Structure and Activity Relationship of Antioxidant Flavonoids from Leaves of Paulownia tomentosa var.tomentosa

摘要

Paulownia tomentosa var.tomentosa(Scrophulariaceae)is a deciduous tree,indigenous to China,widely distributed in Eastern Asia and used in construction and papermaking industry,as well as in traditional medicine to treat cough,bronchitis,phlegm,hemorrhoid,asthma,high blood pressure,and bacterial diarrhea.To date,we have not found any published data on the chemical profile of P.tomentosa var.tomentosa in the literature.In this study,phytochemical investigation on leaves of the title plant led to the isolation of different classes of flavonoids,including two flavan-3-ols,(+)-catechin(1)and(-)-epicatechin(2),a flavanone,naringenin(3),a flavanonol,taxifolin (4),two flavones,apigenin (5)and luteolin(6),and two flavonols,kaempferol (7)and quercetin(8),and their structures were elucidated on the basis of physichemical and spectroscopicai evidence (NMR and MS).Among the isolates,compounds 1,2,3,4,6,7and 8 were the first time found their occourence in genus of Paulownia.The antioxidant activity of the crude extracts,soluble fractions and isolated flavonoids were evaluated by DPPH free radical-scavenging assay.Results suggested that EtOAc and H2O participated fractions and flavonoids 1,2,4,6,7 and 8 showed significantly high antioxidant potential compared with α-tocopherol and BHT,which were used as controls.