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645
First author: Mohammed S. M. Saleh, Department of Pharmaceutical Chemistry, Kulliyyah
of Pharmacy, International Islamic University Malaysia, Indera Mahkota, Kuantan 25200,
Pahang, Malaysia.
E-mail: ksm20085@hotmail.com
Corresponding author: Mohammad Jamshed Siddiqui, Department of Pharmaceutical
Chemistry, Kulliyyah of Pharmacy, International Islamic University Malaysia, Indera
Mahkota, Kuantan 25200, Pahang, Malaysia.
E-mail: jamshed_siddiqui@iium.edu.my
Foundation project: This study was supported by Kulliyyah of Pharmacy, International
Islamic University Malaysia (IIUM), Ministry of Higher Education, Malaysia and Research
Management Centre, IIUM, Kuantan, Malaysia (FRGS 16-042-0541), (RIGS 15-099-0099).
1. Introduction
1.1. Origin and botanical classification
The Arecaceae (syn. Palmae) is one of the leading families of
Angiosperms, and comprises of flowering plants. The family
consists of about 187 genera that are collectively known as palm
species and about 2 522 species (theplantlist.org). The plant of
this family can be found in tropical countries and are abundant in
South East Asian countries like Indonesia, Malaysia, and Thailand.
Asian Pacific Journal of Tropical Medicine 2018; 11(12): 645-652
Asian Pacific Journal of Tropical Medicine
journal homepage: www.apjtm.org
IF: 1.634
How to cite this article: Saleh MSM, Siddiqui MJ, Mediani A, Ismail NH, Ahmed
QU, So’ad MSZ, Saidi-Besbes S. Salacca zalacca: A short review of the palm botany,
pharmacological uses and phytochemistry. Asian Pac J Trop Med 2018; 11(12): 645-652.
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ARTICLE INFO ABSTRACT
Article history:
Received 8 October 2018
Received in revised form 5 November 2018
Accepted 22 November 2018
Available online 26 December 2018
Keywords:
Snake fruit
Salacca zalacca
Arecaceae
Antioxidant
Antidiabetic
Anticancer
Salacca zalacca (Gaertn.) Voss (family Arecaceae) is the snake fruit commonly known in Malay
language as salak in Malaysia. This exotic fruit has diverse and potential pharmacological
properties due to its high antioxidant content. It is often consumed due to its sweet taste. The
abundant natural sugar and fibre along with minerals and vitamin makes it a nutritious fruit.
Phytochemical investigation on this fruit has revealed the presence of flavonoids, phenolics,
glycosides as well as some volatile and aromatic compounds, including gallic acid, quercetin,
chlorogenic acid, epicatechin, proanthocyanidins, lycopene and β-carotene. Pharmacological
studies on the fruit flesh and peel have shown some tremendous antioxidant, anti-inflammatory,
anticancer and antidiabetic potential. This review provides the botanical information of Salacca
zalacca as well as its scientific investigations involving the distinct pharmacological and
phytochemical benefits. This could help in highlighting the lacking data and research gaps on
this plant.
doi: 10.4103/1995-7645.248321 ©2018 by the Asian Pacific Journal of Tropical Medicine. All rights reserved.
Salacca zalacca: A short review of the palm botany, pharmacological
uses and phytochemistry
Mohammed S. M. Saleh1, Mohammad Jamshed Siddiqui1, Ahmed Mediani2, Nor Hadiani
Ismail2,3, Qamar Uddin Ahmed1, Siti Zaiton Mat So'ad1, Salima Saidi-Besbes4
1Department of Pharmaceutical Chemistry, Kulliyyah of Pharmacy, International Islamic University Malaysia, Indera Mahkota, Kuantan 25200, Pahang,
Malaysia
2Atta-ur-Rahman Institute for Natural Product Discovery, Universiti Teknologi MARA, Puncak Alam Campus, 42300 Bandar Puncak Alam, Selangor,
Malaysia
3Faculty of Applied Science, Universiti Teknologi MARA, 40450 Shah Alam, Selangor D. E, Malaysia
4Université Oran1 Ahmed Ben Bella, Laboratoire de Synthèse Organique Appliquée, Département de chimie, Faculté des sciences exactes et appliquées, BP 1524
EL Mnaouer, 31000 Oran, Algeria
646 Mohammed S. M. Saleh et al./Asian Pacific Journal of Tropical Medicine 2018; 11(12): 645-652
Different species that exist in this family are ecologically and
economically important. They are the major cultivated crops that
contribute in various industries including food, pharmaceutical, and
cosmeceutical. Some crops in this family include the oil-palm (Elaeis
guineensis), coconut (Cocos nucifera), pinang (Areca catechu), date-
palm (Phoenix dactylifera) and salak [Salacca zalacca (S. zalacca)][1].
