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Diabetes mellitus is a chronic metabolic disease that develops mainly due to insulin deficiency or resistance to insulin action. All forms of diabetes are characterized by chronic hyperglycemia, which has an important role in the pathogenesis of diabetic complications. Leaves of Smallanthus sonchifolius (Poepp.&Endl.) H. Robinson (yacon) have been used since ancient times to prepare medicinal herbal tea with beneficial health properties. This review aims to discuss some key aspects related to the potential use of S. sonchifolius leaves and their natural biomolecules for the prophylaxis and treatment of diabetes as well as the potential mechanisms of action.
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Article Citation:
Stella Maris Honoré, Susana Beatriz Genta and Sara Serafina Sánchez
Smallanthus sonchifolius (Yacon) leaves: an emerging source of compounds for
diabetes management
Journal of Research in Biology (2015) 5(A): 021-042
Journal of Research in Biology
Smallanthus sonchifolius
(Yacon) leaves: an emerging source of
compounds for diabetes management
Keywords:
Smallanthus sonchifolius; yacón; diabetes; hypoglucemic effect; phenolic
compounds; sesquiterpenic lactones.
ABSTRACT:
Diabetes mellitus is a chronic metabolic disease that develops mainly due to
insulin deficiency or resistance to insulin action. All forms of diabetes are
characterized by chronic hyperglycemia, which has an important role in the
pathogenesis of diabetic complications. Leaves of Smallanthus sonchifolius
(Poepp.&Endl.) H. Robinson (yacon) have been used since ancient times to prepare
medicinal herbal tea with beneficial health properties. This review aims to discuss
some key aspects related to the potential use of S. sonchifolius leaves and their
natural biomolecules for the prophylaxis and treatment of diabetes as well as the
potential mechanisms of action.
021-042| JRB | 2015 | Vol 5 | No A
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www.jresearchbiology.com
Journal of Research in Biology
An International
Scientific Research Journal
Authors:
Stella Maris Honoré,
Susana Beatriz Genta and
Sara Serafina Sánchez
Institution:
Dpto. Biología del
Desarrollo, INSIBIO
(Consejo Nacional de
Investigaciones Científicas y
Técnicas-Universidad
Nacional de Tucumán
(CONICET-UNT).
Chacabuco 461, T4000ILI
San Miguel de Tucumán,
Argentina
Corresponding author:
Sara Sánchez
Web Address:
http://jresearchbiology.com/
documents/RA0502.pdf
Dates:
Received: 31 Dec 2014 Accepted: 19Mar 2015 Published: 12 May 2015
Journal of Research in Biology
An International Scientific Research Journal
Original Research
ISSN No: Print: 2231 6280; Online: 2231- 6299
Progress in Ethno Medicine - Special Issue
INTRODUCTION
Diabetes mellitus is a group of metabolic
disorders resulting from a defect in insulin secretion,
insulin action or both which causes disturbances of
carbohydrates, fat and protein metabolism (ADA 2009;
Patel et al., 2012). There are three main types of
diabetes, namely type 1 diabetes (juvenile diabetes), type
2 diabetes and gestational diabetes. In type 1 diabetes,
the β-cells of the pancreas do not make sufficient insulin.
Type 2 diabetes is the major form of diabetes, accounting
for approximately 9095% of all diabetic cases. This
form of diabetes usually begins with insulin insensitivity,
a condition in which muscle, liver and fat cells do not
respond to insulin properly. The pancreas eventually
loses the ability to produce and secrete enough insulin in
response to food intake. Gestational diabetes is caused by
hormonal changes during pregnancy or by insulin
insufficiency. Glucose in the blood fails to enter cells,
thereby increasing the glucose level in the blood (Hui
et al., 2009).
The long-term diabetes is associated with the
occurrence of complications that reduced quality of life
and increased risk factors for mortality and morbidity
(Strojek, 2003). Hyperglycemia is a common effect of
uncontrolled diabetes and long-term is an important step
in the development and progression of serious damage in
different body systems, especially the nerves and blood
vessels. These alterations are divided into two types.
Micro vascular complications include eye disease,
kidney disease and neural damage which are commonly
named as retinopathy, nephropathy and neuropathy
respectively (Forbes and Cooper, 2013). Macro vascular
complications include accelerated cardiovascular disease
resulting in myocardial infarction and cerebrovascular
disease manifesting as strokes (Luscher and Steffel,
2008; Beckman et al., 2013; Paneni et al., 2013).
Diabetic retinopathy and cardiovascular disease are one
among the leading causes of blindness and deaths,
respectively. The disease is associated with reduced
quality of life and increased risk factors for mortality and
morbidity.
Diabetes mellitus is a common condition that
affects people on both developed and developing
countries. The World Health Organization estimates that
almost 3 million deaths occurring annually are as a result
of diabetes (WHO, 2002) and is a major and growing
public health problem throughout the world. Globally,
382 million people were detected with diabetes in 2013,
and the number is expected to project to 592 million by
2035 (Diabetes Atlas, 2014). This worldwide epidemic
of diabetes has been stimulating the search for new
concepts and targets for the treatment of this incurable
but controllable disease.
Conventional drugs used in diabetes treatment
attempt to improve insulin sensitivity, increase insulin
production and / or decrease the amount of glucose in the
blood. However, in addition to the possible adverse
effects, the existing synthetic drugs have several
limitations (Arumugam et al., 2013). Pharmacological
treatments do not always succeed in maintaining normal
blood glucose levels and avoid long-term consequences
of diabetes (Prabhakar and Doble, 2011). It became
imperative to discover and develop newer, safer and
effective antidiabetic therapeutics which will not only
control diabetes but also its associated complications
(Sridhar et al., 2014). Therefore, it is prudent to look for
options in herbal medicines for diabetes as well.
This review aims to discuss some key aspects
related to the potential use one of the species of the
genus Smallanthus, S. sonchifolius, and their natural
biomolecules for the prophylaxis and treatment of
diabetes as well as the potential mechanisms of action.
Medicinal plants with potential antidiabetic activity
Natural products are the major mine for
discovering promising lead candidates, which play an
important role in future drug development programs.
Medicinal plants have been an integral part of
human healthcare systems for centuries. They have been
Ho noré et al., 2015
022 Journal of Research in Biology (2015) 5(A): 021-042
used either in the form of pure phytochemicals (e.g.
taxol, artemisinin etc.) or crude extracts (single or
combinations) for the treatment of various diseases. The
easy availability, few side effects and low cost make
herbal preparations key players from all available
therapies, especially in rural areas (Arya et al., 2011;
Medagama and Bandara, 2014).
Through the years, several plants has been
considered as a natural source of potent anti-diabetic
drugs playing a key role in the management of diabetes
mellitus. It is suggested that they have a promising future
in diabetic prevention and treatment due to integrated
effects (Singh et al., 2011). Several species of herbs
literature as having antidiabetic activity. Ethnobotanical
information indicates that more than 1000 plant species
are used as traditional remedies for the treatment of
diabetes and these traditional medicines when verified
scientifically provided a number of promising drugs for
new antidiabetic agents (Alarcon-Aguilar et al., 2008;
Upendra Rao et al., 2010; Pandhare et al., 2012). But,
further studies about efficacy, precise mechanisms of
action and safety of herbal extract use need to be
developed.
Several plant-derived products are used in
alternative medicine for the diabetes management being
their biological action related to their chemical
composition. The main compounds responsible for these
and coumarins (Upendra Rao and others 2010; Singh and
others 2011). At times the observed clinical activity has
also been ascribed to group of phytochemicals displaying
synergy. Thus, a single antidiabetic herb with thousands
of phytochemicals may have multiple benefits by
targeting several metabolic pathways (Chang et al.,
2013).
