Introduction: St. John’s Wort (Hypericum perforatum L.) is a plant from the Hypericaceae family commonly occurring in Europe, Asia, Africa and North America. It is used for medical purposes, for example in depression, viral or bacterial diseases, as well as diseases of the digestive system. St. John’s Wort is a source of hypericin as well as flavonoids useful to reduce the harmful effects of free radical action.
The aim of the study was to evaluate the antioxidant activity of alcoholic and aqueous extracts of H. perforatum.
Materials and methods: St. John’s Wort extracts were prepared in ethanol, methanol and isopropanol (each of 40%, 70% (v/v) and undiluted) and in water, with ultrasound-assisted extraction. Plant samples were extracted for 15, 30 and 60 min, and the antioxidant potentials of the extracts evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) aand ferric reducing anti-oxidant power (FRAP).
Results: All the extracts showed antioxidant activity. In the case of the DPPH evaluation, the results ranged 2.42–4.37 mg trolox/g of raw material, which corresponds to 53.89–91.98% radical scavenging activity (RSA). The highest results were obtained for samples extracted for 60 min, with the antioxidant activity of most of them above 4.00 mg trolox/g of raw material. In the case of FRAP evaluation, the reducing power of the extracts ranged 1.40–37.82 mg FeSO4/g of raw material, with the highest results found for samples prepared in undiluted methanol. In contrast, the antioxidant capacity of the aqueous extracts was low.
Conclusions: St. John’s Wort herb showed high antioxidant activity. In most cases, higher potentials were found for the extracts prepared in undiluted alcohols. The type of solvent used and the extraction time influenced the antioxidant properties of the extracts.