S. zalacca (Gaertn.) Voss has different synonyms which include
Calamus zalacca Gaertn., Salacca rumphii Wall., Salacca edulis (S.
sedulis) Reinw., Salacca blumeana Mart., Calamus salakka Willd., S.
sedulis var. amboinensis Becca and S. zalacca var.
S. zalacca or locally known as salak in Malay language, is one
of the common plant species in palm or Arecaceae family. Salak
has various names. It is called ‘pondoh’ in Indonesia, ‘rakam’ in
Thailand, ‘sa laka’ or ‘she pi guo zong’ in China, and ‘yingan’ in
Myanmar[2]. Salacca wallichianna C. Martins is another related
species of salak which is comparably shorter and compact with
edible fruit[2].
Being native to South Sumatra and Southwest Java, it is widely
distributed around Southeast Asian countries, including Malaysia,
Thailand, and Myanmar in abundance. The fruit has also been
introduced to countries of other regions including New Guinea,
Philippines, Queensland and northern Territory of Australia, Ponape
Island (Caroline Archipelago), China, Surinam, Spain, and Fiji. The
fruit of salak palm is known as the snake fruit due to its scaly skin[3].
It is the most common variety of Salacca cultivated in Malaysia,
which is widely distributed around the Borneo Island and east coast
region[3]. This snake fruit has been the local’s favourite for its honey-
like taste. It is famous among the east coast civilians whereby they
grow the salak tree to harvest its fruit and in fact it provides income
to some of the families in this region.
Salak is a good source of carbohydrate and dietary fibre[4]. The
fruit pulp has been reported to possess high antioxidant capacity as
compared to other exotic fruits[3]. The pulps of salak fruit are mainly
consumed either freshly or as juice. They are also processed into
dried fruits, pickles, chips, canned in syrup as well as added as an
ingredient in local food called rojak[5]. Besides, the seed kernels of
young fruits of pondoh (Indonesian salak) are edible. Apart from
the fruit, the salak palm bark of the petioles is also used for matting,
while the leaflets are used for thatching[6].
1.2. Morphology and structure
Salak species are indigenous throughout Indonesia and Malaysia
and are one of the fruit producers. The salak grows as extremely
spiny palm with some of the variants that are almost stemless and
short. This plant could grow up to 6 m height and expected to be
productive for an average of 50 years. They are usually grown in low
land with high humidity[5].
The leaves are about 10 m long, large, and pinnate with shiny and
dark green long petioles with spine and leaflets. The fruit bore by
this palm grows in bunches at the base of tree. It is oval or spindle
shaped with approximately 6 cm long with pale-yellow sweet pulp
covered with elongated end and snake-like reddish brown scales that
brings about the name of snake fruit. The pulps are yellowish-white
and are segmented with a hard-brown seed inside[5]. The unripe
pulps are sour and have sharp taste due to the presence of tannic
acid. However, the ripe pulps are crunchy soft with sweet taste added
to a distinct and pleasant aroma. The unripe pulps are usually made
into pickles, while the ripe pulp is eaten raw[6-9].
2. Nutritional contents
Fruits and vegetables are edible substances from the nature that
brings goodness to human health. It is due to their nutritional
contents that majorly provide biologically active constituents
with distinct medicinal purposes. Fruits are comprised of various
vitamins, minerals, fibres, and sugars that are required in daily
servings. These nutrients are important to hinder different type of
diseases. Most exotic fruits provide multiple proportions of those
nutrients. To our concern, salak contains various phytoconstituents
and nutrients in abundance, comparably with other local fruits[10].
The proximate analysis of salak fruit is sucrose (7.6 g/100 g), fructose
(5.9 g/100 g), fructose (3.9 g/100 g), total sugar (17.4 g/100 g), soluble
dietary fibre (0.3 g/100 g), insoluble dietary fibre (1.4 g/100 g), total
dietary fibre (1.7 g/100 g), water (80 g/100 g), calories (77 kcal/100
g), protein (0.7 g/100 g), ash (0.6 g/100 g) and fat (0.1 g/100 g)
The fruit of salak is a source of natural sugars and dietary fibre.
