Phaseolus calcaratus, the seed of Phaseolus calcaratus has traditionally been used as a herbal medicine. Catechin-7-O-glucoside can be found in the seed of Phaseolus calcaratus. In vitro, this compound has an antioxidant activity leading to a cytoprotective effect. The fractions inhibited LPS-induced nitric oxide production and cyclooxygenase-2 (COX-2) expression in the cells. The ethyl acetate fraction at 100 µg/ml almost completely suppressed NO production, iNOS and COX-2 expression, and TNF-α and IL-6 secretion in cells stimulated with LPS. The fraction also inhibited phosphorylation of extracellular signal-regulated kinase  and p38 in LPS-stimulated cells with the attendant suppression of IκBα nuclear translocation and nuclear factor (NF)-κB activation. Furthermore, PHCR seed extracts contained a large number of phenolic compounds having antioxidant potentials against 1,1-diphenyl-2-picrylhydrazyl  radicals and hydroxyl radicals. We identified catechin-7-O-β-D-glucopyranoside as one of the active compounds responsible for the biological activity of PHCR seed extract.