ABSTRACT
Two new xanthone O-glycosides, polyhongkongenosides A (1) and B (2), together with four known xanthone glycosides, were isolated from the herbs of Polygala hongkongensis Hemsl. Their structures were elucidated on the basis of UV, IR, NMR, and MS spectral data. The antioxidant in vitro activities of 1-6 were determined by the scavenging activities against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals and hydroxyl radicals and their reductive activities to Fe3+. Mangiferin, one of the four known xanthone glycosides, showed potential scavenging effect on DPPH and hydroxy radicals and reductive activity to Fe3+ with IC50 values of 4.7, 13.9, 23.7 microM, respectively.
Subject(s)
Antioxidants/chemistry , Glycosides/chemistry , Polygala/chemistry , Xanthones/chemistry , Biphenyl Compounds/chemistry , Hydrazines/chemistry , Molecular Structure , PicratesABSTRACT
A new dihydroisocoumarins, 6-methoxy-8-hydroxy-3-(4-hydroxyphenyl)isochroman-1-one, named as hongkongenin (1), and seven known flavonoids were isolated from the methanol extract whole plant of Polygala hongkongensis Hemsl. Their structures were established on the basis of UV, IR, NMR, and MS spectral data. It is the first report of the occurrence of isocoumarins in Polygala, and the known compounds 2-8 were isolated from this plant for the first time. Flavonoids showed potent antioxidant activities in vitro against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals, hydroxyl radicals, and reductive activity to Fe3+.
