Acetylcholinesterase inhibition and antioxidant activity of the water extracts of several Hypericum species

Many Hypericum species are widely used in Portugal, as well as in many other countries. In order to define the main components present in the water extracts, three Hypericum species, H. androsaemum and H. perforatum, obtained in the local supermarket, and H. undulatum, collected in an interior region of Portugal, were analysed for their inhibition of acetylcholinesterase and antioxidant activity. H. perforatum from five different suppliers was tested. All species were active, with IC50 values between 0.62 ± 0.06 and 1.79 ± 0.37 mg dry extract/ml. HPLC–diode array analysis indicated that chlorogenic acid, rutin, hyperoside, isoquercitrin, and quercitrin were the main compounds present in the water extracts. Their inhibitory activities, determined as IC50 values, were 196, 86, 66, 63 and 62 μg/ml, respectively. The highest inhibitory activity was found with H. androsaemum and H. undulatum. All the species showed high antioxidant activity (DPPH test). Values of EC50 between 9.0 ± 0.2 and 18.4 ± 0.8 μg of dry extract/ml were obtained.