Showing papers on "Acacetin published in 2002"

Antioxidative flavonoids from leaves of Carthamus tinctorius.

Abstract: A total of eight flavonoids (1-8), including a novel quercetin-7-O-(6″-O-acetyl)-β-D-glucopyranoside (6) and seven known flavonoids, luteolin (1), quercetin (2), luteolin 7-O-β-D-glucopyranoside (3), luteolin-7-0-(6″-O-acetyl)-β-D-glucopyranoside (4) quercetin 7-O-β-D-glucopyranoside (5), acacetin 7-O-β-D-glucuronide (7) and apigenin-6-C-β-D-glucopyrano syl-8-C-β-D-glucopyranoside (8), have been isolated from the leaves of the safflower (Carthamus tinctorius L.) and identified on the basis of spectroscopic and chemical studies. The antioxidative activity of these flavonoids was evaluated against 2-deoxyribose degradation and rat liver microsomal lipid peroxidation induced by hydroxyl radicals generated via a Fenton-type reaction. Among these flavonoids, luteolin-acetyl-glucoside (4) and quercetin-acetyl-glucoside (6) showed potent antioxidative activities against 2-deoxyribose degradation and lipid peroxidation in rat liver microsomes. Luteolin (1), quercetin (2), and their corresponding glycosides (3 &5) also exhibited strong antioxidative activity, while acacetin glucuronide (7) and apigenin-6,8-di-C-glucoside (8) were relatively less active.

Apigenin, Tyrosinase Inhibitor Isolated from the Flowers of Hemisteptia lyrata Bunge

Abstract: From the flowers of Hemisteptia lyrata Bunge, two flavonoids, apigenin (1) and acacetin (2), were isolated. Their structures were established by UV, one- and two-dimensional NMR, and mass spectroscopic methods. Apigenin showed significant inhibition against mushroom tyrosinase with an IC_50 value of 4.56㎍·ml^-1, and appeared to inhibit the polyphenol oxidase activity of tyrosinase in a competitive manner (K_1=2.5×10 exp (-5) M) when L-tyrosine was used as a substrate, but did not inhibit the melanin production of Streptomyces bikiniensis.