups of pre-hypertensive patients who were random-

ized to receive on a daily basis, either a single dose of

E. O. IGWE AND K. CHARLTON

prunes (11.5g), a double dose (23 g) or a glass of water

(control) for 8 weeks. Participants who received either

the single dose or a glass of water on empty stomach

in the morning showed significant reduction in both sys-

tolic and diastolic blood pressure, while the double dose

was associated with only a reduction in systolic blood

pressure. The control (water) group also had significant

increase in serum high-density lipoprotein that was not

seen by prune-treated groups

Plum juice supplementation with the novel-bred Queen

Garnet plum that has higher anthocyanin concentrations

than the usual variant (Santhakumar et al., 2015a) ob-

served an inhibition of platelet aggregation induced by

adenosine diphosphate, collagen and arachidonic acid.

LAXATIVE EFFECT

Studies have also been carried out on the commonly

known laxative effect of prunes, which has been attrib-

uted to its high fibre content. Piirainen et al. (2007)

studied the effect of prunes on individuals with mild gas-

trointestinal symptoms. This study observed that con-

sumption of prune juice reduced the occurrence of

difficulty in defecation. Similarly, consumption of a daily

portion of plum juice before a meal in adults with chronic

constipation softened the stool, provided immediate re-

lief and participants showed more preference to prune

juice than apple juice (Cheskin et al., 2009). Similar re-

sults were also observed with dried plum in patients with

mild to moderate constipation by Attaluri et al. (2011) in

which the effect was attributed to a synergistic effect pro-

vided by sorbitol, dietary fibre and polyphenols.

ANTI-ALLERGY AND ANTIMICROBIAL

PROPERTY

On the anti-allergy capability of plum, Karasawa et al.

(2012) carried out a study with prune extract diet sup-

plementation and injection of mite allergen for 3 weeks.

It was observed that with the prune extract supplemen-

tation, number of sneezing events, total and mite

allergen-specific immunoglobulin E levels were signifi-

cantly lower even though they were unable to identify

any anti-allergic components in the prune extract.

Studying the antibacterial property of plums, Yaqeen

et al. (2013) observed that when tested on five different

gram-positive bacteria, ethanol extracts of prunes exhib-

ited an antibacterial property. This antibacterial prop-

erty was also observed by (Cevallos-Casals et al., 2006)

OTHER EFFECTS

Other reported beneficial health effects of plum include

its effect on liver function in healthy individuals. In a

clinical trial, Ahmed et al. (2010b) observed a significant

reduction in serum alanine transaminase and serum al-

kaline phosphatase (clinical biomarkers of liver health)

with no changes observed in serum aspartate transami-

nase and bilirubin.

Keßler et al. (2002) studied the effect of plum juice on

urinary stone risk factors and observed that plum juice

had no significant effect on urinary composition. How-

ever, a study that utilized the Australian Queen Garnet

plum reported an increase in urinary antioxidant capac-

ity (Netzel et al., 2012).

Farajian et al. (2010) studied the short-term effect of

prunes included as snacks prior to a meal on energy in-

take and satiety in normal-weight individuals. This

study demonstrated that a preload of prunes in com-

parison with a bread product before a meal resulted

in lower energy intake at later meals, including lunch

and the desert (910 Kcal ± 233 on prunes day vs

971 Kcal ± 249 on bread product day. Pvalue 0.010)

as well as increased satiety at all time points tested

between the snack and meal. Similar studies have also

observed similar results (Furchner-Evanson et al., 2010;

Howarth et al., 2010)

DISCUSSION

This systematic literature review identified 73 peer-

reviewed journal articles on the health effects of plum

and its associated products. Despite an increase in

plum-based research that has emerged over the past de-

cade, the level of evidence remains low. Of 25 clinical

studies, nine studies included randomization to a plum

supplementation group, but only one of these studies

adequately described the method of randomization

and blinding. Nonetheless, results from some of the

study outcomes are consistent. Considering bone health

as the main study outcome, the polyphenols present in

the plum appear to be responsible for the benefits.

