Phytochemical contents, antioxidant effects, and inhibitory activities of key enzymes associated with Alzheimer's disease, ulcer, and skin disorders of Sideritis albiflora and Sideritis leptoclada

Abstract

In this study, urease, tyrosinase, cholinesterase inhibitory, and antioxidant activities of various extracts of Sideritis albiflora and Sideritis leptoclada were determined together with the phytochemical contents. In addition, the fatty acid compositions and phenolic compounds were investigated by gas chromatography (GC), gas chromatography-mass spectrometry (GC-MS), and high performance liquid chromatography-diode array detector (HPLC-DAD). Rosmarinic acid and caffeic acid in both Sideritis species were identified as the most abundant phenolic compounds whereas palmitic acid was found as a major fatty acid. The acetone extract of S. leptoclada indicated the highest antioxidant activity in beta-carotene-linoleic acid (IC50: 17.23 +/- 0.11 mu g/ml), DPPH center dot (IC50: 28.14 +/- 0.05 mu g/ml) and ABTS(center dot+) (IC50: 15.18 +/- 0.02 mu g/ml) assays. The acetone extract of S. albiflora (A(0.50): 32.71 +/- 0.44 mu g/ml) was found as the best reductant in cupric reducing antioxidant capacity (CUPRAC) assay. Against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), only the hexane extracts of Sideritis species showed moderate inhibitory activity. Moreover, all extracts of S. albiflora and the hexane extract of S. leptoclada exhibited significantly higher urease inhibitory activity than that of thiourea. Further, in vivo activity studies on extracts and isolated constituents obtained from these species are needed to understand the activity in biological systems.