Smallanthus sonchifolius
Yacon (Smallanthus sonchifolius [Poepp. &
Endl.] H. Robinson) is an Andean crop which belongs to
the family Compositae (Asteraceae) (Grau and Rea
1997). Yacon and related plants were originally
classified under the genus Polymnia (Asteraceae,
Heliantheae, Melampodinae) (Wells 1965; Ohyama
et al., 1990; Asami et al., 1989). However Robinson in
1978 determined that many species of Polymnia genus,
including the yacón, actually belongs to the genus
Smallanthus. The new classification, S. sonchifolius
(Poepp. & Endl.), is currently preferred while the old
name Polymnia sonchifolia Poepp. & Endl. is considered
as synonymous (Grau and Rea 1997; Valentová and
Ulrichová 2003). Common names used in different parts
of the Andes are yacon, llacón, aricoma, jicama and
some derivatives as llaqon, llacum, llacuma, yacumpi,
aricuma, chicama, jíquima and jiquimilla (Grau and Rea
1997; Seminario et al., 2003).
There are records of the use of yacón centuries
before the Incas (NRC, 1989). The oldest yacon
representation has been found in archaeological reserve
Nazca (5001200 A.C.) (Grau and Rea, 1997).
Smallanthus sensu Robinson includes at least 21
species, all American, ranging mostly through southern
Mexico, Central America to northwestern Argentina.
From the Andes, yacon was transferred in the 20th
century through the New Zealand to Japan (Tsukihashi
et al.,1989). Its cultivation was successfully introduced
into Italy, Germany, France and USA though yacon is
still not remarkably diffused there. In 1993, it was
introduced into the Czech Republic in the form of
caudices originating from New Zealand (Valentová
et al., 2001). More recently, it has also been introduced
into Russia (Tyukavin 2002). Among the South
American species, some have been grouped into what
is known as "yacon group" comprising 7 species with
similar morphological characteristics: S. sonchifolius; S.
macroscyphus, S. connatus, S. riparius, S. suffruticosus,
S. meridensis and S. siegesbeckius (Grau and Rea 1997).
The species S. sonchifolius; are perennial herbs,
less frequently shrubs or small trees and only rarely
Journal of Research in Biology (2015) 5(A): 021-042 023
Ho noré et al., 2015
Ho noré et al., 2015
024 Journal of Research in Biology (2015) 5(A): 021-042
annuals. Yacon grows up to 1.5-3 m tall (Figure 1A, B).
The plant is extremely hard and grows in warm,
temperate Andean valleys, but can be found at the
altitudes of 880 to 3500 m. In most cases, just a few
Figure 1. Smallanthus sonchifolius [Poepp. & Endl.] H. Robinson (yacon). A: Plant height. B: Aerial parts
of the yacon plant C: Storage roots and rhizome D: Leaves. E: Glandular trichomes. F: yacon
Inflorescence. From Grau and Rea, 1997; Cabrera WM, 2013. Doctoral Thesis.
plants are cultivated for family consumption (Zardini
1991; Hermann et al., 1999).The plant produces large
tuberous roots similar to sweet potatoes in appearance,
but they have a much sweeter taste and crunchy fresh
and have cylindrical and fistulous stems at maturity
(Figure 1C). Yacon has large crossed opposite leaves,
simple, ovate to ovate-lanceolate, apex acuminate, base
truncated sagital and jagged-serrated margin (Figure 1D).
Winged petiole presents overlapping stipules, often
connate at the leaf base. The average size is 17 cm long x
13.7 cm lat in the middle part of the blade and 17.2 cm in
the basal region.
Trichomes and glands are present in the lower
and upper epidermis with a spherical morphology as a
result of accumulation of secretory products when they
reach the stage of maturity (Figure 1E). The trichomes
are involved in the synthesis of various chemical
compounds that are very important in the interactions of
the plant and in adaptation to biotic and abiotic factors
(Valkama et al., 2003; Wagner et al., 2004).
Like the sunflower, the yacon presents
distributed big leaves of to even along very little ramified
shafts. It represents the typical inflorescence grouping
of yellow-orange flowers, 3 cm in size in a called
structure chapter (Figure 1F).
Chemical constituents
S. sonchifolius, leaves consists of a variety of
chemical compounds. The first report of yacon
composition includes the isolation of four kaurenoids and
four sesquiterpene lactones from the leaves (Kakuta
et al., 1992). Other majority constituents present in
yacon leaves were catechol, terpenes and flavonoids
(Valentová et al., 2001).
Valentova et al.,(2003) extracted dried leaves
in several ways determining two fractions (ethyl acetate
and OF9 fraction) with high content of phenolic
compounds. The compounds were identified as
protocatechuic, chlorogenic, caffeic and ferulic (traces)
acids by RP-HPLC. The presence of large amounts of
phenolic compounds such as protocatechuic, rosmarinic,
gallic, vanillico and gentisic, caffeic acids and their
derivatives were also confirmed by HPLC coupled with
electrochemical detection (HPLC-ECD) (Jirovsky et al.,
2003, Jandera et al., 2005, Valentova et al., 2005; Terada
et al., 2009). Ferulic acid, three isomers of
dicaffeoylquinic acids (Mr = 516), an unknown
derivative of chlorogenic acid (Mr = 562) and an equally
unknown flavonoid were reported for the first time by
Simonovska et al., (2003) as constituents of yacon
leaves. Recently, Genta and others (2010) have
identifyed by IR spectrum, TLC and HPLC three
isomeric dicaffeoylquinic acids such as 3,4-
dicaffeoylquinic, 3,5-dicaffeoylquinic and 4,5-
dicaffeoylquinic as the major constituents of differents
yacon leaves extracts Genta et al., (2010) (Figure 2).
Interestingly, ethanol extracts and decoction
extracts of five landraces of S. sonchifolius revealed the
presence of higher amount of flavonoids, as luteolin 3′,7-
O-diglucoside and luteolin 7-O-glucoside together with
apigenin and luteolin (Russo et al., 2014).
Kakuta and others (1992) determined in the
methanol extract of yacon leaves the presence of
entkaurenoic acid and related diterpenoid substances (ent
-kaur-16-en-19-oic acid 15-angeloyloxy ester, 18-
Journal of Research in Biology (2015) 5(A): 021-042 025
Ho noré et al., 2015
Figure 2. Major chemical constituents present in yacon
leaves decoction. Caffeic acid (1), chlorogenic acid (2) and
three dicaffeoylquinic acids: 3,4-dicaffeoylquinic (3); 3,5-
dicaffeoylquinic (4)¸ 4,5-dicaffeoylquinic (5) and the
sesquiterpene lactone enhydrin (6). Original.
angeloylo x y - e n t-kaur - 16-en-19-o i c a c i d and
15-angeloyloxy-ent-kauren-19-oic acid 16-epoxide. The
authors suggested that these compounds probably play a
certain physiological role in the defense mechanisms of
this plant and it is highly pest-resistant. In the damaged
leaves of yacon, Hashidoko et al., (1993, 1994) found
4-hydroxystyrene and 3,4-dihydroxystyrene that were
probably formed by oxidative decarboxylation of
p-coumaric and caffeic acids by enzymatic systems of
epiphytic bacteria. Twelve novel diterpenoids: were
found by Dou et al.,2008; 2010; Ragasa et al., 2008; Qiu
et al.,2008; Raga et al.,2010; Zheng et al., 2010).
Dou et al., (2008) determined the presence of
Smallanthaditerpenic acids A, B, C and D in yacon
leaves together with the presence of chlorogenic and
caffeic acid. Recently, two new acyclic diterpenes
derived from geranylnerol smallanthaditerpenic acids
E and F were isolated by Mercado et al., (2010).
Significant variations in leaf phenolics content could be
determined in plants cultivated in different places and
collected in different times of the year (Valentová et al.,
2006, Xiang et al., 2010).
Phytochemical studies of yacon leaves also
showed the presence of several melampolide-type
sesquiterpene lactones such as sonchifolin, uvedalin,
enhydrin, fluctuanin (Inoue et al., 1995, Lin et al., 2003,
Schorr et al., 2007, Hong et al., 2008). These substances
are also contained in other Smallanthus species, e.g.
