Chemical composition, antioxidant activity and antitumor activity of tumorous stem mustard leaf and stem extracts

The swollen succulent stem of tumorous stem mustard (<i>Brassica juncea</i> var. <i>tumida</i> Tsen et Lee) is the raw material in the processing of Chinese <i>Fuling</i> zhàcài. We found that total polyphenols and flavonoids contents of tumorous stem mustard leaf extracts (TSMLE) were significant higher than that of tumorous stem mustard stem extracts (TSMSE). The percentage of isorhamnetin 5-O-hexoside, methyl quercetin O-hexoside, and luteolin O-hexosyl-O-hexosyl-O-hexoside in TSMLE were 170, 230 and 694 times higher than that in TSMSE. TSMLE presented stronger antioxidant capacity against 2,2'-Azino-bis[3-ethylbenzothiazoline]-6-sulfonic acid cationic free radical (ABTS⁺) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radicals, and it also showed higher reducing power and ferric reducing antioxidant power. Both TSMLE and TSMSE inhibited lung carcinoma cell growth in a dose-dependent manner, while TSMLE was more effective against A549 cells than TSMSE. This is the first report indicates that tumorous stem mustard, especially its leaf, is a potential diet source in preventing of oxidative stress and cancer.