Methanolic extracts of edible plants and seaweeds were tested for their inhibitory activity against Jack bean urease. Quercetin-4′-O-β-D-glucopyranoside was isolated from Allium cepa as a urease inhibitor with an IC50 value of 190 μM-. Quercetin and two quercetin glycosides, avicularin and guaijaverin, were isolated from Psidium guajava as urease inhibitors with respective IC50 values of 80 μM-, 140 μM-, and 120 μM-.