However, Hooshmand and Arjmandi (2009) suggested

that even though dried plum polyphenols have some

bone modulating properties, the synergistic effect of

these polyphenols, together with potassium and vitamin

K, is required to produce potent effects on bone mass

and microarchitecture and to reverse ovariectomy-

induced bone loss in mature animals. Regardless,

compared with other dried fruits (apple, apricot, grape

and mango), only the dried plum exhibited an anabolic

effect on trabecular bone in the vertebra and prevented

bone loss (Rendina et al., 2013).

Some of the findings from the in vitro studies have

been confirmed in animal studies but remain to be

confirmed in human clinical trials. Most of the available

human trials used the dried version of plums rather than

fresh fruit, thus limiting translation to dietary messages

of the positioning of plums in a healthy diet. The drying

process significantly decreases anthocyanin and flavonol

content of plums (Piga et al., 2003). The effect of other

processing methods on the antioxidant properties of

plums has been studied by Valero et al. (2012).

Blanching decreased the tannins and antiradical effi-

ciency of the fruits but increased the total polyphenol

content, while osmotic dehydration had no effect on

the total polyphenol and ferric reducing power. Fresh

plums also have a higher free radical scavenging capac-

ity (superoxide and peroxy radicals) and antioxidant ac-

tivity than dried plums (Morabbi Najafabad and Jamei,

2014). Regardless, prunes are known to contain higher

levels of phenolic compounds than most fruits and also

possess higher radical scavenging activity, even possibly

HEALTH EFFECTS OF PLUMS (Prunus domestica AND Prunus salicina)

the highest in dried fruit and vegetable products present

in human diet (Shahidi, 2012). Further studies are re-

quired to compare the health effects of fresh plum, plum

juice and dried plum in human trials.

Extraction methodology is also an important factor in

plum-based research as different solvents have shown

some disparity in extracts. Estimating the antioxidant

capacity of the whole plum fruit, Dhingra et al. (2014)

observed that in extracting the bioactive compound in

plum, the ethyl acetate and butanol fraction showed

the most antioxidant potential in comparison with the

hexane and aqueous fraction.

Evidence included in this systematic review was gath-

ered from studies that differed in a number of ways, in-

cluding population studied, study design, outcome

measures and methods of randomization. This limits

comparison between studies. Limitations related to dif-

ferent study designs are particularly evident in the

animal studies that show inconsistent results. For exam-

ple, Kuo et al. (2015) observed significant outcomes on

cognition using the Morris water maze task on mice

fed a high-cholesterol diet with 2% dried plum supple-

mentation. Conversely, Shukitt-Hale et al. (2009)

showed that plum juice, but not a dried plum powder

(2% concentration), was effective in alleviating cogni-

tive deficits in aged rats. This may possibly be explained

by a difference in the dosage of nutrients provided in

the two studies, or the food matrix, or both

(Wesche-Ebeling et al., 1996) but remains to be

elucidated in dose-response studies.

There have been no reports on the side effects associ-

ated with daily consumption of plum and its associated

products. Studies have shown that consumption of dried

plum over a long period has no significant effect on the

levels of insulin and glucose or bowel function

(Hooshmand et al., 2013; Lucas et al., 2004). Regardless,

plums are known to contain considerable levels of oxa-

lates, which occur naturally and may increase the risk

of kidney stone formation (Ruan et al., 2013). High levels

of oxalate in the body inhibit the absorption of calcium,

thereby resulting in precipitation of calcium, which can

result in stone formation in the kidney and bladder

(Massey, 2003; Weaver et al., 1987). Keßler et al. (2002)

observed that plum consumption had no significant ef-

fect on the risk factors associated with kidney stone de-

velopment. These potential side effects have not been

reported with usual plum consumption; however, it is im-

portant to identify the upper level of safe intake.

