Abstract: In this study,the chemical constituents and antioxidant activities of Didissandra sesquifolia C.B.Clarke were investigated for the first time.A total of 15 phenolic compounds were isolated and identified by a variety of chromatographic and spectroscopic techniques,including 4-hydroxyphenethyl alcohol (1),vanillic acid (2),6-hydroxyluteolin-7-O-glucuronide (3),stachanin A (4),scutellarein(5),calceolarioside E (6),verbasoside (7),calceolarioside A (8),calceolarioside B (9),plantainoside A (10),isonomioside A (11),scutellarein-6-O-glucoside-7-O-methylester (12), rhamnocitrin-3-O-β-D-glucosid (13),1,4-dihydroxy-2-hydroxymethyl-9,10-anthraquinone (14) and 1,4-dihydroxy-2-methylanthraquinone (15).All the compounds were isolated from the genus Didissandra plant for the first time.The in vitro antioxidant activities of the main chemical components and fractions were evaluated by DPPH,ABTS,and FRAP assays.And the results showed that the antioxidant activities of compounds 9,10 (5.14±0.36,5.35±0.04 mmol VCE/g) were close to ascorbic acid (5.68±0.10 mmol VCE/g).In addition,the total reducing ability of compounds 6-11 was higher than that of FeSO₄,which showed excellent antioxidant activity and laid the foundation for the development of natural antioxidants and the screening of drug lead compounds.

Key words: Didissandra sesquifolia C.B.Clarke, chemical constituent, isolation and identification, antioxidant activitity