Two New Flavonoids and Other Phytochemicals from Endemic Phryna ortegioides (Fish. & C.A.Mey.) Pax & K. Hoffm and Their Antioxidant Potentials

Two new flavonoidsnamely 7,5′-dimethoxyisoetin (1) and homoorientin-6′′-4-O-methyl-myo-inositol (2) together with six known compounds were isolated and identified as isoorientin (3), genkwanin(4), dihydrokaempferol,7,4′-dimethylether (5), eriodictyol 7,4′-dimethylether (6), D-(+)-pinitol (7) and 3-O-β-D-glucopyranosyl spinasterol (8) from the aerial parts of endemic Phryna ortegioides for the first time. Their chemical structures were determined by 1D ( 1H, 13C and DEPT) and 2D (COSY, HSQC, ROESY, NOESY, TOCSY and HMBC) NMR and mass spectrometry. The antioxidant properties of pure secondary metabolites were analyzed on the basis of ferric thiocyanate method. Compound 1 displayed the highest antioxidant activity with an inhibition rate of 98.09% at a concentration of 100 µg/mL.