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Litchi good for heath from skin to heart: An overview of litchi functional activities and compounds

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Abstract

Litchi industry in China at present suffers from seasonal overproduction, which causes heavy burden in marketing the fresh fruit. Development of processing industry provides a way out from this difficult situation. Large quantity of scrap materials of skin and seed will be produced from processing and await utilization. Health promoting effects and medical functions of litchi tissues were well documented in ancient China. Modern phytochemistry and pharmacology provide sound evidences of litchi's health promoting and medical functions, and functional compounds in the fruit are being discovered. This paper provides an overview of the studies of antioxidant activities in various fruit tissues of litchi, 'heating' effect of and allergens in the flesh, anti-cancer effect of the peel, and anticancer, antivirus and diabetes-controlling effects of the seed.
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Litchi Good for Heath from Skin to Heart: an Overview of Litchi
Functional Activities and Compounds
Y. Wang, H.C. Wang, Z.Q. Hu, H.B. Chen,
G.B. Hu and X.M. Huang* Z.K. Zhou
Dongguan Campus
College of Horticulture
South China Agricultural University
Guangzhou 510642
China
*Corresponding author
Guangdong Medical University
Dongguan 532808
China
Keywords: Litchi chinensis Sonn., antioxidant, heating effect, allergens, anticancer,
antivirus, anti-diabetes
Abstract
Litchi industry in China at present suffers from seasonal overproduction,
which causes heavy burden in marketing the fresh fruit. Development of processing
industry provides a way out from this difficult situation. Large quantity of scrap
materials of skin and seed will be produced from processing and await utilization.
Health promoting effects and medical functions of litchi tissues were well
documented in ancient China. Modern phytochemistry and pharmacology provide
sound evidences of litchi’s health promoting and medical functions, and functional
compounds in the fruit are being discovered. This paper provides an overview of the
studies of antioxidant activities in various fruit tissues of litchi, ‘heating’ effect of
and allergens in the flesh, anti-cancer effect of the peel, and anticancer, antivirus
and diabetes-controlling effects of the seed.
INTRODUCTION
With its charming appearance and delicious taste, fresh litchi is loved by all
peoples. Despite this, litchi is entitled ‘heating food’ according to Chinese traditional
medicine because some people become irritated after taking litchi, which drives away
some consumers from fresh litchi.
After the rapid development of litchi in the 1990s, seasonal overproduction has
become a major problem in China. The situation demands an effort to develop a
considerable litchi processing industry. Skin and seed to be produced as scrap materials in
large amount from litchi processing await comprehensive utilization. In fact, there is a
great potential in utilization of the scrap materials. Since ancient times, Chinese people
have realized the health promoting and medical functions of various litchi tissues.
According to Ben Cao Gang Mu, an ancient monograph of herbal medicines written by
the famous doctor, Li Shizheng in Ming Dynasty, litchi flesh promotes body fluid
production and improves sense, intelligence and Qi; litchi skin can be used to cure
dysentery, metrorhagia and eczema; and litchi seed, which is ‘warm and Qi smoothening’,
can be used for killing pains in stomach, hernia and blood gas. Modern phytochemistry
and pharmacology provide sound evidences of litchi’s health promoting and medical
functions, and functional compounds in the fruit are being discovered.
FUNCTIONAL ACTIVITIES AND COMPOUNDS IN LITCHI FLESH
Litchi flesh is rich in nutritional and functional compounds. According the data
released by USDA (see http://www. nal.usda.gov/fnic/foodcomp/cgi-bin /list_nut_edit.pl),
100 g of litchi flesh contains 16.5 g sugars, 276 kj energy, 0.83 g protein, 0.44 g fat, 0.44
g ash, 1.3 g edible fiber, 5 mg Ca, 0.31 mg Fe, 10 mg Mg, 31 mg P, 171 mg K, 1 mg Na,
0.07 mg Zn, 71.5 mg vitamin C, 0.011 mg thiamin, 0.065 mg riboflavin, 0.603 mg Niacin,
0.1 mg vitamin B6, 14 mg folate, 0.07 mg vitamin E, 0.007 mg tryptophan, 0.041 mg
lysine and 0.009 mg methionine. Taking 100 g litchi flesh satisfies 2-4% of the daily
demands for P, K, Mg, Fe, Zn and Mn and 22% for Cu (Wall, 2006).