S. uvedalia, S. fruticosus and S. maculatus, as well as
species from the genus Melampodium (Asteraceae),
which has given the name to these compounds
(Bohlmann et al., 1980; 1984; Castro et al., 1989). Six
new lactones were identified recently propionate and
butirate analogs of sonchifolin, tiglate analog on C8 of
polymatin B, fluctuadin, polymatin C and the aldheyde
derivative on C14 of uvedalin (Mercado et al., 2010).
Among these lactones, enhydrin is the most
abundant one isolated from yacon leaves (Schorr and Da
Costa 2005). It was suggested that this compound comes
presumably from intact glandular trichomes of yacon
leaves, given that the sesquiterpene lactones are
produced and stored in these numerous Asteraceae
epidermal structures (Mercado et al., 2006; Lopes et al.,
2013). While most of the methods concerning the
quantification of sesquiterpene lactones are focused on
the preparation of extracts from powdered plant material,
Schorr and Da Costa (2005) evaluated the enhydrin
content in diverse leaf rinse extracts as well as in foliar
glandular trichomes of intact leaves. Such an approach
can be used as a procedure in chemical quality control of
S. sonchifolius or its derived preparations. GCMS
analysis of similar preparations showed 94.1% enhydrin
and 5.9% uvedalin (Genta et al., 2010). A wide range of
essential oils such as beta-pinene, caryophylene, y-
cadinene, β-phellandrene, β-cubebene, β-caryophyllene
and β-bourbonene has been reported from leaves and its
relative content was important for specification of yacon
varieties (Adam et al., 2005; Li et al., 2009).
Antidiabetic activity
Yacon leaves have been used for centuries by
the original inhabitants from the Andes valley as
tradicional folk medicine to treat cronic diseases
(Kakihara et al., 1997). In Japan, yacon leaves are used
alone or in combination with common tea leaves to
prepare medicinal infusion. In a first attempt to
scientifically validate its use, Volpato et al., (1997)
suggest that yacon leaves can reduce blood glucose
levels. In the past decade scientific evidence for the
antidiabetic activity of the water extract of yacon leaves
leaves in an experimental model of diabetes induced by
STZ in rats was done (Aybar et al., 2001). Streptozotocin
(STZ) injection in rats has been described as a good
experimental model to study the effects of drugs on
diabetes and some changes occurring in this state. In this
model there is destruction of the β-cells of the islet of
Langerhans of the pancreas (Lenzen et al., 2008). The
results showed that the intraperitoneal administration of
STZ effectively induced diabetes in normal non-fasted
Ho noré et al., 2015
026 Journal of Research in Biology (2015) 5(A): 021-042
rats in a dose depended manner. This was reflected by
glycosuria, high glycemia, polyphagia, polydypsia and
body weight loss compared with normal control rats. The
administration of 2% yacon tea and 10% yacón
decoction for a 30 day period significantly inhibited the
hyperglycemic action of STZ. Diabetic manifestations in
yacon- treated rats were reduced as revealed by clinical
parameters. Interestingly, lipid profile of diabetic
animals was improved and the altered creatinine and
albumin concentrations were normalized (Aybar et al.,
2001; Honoré et al., 2012). Moreover, yacon decoction
proved to have a hypoglycemic effect on healthy,
transiently hyperglycemic and diabetic rats, a fact that
led to suppose that a certain pancreatic activity was
necessary for such an effect to occur. Yacon decoction
also caused a significant decrease in the hyperglycemic
peak during the glucose tolerance test which was fairly
comparable to that of glymepiride.
Thereafter, similar results were reported by
Baroni et al., (2008) using crude extracts of yacon leaves
obtained by hot or cold aqueous extraction or hydro-
ethanolic preparation. Yacon leaf extracts have also
shown hypoglycemic activity on KK-Ay mice, which
suffer from genetically induced diabetes and in alloxan
diabetic mice (Miura et al., 2004, Miura 2007; Raga
et al., 2010). Furthermore, a clinical study has shown
that ingestion of yacon leaf and stem powder was
effective to reduce post-prandial peak of glucose in
humans (Ogose et al., 2006).
The bioactivity screening of five organic
extracts of yacon leaves provided an effective guide for
the identification of the most active hypoglycaemic
compounds. The methanol, butanol and chloroform
extracts were found to have an effective hypoglycemic
activity at minimum doses of 50, 10 and 20 mg/kg body
weight, respectively. Oral administration of a single-dose
of each extract produced a slight lowering effect in the
fasting blood glucose level of normal healthy rats,
whereas each extract tempered significantly the
hyperglycemic peak after food ingestion. Moreover,
Genta and others 2010 observed that daily administration
of different extracts of yacón leaves during 8 weeks
produced an effective glycemic control in diabetic
animals with an increase in the plasma insulin level.
These results were in concordance with previous in vitro
studies where organic fractions and aqueous extracts
from S. sonchifolius leaves reduced glucose production
via gluconeogenesis and glycogenolysis pathways in rat
hepatocytes (Valentová et al., 2004). The phytochemical
analysis of the most active fraction the butanol extract,
revealed that caffeic, chlorogenic and three
dicaffeoilquinic acids were significant components
(Genta et al., 2010) (Figure 2). These chemical
compounds have been involved as active principles in
glucose metabolism regulation (Nicasio et al., 2005;
Jung et al., 2006). Thus, caffeic acid produced a marked
plasma glucose-lowering effect in diabetic rats (Hsu
et al., 2000) while chlorogenic acid improved glucose
tolerance and insulin resistance in obese (fa/fa) Zucker
rats (Rodríguez de Sotillo et al., 2002, Ong et al., 2013).
Additionally, enhydrin, the major sesquiterpene
lactone of yacon leaves (Figure 2), was found effective
to reduce post-prandial glucose and useful in the
treatment of diabetic animals (minimum dose: 0.8 mg/kg
body weight). These results validated for the first time
the antidiabetic effect of this sesquiterpene constituent
(Genta et al., 2010). However the hypoglycemic effect
had previously been suggested together with a number of
biological activities (Hwang et al., 1996; Kawashima
et al., 2001). During the last few years, some new
compounds isolated from yacon leaves were proved to be
also responsible of the anti-diabetic properties in alloxan-
induced diabetic mice (Raga et al., 2010).
Recently Ogose et al., (2009) examined the
inhibitory effect of a single ingestion of a test food which
consisted in leaves and stem extract on postprandial
blood glucose in subjects with normal blood glucose or
borderline diabetes suggesting that a diet containing
Journal of Research in Biology (2015) 5(A): 021-042 027
Ho noré et al., 2015
yacon would be useful for diabetes prevention.
Hipoglycemic and anti-hiper glycaemic activities
The most important goal in the management of
diabetic patients is to maintain blood glucose level as
close to normal as possible (Mooradian and Thurman
1999). In addition, postprandial hyperglycemia or
hyperinsulinemia are independent risk factors for the
development of macrovascular complications of diabetes
mellitus (Kim et al., 2000). There are several possibility
for the mechanisms by which the plant reduces blood
glucose concentration: reduction of the intestinal
absorption of glucose, increase in glucose uptake by
tissues and organs, increased release of insulin through
stimulation of the β-pancreatic cells, resistance to the
hormones that increase the rate of glucose release,
increase of the number and sensitivity of the insulin
receptors and decreased release glycogen degradation,
among others (Negri 2005).
Aquous extracts of S. sonchifollius leaves
administered by 30 days were found to significantly
increase circulating insulin levels and decreased blood
glucose level in STZ-diabetic rats (Aybar et al., 2001,
Honoré et al., 2012). So, leaf phytochemical leaves
compounds, responsible for its hypoglycemic activity
may have the ability to increase the number of β-cells,
stimulate insulin synthesis/release from pancreatic
β-cells, inhibit insulin degradation or of both.
