Le WANG, Entai HOU, Wenjin XU, Haiyan HUANG, Yarong MA, Boyu LEl, Xia ZHANG,Jiang GONG, Shifeng Nl＊＊

1. College of Life Science and Technology, Xi’an Jiaotong University, Xi’an 710049, China;

2. College of Life Science, Northwest University, Xi’an 710069, China;

3. School of Medicine, Tibet Nationality College, Xianyang 712082, China

lntroduction of Koelreuteria spp.

Taxonomy

Koelreuteria spp. (Sapindaceae)is deciduous tree. A total of 4 species belonging to Koelreuteria have been found across the world. Among them,3 species and 1 variant are distributed in China, including Koelreuteria integrifoliola Merr, K. bipinnata Franch,K. minor Hem and Koelreuteria henryi Dummer. In China, the Koelreuteria spp.is distributed in Jiangsu,Zhejiang,Anhui, Hunan, Hubei, Henan and Shandong. Koelreuteria spp. has upright shape, leafy canopy, vigorous growth, but fewer pests and diseases.It can be used in road greening, landscaping, overshadowing and shelter belt. In addition, Koelreuteria spp. can also be used as raw material for extracting tannin[1].

Chemical Composition

Leaves

The main constituents in leaves of Koelreuteria spp. are flavonoids, lignans,gallic acid derivatives and sitosterol derivatives,including kaempferol-3-O-rhamnoside, kaempferol-3-Oarabinoside, 2"-galloylhyperin, 2"-galloylquercitrin,hyperin,quercitrin,koelreuterin-1, austrobailignan-1, austrobailignan-2, ethyl-p-digallate, p-digalloyl acid, ethyl-m-digallate, m-digalloyl acid, gallic acid, methyl galloyl acid,ethyl galloyl acid,β-sitosterol and β-sitosterol-3-O-glucoside[2].

Mahmoud[3]ever isolated successfully two kinds of flavonol glucoside from leaves of Koelreuteria henryi Dummer.

Seeds

Ma[2]reported that the main constituents isolated from seeds of Koelreuteria spp. are cyanolipids, saponins, flavonoids and glycerides, such as 3-O-myristoyl-1-cyano-2-methyl-1,2-propene, 3-O-14, 15-eicosylenoyl-1-cyano-2-methyl-1, 2-propene, 3-O-14,15-eicosylenoyl-4-O-stearoyl-1-cyano-2-oxymethyl-1, 2-propene, quercitrin,1-O-hexadecanolenin, triolein, 14, 15-eicosenic acid,paniculatonoid A,pan-iculatonoid B, 3-O-(6’-linoleicoyl-Dglycopyranoside)-β-sitosterol, β-sitosterol, Koelreuteria saponin A and Koelreuteria saponin B.

Gao et al. reported that the contents of crude fat, crude protein and crude fiber in seeds of Koelreuteria paniculata Laxm. and Koelreuteria bipinnata Franch in Zhengzhou,Henan were up to 51%, 24.3% and 26.13%-28.12%, respectively[4]. They also determined the vitamins contents.The results showed the contents of VA, VD2and VE in seeds of Koelreuteria bipinnata Franch were 22.29-70.28, 0.223-2.117 IU/g and 0.245-3.059 mg/100 g,and in seeds of Koelreuteria paniculata Laxm.were 43.95-91.71, 0.035-2.707 IU/g and 0.165-7.002 mg/100 g,respectively[5].

The ripe seeds of Koelreuteria paniculata Laxm. were pink or red.They were good resources of natural pigments. Under conditions of 1 ∶40(g/ml) of solid-liquid ratio, 1.0 of pH(adjusted with 10% hydrochloride),60 ℃of extraction temperature, 60 min of extraction time and 50%ethanol as extraction solvent, the extraction efficiency was higher[6]. The maximum absorption wavelength of acid ethanol crude extract of natural pigments from seeds of Koelreuteria paniculata Laxm. and Koelreuteria bipinnata Franch in Zhengzhou was 336 nm[7].

There were studies showing that the oil content in seeds of Koelreuteria integrifoliola Merr reached 54.40% .The seed oil contained 5 kinds of saturated fatty acids and 3 kinds of unsaturated fatty acids.Among them, the unsaturated fatty acids content accounted for more than 75.26% , including oleic acid (31.07%), eicosenoic acid(35.07%)and erucic acid(9.12%)[8].

Yuan[9]reported that the optimum conditions for extracting flavonoids from seed peel of K. paniculata Laxm.were as follows: 40% ethanol as extraction solvent, solid-liquid ratio of 1∶30 and refluxing time of 120 min.