Proc. 3r
d
IS on Longan, Lychee & Other Fruit
Trees in Sapindaceae Family
Eds.: Qiu Dongliang et al.
Acta Hort. 863, ISHS 2010
646
Apart from nutrition value, litchi flesh has also such functions as improving
digestion and blood circulation, moistening skin and alleviate anaemia symptom (Chi et
al., 2005). However, active compounds and mechanisms of these functions are unknown.
Antioxidant activity of litchi flesh is well documented. In addition to vitamin C and E,
litchi flesh contains antioxidant polysaccharides (Wu et al., 2004) and flavonoids
including procyanidin A2 and leucocyanidin (Van Rooyen et al., 1983). Polysaccharides
in litchi flesh is effective to eradicate O2· and was reported to significantly suppress lipid
peroxidation in liver of rat (Wu et al., 2004). Li et al. (2004) obtained a 3.3% recovery of
polysaccharides in litchi flesh.
However, based on Chinese traditional medicine, litchi flesh is a typical ‘heating’
food. Excessive taking causes ‘heating symptoms’ including sore and swell in throat,
boils in mouth, tongue and face and tonsillitis. ‘Heating’ effect of litchi, which is only
shown in some individuals, is not understood in terms of mechanism and effective
substances. Huang and Wu (2002) showed that ‘heating’ foods, including litchi flesh,
induced in vitro RAW264.7 macrophase to produce more prostaglandin E2 (PGE2), which
mediates proinflammation reaction, while ‘cooling’ foods like bitter melon did not have
this effect, suggesting that ‘heating’ effect might be an inflammation reaction in nature.
The effective substances are unknown either.
In Europe, there are records of cases where some individuals develop symptoms,
including above mentioned ‘heating symptoms’. Researchers attributed these symptoms
to allergic reaction or anaphylactic reaction to litchi flesh (Fäh et al., 1995; Niggemann et
al., 2002; Hoppe et al., 2006a, b; Raap et al., 2007). Allergic symptoms reported thus far
include mouth itch, swell of eye lip, eczema, herpes, sore and swell in throat, difficulty in
breath, rhinitis, stomachache (Hoppes et al., 2006a, b), skin itch, urticaria, agioedema
(Raap et al., 2001), allergic shock (Fäh et al., 1995). Cases of litchi takers with similar
allergic symptoms were also reported in China (Wang and Wang, 2006; Xu et al., 2005;
Gao and Wang, 2001). There is some information about allergens in litchi flesh. Fäh et al.
(1995) found that litchi flesh contained rich panallergen profilin, which was further
proved by Niggemann et al. (2002), who found interaction between latex and litchi flesh.
Zhang et al. (2006) cloned a complete length of profilin gene from litchi. Raap et al.
(2007) described one case of allergic reaction to litchi which was not caused by profilin
but might be anaphylactic reaction to mugwort. Hoppe et al. (2006a) separated series
protein allergens with molecular weight ranging from 14 to 70 kD from litchi flesh. One
of them, a 28 kD protein, was identified as triose-phosphate isomerase based on N-end
amino acid sequence. This enzyme is a key one in sugar metabolism.
Both ‘heating’ effect and allergic reaction are highly individual depended and their
symptoms have some similarities. However, there is no researcher equating the two
phenomena.
There are also reports showing over-taking causes so called ‘litchi sickness’ with
typical symptoms of hypoglycermia (Xie, 2005). Xie (2005) attributed this effect to
fructose in litchi, but his explanation lacked for clinical and pharmacological evidence. In
fact, litchi flesh is rich in sugars including sucrose, fructose and glucose, proportions of
which differ according to cultivars (Wang et al., 2006). Therefore, the assumption that
over-taking reduces blood sugar awaits absolute evidence.
