A new xanthonolignoid and other constituents of Psorospermum aurantiacum (Hypericaceae) stems with antibacterial and antioxidant activities

Abstract

The ethyl acetate fraction of Psorospermum aurantiacum stems has furnished cadensin H ( 1 ) a new compound belonging to the class of xanthonolignoid alongside with six compounds: 1,5,6-trihydroxy-7-methoxyxanthone ( 2 ), betulinic acid ( 3 ), 1,7-dihydroxyxanthone ( 4 ), betulin ( 5 ), lupeol ( 6 ) and stigmasterol glucoside ( 7 ). The crude methanolic extract and ethyl acetate fraction, as well as some major isolated compounds were evaluated for antibacterial and antioxidant activities. Shigella flexneri, Staphylococcus aureus, SSalmonella. typhi, EEscherichia coli and Klebsiella pneumonia , were used as test organisms. The crude extract has moderate activity against Shigella flexneri , methicillin-resistant Staphylococcus aureus, SSalmonella. typhi and EEscherichia. coli strains with MICs values ranging from 125 to 500 µ g/mL, and MBC of 500 µ g/mL for Staphylococcus aureus, SSalmonella. typhi and EEscherichia. coli . While the ethyl acetate fraction has moderate activity against S. flexneri , methicillin resistant S. aureus, SSalmonella. typhi and EEscherichia. coli with MIC ranging from 250 to 1000 µg/mL and MBC from 500 to 1000 µg/mL for S. flexneri, S. aureus, E. coli strains. Among all the compounds tested, only 1,5,6-trihydroxy-7-methoxyxanthone showed moderate activity on all bacterial strains with MICs values from 12.5 to 50 µ g/mL and MBC of 25 µg/mL and 100 µg/mL on methicillin-resistant S. aureus , 100 µg/mL on EEscherichia. coli . DPPH for radical scavenging and iron reducing antioxidant (FRAP) were used to evaluate antioxidant activity. Compound ( 2 ) showed important activity with the first reagent while compound ( 1 ) showed moderate activity with the second reagent. The structures of the isolated compounds were established using modern spectroscopic methods including 1D and 2D NMR and High-resolution mass spectrometry and by comparing with data reported in the literature. • Isolation of 7 compounds from the stems of psorospermum aurantiacum (Hypericaceae). • Four of the compounds isolated are found for the first time in the genus psorospermum. • First report of antioxidant activities of compounds isolated from the stems of psorospermu m .