Inmunohistochemical procedure showed that the amount
of insulin secreating β-cells of the islets of Langerhans is
greater in yacon treated-diabetic rats in comparison to
control group suggesting that yacon also have the
potential to protect it from STZ-induced damage in
experimental animals (Honoré et al., 2012) (Figure 3).
Enhidryn were also found to increase the number of
β-cells and insulin mRNA levels in pancreatic islets of
STZ-diabetic rats (Serra Barcellona et al., 2014).
In addition, an insulin-like effect of yacón
leaves extracts has been reported in FAO cells, a
hepatoma cell line, which not requires specific insulin
supplementation of the culture medium (de Waziers and
others 1995; Valentova et al., 2004). Using this model,
Valentova et al., (2005) showed that differtent organic
extracts of S. Sonchifollius were able to down-regulated
CYP2E and cytochrome CYP2B mRNA expression
similarly to insulin.
Ho noré et al., 2015
028 Journal of Research in Biology (2015) 5(A): 021-042
Figure 3. Effects of 10% yacon decoction on insulin. A: Immunofluorescence
staining of insulin in the pancreas. Representative histological sections of pancreatic
islets of control, yacon-control, STZ and STZ-yacon rats incubated with anti-insulin
antibody. Bars: 50µm. B: Quantitative analysis of insulin positive area. Data
expressed as means ± DE, (p<0.05, n=10). C: Fasting plasma insulin levels. Data
expressed as means ± DE, (p<0.05, n=10). From Honoré and others 2012. Food and
Chemical Toxicology 50:1704-1715.
In that sense, it has been proposed that
antidiabetic effect of S. sonchifollius observed in vivo is
probably due not only due to its effects on plasma insulin
concentration, but also, to a specific action on hepatic
metabolism. Valentova et al., (2005), have demonstrated
that organic yacon leaf extracts were able to reduce
glucose production in hepatocyte primary cultures by
inhibition of gluconeogenesis and glycogenolysis
pathways.
Also, Baroni et al., (2014) demonstrated that
diabetic rats treated with yacon extracts presented a
significant improvement in the glucose-6-phosphate
dehydrogenase (G-6-PDH) activity. Furthermore, it was
observed that yacon treatment increased the hepatic and
muscle glycogen content and caused a reduction in
hepatic Aspartate Aminotransferase (AST) activity in
diabetic rats.
Probably these effects could be due to the
presence of polyphenolics compounds as chlorogenic
acid and its derivatives in yacon leaves, which, has been
shown to be competitive inhibitors of glucose-6-
phosphatase reducing glucose production in isolated
perfused rat liver (Arion et al., 1997; Hemmerle et al.,
1997).
Several reports have mentioned that many
phytochemical compounds may also act as hypoglycemic
by delaying the transfer of glucose from the stomach to
the small intestine, the main site of glucose absorption
and by inhibiting the glucose transport at the site of
intestinal brush border membranes (Tiwari and Rao
2002).
In this context, Matsuura et al., (2004) analyzed
the inhibitory effects on the intestinal digestion and
absortion of sugar of Japanese commercial health teas,
including yacon. However, the authors observed no
significant changes in portal plasma glucose
concentration after administration of health teas during
continuous intragastric infusion of sucrose.
Polyphenolics derived from aqueous extracts
have been reported to inhibit a-amylase and sucrase, and
have been shown to be the principle substance for
suppressing postprandial hyperglycemia. Furthermore,
these polyphenolics also inhibit glucose transport across
the intestine by inhibiting sodium glucose co-transporter
(S-GLUT-1) (Kobayashi et al., 2000). Oboh and others
(2015) provided evidence that both caffeic and
chlorogenic acid derivatives identified in extracts from
yacon leaves inhibited α-amylase and α-glucosidase
activities in a dose-dependent manner. Moreover, the
esterification of caffeic acid with quinic acid, producing
chlorogenic acid, reduces their ability to inhibit
α-amylase and a-glucosidase activities. In a previous
study another phenolic component from yacon leaves,
the tricaffeoylaldaric acid, has been demonstrated to
have strong antioxidant and α-glucosidase activity
(Terada et al., 2009).
In vivo and in vitro studies in normal and
diabetic rats showed that the sesquiterpenic lactone
enhydrin has an inhibitory effect on α-glucosidase
activity in a dose-dependent manner (Serra Barcellona
et al., 2010). Also, Xiang et al., (2010) observed the
same inhibitory effect of smallanthaditerpenic acids A,
B, C and D isolated from yacon leaves, all of which may
account for the effective capacity of the leaves to
attenuate intestinal glucose absorption.
Antioxidant activity
Oxidative stress has been linked to the
development of most chronic diseases (Valko et al.,
2007; Chang and Chuang 2010). Specifically, in
diabetes, it is thought to play a role in both pathogenesis
and course of the disease (Baynes 1991; Chang and
Chuang 2010). Diabetes creates a condition conducive
for the promotion of oxidative stress, and in turn free
radicals produced in excess from glucose auto-oxidation
and protein glycation with a simultaneous decline of the
antioxidant defense system that mediate some of the
harmful effects of hyperglycemia, which manifest as
Ho noré et al., 2015
Journal of Research in Biology (2015) 5(A): 021-042 029
complications of the disease (King and Loeken 2004,
Giacco and Brownlee 2010). Much scientific evidence
revealed that antioxidant defense system represents a
complex network with interactions, synergy and specific
tasks for a given antioxidant. So, effort to find suitable
antidiabetic and antioxidant therapy are necessary.
The leaves of yacon have high content of
phenolic compounds, recognized for their ability to
capture free radicals. Thus, the presence of
protocatechuic, chlorogenic, caffeic and ferulic acids in
the two fractions extracted from S. sonchifolius leaves
showed potent antioxidant activity in 1,1-diphenyl-2-
picrylhydrazyl and xanthine/XOD superoxide radical
scavenging tests, they inhibited the lipoperoxidation of
rat liver subcellular membranes and they protected rat
hepatocytes against oxidative injury (Valentovà et al.,
2003; 2004; 2005). Hot water extract of the aerial part of
yacon also showed potent free radical-scavenging
activity and inhibitory effects on lipid peroxidation in rat
brain homogenate, being 2,3,5-tricaffeoylaltraric acid the
major component in the fraction (Terada et al., 2006).
As was mentioned above, Baroni et al., (2014)
demonstrated in vivo that hydroethanolic extracts of
S. sonchifolius improved the activity of G-6-PDH.
Increased expression of this enzyme has been associated
with increased glutathione levels and resistance to
oxidative stress (Oberley 1988). Previous reports have
indicated that the NADPH produced by G-6-PDH
participates in the elimination of reactive oxygen species
via glutathione peroxidase and catalase in both hepatic
and extrahepatic tissues (Salvemini et al., 1999).
Preliminary studies confirmed the strong
antioxidant potential of yacón leaves and the isolated
compound enhydrin of in normal and diabetic rats (Serra
Barcellona et al., 2012a).
Renal protective effect
Diabetic nephropathy is considered as the most
common cause of renal damage and is the major
microvascular complication in long-standing patients of
both type 1 and type 2 diabetes mellitus, leading to end-
stage renal disease (Schrijvers et al., 2004; Kanwar et al.,
2008). Pathological changes such as expansion of
mesangial cells, accumulation of extracellular matrix
proteins, thickening of glomerular and tubular basement
membranes, tubulointerstitial fibrosis, glomerulosclerosis
and renal endothelial dysfunction occur in the diabetic
Ho noré et al., 2015
030 Journal of Research in Biology (2015) 5(A): 021-042
Figure 4. Effects of 10% yacon decoction on ultrastructural changes in
diabetic kidney. Glomerular ultrastructure and tubulointerstitial
ultrastructure of control, STZ and STZ-yacon rats. Segmental thickness
of glomerular basement membrane and excessively deposited
tubulointerstitial matrix were observed. Yacon decoction treatment
improved STZ-induced renal ultrastructural abnormalities. Bm:
Basement membrane; Pc: podocyte; Mi: mitochondria; Cap: capillary.