FUNCTIONAL ACTIVITIES AND COMPOUNDS IN LITCHI SKIN
Antioxidant
Traditionally, litchi skin is useful to prevent the ‘heating effect’ from taking litchi
flesh. How it ‘cools’ the flesh is unknown. However, the antioxidant activity of litchi skin
is well defined (Guo et al., 2003; Surinut et al., 2005). Litchi skin contains free radical
scavenging compounds like ascorbic acid, glutathione, carotenoids, polysaccharides
(Huang and Wu, 2006; Yang et al., 2006), as well as rich phenolic substances including
flavonoids (flavonols and anthocyanins) and phenolic acids (Li and Jiang, 2007). Zhang
et al. (2000) found epicatechin, procyanidin B2, epigallocatechin and procyanidin B4 are
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among the major flavonoids in fruit skin of ‘Huaizhi’. Analysis conducted by
Sarini-Manchado et al. (2000) showed that molymerized tannins (procyanidins) were the
most abundant (0.4% fresh weight) in ‘Guiwei’ skin, followed in order by epicatechin
(0.17%) and procyanidin A2 (0.07%), anthocyanins (0.04%) and flavanols (0.04%).
There are studies showing fruit antioxidant activity is closely related to concentrations of
total phenols, esp. anthocyanins and procyanidins (Luximon-Ramma et al., 2003), hence
flavonoids in litchi skin contribute the major part of its antioxidant activity. Different
types of flavonoids differ in antioxidant activity. Zhao et al. (2006) found procyanidin B2
was stronger in scavenging hydroxyl free radical and superoxgen anion than procyanidin
B4 and epicatechin, while epicatechin is more active in eradicating DPPH than the other
two flavonoids.
Litchi fruit development is accompanied by changes in chemical compositions
including phenolic substances (Huang and Wu, 2006). Hence, antioxidant activity in skin
at different maturity differs. Zheng et al. (2003) found skin of immature fruit had a much
stronger antioxidant activity than that of mature fruit. Cultivars also differ in quantity and
quality of phenolics including flavonoids, so do their antioxidant activities.
Anti-Cancer Activity
Litchi skin is rich in insoluble fiber (40% on dry weight) (Li et al., 2006), which
prevents rectum cancer, diabetes and heamorrhoids. Wang et al. (2006a) reported that
water soluble alcohol extract from litchi skin significantly inhibited growth of human
hepatoma cells in vitro, and that feeding mice carrying liver cancer with litchi skin extract
suppressed cancer development. In both cases, the anticancer effect was dosage- and
time- depended. Dosages at 0.14, 0.3 and 0.6 g/kg/d led to a cancer inhibiting rate of 17.3,
30.8 and 44.0%, respectively. Wang et al. (2006b) further found litchi skin extract also
effective to suppress breast cancer. They found litchi skin extract caused changes in gene
express pattern, induced programmed cell death and suppressed multiplication in cancers
cells (Wang et al., 2006a, b). However, active ingredients in litchi skin were not indicated
in their studies. A study made by Zhao et al. (2007) indicated that flavonoids (epicatechin
and procynidin B2) were effective to suppress human breast cancer cells and human lung
fibroblast (HELF), although their toxicity to cancer cells was lower than that of paclitaxel.
FUNCTIONAL ACTIVITIES AND COMPOUNDS IN LITCHI SEED
Chemical Composition of Litchi Seed
Litchi kernel contains starch (40.7%), crude fiber (24.5%), proteins (4.93%) and
minerals including Mg (0.28%), Ca (0.21%) and P (0.11%). Fatty acids include 12%
palmitic acid, 27% linoleic acid, 11% linoleic acid, 42% cyclopropanoic fatty acids
(CPFA), among which dihydrosterculic acid accounts for 37%, cis-7,
8-methylenehexadecanoic acid 4%, cis-5,6-methylenetetradecanoic acid 0.4%, and cis-3,
4-methylenedodecanoic acid 0.1% (see Ding, 1999). Litchi seed contains also phenolic
acids and flavonoids such as methyl 5-O-p-coumaroylquinate, protocatechuic acid,
cyanidin-3-O-glu, cyanidin-3-O-rut and malvidin-3-acetyl-O-gluoenin (see Ding, 1999).
21 amino acids were detected by Huang and Chen (2007), among which 4 were unknown.