The increased interest in plum-based research has

been attributed to the fruit’s high levels of polyphenols

and more recently its anthocyanin (a sub-class of flavo-

noids) content. Anthocyanins are water-soluble plant

pigments that are particularly conspicuous in fruits and

flower tissues where they are responsible for the diverse

range of red, blue and purple colours. Anthocyanins

are one of the most versatile subclasses of flavonoids

that are known to protect chloroplasts from

photodegradation by absorbing high-energy quanta,

while scavenging free radicals and reactive oxygen spe-

cies. The key characteristic that differentiates anthocya-

nin glycosides from other subclasses of flavonoid

glycosides is their ability to be absorbed after oral inges-

tion, although to a limited extent. In nature, about 17

different anthocyanins have been discovered, but only

six (cyanidin, delphinidin, petunidin, peonidin,

pelargonidin and malvidin) have been shown to be of

dietary importance and are ubiquitously distributed

(Jaganath and Crozier, 2010). The major anthocyanins

found in the plum are cyanidin (3-rutinoside,

3-glucoside and 3-xyloside) and peonidin (3-rutinoside

and 3-glucoside) (Usenik et al., 2009). Anthocyanins

are absorbed in the small intestine and colon and

transported in human serum and urine, mainly as me-

tabolites to reach target cells (Talavéra et al., 2004;

Kay, 2006). Anthocyanins are known to be natural anti-

oxidants and have generated a great amount of interest

among researchers in the last decade. This trend has

also been observed among plum breeders as different

varieties of plum are cultivated through hybridization.

One of these hybrids is the Australian Queen Garnet

plum, a hybrid of the Japanese plum developed through

a breeding programme funded by the Queensland Gov-

ernment in Australia. This novel-bred Queen Garnet

plum is known for its exceptionally high anthocyanin

levels, reaching up to 277 mg per 100 g fruit (Fanning

et al., 2013). Even though levels of anthocyanin content

in fruits progressively increase during fruit development

and ripening, this is more than two times higher than the

total anthocyanin content of regular plums that has been

reported to range from 5 to 173 mg per 100 g across

harvest years (Miletic et al., 2012). The beneficial health

effects of these levels of anthocyanin found in the Queen

Garnet plum are currently being researched. Preliminary

studies using this variant of plum have demonstrated anti-

thrombotic activity in humans (Santhakumar et al., 2015a)

and a beneficial effect on metabolic syndrome in rat

models, in vivo and in vitro bioactivity (Bhaswant et al.,

2015). It is important that similar studies be performed with

different hybrids of plum to confirm their beneficial health

effects in the fight against chronic diseases.

Other parts of the plum fruit that are usually

discarded or used in animal feed may also provide food

components that confer health benefits. The plum

pomace, a by-product (pulpy residue) from plum juice

has been reported to contain 38-49% dietary fibre and

have antioxidant and anti-inflammatory properties that

have been demonstrated in vitro (Milala et al., 2013).

CONCLUSION

In conclusion, this systematic review has identified an

emerging body of evidence that demonstrates the bene-

ficial health effects of plum consumption. The largest

amount of evidence to date relates to prevention and

management of osteoporosis, which shows promising

evidence as an adjunctive therapy. However, many of

the study designs were of low quality; therefore, it is im-

portant that well designed human trials are conducted to

confirm these observed effects. Consideration of the nu-

tritional composition of plums and prunes and the ef-

fects of processing on their bioactivity is also important

for future research. Elucidation of the mechanism of ac-

tion of plum polyphenols, identification of potential ad-

verse effects and the effects of dosage on outcomes is

necessary to inform dietary guidelines for chronic dis-

ease prevention and management.

Conflict of Interest

The authors of this manuscript have no conflict of interest to declare.

E. O. IGWE AND K. CHARLTON

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HEALTH EFFECTS OF PLUMS (Prunus domestica AND Prunus salicina)

A Systematic Review on the Health Effects of Plums ( Prunus domestica and Prunus salicina )

Abstract and Figures