Evaluation of chemical composition, antioxidant and anti-acetylcholinesterase activities of Hypericum neurocalycinum and Hypericum malatyanum

This study was conducted to evaluate the chemical composition, antioxidant and anti-acetylcholinesterase (anti-AChE) activities of methanolic extracts of H. neurocalycinum and H. malatyanum, two endemic species of the Turkish flora. HPLC-DAD analysis indicated that two naphthodianthrones (pseudohypericin and hypericin) together with chlorogenic acid, rutin, hyperoside, isoquercitrin, kaempferol, quercitrin, quercetin, amentoflavone and hyperforin are the main compounds present in the methanol extracts. The extracts were tested in vitro for their antioxidant activities including, inhibition of lipid peroxidation in liposomes, induced by Fe3 +/ascorbate system, scavenging effect on DPPH and superoxide anion radicals, and ferric ion reducing antioxidant power (FRAP). H. neurocalycinum demonstrated stronger antioxidant properties than H. malatyanum due to higher activity on scavenging DPPH (EC50 = 2.49 ± 0.09 mg/mL) and superoxide anion radicals (EC50 = 0.613 ± 0.05 mg mg/mL), and inhibition of lipid peroxidation (EC50 = 2.49 ± 0.09 mg/mL). This difference in activity seems to be due to the presence of higher amounts of the antioxidant compounds (flavonoids) such as rutin, quercetin and kaempferol in H. neurocalycinum extract. The antioxidant activities of the extract may be attributed to their reducing capabilities. At 5 mg/mL H. neurocalycinum (FRAP value = 2.39 ± 0.039 mM Fe2 +) and H. malatyanum (FRAP value = 2.23 ± 0.013 mM Fe2 +) showed high ability to reduce Fe3 + to Fe2 +. The extracts were tested also for their in vitro AChE inhibitory activities. H. neurocalycinum inhibited 72.24 ± 0.39% of AChE activity at a concentration of 5 mg/mL. It was concluded that H. neurocalycinum is more effective AChE inhibitor and antioxidant than H. malatyanum.