There were reports indicating litchi seed contains a special amino acid,
α-methylenecyclopropylglycine (see Ding, 1999). Volatile compounds including ketons,
aldehydes, esters, alcohols, enes and terpenoids with unknown functions were also
detected in litchi seed (Shen, 1988; Ding, 1999; Le and Fu, 2001; Chen et al., 2005; Guo
and Pan, 2006). Tu et al. (2006) found sterol derivatives, while Yang et al. (2004)
measured crude saponin in litchi seeds.
Functional Activities and Pharmacological Studies
Dried litchi seed is characterized by traditional Chinese medicine as slightly bitter,
warming, Qi flow promoting, cold-driving, pain-killing, and liver- and kidney–tonifying
(see Tian, 2005). There are abundant information on the health promoting and medical
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functions of litchi seed, including antioxidant, anti-cancer, anti-virus, controlling diabetes,
and reducing blood lips.
Antioxidant Activity
As mentioned above, litchi seed contains flavonoids, which contribute to the
antioxidant activity of the seed. Water and ethanol extracts from litchi seed were found to
reduce the damage caused by free radicals and promoted SOD activity in alloxan
momohydrate (ALX) treated mice (Pan et al., 1999).
Anti-Cancer Eeffect
Xiao et al. (2007) and Wang et al. (2007) reported in the same year that water
extract of litchi seed or litchi seed pellets were effective to suppress tumor and hepatoma.
Water extract of litchi seed at dosage of 62.5 kg/kg.d obtained 30% suppression on
hepatoma tumor in mice (Wang et al., 2007). Xiao et al. (2007) found that extract from
litchi seed inhibited the formation of telomere in heptoma cells and thus their cell
division.
Reducing Blood Sugars and Lipids
There have been reports about the effects of litchi seed in reducing blood sugars
and lipids and in promoting the function of liver (Wu et al., 1991; Zheng et al., 1998; Pan
et al., 1999; Guo et al., 2003). Results obtained by Wu et al. (1991), Zheng et al. (1998)
and Pan et al. (1999) showed that the water extracts of litchi seeds reduced blood sugar in
rat suffering from diabetes induced by ALX and that the effect was similar to that of the
anti-diabetes drug, biguanides. And it was found that litchi seed extract was safer and the
effect lasted longer (over 1 week) than biguanides (Zheng et al., 1998). Pan et al. (1999)
suggested that litchi seed extract reduced blood sugar because it inhibited glucose uptake
by blood capillary but promote glucose uptake in ambient tissues. Guo et al. (2003) also
found that litchi seed extract alleviated sugar metabolism disorder and improved
sensitivity to insulin in rat suffering from insulin resistant Type 2 diabetes (T2DM)
induced by streptomycin, and therefore reduced blood sugar.
There is little information about active anti-diabetes and lipid-reducing substances
in litchi seed. Ning (1996) attributed the abundant unsaturated fatty acids to blood
lipid-reducing effect of litchi seed. Some authors suggested that
α-methylenecyclopropylglycine in litchi seed was the effective to reduce the blood sugar
and glucogen in liver in mice treated with ALX (Huang, 1994); while others believed
anti-diabetes activity was related to saponins (Guo et al., 2003; Yang and Liang, 2004).
Anti-Virus Effects
There have been not a few reports about the anti-virus effects of litchi seed
extracts, which were effective to hepatitis B virus (Zheng and Zheng, 1992; Li, 1997; Pan
et al., 2000; Xu et al., 2004; Xiao et al., 2005; Jiang et al., 2008), respiratory syncytial
virus (RSV) (Liang et al., 2006), influenza virus (Luo et al., 2006) and SARS coronavirus
(Gong et al., 2008). Zheng and Zheng (1992) found that litchi seed was the second most
effective to control hepatitis B among 1000 tested herbal medicines. Pan et al. (2000)
found direct inhibition on in vitro expression of HbsAg and HBV-DNA. Yang et al.
(2001) showed that both water and alcohol (50%) extracts from litchi seeds were effective
to inhibit HbsAg and HbeAg, but water extract was more effective on HbeAg, while
alcohol extract more effective on HbsAg. Xu et al. (2004) examined 6 extraction fractions
of litchi seed, all showing strong effects in inhibiting the expression of HBsAg and
HbeAg in Hep G 2.2.15 cell line, with an inhibiting rate reaching 90.9 and 84.3% on
HBsAg and HbeAg, respectively. Most authors attribute anti-virus effect of litchi seed
extracts to its flavonoids (Luo et al., 2006; Liang et al., 2006; Gong et al., 2008), while
Jiang et al. (2008) suggested that saponins in litchi seed was the effective component.