Bars: (A) 0.8µm; (B-C) 50µm. From Honoré and others 2012. Food and
Chemical Toxicology 50:1704-1715.
kidney (Kanwar et al., 2008). For this reason, in the last
years has intensified the search for new therapeutic
agents that can prevent the onset of nephropathy or delay
the progression of glomerulosclerosis.
A number of studies have now definitely proved
that improved metabolic control that achieves near-
normoglycemia can significantly decrease the
development and progression of diabetic nephropathy
and the early identification of microalbuminuria is
considered to be clinically relevant (Gomes et al., 1997).
Aybar et al., (2001) showed that yacon tea treatment
improves the general condition of diabetic rats and tends
to restore certain normal renal parameters. Honoré et al.,
(2012) demonstrated an effective renoprotective action
of 10% yacon decoction. Indeed, the treatment for 4
weeks of attenuated diabetes induced renal dysfunction
by r e d u ci ng mesangi a l ma trix expansi o n ,
tubulointerstitial fibrosis and tubular atrophia in diabetic
rat (Figure 4). These findings were correlated with down-
regulated expression of TGF-β 1/Smad signaling, a
cytokines involved in kidney fibroblast activation and
proliferation (Balakumar et al., 2009; Liu 2011). In fact,
in this study, yacon treatment down-regulated Smad2/3
phosphorylation blocking TGF-β signaling, particularly
in areas where severe tubulointerstitial fibrosis had been
observed. Moreover, Serra Barcelona et al., (2012)
showed that yacon leaves decoction had an important in
vivo antioxidant activity in the kidney of diabetic rats,
protecting cells from lipid peroxidation slowing down
the progression of early diabetic nephropathy.
Other pharmacological activities
Anti microbial activity
The ne wly identifed compound, 8b-
tigloyloxymelampolid-14-oic acid methyl ester isolated
from yacon leaves, exhibited a potent antimicrobial
activity against Bacillus subtilis and antifungal activity
against Pyricularia oryzae. Also, fluctuanin exhibited the
strongest antibacterial activity against B. subtilis among
six identified sesquiterpene lactones present in the yacón
leaves extract (Lin et al., 2003). In addition, different
aquous and organic extracts of yacon leaves have
demonstrated antimicrobial activity against Methicillin-
resistant Staphylococcus aureus (Joung et al., 2010).
Furthermore, Choi et al., (2010) showed that enhydrin
can be considered as an antibacterial compound against
against 2 strains of Methicillin-resistant Staphylococcus
aureus ATCC 33591, ATCC 25923.
Anti parasitary activity
In a recent work, the trypanocidal activity of the
species S. sonchifolius has been evaluated by in vitro
assays (Frank et al., 2013). Dichloromethane extract of
the leaves induced a significant growth inhibition when
tested against Trypanosoma cruzi epimastigotes.
Through chromatographic separations of the more active
fractions, the authors have isolated three structurally
related germacranolide melampolide-type sesquiterpene
lactones, which were identified as enhydrin, uvedalin,
and polymatin B. According to the results, enhydrin and
uvedalin might have potential as agents against Chagas
disease and could serve as lead molecules to develop
new drugs (Fabian et al., 2013).
Anti inflammatory activity
Two new melampolide-type sesquiterpene
lactones, 8b -epoxyangeloyloxy-9a-ethoxy-14-oxo-
acanthospermolide and 8b -angeloyloxy-9a-ethoxy-14-
oxo-acanthospermolide, together with eleven known
lactones isolated from yacon leaves shown to inhibit
nitric oxide (NO) production in LPS-stimulated murine
macrophage RAW 264.7 cells (Hong et al., 2008). This
action is interesting since, NO is involved in
physiological and pathological process, such as
vasodilation and chronic or acute inflammation (Hobbs
et al., 1999).
On the other hand, yacon leaf rinse extract
exhibited topical antiedematous activity in vivo. This
activity may be a consequence of an anti-inflammatory
action, as evidenced by neutrophil migration inhibition,
Ho noré et al., 2015
Journal of Research in Biology (2015) 5(A): 021-042 031
and NO, TNF-α and PGE2 inhibition. The authors also
showed that both sesquiterpene lactones and chlorogenic
acid derivatives contribute to the anti-inflammatory
action, suggesting that yacon leaves could have a
potential use as topical anti-inflammatory agent (Oliveira
et al., 2013)
Anti cancer activity
The sesquiterpenic lactones isolated from yacon
leaves enhydrin, uvedalin and sonchifolin caused
cytotoxicity to HeLa cells through induction of apoptosis
(Siriwan et al., 2011). These authors have been
demonstrated for the first time, that yacon sesquiterpenic
lactones can induce apoptosis via increased activation of
caspase-3/7. These finding were supported with the
evidence of morphol ogica l ana lysis, lacta te
dehydrogenase release and DNA synthesis inhibition.
Furthermore, sesquiterpenic lactones can inhibit the
activation of NF-κB binding protein. Interestingly,
enhydrin may possibly have another mechanism of high
anti-cervical cancer activity because caspase-3/7 activity
was lower than uvedalin and sonchifolin even though its
cytotoxicity showed the greatest values. These new
findings may offer information for further development
of new chemotherapeutic agents or its analogs for
cervical cancer therapy.
Other biological effects
Mycotoxins are probably the best known and
most intensively researched in the world. Particularly,
aflatoxins are toxic metabolites produced by certain
fungi in/on foods and feeds and have been associated
with various diseases in human beings and domestic
animals (Eaton and Groopman, 1994). Aqueous extract
and isolated compounds from Polymnia sonchifolia
leaves have found to inhibit Aspergillus flavus growth
and production of aflatoxin B1 (Pinto and others 2001;
Gonçalez et al., 2003, Fernandes et al., 2005; Pak et al.,
2006). Whereby, yacon can be used as an alternative
method in the chemical control of mycotoxin production.
Safety
Despite the traditional use of decoction yacon
leaves, in the literature there are few studies that evaluate
the toxic potential of both yacon leaves extract and pure
compounds (de Oliveira et al., 2011; Fernandes et al.,
2005; Genta et al., 2010; Ogose et al., 2009; Siriwan
et al., 2011).
The degree of side effects or toxicity presented
by extracts or compounds of medicinal plants depends on
many complex factors. The effects of a single large dose
of a toxic substance may not necessarily reflect the risks
associated with the long- term low-level consumption
commonly used in folk medicine. In addition, long-term
studies are essential to determine a range of bioactivities
to a no-observed-adverse-effect level (NOAEL) (Serra
Barcellona and others, 2012b; Alexeeff et al., 2002).
The safety of yacón consumption was evaluated
at first time in an acute toxicity test. Normal healthy rats
treated with 2, 5, 10 times greater than the effective dose
of different organic extract of yacón leaves or isolated
compund enhydrin, evidenced no deaths or noticeable
signs of acute toxicity. (Genta et al., 2010; 2012).
Moreover, Ogose et al., (2009) judged that the
administration of yacon extracts to rats for two
generations had no effects on either the reproductive
functions or the development of the liveborn pups.
A recent acute toxicity experiment tested a
specific range of doses of the 10% yacon leaves
decoction (25, 50 and 100 times) and enhydrin (100, 200
and 400 times) for the effective hypoglycaemic dose. Up
to 14 days of administration no signs of toxicity or
deaths were recorded suggesting that the LD50 of the
10% decoction and of enhydrin would be above 14.0 and
0.32 g/kg bw, respectively (Serra Barcellona et al.,
2012b). These values were significantly higher than the
effective hypoglycaemic doses (Aybar et al., 2001;
Honoré et al., 2012). Also 10% decoction orally
administered were found non toxic, at least up to the
maximum level assayed (0.28 g/kg bw/day). Similarly,
Ho noré et al., 2015
032 Journal of Research in Biology (2015) 5(A): 021-042
isolated enhydrin had no toxic effects at a dose range of
0.4 to 8.0 mg/kg bw/day (Serra Barcellona and others
2012b).