Sutiashvili[10]identified the flavonoids and cycloartane-type saponins newly found in seeds of Koelreuteria paniculata Laxm.

Bark

Lei isolated a new anhydride constituent, paniculatic anhydride from bark of Koelreuteria paniculata Laxm[11].The paniculatic anhydride-like components have certain dangers for human bodies. So the operators should be much careful during the extraction of chemical components from the bark of Koelreuteria paniculata Laxm. He also isolated 3 saponins from the bark of Koelreuteria paniculata Laxm. The 3 saponins were identified as 3β-hydroxy-28-lupine, 3β, 28-dihydroxy-lupane and 3β-hydroxy-28-lupinicacid. They are all first found in Koelreuteria paniculata Laxm.

Branches

The chemical components in branches of Koelreuteria paniculata Laxm. included p-digalloyl acid, m-digalloyl acid, 2″-galloylquercitrin, gallic acid, ethyl galloyl acid, ellagic acid,quercitrin, hyperin, 2″ -galloylhyperin,β-sitosterol and β-sitosterol-3-O-glucoside[13].

Flowers

A total of 9 components were extracted from the position of flowers of Koelreuteria paniculata Laxm. where large amounts of ethyl acetate was extracted. They were daucosterol,gallic acid, kaempferol, luteolin,kaempferol-3-O-(6"-acetyl)-β-D-glucosidase, 2"-O-acetylhyperin, 2"-galloylhyperin, hyperin and kaempferol-3-Oβ-D-glucoside[14]. In the position of flowers of Koelreuteria paniculata Laxm. where chloroform was extracted,coumarins were also isolated, including acetyl umbelliferone and 6-benzoyl-umbelliferone[14-15]. Lee[16]isolated galloylRh and a new lignin-glucoside from leaves of Koelreuteria henryi Dummer. They all have certain resistance against DPPH (1,1-diphenyl-2-picrylhydrazyl).

Pharmacology

Protecting cardiovascular system

Ethyl galloyl acid has certain antiplatelet aggregation effect. It can enhance the dissolution of fibrin and promote the dissolution of thrombus[2,17].In addition, flavonoids can also improve blood circulation and reduce cholesterol content[2,17-18].

Antioxidation and antiaging

The oxygen free radicals inside bodies have oxidative effects on cells and tissues.So the scavenging of oxygen free radicals will protect cells from oxidative damage, thereby fighting aging. Studies have shown that the 2"-O-galloylquercitrin in leaves of Koelreuteria paniculata Laxm. can scavenge xanthine oxidase (XO)radicals[2]. Gallic acid and ethyl galloyl acid have characteristics of phenolic constituents.They can be used as hydrogen donors for oxidizing free radicals.In addition, they can also provide hydrogen atoms for free radicals in the lipid oxidation reaction chain, terminating the chain reaction, thereby fighting oxidation[19].Flavonoids can also scavenge oxygen free radicals inside bodies, and they are relatively strong antioxidants[2,18-19]. Chen et al.[20]found that the antioxidants inside Koelreuteria spp. can be rapidly screened out by combining the DPPH (or XOD)and LC-MS/MS. They also found that the polyphenols in the ethanol extract of Koelreuteria paniculata Laxm. have antioxidant effects[21].Kumar et al.[22]reported that the chloroform and ethyl acetate extracts of Koelreuteria paniculata Laxm.have certain DNA-protection and anti-oxidation potentials.

Anticancer

Protein tyrosine kinase(PTK)is related to occurrence of cancers.But the kaempferol-3-O-rhamnoside, kaempferol-3-O-arabinoside and quercetin extracted from leaves of Koelreuteria paniculata Laxm.can inhibit the activity of PTK[2,17,23].

Koelreuterin-1 has specific toxicity to human ovarian cancer and melanoma cells[2,17]. Song et al.[24]reported the cytotoxic activities of three cochinchins, koelreuterin-1, austrobailignan-1 and austrobailignan-2, extracted from leaves of Koelreuteria henryi Dummer. The three cochinchins, isolated from the weakly polar of extract of Koelreuteria paniculata Laxm., all have cyclolignan lactone structure. In vitro, they all have cytotoxicity to 8 cell lines through inhibiting the activity of microtubule polymerization protease[1,2,25]. Chin et al.[26]found the ethanol extract of Koelreuteria paniculata Laxm. can inhibit the metastasis of renal cancer cells(RCCs). Chiang et al.[27]found the extract of Koelreuteria paniculata Laxm.can enhance the anti-cancer effect through inhibiting the activity of dihydrodiol dehydrogenase(DDH).