Besides, salak pulp is reported to contain minerals and vitamins in
abundance. The mineral content and vitamins that can be found in
Salacca, that was previously measured phosphorous (1 161 mg/kg),
potassium (11.339 mg/kg), calcium (220 mg/kg), magnesium (607
mg/kg), sodium (231 mg/kg), iron (12.0 mg/kg), manganese (10.4
mg/kg), copper (3.36 mg/kg), zinc (10.4 mg/kg), boron (5.07 mg/kg),
sulfur (5.07 mg/kg), ascorbic acid (400 mg/kg), carotene (5 mg/kg),
thiamine (20 mg/kg), niacin (240 mg/kg), riboflavin (0.8 mg/kg) and
folate (6 mg/kg)[2,11,12].
3. Phytochemical contents
The Salacca cultivars have been studied for their phytochemical
constituents using various techniques. Wong and Tie reported on
the volatile compounds present in the pulp of S. sedulis Reinw. The
identification of about 46 compounds were detected comprising of
mostly carboxylic acids (15.9%), alcohols (1.3%), aldehydes (0.8%),
ketones (0.7%), sulphur-containing compounds (0.2%), and aromatic
hydrocarbons (0.3%). Specifically, the most prominent compounds
647
Mohammed S. M. Saleh et al./Asian Pacific Journal of Tropical Medicine 2018; 11(12): 645-652
viz., methyl 3-hydroxy-3-methylpentanone and methyl (E)-3-
methylpenta-2-enoate were found to be about 25.0% and 23.4%,
respectively.
The growth, maturation, and harvesting age of a fruit plant is
crucial in determining its phytochemical contents. Upon maturation,
the composition of various compounds in the plant and its parts may
be varied[7]. Likewise, the sugar and volatile compounds content
in snake fruit were reported to change drastically. Salak have been
reported that the sugars (glucose, fructose, and sucrose) levels were
at the optimum levels towards the end of maturation period[13].
Some of the major volatile compounds that were identified in
solvent-assisted flavour evaporation and solvent extracts were the
methyl esters of carboxylic acids which include the butanoic acid,
2-methylbutanoic acid, hexanoic acid and pentanoic acid. The
methyl esters were measurably increased during the maturation
process initiated after about 5 to 6 months after pollination. Another
minor aromatic compound identified in the solvent-assisted flavour
evaporation extract was furaneol or 4-hydroxy-2,5-dimethyl-3(2H)-
furanone[13].
A subsequent study was carried out by the same group of
researchers, where the volatile compounds of S. sedulis were
identified using electronic nose device equipped with a sensor array
and mass spectrometry fingerprinting. About 10 compounds were
identified which include six methyl esters, two carboxylic acids, an
alcohol, and furaneol with the most distinctive odour namely 2,5-
dimethyl-4-4-hydroxy-3(2H)-furanone. A similar compound was
also reported by the same group[14].
Apart from that, another study was conducted on Salacca
endulis pulp to quantify the lycopene and β-carotene levels using
chromatographic technique. Carotenoids are the precursor of vitamin
A that play an important role as the antioxidant in quenching oxygen
radical, anti-inflammatory agent, immunity regulatory process, and
cancer prevention[15]. An investigation revealed that the salak pulp
juice contains 1 130 and 2 997 µg in 100 g of sample of lycopene
and β-carotene, respectively. The same study also measured the
vitamin A activity which was expressed as µg of retinol equivalent
in 100 g of the fruit. The result showed a significantly high content
of the observed vitamin with 500 µg of retinol equivalent per 100 g,
compared to other local fruits that were analysed along with other
fruits including guava, mango, watermelon, papaya, sawo, jackfruit,
kedondong, and orange. This indicates the potential of salak fruit as
a rich antioxidant source[15].
In another study, a new technique was applied in an effort to
identify antioxidants present in salak. In this study, high performance
liquid chromatography technique paired with mass spectrometry
was used for the elucidation of compounds structure. Some of
the bioactive constituents identified and elucidated for the first
time in salak fruit were chlorogenic acid, (-)-epicatechin, and
proanthocyanidins[16].
