Chemical Constituents And Antioxidant Activities Of Brassica Rapa L. Flowers

Brassica rapa L.(Cruciferae),namely "turnip",originated in the Mediterranean sea,Afghanistan,Pakistan,is a biennial herb.It is distributed and cultivated throughout China.Commonly,B.rapa,with branched stems,can rise to 100 cm.A large global white-fleshed root develops at the base of the leaf petioles.The roots,seeds and pollen of B.rapa have been used for the treatment of mastitis,sore and blood stasis in traditional Chinese medicine.The flowers of B.rapa are abundant in China and its pollen has a remarkable nutritional value.So far,bioactivity studies on its pollen have been well conducted.However,there have been few reports on the chemical constituents of B.rapa flowers.In this dissertation we described the isolation and identification of chemical constituents from B.rapa flowers,as well as their antioxidant activities.23 compounds were separated and identified as follows by spectroscopic analysis and physicolchemical characters.blumenol A(1),(6S,9S)-roseoside(2),alangionoside C(3),pisumionoside(4),5'-deoxy-5'-methylamino-adenosine(5),5'-deoxy-5'-methylamino-9-(a-L-lyxofuranosyl)adenine(6),2-(1-hydroxyethyl)phenol(7),phenyl-O-?-D-glucopyranoside(8),benzyl-O-?-D-glucopyranoside(9),2-phenylethyl-O-?-D-glucopyranoside(10),salidroside(11),2-(2-hydroxyphenyl)ethanol-O-?-D-glucopyranoside(12),8-O-?-D-glucopyranosyl-(7S)-phenylethylene glycol(13),8-O-?-D-glucopyranosyl-(7R)-phenylethylene glycol(14),sachaliside(15),(2)-p-coumaryl-O-?-D-gluopyranoside(16),4-methoxybenzyl-O-?-D-glucopyranoside(17),2,4,6-trimethoxyphenyl-1-O-?-D-glucopyranoside(18),3,4,5-trimethoxybenzyl-O-?-D-glucopyranoside(19),zingerone 4'-O-?-D-glucopyranoside(20),dorycnioside(21),(+)-syringaresinol-O-?-D-glucopyranoside(22),kaempferol 3-O-?-D-sophoroside(23).Among them,6 was new compound;13,14,16 were new natural products;compounds 1-5,7-12,15,17-23 were obtained from the genus of Brassica L.for the first time.The antioxidant activities of the 21 compounds were evaluated in vitro.Among them,compounds 1,13,14,22 exhibited strong DPPH radical scavenging capacity,with ICso value of 47.30 ?M,45.17 ?M,48.70 ?M and 39.47?M,respectively.And compound 7,11,12,15,16,22 showed high ABTS radical scavenging capacity,with IC50 value of 47.62 ?MM,46.70 ?M,44.39?M,69.73?M,34.86?M and 75.87 ?M,respectively.Comparing the relationship between the structures of 21 compounds and their antioxidant activities,we concluded that compounds with hydroxyl were the bioactive substance of B.rapa flowers.