Antivirus

It has been proved that a new saponin, isolated from leaves of Koelreuteria paniculata Laxm. has antiviral activity[28].

Antibacteria

The antibacterial tests showed that the antibacterial effects of leaves of Koelreuteria paniculata Laxm. on the 11 kinds of pathogenic bacteria are much better than those of Coptis chinensis, Viola mandshurica and Senecio scandens, which are commonly used in clinic as anti-inflammatory drugs.Moreover,the inhibiting effects of ethyl galloyl acid on E.coli and B. subtilis are all better than those of other esters of gallic acid[2,29-30].However,the inhibiting effects of flavonoids extracted from flowers of Koelreuteria paniculata Laxm.have certain selectivity on pathogenic bacteria[31].Mostafe et al.[32]found that the ethyl galloyl acid, isolated from the ethanol extract of Koelreuteria paniculata Laxm.,has certain antibacterial effect.

Anti-inflammation

Flavonoids can inhibit the exudation of inflammatory enzymes, thereby promoting healing of wounds and relieving pain.The flavonoids contents in seeds, branches and leaves of Koelreuteria paniculata Laxm.were 1.78%,0.27% and 0.45%, respectively[18]. In addition,two new components,paniculatonoid A and paniculatonoid B were found in seeds of Koelreuteria paniculata Laxm[33].A total of 11, 7 and 8 flavonoids spots were isolated in leaves, seeds and nutshell of Koelreuteria paniculata Laxm[34]. The galloylRh and a new lignin-glucoside isolated from leaves of Koelreuteria henryi Dummer have certain resistance against DPPH (1, 1-diphenyl-2-picrylhydrazyl)[16].

Inhibiting activity of tyrosine kinase

Abou-Shoer reported that the flavonoids extracted from K. henryi Dummer can be used as inhibitors against protein tyrosine kinase.

Clinical Application

The “Shen Nong’s Herbal”records that Koelreuteria spp. is bitter in taste, cold in nature and nontoxic. It has functions of removing heat from the liver, improving eyesight, reducing swelling and relieving pain. It is mainly used to treat swelling and pain of eyes,tearing and canthus fester.

In the private sector, the flowers and roots of Koelreuteria paniculata Laxm.are commonly used to disperse wind, clear heat, suppress cough and kill insects. The roots and flowers of Koelreuteria integrifoliola Merr all can be used as drugs for suppressing cough and expelling roundworms.

Others

Excellent nectar source

Koelreuteria integrifoliola Merr and K. bipinnata Franch have long flowering phase and rich pollen.Even till the fruits are ripe and the membranous pods start to split, a small amount of honey will also be secreted[37-38].

Woody vegetable

The buds of Koelreuteria paniculata Laxm., also called as Muli buds,are a kind of natural and non-contamination green vegetable. It can prevent diabetes, cancers and cardiovascular diseases, and has high medical value of health care[39-40].

Extracting natural pigments

The ripe seeds of Koelreuteria paniculata Laxm. are pink or red, so they are excellent and natural pigments resources[4-7].

Purifying the air

Koelreuteria paniculata Laxm.can be used on control SO2pollution. At the same time,it also has antibacterial bactericidal effects. In some epidemic areas where the pathogenic bacteria is mainly spread by air, the planting of Koelreuteria paniculata Laxm. plays an important practical role in disease control[41].

Processing wastewater

The seeds of Koelreuteria paniculata Laxm. can be used as natural and organic polymer flocculants. They have strong flocculating activity and good development prospect[42-43].

Corrosion inhibitor

The seed extract of Koelreuteria paniculata Laxm. is an environmentfriendly corrosion inhibitor. It is characterized by wide source, low cost,easy biodegradation, direct emission and little harm to environment[44].

Processing mine waste

The biological absorption coefficients of Koelreuteria paniculata Laxm.differ greatly among different trace elements. The Koelreuteria paniculata Laxm. has higher enrichment capacity for manganese and iron[45].

Conclusions and Prospects

Koelreuteria spp. is an important class of landscape tree. Currently, the researches on composition of Koelreuteria spp. have been relatively thoroughly. However, there are rare reports on the pharmacology and health value of Koelreuteria spp. So there have been no medicines or formulations developed from Koelreuteria spp.Therefore,the pharmacology and health value of Koelreuteria spp. are needed to be further discussed in depth so as to develop related pharmaceutical products, thereby better serving human health.

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