The beneficial effects associated with the
consumption of organic or aqueous extracts of yacon
leaves for long periods might suggest that they have a
high safety margin (Valentova et al, 2003, 2005; Genta
et al., 2010; Honoré et al., 2012; Serra Barcellona et al.,
2012b). However, de Oliveira et al., (2011) showed that
prolonged oral administration (90 days) of 2% of yacon
leaves infusion and a leaf rinse extract was associated
with kidney damage and attributed it to the presence of
sesquiterpene lactones and flavonoids as 3-O-
methylquercetyn in the extract. Such differences could
be related to the the differences in the phytochemical
preparations analyzed by both groups. Moreover, it is
well known that chemical composition of yacon leaves
could present significant differences among the studied
landraces and different times of the year collection
(Russo et al., 2010; Xiang et al., 2010).
In vitro cytotoxicity assays were performed with
a selection of different cell lines based in the main target
organs. Cytotoxicity study based in metabolic
competence assay, showed a concentration-dependent
decrease in mitochondrial function and consequently in
cell viability. COS1 cells were the most resistant to the
treatment with both 10% yacon decoction or enhydrin
and the normal epithelial Vero cells showed intermediate
values of IC50, very similar to epithelial-like CHO-K1
cell line, evidencing the different response to potential
adverse or toxic effects of the extracts or pure compound
under investigation (Serra Barcellona et al., 2012b).
However it is interesting to mention that in vivo toxicity
studies unlike the in vitro assays, the effects of an oral
dose are subject to systemic bioavailability and hepatic
metabolism, pharmacokinetic processes that are absent in
a cell culture model (Singh, 2006).
CONCLUSION
S. sonchifollius, popularly known as yacón, is
the species among all Andean food plants which is that is
the most likely to attract worldwide attention in the near
future because of its wide range of uses.
Different aqueous and organic extracts or even
isolated biomolecules from yacon leaves have been
tested for their antidiabetic properties using both in vivo
and in vitro approaches and were reviewed here. Some of
these compounds show promising effects, indicating that
dietary intake of phytochemicals present in yacon leaves
could be a promising strategy for the management of
diabetes.
The combination of radical scavenging,
cytoprotective and antihyperglycemic activity makes
S. sonchifollius leaves a good candidate for preventing or
treating chronic disease involving oxidative stress.
Additionally, toxicity studies of S. sonchifollius extract
and isolated compounds have demonstrated their safety
when taken in recommended doses.
Therapies based on yacon phytochemicals could
constitute a novel pharmacological approach that would
reinforce existing treatments.
Conflict of Interest
The authors declare that there are no conflicts of
interest.
ACKNOWLEDGMENTS
This work was supported by Grants from
Consejo Nacional de Investigaciones Científicas y
Técnicas (CONICET), the Secretaría de Ciencia y
Tecnología, Universidad Nacional de Tucumán (CIUNT)
and Agencia Nacional de Promoción Científica y
Tecnológica (ANPCyT) to S.S.S. The authors thank the
past and present members of the Sánchez’s lab, who
contributed with comments, data, and discussions. S.S.S.
and S.M.H are career investigators of CONICET
(Argentina). The authors also apologize to all colleagues
Ho noré et al., 2015
Journal of Research in Biology (2015) 5(A): 021-042 033
whose relevant work could unfortunately not be cited
here because of space limitations.
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... This is known as gestational diabetes. [2] Insulin resistance caused dysfunction in β cells. Because the primary function of β-cells is to store and secrete insulin in response to glucose load, this dysfunction triggers β-cells lose the ability to adequately sense blood glucose concentration or to release sufficient insulin in response. ...
... [15] Discussion Yacon leaves extract consists of various chemical compounds. [2] This result was in line with previous study that tuberous roots, leaves, and rhizome of S. sonchifolius from various genotypes (New Zealand, Ecuador, Bolivia, Germany) contained various total phenol 34.94-68.49 mg/g. ...
... [22] Butanol extract on yacon leaves showed the presence of three dicaffeoilquinic, caffeic, and chlorogenic acids. [2,23] Previous research also stated the presence of chlorogenic acid, gallic acid, ferulic acid, and caffeic as phenolic compounds from the hydroethanolic extract in yacon. [24] Five races of S. sonchifolius were tested, the ethanol extract and the decoction extract were proved to produce a higher number of flavonoids, like luteolin 7-O-glucoside and luteolin 3′,7O-diglucoside together with luteolin and apigenin. ...
... In water as well as in organic solvents, these structures are insoluble [63], self-sterile [64,65] and stable up to 300° C and pH range of 2-11. Using ultrasound-assisted synthesis techniques, Trotta and colleagues produced cyclodextrin nanosponges [86] and examined them for anti-tumor drugs [66]. Efavirenz is a class II drug, a non-nucleoside reverse transcriptase inhibitor widely used for HIV [67]. ...
... Natural product-based materials are currently considered to be the key ingredients in the preparation and processing of new nanoformulations as they have interesting features such as biodegradability, biocompatibility, availability, renewability and low toxicity [85][86][87]. In addition to the aforementioned properties, biomaterials are largely capable of undergoing chemical modifications, ensuring unique and desirable properties for potential nanomedicine uses [88,89]. ...
... Similarly, plant extracts are used for synthesis in which the extract is mixed with the metal precursor and incubated further at room temperature or boiling temperature for a definite time or exposed to light as an external stimulus [94]. Currently, natural product-based materials are considered essential ingredients in the preparation and production of nanoformulations as they have fascinating characteristics such as biodegradability, biocompatibility, sustainability, renewable energy and low toxicity [85,86,95]. In addition to the above mentioned properties, biomaterials are, for the most part, capable of undergoing chemical modifications, guaranteeing them special and attractive properties for future applications in the field of nanomedicine [89,96,97]. ...
Article
Full-text available
... One group of compounds that can play an essential role in antioxidant and antidiabetic properties of yacon leaves is phenolic compounds. The compounds were identified as chlorogenic, caffeic, ferulic, gallic, and gentisic acids [77], also protocatechuic, rosmarinic, vanillic and gentisic acids, as well as 3,4-dicaffeoylquinic, 3,5-dicaffeoylquinic and 4,5-dicaffeoylquinic isomers of dicaffeoylquinic acid [86]. ...
... S. sonchifolius leaves are rich in flavonoids, such as luteolin 3′,7-O-diglucoside and luteolin 7-O-glucoside together with apigenin and luteolin [86], 5, 7-dihydroxy-4′-methoxyflavonol, 5, 7, 3′-trihydroxy-4′-methoxyflavonol, 5-hydroxy-4′methoxy-7-O-glycosilflavone and 7,4′-dihydroxy-3,5′-dimethoxyflavone [87]. Presence of polyphenols in yacon leaves predetermine its acrid and astringent flavor and characteristic odor. ...
... Yacon leaves contain a wide range of essential oils such as beta-pinene, caryophyllene, y-cadinene, β-phellandrene, β-cubebene, β-caryophyllene and β-bourbonene [86]. ...
Chapter
Full-text available
Phytochemicals derived from different plants are promising therapeutic agents. Herbal compounds can be used under diseases, etiological causes of which are alterations of carbohydrate, protein, and lipid metabolisms, along with increased oxidative stress and chronic low-grade inflammation. Potential sources of biologically active substances may be grape wine, rich in phenolic compounds. Well-studied examples of polyphenols are phenolic acids, catechins, anthocyanins, and flavonoids, etc. Another source of biologically active compounds is yacon (Smallanthus sonchifolius Poepp. & Endl.). The aboveground part of yacon is rich in phenolic compounds and terpenes. Main biologically active substances from tuberous roots of yacon are fructooligosaccharides and phenolic compounds. The section will be devoted to the analysis of hypoglycemic and antioxidant effects, and molecular targets of the complex of biologically active substances derived from red wine and yacon.