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Other Functions
Litchi seed is especially effective to cure haemorrhoids (Deng, 2006).
PROBLEMS AND PROSPECTS
There is no doubt that litchi fruit possesses health promoting and some medical
functions. However, research in their mechanisms and active substances are still in its
infantry. Except for antioxidants in the skin and allergens in the flesh which are well
understood, other functions, such as anti-virus, anti-cancer and anti-diabetes, have been
studied based on crude components rather than purified substances. Litchi fruit is
ill-reputated as ‘heating’ food in China, which drives away numerous consumers from
taking litchi. In fact, ‘heating’ symptoms occur only on small percentage of people. What
are ‘heating’ substances in litchi? What are the mechanisms of ‘heating’ effect of litchi?
Why different people respond differentially to litchi? What is the relation between
‘heating effect’ and allergic reaction? Answering these questions will help to prevent
‘heating’ symptoms by taking litchi, and clear the ill reputation of ‘litchi heating’.
Solving the problems of seasonal overproduction of litchi has now become the
biggest issue in litchi industry in China. Development of processing industry, which is
one of the most important solutions, will generate large quantities of skin and seed as
scrap materials. As mentioned above, these are potential materials for anti-cancer,
anti-virus and anti-diabetes drugs. Their utilizations await a joint effort in understanding
these functions from researchers in fruit science, medicine, phytochemistry and
pharmacology.
ACKNOWLEDGEMENTS
This study has been supported by Ministry of Agriculture (Project No.
nyhyzx08-031 and 2006G31) and Dongguan Bureau of Science and Technology (Project
No. 2008108101051).
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... It was the favourite fruit of many of the Chinese emperors. The fruit aril is a rich source of several nutritional and health promoting functional compounds (Wang et al. 2010, Wang et al. 2011, Zhang et al. 2013,Su et al. 2014. Litchi pulp contains sugars in the form of sucrose, fructose and glucose which vary in magnitudes among the cultivars. ...
... Moreover, litchi fruit is instrumental in alleviating the symptoms of anaemia. It has been documented by many workers that the fruit is helpful in improving the digestion and blood circulation (Chi et al. 2005, Wang et al. 2010, Kitadate et al. 2014. The thin pericarp of the litchi fruit is a treasure trove of several functional compounds like anthocyanins, flavan-3-ol derivatives including (-)-epicatechin and proanthocyanidins A1, A2, B2 and B4 (Liu et al. 2007, Jiang et al. 2013). ...
... The traditional Chinese as well as Indian medicine system have recorded several advantages of consuming litchi fruits like improving the digestive, circulatory, excretory and reproductive systems (Zhang et al. 2013, Wang et al. 2010. The contemporary research has also revealed many important functional qualities of litchi fruit like anti-adiposity, antioxidant, anticancer, hepato-protective, antibacterial, anti-hyperlipidemic, antiplatelet, anti-hyperglycaemia, anti-mutagenic, anti-pyretic, antiinflammatory and antiviral properties (Devalaraja et al. 2011, Ibrahim andMohamed 2015). ...
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... Litchi seeds reported to have no inhibition on Cox B3 in HeLa cells, but showed potent antiviral action on RSV long strain, HSV-1 and HSV-2 standard strain in concentration dependent manner with IC 50 value of 32.3, 27.9 and 20.4 μg/mL. In addition, litchi seeds inhibited the replication of HSV-1 in Vero cells thereby showing a high anti-HSV effect (Wang et al., 2008). These findings may provide important insights for the potential discovery and development of litchi seed based novel therapeutic agents against virus strains. ...
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A delicious fruit, Litchi chinensis, is commercially grown for food consumption and has numerous health benefits. Since it has numerous biological functions, this fruit has increasingly gained huge amount of popularity. Every part be its seed, pulp or coat equally is nutritionally important and valuable since it contains benefits like antioxidant, cancer disruptive and antimicrobial properties. This chapter helps to bring into limelight the structure, properties and nutritional values of the fruit along with numerous health benefits.
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