Phenolic composition and antioxidant properties in different organs of Hypericum elongatum and Hypericum orientale

This study investigates the phytochemical composition and antioxidant capacity of two underexplored Hypericum species, H. elongatum and H. orientale. Methanolic extracts of flowers, leaves, and stems were evaluated for total phenolic content (TPC), total flavonoid content (TFC), and antioxidant activity using DPPH, FRAP, and CUPRAC assays. 24 phenolic compounds were quantified by high-performance liquid chromatography with diode-array detection (HPLC-DAD). The TPC values ranged from 7.6 to 37.9 mg GAE/g, and TFC values from 1.9 to 10.7 mg QE/g. H. orientale generally showed higher phenolic and flavonoid levels, with its flower extract exhibiting the highest TPC (37.87 ± 1.86 mg GAE/g) and TFC (10.66 ± 0.30 mg QE/g). All extracts demonstrated notable antioxidant activity. Remarkably, the H. elongatum leaf extract had a very low DPPH IC₅₀ value (0.02 mg/mL), indicating strong radical-scavenging capacity. Its leaf also showed the highest FRAP value (299.38 ± 13.99 µmol FeSO₄·7H₂O/g) among all samples. The dominant phenolics in both species were catechin and epicatechin; kaempferol was detected only in H. orientale flowers (75.91 mg/kg). Hypericin was present in all tissues, with the highest concentration in H. orientale leaves (27.5 mg/kg). These findings highlight the significant antioxidant potential of both species, particularly in their flowers and leaves and suggest they may serve as valuable sources of natural antioxidants in phytomedicine.