Abstract: 4-Hydroxyacetophenone (1),syringic acid (2),chrysoeriol (3),vanillic acid (4),4-hydroxy-3-methoxy benzene ethanol (5), N-［2-(3,4-dihydroxyphenyl)-2-hydroxyethyl］-3-(4-methoxyphenyl)prop-2-enamide (6) and isorhamnetin-3-O-rutinoside (7) were isolated from Petrosimonia sibirica L. for the first time. In vitro antibacterial activity of these compounds was evaluated by MTT assay.The results revealed that most of these compounds exhibited significant activity.The antimicrobial activities of compound 2 against Bacillus subtilis,of compound 5 against Escherichia coli,and of compound 7 against Xanthomonas vesicatoria and Alternaria solani, were found to be stronger than those of the positive control,streptomycin sulfate.The antioxidant potential was evaluated by DPPH and FRAP methods.The results demonstrated that compound 6 was the most effective in DPPH method,with IC₅₀ value of 0.2452 mg/mL.Compound 5 was relatively active and showed potent antioxidant effect compared to standard ascorbic acid in FRAP assay,with FRAP value of 9.402 mmol/g.

Key words: Petrosimonia sibirica L., antibacterial, antioxidant, MTT, DPPH, FRAP