In the same year, compounds responsible for the characteristic aroma
of three different cultivars of snake fruits (pondoh hitam, pondoh
super, and gading) were analyzed through gas chromatography-mass
spectrometry and GC-olfactometry using the nasal impact frequency.
Twenty-four compounds strongly associated with the distinct
snake fruit aroma were identified. A methyl ester namely methyl
3-methylpentanoate was found responsible for the authentic snake
fruit odour. Apart from that, the compounds that cause a sweaty
flavour were identified as 2-methylbutanoic and 3-methylpentanoic
acids. Other compounds identified include methyl 3-methylbutenoate
that occurs in over ripen fruit, methyl 3-methyl-2-pentanoate with
woody smell, and 2,5-dimethyl-4-hydroxy-3[2]-furanone that gives
the caramelised odour[16]. The new volatile compounds identified
in snake fruit were methyl dihydrojasmonate and isoeugenol which
have considerable odour impact on the fruit[17]. This study isolated
a sterol (3β-hydroxy-sitosterol) and carboxylic acid (2-methylester-
1-H-pyrrole-4-carboxylic acid) from the ethyl acetate extract of the
snake fruit[18].
Other study conducted analysis on the bioactive compounds in
salak fruit. The vitamin C and polyphenol content were found to
be significantly high as compared to mangosteen fruit (Garcinia
mangostana) with 13.28 mg ascorbic acid equivalent (AAE) and
8.46 mg gallic acid equivalent (GAE) per gram fruits, respectively.
Along with this, flavonoids, anthocyanins, tannins, and β-carotene
content were also measured to be 0.31 mg catechin equivalent (CE),
3.14 µg CE, 9.74 mg cyanidin-3-glucoside equivalent, 6.48 mg CE,
and 1.17 µg per gram fruit, respectively[19].
In a comparative analysis using salak fruit and mangosteen
fruit, the content of dietary fibres, mineral, and trace metals were
measured. The polyphenols content of salak (217.1 mg of GAE)
was higher than that of mangosteen (190.3 mg of GAE) while the
flavonoids content reported were 61.2 mg and 54.1 mg CE per 100 g
fruit, respectively. Meanwhile, the trace elements analysis showed
the level of sodium (1.9 mg), potassium (191.2 mg), manganese (2.5
mg), and zinc (0.3 mg) per 100 g of fruit, which were significantly
higher in salak fruit than mangosteen. Apart from the fruit of salak,
the juice of the ripe aril of Salacca was investigated for its total
phenolic and vitamin C. The amount measured was 176.0 µg GAE
and 98.28 µg AAE per gram sample[20].
Meanwhile the two isolated compounds obtained from the
Indonesian cultivar of S. sedulis of Bongkok variant were studied.
The compounds were purified from ethyl acetate fraction and
identified as 3-hydroxystigmastan-5(6)-en that belongs to the
β-sitosterol group (white crystal) and pyrolle-2,4-dicarboxylic acid-
methyl ester (orange solid- amorphous). Besides, the same variant of
snake fruit was also reported to contain several phytoconstituents in
abundance including the terpenoids, flavonoids, tannins, alkaloids,
and quinones. However, saponins were not detected during the
phytochemical screening[21].
648 Mohammed S. M. Saleh et al./Asian Pacific Journal of Tropical Medicine 2018; 11(12): 645-652
Another species of Salacca that was investigated for its bioactive
compounds was the Salacca wallichiana Mart. The fruit flesh,
female flower, root, and seeds were used to obtain dichloromethane
extracts from which the bioactive compounds were isolated.
Compounds isolated from the fruit flesh include the monogalactosyl
diacylglycerols, β-sitosteryl-3β-glucopyranoside-6’-O-fatty acid
esters, β-sitosterol, and triacylglycerols. The β-sitosterol and
β-sitosterone were obtained from the female flower extract, a
mixture of β-sitosterol and stigmasterol was isolated from the
root, and β-sitosteryl-3β-glucopyranoside-6’-O-fatty acid esters,
triacylglycerols, and linoleic acid were isolated from the seeds[22].
