Pseudohypericin and Hyperforin in Hypericum perforatum from Northern Turkey: Variation among Populations, Plant Parts and Phenological Stages Effect of hyperforin on learning and memory abilities and Aβ1-42, βAPP and BACE1 protein expressions in hippocampus of Alzheimer‘s disease model mice Advances in studies on synthesis and neuropharmacology of hyperforin and its derivatives Quantitative determination of hyperforin in Hypericum perforatum by HPLC Chemical unstability and pharmacological activity of hyperforin