Chemical Composition Of Onion And Onion Seeds

Onion(Allium cepa L.) is the plant of Allium L.of Liliaceae,it is a vegetable crop distributed all over mainland China and is used not only as food but also as medicine.It is claimed that red onion have a lot of bioactivities,such as eliminating inflammation, promoting blood flow,lowering blood fat and blood sugar,checking diarrhea,anticancer, diuresis,et al.There are diverse constituents in this plant,including sulfides,flavanoids, steroidal saponins,nitrogenous compound and prostanoids et al.The onion seeds are used as a traditional herb medicine of the Uygur(Uighur) nationality in Xinjiang,which can improve the functions of internal organs,treat diarrhoea,fervescence,calentura and puffiness of face and eye,promote blood flow,and prevent ectroma.Now,there is fewer report about the constituents of the onion seeds,and pharmacologycal reports about it has not been found in the world as well.In order to find the active principles from this medicinal plants,develop and utilize the resource of Chinese medicine,the project have investigated the chemical constituents and bioactivities of onion and its seeds.The preliminary screening of onion seeds and onion showed that onion seeds extract has conspicuous activity to inhibite the enzyme PTP1B in vitro,while the EtOAc extract of onion could inhibite the growth of BGC-823 in vitro;Another test was studied in Hongkong Chinese University for the hypolipidemic activity of freeze drying powder of onion,which indicated that it can lower total cholesterol and blood fat effectively and improve other blood fat indexs such as the content of LDL,HDL and their ratio.Above all,there may be some highly active compounds in lowering blood sugar,blood fat and anticancer in the plant of onion and its seeds.34 compounds have been isolated from the extract of onion and its seeds,and the LC-MSⁿ method has been applied to identify the gross saponins of the BuOH extract from onion.27 compounds,including 13 new steroidal saponins were identified as: Tianshi acid(1),N-trans-feruloyl tyramine(2),β-sitosterol-3β-glucopyranoside-6'-palmitate (3),β-sit os terol(4),daucosterol(5),tryptophane(6),adenine riboside(7), Alliofuroside A(8),22-OCH₃-alliofuroside A(9),26-O-(β-D-glucopyranosyl)-22-O-methyl-(25R)-furost-5-en-1β, 3β,22α,26-tetrol 1-O-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranoside(10), 26-O-(β-D-glucopyranosyl)-(25R)-furost-5-en-1β,3β,22α, 26-tetrol 1-O-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranoside(11),26-O-(β-D-gl-ucopyranosyl)-(25R)-furost-5, 20(22)-dien-3β,26-diol 3-O-β-D-glucop- yranosyl-(1→4)-[α-L-rhamnopyranosyl-(1→2)]-β-D-galactopyranoside (12),26-O-(β-D-glucopyranos- yl)-(25S)-furost-5,20(22)-dien-3β,26-diol 3-O-β-D-glucopyranos-yl-(1→4)-[α-L-rham nopyranosyl-(1→2)]-β-D-galactopyranoside(13),26-O-(β-D-glucopyranosyl)-(25R)-furost-5-en-3β, 22α,26-triol 3-O-β-D-glucopyra-nosyl-(1→4)-[α-L-rhamnopyranosyl-(1→2)]-β-D-galactopyranoside (14),26-O-(β-D-glucopyra- nosyl)-22-Omethyl-(25R)-furost-5-en-3β, 22α,26-triol3-O-β-D-glucopyranosyl-(1→4)-[α-L-rhamnopyranosyl-(1→2 )]-β-D-galactopyranoside(15),26-O-(β-D-glucopyranosyl)-(25S)-furost-5,22(23)-dien-1β, 3β,22α,26-tetrol 1-O-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranoside(16), 26-O-(β-D-glucopyranosyl)-(25R)-furost-5,22(23)-dien-1β,3β,22α,26-tetrol 1-O-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranoside (17),26-O-(β-D-glucopyranosyl)-(25R)-furost-5, 20(22)-dien- 1β,3β,26-triol 1-O-α-L-rhamnopyranosyl-(1→2)-α-L-arabi-nopyranoside (18),26-O-(β-D-glucopyranosyl)-(25S)-furost-5,20(22)-dien-1β,3β,26-triol 1-O-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranoside(19),26-O-(β-D-gluco-pyranosyl)-(25S)-furost-5, 20(22)-dien-1β,3β,26-triol 1-O-α-L-rhamnopyranosyl-(1→2)-β-D-galactopyranoside(20),26-O-(β-D-glucopyranosyl)-(25S)-furost-5-en-1β, 3β,22α,26-tetrol 1-O-α-L-rhamnopyranosyl-(1→2)-β-D-galactopyranoside(21) (Compounds 1-21 have been isolated from onion seeds);quercetin(22),quercetin-4′-O-glucopyranoside(23),isorhamnetin(24),β-sitosterol(4),protecatechuic acid(25), quercetin-3,4′-di-O-glucopyranoside(26)(Compounds 4 and 22-26 have been isolated from onion);26-O-(β-D-glucopyranosyl)-(25R)-furost-5-en-1β,3β,22α,26- tetrol 1-O-α-L-rhamnopyranosyl-(1→2)-β-D-galactopyranoside(27)(Compound 27 have not been isolated from onion,but its structure have been identified by LC-MSⁿ method,as well as compounds 8-11 and 21).Compounds 1-9 were known compounds,Compounds 10-21 and 27 were new compounds;compounds 1-4 were isolated from the genus Allium for the first time,compounds 5-7 were isolated from this plant for the first time.The screened compounds from onion and onion seeds showed no effect to inhibite the enzyme PTP1B and no cytotoxicity to some tumor cells such as HCT-8,Bel-7402, BGC-823,A549 and A2780;The flavonoid(glycoside) from the EtOAc extract of onion showed strong antioxygen activity;All these compounds are in the screening of hypolipidemic activity in vitro.