The spectroscopy instrumental analysis of the salak fruit flesh and
shell using UV-VIS and FT-IR showed the peak absorbance at the
wavelengths that correspond to phenolic acids and their derivatives
(flavonols, flavones, phenylpropenes, quinones), flavonoids,
quinines, coumarins, polysaccharides, and protein[23]. Evidently, the
salak fruit is rich with various bioactive compounds that may benefit
to human health by means of its natural sugar, minerals, vitamins,
and antioxidants contents. All reported compounds identified and/or
elucidated from the salak fruit are tabulated in Table 1.
4. Pharmacological uses
4.1. Antioxidant potential of salak
The human body is comprised of a complex system undergoing
various cellular activity or metabolism that produces free radicals,
such as reactive oxygen and nitrogen species. These radicals involve
in the pathogenesis of certain oxidative stress that are closely related
to the diseases like neurological degenerative and cardiovascular
diseases, carcinogenesis, rheumatoid arthritis, and ulcerative
colitis[27]. Sufficient intake of dietary antioxidants is important to
combat the free radical activity in the body. Plants provide a variety
of antioxidants that may benefit human health. There are various
analytical methods that can effectively be used to analyse the
antioxidants potential of these plant sources[27].
Various in vitro scientific studies have been carried out to
investigate the antioxidant capacity of salak, especially in the fruit
flesh. Antioxidant effect of salak fruit through 2,2′-azinobis-(3-
ethylbenzothiazoline-6-sulfonic acid) (ABTS•+) assay in which it
exhibited about 260 mg ascorbic acid equivalent antioxidant capacity
(AEAC) and 2.4 mg ascorbic acid per 100 g sample through HPLC
quantification. The same study reported the DPPH scavenging
activity with >250 AEAC (mg/100 g). The correlation between the
assays was ascertain to be good with high activity as compared to
other local fruits investigated along[23].
Table 1
Phytoconstituents content in salak fruit.
Compound(s) Plant part(s) References
Methyl 3-hydroxy-3-methylpentanone Ripe fruit [7]
Methyl (E)-3-methylpenta-2-enoate
Sugars: Glucose, Fructose, Sucrose Ripe fruit [13]
Butanoic acid
2-Methylbutanoic acid
Hexanoic acid
Pentanoic acid
4-Hydroxy-2,5-dimethyl-3(2H)- furanone
Methyl 3-methylbutanoate Fruits (from
different stages
of maturity)
[14]
Methyl 3-methylpentanoate [24]
Methyl 2-methyl-2-butenoate
2-Methylbutanol
Methyl hexanoate
Methyl 3-methyl-2-pentenoate
2-Methylbutanoic acid
3-Methylpentanoic acid
Methyl 3-hydroxy-3-methylpentanoate
Furaneol
Methyl 4-hydroxy-3-methyl-2-pentenoate
Acetic acid
Lycopene Pulp juice [15]
β-Carotene [19]
Chlorogenic acid Fruit pulp [23]
(-)-Epicatechin
Proanthocyanidins
Methyl dihydrojasmonate Fruit pulp [17]
Isoeugenol
3β-Hydroxy-sitosterol Fruit pulp [18]
2-Methylester-1-H-pyrrole-4-carboxylic acid
Polyphenols Fruit pulp [19]
Flavonoids
Flavanols
Anthocyanin
Tannin
3-Hydroxystigmastan-5(6)-en Fruit pulp [21]
Pyrolle-2,4-dicarboxylic acid-methyl ester
Terpenoid
Alkaloid
Quinones
p-Cresol Fruit pulp [5]
Catechol
4-Methyl catechol
Chlorogenic acid
Caffeic acid
Epicatechin
L-DOPA
Gallic acid
Monogalactosyl diacylglycerols Fruit pulp [22]
β-Sitosteryl-3β-glucopyranoside-6’-O-fatty
acid Esters
Seeds
β-Sitosterol Roots
Triacylglycerols Female flower
β-Sitosterone
Stigmasterol
Linoleic acid
Gallic acid Peel [25]
Caffeic acid
Ferulic acid
Chlorogenic acid
Quercetin
Rosmarinic acid
Xanthophyll Fruit [26]
Zeaxanthin
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Mohammed S. M. Saleh et al./Asian Pacific Journal of Tropical Medicine 2018; 11(12): 645-652
In vivo study was carried out which characterised the snake fruit for
its polyphenols content (14.9 mg GAE/g) and antioxidant potential
[72.9 µmol trolox equivalent (TE)/g]. Its effect on plasma lipid and
antioxidant activity in hypercholesteraemic rats was investigated.
