Comparison of the endemic Azorean Hypericum foliosum with other Hypericum species: antioxidant activity and phenolic profile

Abstract

Water extracts of Hypericum foliosum (HF) from five Azorean Islands were analysed for their antioxidant activity and total phenolic contents. The results were compared with those from medicinal Hypericum species (H. perforatum, H. androsaemum and H. undulatum) and also with Azorean green tea. HF exhibited strong scavenging activity (87–91%) and moderate inhibition of linoleic acid oxidation (56–72%), and presented no significant difference to the other studied plants; in contrast, the synthetic antioxidant butylated hydroxyltoluene showed antioxidant activity values of 22% and 88%, respectively. The average value of phenolics in HF was higher than that in the other Hypericum species and lower than that in tea. Additionally, the phenolic profiles of the Hypericum species were compared by reverse phase-high performance liquid chromatography/ultraviolet (RP-HPLC/UV). The method presented permits the simultaneous determination of phenolic acids, flavonoids, hypericin and hyperforin within 55 min. The most similar profile was observed between HF and H. androsaemum. This study indicates that HF is a source of bioactive compounds with potential health benefits.

Keywords:

• Hypericum foliosum Aiton
• DPPH radical scavenging
• β-carotene/linoleic acid assay
• total phenolic content
• phenolic compounds
• RP-HPLC/UV

Acknowledgements

We especially thank Mr Roberto Resendes (Department of Biology, University of Azores) for providing help in the collection and identification of HF samples and Gorreana Tea Plant factory for the kindly donation of Azorean green tea samples. This study was financially supported by funds from Science and Technology Foundation (FCT-Portugal) project PTDC/AGR-AAM/70418/2006 (Hypericum Biotech).