Comparison of the phytochemical composition and antioxidant activity of seeds from different Hypericum species

H. perforatum is widely used in phytomedicine, among others, for the treatment of depressive episodes [1]. The aerial parts of Hypericum species are known for their complex spectrum of secondary metabolites [2]. Interestingly, subterraneous parts received less attention. Especially data for seeds are scant in literature. The aim of the present study was to systematically compare the seeds of two species, i.e. H. perforatum and H. tetrapterum, with regard to their metabolite profile. For this purpose, seeds were extracted with dichloromethane and methanol and analyzed by HPLC-DAD-MSⁿ and GC-MS. Moreover, the free radical scavenging capacity of methanolic seed extracts was quantified using the DPPH antioxidant assay. H. perforatum and H. tetrapterum yielded a fatty oil fraction amounting to 30.5% and 18.0% of the seed weight, respectively. Xanthone derivatives, i.e. tetrahydroxyxanthones (THX), xanthone-glycosides and xanthone-sulfonates, were assigned in the methanolic extracts of both species. For structure elucidation, one representative xanthone, namely 1,3,6,7-THX, was synthesized. Total THX contents were quantitated, resulting in 1.25 g/kg (H. perforatum) and 0.27 g/kg (H. tetrapterum). H. perforatum extracts (IC₅₀= 8.73 mg/L) and 1,3,6,7-THX (IC₅₀= 3.02 mg/L), exhibited good DPPH free radical scavenging activity compared to trolox (IC₅₀= 6.61 mg/L). The seeds of Hypericum were found to be a rich source of fatty oil and phenolic compounds exhibiting antioxidant activity, which was attributed to the remarkable xanthone contents. The results indicate, that Hypericum seeds might have promising potential in cosmetic and medicinal products.

[1] Rodríguez-Landa JF, Contreras CM. Phytomedicine 2003; 10:688 – 699.

[2] Brolis M, Gabetta B, Fuzzati N, Pace R, Panzeri F, Peterlongo F. J Chromatogr A 1998; 825: 9 – 16.