Prenylflavonoids from propolis collected in Chiang Mai, Thailand

Abstract Three new prenylflavonoids, 3-hydroxy-5′-methoxy-licoflavanone (12), 3′-hydroxy-5′-methoxy-glabranin (13), and 5′-methoxy-lespedezaflavanone C (17) were isolated for the first time from propolis collected from Chiang Mai in northern Thailand. The structures of the new compounds were determined by MS and NMR spectroscopy. Seventeen other known compounds, including 4′-methyl-8-prenyltaxifolin (1), 6-prenyleriodictyol (2), abyssinone V (3), munduleaflavanone B (4), euchrestaflavanone A (5), cathayanon H (6), licoflavanone (7), 8-prenylnaringenin (8), exiguaflavanone K (9), flowerine (10), 8-dimethylallyltaxifolin (11), isolicoflavonol (14), (S)-2-(3,4-dihydroxyphenyl)-5,7-dihydroxy-8-(3-hydroxy-3-methylbutyl)chroman-4-one (15), lespedezaflavanone C (16), gancaonin E (18), 5,3′-dihydroxyisobavachin-7-O-methyl ether (19), and carphorin B (20) were also identified based on their MS, NMR, and electronic circular dichroism spectra.