Isolation of antimicrobial compounds from guava (Psidium guajava']java L.) and their structural elucidation

Four antibacterial compounds were isolated from,leaves of guava (Psidium guajava L.), and the structures of these compounds were established on the basis of chemical and spectroscopic evidence. Two new flavonoid glycosides, morin-3-O-alpha-L-lyxopyranoside and morin-3-O-alpha-L-arabopyranoside, and two known flavonoids, guaijavarin and quercetin, were identified. The minimum inhibition concentration of morin-3-O-alpha-L-lyxopyranoside and morin-3-O-alpha-L-arabopyranoside was 200 mug/ml for each against Salmonella enteritidis, and 250 mug/ml and 300 mug/ml against Bacillus cereus, respectively.