After approximately 4 weeks of diet supplemented with snake fruit,
a significant reduction in plasma lipid and increase in antioxidant
activity were observed. Some of the parameter observed include the
fibrinogen fraction (solubility and mobility of the protein bands in
SDS electrophoresis). It was concluded that the snake fruit contains
bioactive compounds with positive effect on hypercholesteraemic
rats[39].
A comparative study on the antioxidant assay was performed using
DPPH and ABTS between the snake and mangosteen fruits. The
snake fruit showed significantly higher activity than mangosteen
with the DPPH and ABTS activities of 110.4 and 2 016.3 µg TE/g,
respectively. Other Salacca sp. that was studied and reported includes
the Salacca conferta (assam kelubi) which grows in swamp areas.
The phenolic content measured was 1 455.29 mg GAE per 100 g
of the edible portion, while the antioxidant capacity was measured
based on the β-carotene bleaching assay as 84.68%±8.69%[28].
The investigation on salak fruit juice using its ripe aril showed
a remarkable antioxidant activity with the initial screening of
total phenolic content of 175.99 µg GAE and 98.28 µg AAE of
vitamin C per g sample, respectively. Meanwhile, the DPPH and
FRAP activities were observed as 421.56 µg vitamin C equivalent
antioxidant capacity per gram and 1 556.79 µg TE antioxidant
capacity per g sample, respectively[18]. This is followed by a study
where the salak core (fruit flesh) and shell were analysed for their
antioxidant activity using the DPPH scavenging activity and total
flavonoid content. The core and shell hydro-alcoholic extracts
were found to be active in the DPPH assay at 82.67 and 73.13%,
respectively[18].
The antioxidant capacity of four different varieties of this species
available in Sabah were investigated and compared. Their study
reported that the total flavonoid content of the four varieties ranged
from 4.9-7.1 mg CE/g of dry sample, while the total phenolic
content was of 12.6-15.0 mg GAE per g dry sample, both in dry
basis. Meanwhile, the DPPH scavenging activity was expressed as
ascorbic AEAC and FRAP as µM ferric reduction to ferrous in 1 g
sample, in dry basis, respectively. The DPPH activity was measured
to be between 691.5-922.5 AEAC mg per 100 g sample, while the
FRAP value was between 113.3-91.6 µM FeSO4/g. Conclusively,
their results displayed a very good antioxidant activity of the Salacca
varieties although slight variations were observed among different
varieties[3].
Antioxidants are also strongly related to skin whitening and
lightening agents. Ascorbic acid is one of the potential compounds
that has been reported to have skin whitening effect. However,
due to its toxic effect in excessive amount, the usage of it has been
limited[29]. Therefore, the naturally occurring compounds especially
the antioxidants from the plant source have been extensively
evaluated in recent times. Majorly, the anti-tyrosinase compounds
which are effective in lightening the skin colour. Commonly, the
polyphenols and flavonoids are known to be the best tyrosinase
inhibitors[29]. Snake fruits are known to possess high antioxidants as
compared to apple and grapes[3]. In a randomised double- blinded,
the skin lightening cream was prepared and optimised with 3% of
the Salacca ethanolic extract. The skin melanin index showed a
significant reduction comparably better than the base cream used in
the study. The finding showed that the Salacca fruit extract can be
used as the potential material in the preparation of skin whitening
cream in cosmeceutical industry[29].
Apart from the pulp, the peel of salak fruit has been reported to
possess various polyphenols that are responsible for its antioxidant
activity. Evaluated the ethyl acetate extract of the S. sedulis peel on
DPPH (IC50: 2.93 µg/mL), ABTS (IC50: 7.93 µg/mL), and FRAP
(EC: 7844.44) activities. The result showed the potential good
antioxidant capacity of the peel[25].
4.2. Antidiabetic potential of Salacca zalaaca
Along with hyperglycaemia condition, dyslipidaemia is also
another common feature related to diabetes mellitus (DM) type 2.
Dyslipidaemia is a common metabolic abnormality of body fat. In
the case of DM, the glucose is unable to provide energy. Thus, the
lipolysis will actively provide energy to the DM patients where the
breakdown of fat leads to the uncontrolled elevated level of free
fatty acids, cholesterol, and triglycerides that increase the risk of
cardiovascular diseases[30]. Therefore, it is crucial to control lipid
level among DM patients. With this respect, an in vivo study was
carried out to understand the role of snake fruit in the management
of dyslipidaemia. The results of the study revealed that the diet
supplemented with 5% snake fruit improves the plasma lipid level of
the rats fed with high cholesterol diet[31].
