Antioxidant activity and phenolic acid constituents of two andean Hypericum L. species from Colombia

Abstract

Antioxidant capacity of extracts of different polarity obtained from two Hypericum L. species (H. juniperinum and H. mexicanum) was assessed by means of total polyphenolic content (TPC), 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay, 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) assay, ferric reducing antioxidant power (FRAP) assay and oxygen radical absorbance capacity (ORAC) assay. Their phenolic acid composition was also determined by HPLC. The ethyl acetate extract of H. juniperinum was the most active in the ABTS, FRAP and TPC assays with 10867.48 μmol TEAC/g, 242.80 mg AAE/g and 491.08 mg GAE/g respectively. On the other hand, the methanol extract obtained from H. mexicanum appeared as the most active extract in the DPPH assay (3714.23 μmol TEAC/g). Similarly, the butanol fraction coming from the methanolic extract of H. mexicanum showed the highest activity in the ORAC assay (12910.06 μmol TEAC/g). HPLC analysis of the extracts revealed the presence of phenolic acid compounds, such as chlorogenic (50.09 mg/g) and p-coumaric acids (63.36 mg/g) in H. mexicanum and p-coumaric acid (8.45 mg/g) in H. juniperinum. A high correlation between antioxidant activity and total polyphenol content was established. Specifically, H. mexicanum exhibited the highest ORAC capacity, which may be associated with the high content of chlorogenic and p-coumaric acids present in medium to polar extracts. Our results constitute a significant contribution to the study of antioxidant activity and the determination of the phenolic acid profile in both species. The analysed extracts showed promising antioxidant activity that could be useful in the pharmaceutical, cosmetic and food industries.