... There are several possibilities of the mechanisms by which the plant reduces blood glucose concentration: reduction of the intestinal absorption of glucose, increase in glucose uptake by tissues and organs, increased release of insulin through stimulating the β-pancreatic cells, resistance to the hormones that increases the rate of glucose release, increase of the number and sensitivity of the insulin receptors and the decrease of glycogen degradation rate, among others [12]. ...
... The antioxidant effect of leaf extract may be caused by the presence of phenolic compounds like caffeic acid and its derivatives (2,3,5-tricaffeoylaltraric acid, 3, 5-dicaffeoylquinic acid, 1,5-di-O-caffeoylquinic acid) chlorogenic acid, protocatechuic acid and ferulic acid, which show antioxidant and free radical scavenging activity [12,13,14,15,30,31]. ...
... Previous phytochemical research of Yacon leaves has shown it contains sesquiterpene lactones such as sonchifolin, uvedalin, enhydrin, fluctuanin, polymatin B, fluctuadin, and polymatin C, and along with melampolide compounds [5]. Further analysis showed flavonoid compounds such as quercetin [6], polyphenolic compounds such as chlorogenic acid, ferulic acid, and caffeic acid derivatives such as 1.5-O-di-caffeoylquinic acid (1,5-CQA), 4,5-O-di-caffeoylquinic acid (4,5-CQA), and 3,5-O-di-caffeoylquinic acid (3,5-CQA) [7]. ...
... The reported caffeic acid derivative compounds were reported to have strong antioxidant properties, capable of blood glucose reduction through inhibition of the α-glucosidase enzyme. In addition, enhydrin has been observed in the increase of β-pancreatic cells in streptozotocin (STZ)induced diabetogenic mouse pancreatic cells [5]. ...
Article
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Smallanthus sonchifolius [Poepp. & Endl.] H. Robinson (Asteraceae) also known as Yacon or insulin plant, is traditionally used for treating diabetes. Varying geographical origins and postharvest handling, however, seem to affect quantitative and qualitative metabolites in the leaves of Smallanthus sonchifolius [Poepp. & Endl.] H. Robinson (Yacon). The study was conducted to compare and differentiate metabolites profile/fingerprint of Yacon leaves which were grown and obtained from different locations in Pulau Jawa i.e. Lembang (Jawa Barat) and Wonosobo (Jawa Tengah). Three different solvents (95% ethanol, 50% ethanol and water) were used to synthesize Yacon leaves extracts, in order to determine the suitable solvent to produce discernable differentiation through FTIR and HPLC-based metabolomics. Principal Component Analysis (PCA) of FTIR data (4000–400 cm1 wavenumber) indicated that Yacon leaves extracted with ethanol at 95%, had a distinctive FTIR fingerprint profile when compared to others. However, the FTIR-based PCA could not differentiate the extracts based on their geographical origins, although PCA analysis of HPLC-data successfully differentiated the extracts based on their geographical origins. Furthermore, the prominent peak for the leaves extract from Lembang and Wonosobo as regards retention time, was observed at 21.59–25.10 min and 20.69–21.695 min respectively. Notably, R2Y and Q2 value obtained by cross-validation and permutation tests showed all multivariate models were statistically reliable. Overall, there is the need to conduct further research using a more sophisticated tool such as LC-MS, to identify which metabolites represented by the aforementioned FTIR and HPLC data.
... AEIC: acarbose equivalent inhibition capacity, AE: acarbose equivalent, D.W.: dry weight of sample Oboh et al. 2015) and α-glucosidase inhibition (Terada et al. 2003(Terada et al. , 2006. Sesquiterpenic lactone enhydrin and smallanthaditerpenic acids in yacon leaves may be other candidate constituents (Honoré et al. 2015). Interestingly, the AEIC values (45.2-79.9 ...
Article
Yacon, an Andean crop, was historically introduced into Japan for local consumption of its tuberous roots as a sweet vegetable. We recently examined the multi-functional effects of yacon herbal tea to establish the aerial part as a health food material. The current study aimed to investigate whether any functional differences exist among the yacon leaves from four domestic cultivars—‘Sarada otome’ (SY201), ‘Andesu no yuki’ (SY206), ‘Sarada okame’ (SY217), and ‘Andesu no otome’ (SY237)—and a Peru A line (SY11) maintained for several years in the Aso area of Kyushu. The total polyphenol content (TPC) and antioxidant activity of cultivar SY237 exceeded those of SY11, but the values for individual cultivars were inconsistent over the tested years. In carbohydrate-hydrolyzing enzyme inhibition assays, there was a large variation in all cultivars among the tested years, with three cultivars including SY237 partially demonstrating α-glucosidase inhibition comparable to or stronger than that of SY11. Based on multivariate analysis with functional data from over four years, the characteristic positioning of these yacon cultivars was systematically visualized. As a result, we found that SY237 could be a candidate cultivar that is partially superior to SY11, although the yearly variance should be considered.
... Smallanthus sonchifolius is used as the remedy of diabetes. The similar use of the plant was previously reported [67]. Leaves of Centella asiatica are used to cure throat pain. ...
Article
Full-text available
In Nepal, about 7000 vascular plants are noted. Some plants are medicinally important, so need to be explore for their medicinal value. Primary data for this research was collected by interviewing respondents. Secondary data was collected by reviewing early published research works on the internet. All herbaria were identified with the help of villagers, books, the internet, and by visiting of National Herbarium and Plant Laboratories (NHPL), Nepal. 35 plant species belonging to 28 families and 35 genera were documented as medicinal plants in the study area. Among these species, more plants were found to be herbs (51%) and the most useful parts were leaves (27%). Throat pain was the most common disease cured by more plant species (8 spp.). The most-used plant species were Acorus calamus, Terminalia chebula, Zanthoxylum armatum, Swertia chirayita, Phyllanthus emblica, Ageratina adenophora, Drymaria cordata, Curcuma caesia, Amomum subulatum, and Cinnamomum camphora. The Rai community of this area is rich in knowledge of traditional medicines. Elderly persons are found to be more thinkable about the curative properties of plants, methods of preparation, and diseases diagnosis than young people. Ethnomedicinal knowledge is important for various diseases in the Rai community. Conservation and preserve these plants for future generation as well for the reasons of traditional knowledge is going extinct gradually. The main purpose of this research was to find out the medicinal plants used by the Rai community of Khoksik village in Ramprasadrai Rural Municipality-8 in Bhojpur district.
... T he yacon is a plant originating from the Andean regions and has been used in folk medicine for its medicinal properties for the treatment of diabetes and cholesterol disorders. 1,2 This plant belongs to the family Asteraceae, also known as Compositae, and its scientific name is Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson. ...
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Yacon is an Andean plant that has been used in folk medicine for its medicinal properties. The beneficial effects of this plant are possibly due to the high content of phenolic compounds present in its leaves and roots. This study evaluated the in vitro toxicity of the hydroalcoholic extract of leaves and roots from yacon (1, 10, 50, and 100 μg/mL) through cell viability tests, genotoxic and mutagenic activity in leukocytes culture cells; and cytotoxicity and apoptosis cell death (1, 10, 50, 100, and 500 μg/mL) in cell line originally established from the primary mouse embryonic fibroblast cells that were cultured by the designated protocol, so-called 3T3 protocol "3-day transfer, inoculum 3 × 105 cells" (3T3 cell line). No mutagenic and cytotoxic activities were observed in leukocyte cultures. Cytotoxic activity was evidenced in the highest concentrations of yacon leaf extract (50 and 100 μg/mL), whereas all concentrations tested with yacon leaf extract there was induction for apoptosis in the 3T3 cells. Genotoxic potential was observed only at higher doses of leaf (50 and 100 μg/mL) and root (100 μg/mL) extract. These results suggest that yacon leaf at high concentrations may present toxic potential showing concentration-dependent behavior; however, in vivo studies should be performed to validate these results.
