Antioxidant activity of flavonoids from Croton sphaerogynus Baill.

Since the early days of medicine, chemical substances derived from animals, plants, and microorganisms have been used for treatment of various diseases. Among these, products derived from plants have dominated the pharmacopoeias for thousands of years, providing an inexhaustible source of medicinal resources. Croton L. is the second largest genus of Euphorbiaceae, comprising about 1300 species of trees, bushes, and herbs. Croton sphaerogynus Baill. belongs to the same clade of Croton cajucara Benth, used in traditional medicine. The aim of this study was to characterize the antioxidant activities of extracts and isolated flavonoids obtained from leaves of C. sphaerogynus. Chemical composition of leaf extracts and its fractions (flavonoid contents) and in vitro antioxidant properties were examined. Two flavonoids were isolated: quercetin 3-O-methyl ether and kaempferol 3-O-methyl ether. Antioxidant activity was higher, especially for fractions composed mainly by quercetin 3-O-methyl ether compared to crude extract and other fractions. For those fractions, EC50 values were found to be close to the ones presented by quercetin when they were analyzed for their radical scavenging activities.