A New Isoflavone Xylopyranoside and Isoflavone Derivatives from the Roots of Ochna integerrima and Their DPPH Radical Scavenging Activity

Ochna integerrima (Louri) Merr. is one of the two species of the genus Ochna (family Ochnaceae) found in Thailand. Its bark is used in traditional Thai medicine to treat digestive disorders. Phytochemical investigation of the crude MeOH extract of the root woods of O. integerrima furnished an unreported isoflavone glycoside, gerontoisoflavone A-4'-O-β-D-xylopyranoside (1), together with the previously described irisolone methyl ether (2), iriskumaonin methyl ether (3), iriskumaonin (4), gerontoisoflavone A (5), isoprunetin (6), a flavone glycoside, vitexin (7), and a chromone derivative, lophilone A (8). The structure of 1 was elucidated by 1D and 2D NMR spectral analysis as well as HRMS data. Compounds 1-7 were evaluated for their 2,2-diphenyl-1-picrylhydrazil radical (DPPH⋅) scavenging activity and antiplasmodial activity against a chloroquine- and pyrimethamine-resistant strain of Plasmodium falciparum (K1). Compounds 5 exhibited strongest scavenging activity, with a scavenging concentration at 50 % (SC ) of 137.7 μM, while 4 and 6 displayed weak scavenging activity, with SC values of 4 and 5 times higher than that of 5. None of the tested compounds showed antiplasmodial activity against P. falciparum (K1) at a concentration of 5 μg/mL.