Context: Hypericin, isolated from Hypericum perforatum L. and about another 300 Hypericum species (Guttiferae), is one of the most powerful photosensitizers found in nature.
Objective: The aim of this study was to assess the variability of chemical composition and biological activities of four H. perforatum samples, collected at different altitudes in the South Apennine of Italy.
Materials and methods: MTT assay was used to evaluate the antiproliferative activity of different samples concentrations (0.6-100 µg/mL) after irradiation at 365 nm. The inhibition of nitric oxide production was evaluated after 24 h of incubation using the macrophage cell line RAW 264.7 and sample solutions ranging from 12.5 to 1000 µg/mL. Antioxidant activities were evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay and β-carotene bleaching test (ranges were 12.5-1000 and 1-400 µg/mL, respectively). Chemical composition was evaluated through HPTLC, and different contents of hypericin and rutin have been observed.
Results: The most phototoxic sample was collected from Zumpano (no. 1 at 370 m), with IC50 values of 24.61 ± 0.02 μg/mL. Sample no. 1 showed also the best radical scavenging activity (IC50 value of 9.18 ± 0.03 μg/mL) and the best antioxidant activity (IC50 value of 10.04 ± 0.03 μg/mL after 30 min of incubation). Best activity of extract no. 1 was well in accordance with chemical data, including the phenolic total content and particular metabolome profile.
Discussion and conclusion: This paper confirms the usefulness in maintaining the exploration of H. perforatum activities, in order to confirm its potentiality as a multipurpose plant.
Keywords: Anti-inflammatory; HPTLC; antioxidant; hypericin; melanoma; phenolic compounds; phototoxicity.