Antibacterial and antioxidative compounds from Cassia alata Linn.

Abstract

Phytochemical investigation of Cassia alata Linn. led to the isolation of six known anthraquinones: aloe-emodin (1), emodin (2), ω-hydroxyemodin (3), lunatin (4), physcion (5), and ziganein (6), six flavonoids: apigenin (7), 7,4'-dihydroxy-5- methoxyflavone (8), diosmetin (9), kaempferol (10), luteolin (11), and trans-dihydrokaempferol (12) as well as one stilbene, trans-resveratrol (13). Their structures were elucidated on the basis of spectroscopic methods, including UV, IR, NMR and MS. Nine compounds (3-9 and 12-13) were reported for the first time as metabolites of C. alata. Compound 2 exhibited strong antibacterial activity against methicillin resistant S. aureus (MRSA)-SK1 and B. cereus TISTR 687 with MIC values of 4 and 8 µg/mL, respectively. Compound 10 was found to exhibit antioxidative activity with IC50 value of 9.67 µM that was three times stronger than that of ascorbic acid (IC50 25.41 µM).