Thesis
The demand of healthy food is constantly increasing in Germany, as well as in developed countries in general. Here "healthy" is not clearly defined but it is often associated with foods indicating a low caloric value and further health-promoting benefits such as a high proportions of dietary fiber, phenols or antioxidants. In contrast, the proportion of obese people and the number of chronic diseases such as diabetes type II and obesity are increasing. As a result, the European Commission recommended to reduce the sugar content and the caloric value of food products, especially in sweetened beverages, breakfast cereals and dairy products by 10%. In general, a distinction can be made between artificial and natural sweeteners. Natural sweeteners such as honey, agave nectar or rapadura occur naturally and do not have to be artificially produced or synthesized. Disadvantages here are the high production costs as well as the high calorie value which is similar to conventionally used sugar. Artificial sweeteners, on the other hand, which are also known as "high-intensity sweeteners", have been artificially produced or synthesized. Examples are aspartame, saccharin or sucralose. They often have a lower calorie value (except for sugar alcohols such as xylitol or sorbitol) and are more economical to produce, which makes them particularly attractive for food producers. However, artificial sweeteners are suspected of being harmful to health or even carcinogenic. As a result, the consumer acceptance of artificial sweeteners is decreasing and the demand for natural sweeteners as alternatives is increasing. A possible alternative as a natural sweetener is yacon (Smallanthus sonchifolius). Yacon is a tuberous root crop native to the Andean region. The roots store carbohydrates mainly as fructooligosaccharides (FOS). These FOS cannot be digested by the human intestinal tract, and therefore do not cause a noticeable increase of blood glucose level. In addition, high amounts of fiber, phenols and antioxidants lead to further health promoting benefits. So far, yacon has been cultivated mainly in the Andean region in smallholder structures. Therefore, there are several open questions regarding the cultivation of yacon in Europe, especially in the area of propagation, choice of genotypes and adapted nitrogen fertilization. Especially the propagation is an important factor, as it is normally done by seedlings of mother plants or single rhizome pieces, both with pre-cultivation in the greenhouse. This is expensive and leads to a price of 3.60 € for young plants. In addition, the influence of genotype and amount of nitrogen fertilization on tuber yield and sugar composition has not been investigated yet. These open questions regarding the cultivation of yacon in Europe outline the following objectives: • to evaluate differences between direct planting and pre cultivation of rhizomes in two ways with regard to yacon growth, development, tuber yield formation and cost distribution; • to investigate the yield potential of different yacon genotypes with regard to tuber yield, sugar yield and tuber composition under the given climatic conditions of Europe; • to determine the influence of different nitrogen levels on nitrogen uptake, tuber yield formation and amount of monosaccharides and polysaccharides as well as total sugar; • to investigate the environmental impact and the production costs of different yacon cultivation systems to determine the most sustainable cultivation method. To achieve the objectives, field trials were carried out a from 2016 to 2018. As a result, four scientific publications were developed, which formed the body of this thesis. Publication I focused on the differences between a propagation with pre-cultivation in the greenhouse (DSAB), rhizome pieces with pre-cultivation in the greenhouse (RP1) and a direct planting of rhizome pieces (RP2) in agronomic and economic terms. RP1 achieved the highest yield with 29.8 t ha 1 FM and differed significantly from the other treatments with 21.3 and 17.8 t ha-1 FM (DSAB and RP2, respectively). With regard to the cost per kg of produced yacon, RP1 was also convincing, which can be explained by a high tuber yield and comparatively low propagation costs. DSAB was the most expensive treatment and is therefore not recommended. Contrary to that RP2 has a high potential for mechanization and yield increases. Publication II investigated the differences between nine different genotypes with respect to tuber yield and sugar composition. The three genotypes red-shelled, brown-shelled and Morado achieved the significantly highest tuber yields with 46.6, 43.5 and 41.6 t FM ha-1. Also the sugar contents were outstanding with up to 66% of the DM in the red-shelled genotype. As a result, the sugar yields of these three genotypes were highest with 2.2, 2.0 and 1.9 t ha-1 in the same order as the tuber yields. In Publication III the influence of different amounts of nitrogen fertilizer (0, 40 and 80 kg ha-1) on tuber yield, sugar composition and nitrogen uptake of the brown- and red-shelled genotype was investigated. Both genotypes reached highest tuber yields of 50 and 67 t FM ha-1 at the highest nitrogen fertilizer amount (brown- and red-shelled, respectively). Contrary to this responded the total amounts of sugar and FOS. Both decreased with increasing amounts of nitrogen. With decreasing amounts of FOS, the proportion of FOS with higher degree of polymerization (DP) increased. With regard to the nitrogen utilization efficiency of both, tubers and the entire plant, a nitrogen amount of 40 kg N ha-1 seems to be sufficient and recommendable. Publication IV examined the ecological and economic sustainability of the cultivation of two genotypes (brown- and red-shelled), each with pre-cultivation in the greenhouse and as direct planting, with three different nitrogen fertilizer levels. The aim was to investigate the environmental impact and production costs of different yacon cultivation systems. Considering the costs, the highest fertilizer amount (80 kg N ha-1) led to the lowest production costs and also to comparatively low environmental impacts per functional unit (1 kg FOS). The red-shelled genotype performed better, both in terms of cost and environmental impact. This was mainly due to higher tuber yields. Overall, the preceding publications showed that the cultivation of yacon in Europe is possible and offers new possibilities for farmers. Embedding yacon successfully into existing cropping systems and crop rotations seems to be possible. The farmer has the opportunity to establish a promising new crop with great value potential on his farm in order to cover the increasing demand for raw materials for natural sweeteners.
Thesis
Yacon (Smallanthus sonchifolius Poepp. & Endl.) as an underutilized crop, native to the Andean region, has attracted growing attention. The tuberous roots of yacon have been advertised as an alternative low caloric plant source for replacing sucrose. In fact, yacon has gained recognition based on the fact that its sweet tasting tuberous roots and its leaves have a favourable phytochemical content to be included in a range of functional food products. The leaves on the one hand are a significant source of health promoting phenolic compounds and their extract exerts certain biological activities such as antioxidant activity and hyperglycemic effects. The tubers on the other hand consist of carbohydrates including simple sugars, namely, fructose, glucose, sucrose and fructooligosaccharides (FOS). The FOS - representing the dominant polysaccharide in the tubers - are sweet tasting, prebiotic, and non-digestible oligosaccharides. Therefore, their consumption imposes several health benefits such as lowering the energy intake while enhancing the beneficial microflora of the colon. It is noted that 60-70 % of the dry matter content of yacon tubers is composed of FOS. Besides, yacon tubers are a remarkable source of biological components such as phenolic compounds. Thus, yacon is considered as multifunctional plant food. The main objectives of this thesis were to 1) differentiate between the quality of young and old yacon leaves of two cultivars (red and white) in terms of their total phenolic content (TPC), total flavonoid content (TFC), antioxidant activity when using ohmic-assisted decoction (OH-DE) and decoction (DE) as well as energy consumption of extraction process, 2) differentiate between various parts of yacon tubers (flesh, peel and whole tuber) of seven cultivars in terms of their simple sugar (fructose, glucose and sucrose) content, TPC, TFC and antioxidant activity, 3) examine the TPC and antioxidant activity of yacon tubers of two cultivars (red and white) one week and three weeks after the harvest and under the influence of different pre-treatments before drying, and 4) determine the effect of drying on quality of yacon chips produced from two cultivars (red and white) at two time intervals after harvest. Overall, this thesis provided a broad dataset und information with regard to phytochemical contents of yacon leaves and tubers of different cultivars grown under the environmental conditions of southwestern Germany. However, further studies with regard to the determination of individual functional constitutes of leaves and tubers of yacon, their mechanism of action and effectiveness in promoting the health benefits, and their safety is essential. Moreover, with regard to novel product development from yacon leaves and tubers, further studies are strongly suggested to ensure the sustainability of final food products by optimizing energy consumption and environmental impacts of the whole food supply chain for such products as well as their quality.
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