Chemical constituents of the Vietnamese plants Dalbergia tonkinensis Prain and Cratoxylum formosum (Jack) Dyer in Hook and their DPPH radical scavenging activities

Abstract

Phytochemical investigations of the leaves and roots of Dalbergia tonkinensis led to the isolation of a new isoflavone glycoside derivative, isocaviunin 7-O-β-D-apiofuranosyl-(1 → 6)-β-D-glucopyranoside (1), and a new scalemic sesquiterpene lactone, 3,7-dimethyl-3-vinylhexahydro-6,7-bifuran-3(2H)-one (2), along with the previously known compounds 3-16, and nine other known compounds 17-25 were isolated from the leaves of Cratoxylum formosum. The chemical structures of the isolated compounds were elucidated by 1D- and 2D-NMR analyses as well as MS spectroscopic data. The results suggest that flavonoids are characteristic of both plants. In the DPPH radical scavenging assay, (3 R)-vestitol (5) and isoquercetin (24) possessed the strongest antioxidative IC₅₀ values of 42.20 µg/mL and 45.63 µg/mL, respectively, and their values were comparable to that of the positive control catechin (IC₅₀ 42.98 µg/mL).