Enhanced antioxidant activity of pericarp extract from black Dimocarpus longan Lour.

Abstract

Dimocarpus longan Lour. is a commercial plant that is widely grown in Asia. A large amount of its pericarp is discarded as waste. The use of this pericarp would not only reduce waste but would also increase the value of this plant. Therefore, this study aimed to investigate the chemical composition and antioxidant activity of D. longan pericarp. Furthermore, a novel black D. longan was produced and compared with the traditional dried D. longan. Various solvents, including petroleum ether, ethyl acetate, and 95% v/v ethanol, were used for extraction. The total phenolic content was investigated with the Folin-Ciocalteu assay, and the gallic acid content was determined with high performance liquid chromatography. The antioxidant activity of the extracts was investigated using 2,2-diphenyl-1-picrylhydrazyl,2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) and the ferric reducing antioxidant power assay. The results indicate that a higher greater extract content can be obtained from black D. longan than from dried D. longan. The ethyl acetate extract of black D. longan pericarp contained the highest total phenolic and gallic acid contents: 11.8 ± 0.0 mg and 9.4 ± 0.0 mg/g of extract, respectively. These concentrations are significantly higher than those extracted from dried D. longan pericarp using the same solvent (p < 0.001). Moreover, the antioxidant activity of D. longan was enhanced after being processed to form black D. longan. The ethyl acetate extract possessed the greatest ferric reducing power and radical scavenging activity. Therefore, we suggest that it is a potential source of natural antioxidants that could be used in cosmetic applications.