Another variant of Salacca was investigated for its effect on the
lipid profile in diabetic subjects induced with streptozotocin (STZ).
Vinegar was prepared using Salacca fruit and the STZ-induced rats
were treated with it. The study concluded that the high content of
polyphenols in the vinegar has significant effect on the lipid profile
as well as the blood glucose level in the STZ-induced diabetic rats.
Conclusively, the blood glucose level was found to decrease upon
treatment with about 0.4 and 0.7 cubic centimetres of the Salacca
vinegar. Besides, the LDL, triglycerides, and cholesterol levels
were effectively decreased while the HDL was increased after the
treatment[30]. This indicates the effectiveness of the Salacca fruit on
the observed condition.
650 Mohammed S. M. Saleh et al./Asian Pacific Journal of Tropical Medicine 2018; 11(12): 645-652
Vinegar prepared from fruits of different variants of Salacca further
showed significant results with improved lipid profile and controlled
glucose level along with potential capability of the Swaru Salacca
vinegar to regenerate damaged pancreatic cells in the STZ-induced
rats. Vinegar produced using the snake fruit showed effective action
in regulating the blood glucose level thus reducing the glycaemic
index in the treated diabetic subjects. The antioxidants and acetic
acid present in the vinegar exhibited the antidiabetic potential of the
snake fruit vinegar through regenerating the pancreatic beta cells and
regulating the lipid profile[32].
The antidiabetic potential of salak fruit was also assessed through in
vitro assays using α-glucosidase (digestive enzyme). As a matter of
fact, α-glucosidase breaks down starch and disaccharides to glucose.
Hence, an inhibitor of the digestive enzymes is of therapeutic
interest in type 2 diabetes, since it helps to slow down the release of
glucose from oligosaccharides, thereby lowers post-prandial levels
of glucose in diabetic patients. In this regard, the flesh of salak fruit
was extracted using six different ratios of ethanol-water (100%,
80%, 60%, 40%, 20% and 0%) and their inhibitory effect against
α-glucosidase was ascertained. The results showed that 100% and
60% had the lowest IC50 values viz., 15.94 µg/mL and 19.15 µg/mL,
respectively against α-glucosidase. While, the water extract showed
the lowest activity with IC50 at 271.46 µg/mL[33].
4.3. Antihyperuricemic potential of salak
Studies have indicated the capacity of salak fruit in stabilising
the elevated uric acid level thus managing the gout inflammation.
Xanthine oxidase is the enzyme that is responsible for the breakdown
pathway of purine bases thus generates the reactive oxygen. In
the form of xanthine oxidoreductase, it catalyses the oxidation of
hypoxanthine to xanthine that subsequently produces uric acid. Excess
production of uric acid leads to the formation of uric acid crystals
which are accumulated in the joints, thereby causing the inflammation
and intense pain of a gout attack[24,34]. The two compounds isolated
in snake fruit namely 3β-hydroxy-sitosterol and 2-methylester-1-
H-pyrrole-4-carboxylic acid were tested for their xanthine oxidase
inhibition activity to alleviate the symptoms associated with gout. The
first compound was regarded inactive and the latter exhibited a good
activity with the IC
50
value 48.86 µg/ mL[24].
The in vivo investigation of antihyperuricemic effect of salak fruit
ethanol extract showed significant reduction in the serum uric
acid level as compared to control group upon administration at
200 mg/kg body weight, after induction using potassium oxonate
intraperitoneally and oral uric acid simultaneously. The urine uric
acid level was also determined which showed significant increase
in the urine uric acid excretion as compared to the control group,
however it was found lower than the control drug (probenecid)
used. This suggests that the mechanism of action of salak fruit’s
ethanol extract as an anti-hyperuricemia agent is via the inhibition of
xanthine oxidase activity[35] .
4.4. Anticancer potential of S. zalacca
Cancer is one of the major leading causes of mortality and
morbidity globally. Despite the advancement in the medical field
and treatments, significant deficiencies can still be observed which
require more improvement. Chemotherapy remains the routine
therapy for the treatment of cancer, however, the unavoidable
deleterious side effects associated with the chemotherapy during the
treatment process still remain great challenge to overcome cancers.
