Isolation, Characterization, and Nitric Oxide Production Inhibitory Activities of the Metabolites From Psidium Guajava L.

Thirteen compounds, including catechin (1), gallocatechin (2), quercetin (3), myricetin (4), kaempferol 3-O-α-ʟ-arabinofuranoside (5), avicularin (6), guaijaverin (7), quercetin-3-O-β-ᴅ-galactopyranoside (8), quercetin-3-O-β-ᴅ-glucopyranoside (9), quercetin-3-O-β-ᴅ-glucuronide (10), casuarinin (11), ursolic acid (12), and 4-methoxy-3,5-dihydroxybenzoic acid (13) were isolated from the leaves of Psidium guajava. The structures of these compounds were elucidated by modern spectroscopic methods (MS, 1H/13C-NMR) and compared with those reported data. Additionally, all isolated compounds were evaluated for their inhibitory effects on NO production. Among them, compounds 3, 8, 10, and 11 showed inhibitory effects on NO production within IC50 values of 19.30 – 42.86 µM. Compound 13 was firstly isolated from Psidium guajava.