Determination of phenolic compounds in Diospyros lotus by RP-HPLC-DAD and evaluation of antioxidant and cytotoxic properties

Abstract

This research aimed to extract and profile phenolic compounds from seed and fruit of Diospyros lotus, evaluate and compare the antioxidants and cytotoxic potential of the extracts. Seven phenolic acids and four other flavonoids extracts were subsequently obtained following different extraction methods. The extracts were evaporated, lyophilized, and prepared for RP-HPLC-DAD, MTT assay, and antioxidant evaluation by the ferrous ion chelating, ferric ion reducing power, FRAP, DPPH•, •OH and NO• scavenging methods. The RP-HPLC-DAD revealed an epigallocatechin, a flavonoid, and fourteen phenolic acids. Phenolic compounds with the highest concentrations are epigallocatechin (1460.80 ± 10.74 µg/gDW), gallic acid (1167.11 ± 4.04 µg/gDW) and t-cinnamic acid (244.45 ± 3.61 µg/gDW). The bound phenolic acids from acid hydrolysis-1 (BPAH-1) extract of the fruit sample exhibit the highest DPPH• activity, reducing power, and FRAP. The flavonol extract of the fruit sample unveils the highest Fe2+ chelating effect. The BPAH-1 and BPAH-2 extracts of the seed reveal the highest •OH and NO• activities, respectively. Seed sample gave the highest total phenolic/flavonoid/tannin contents. The cytotoxicity of the extracts on HepG2 cell lines > HeLa cell lines and the effects are more pronounced 48 h after treatments. Specifically, flavan-3-ol methanolic and BPAH-2 extracts of the seed, and flavan-3-ol methanolic and BPAH-1 extracts of the fruit show good cytotoxic effect against HepG2 cell lines (IC50 < 37 µg/mL). This research unveils the potential of D. lotus seed and fruit as possible antioxidant and anticancer agent. The antioxidant and cytotoxicity properties observed from the samples might be due to the phenolic compounds determined.