Alternative treatments to reduce the cancer cells are still relied upon
the plant sources. Plants have been reported to possess enormous
potential to provide effective anticancer action. Likewise, the salak
fruit has been found to exhibit an anticancer effect against human
lung cancer (A549), human hepatoma (HepG2), human colon
cancer (HT-29), and human breast cancer (MCF-7) cell lines. The
antiproliferative effect of salak pulp, peel, and seed extracts were
significant on all cell lines[36].
The two compounds isolated from the Salacca fruit (S. sedulis) were
pyrolle-2,4-dicarboxylic acid-methyl ester and 3-hydroxystigmastan-
5(6)-en (β-sitosterol). The first compound was discovered to
possess cytotoxic activity against MCF-7 and T47D (breast cancer
stem) cell lines. The latter was then investigated for the similar
anticancer effect, whereby the cytotoxicity assay revealed that
3-hydroxystigmastan-5(6)-en (β-sitosterol) inhibited the proliferation
and viability of MCF-7 and T47D cell lines with an IC50 value of
45.414 0 and 1.194 2 µg/mL, respectively[19].
4.5. Cytotoxicity study
The salak fruit extract has been analysed for its cytotoxicity
level against Vero cells and normal human fibroblast (NHF) cell
line correlated to its antioxidant capacity. The Vero cells showed
non-cytotoxic effect at 50 µg/mL concentration. Meanwhile, the
cytotoxicity of salak fruit extract in NHF cell line was based on the
biosynthesis of collagen and elastin, fibres in NHF cells function in
the elasticity and firming. These fibres production and degradation
are influenced by the collagenase and elastase which can be altered
by free radicals. However, the salak plum ethyl acetate extract which
showed viability of more than 75% at the concentration between
5-40 µg/mL was observed to be effectively reduce the oxidant (H2O2-
mediates the NHF cell death) content. This indicates the cellular
antioxidant potential of the salak fruit extract that was effectively
measured by the reduction in the content of observed oxidant which
was considered the main reason for cell apoptosis and necrosis[25].
651
Mohammed S. M. Saleh et al./Asian Pacific Journal of Tropical Medicine 2018; 11(12): 645-652
4.6. Other uses
Plant parts can be used for other purposes in different industries in
addition to their medicinal effects. Likewise, the salak fruit has been
reported to be used in the food industry to isolate yeast meant for
bread leavening agent. It relatively showed better quality than the
commercial baker’s yeast by means of desired leavening ability and
colour development of the bread crust and crumb[37].
The salak fruit is also used in the making of fruit tea with
combination of other local fruits (pineapple and longan) and
hed krang (Schizophyllum commune) as the main ingredient.
The composition of high antioxidants has driven this product
development which is then optimised. The optimum formula of
desired fruit tea contains the ratio of pineapple, salak, and longan of
20:20:60, respectively, added with 20% (w/w) of hed krang. Upon
analysis of the chemical, physical, and microbiological properties
as well as the sensory evaluation, the product seems to have great
potential of acceptance by consumers and could be a power packed
healthy drink[38].
5. Conclusion
Salak (S. zalacca) fruit have been cultivated in various countries for
its fruits that are consumed for nutritious content as well as for its
sweet taste and distinct flavour. It has also been commercialised in
local and international markets thus vastly contributes to economic
value. Despite its taste, the fruit has also been reported to be a
good source of antioxidant with potential bioactive compounds as
well as natural sugar. This review has presented a comprehensive
information on the nutritional and phytochemical contents with the
pharmacological uses of the snake fruit. However, the investigation
on the mode of action is still lacking, thus critical further studies are
required to fulfil this gap and also to validate other traditional uses
of this plant. Intensive laboratory investigations using different parts
of the salak (S. zalacca) along with the isolation techniques shall
provide more details on the bioactive compounds that are yet to be
discovered in this plant of high medicinal value.
Acknowledgments
The authors wish to thank the Kulliyyah of Pharmacy, International
Islamic University Malaysia (IIUM), Ministry of Higher Education,
Malaysia and Research Management Centre, IIUM, Kuantan,
Malaysia for supports and the grant provided (FRGS 16-042-0541),
(RIGS 15-099-0099).
Conflict of interest statement
The authors declare no conflict of interest.
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