Determination of Active Components in St. John's Wort (Hypericum Perforatum) by Capillary Electrophoresis with Electrochemical Detection

Abstract

St. John's Wort (Hypericum perforatum) is a medicinal plant which has been known in traditional medicine as an anti-inflammatory and healing agent. Nowadays, the alcoholic extract of its aerial parts finds wide application for its antidepressant activity. A capillary electrophoresis method for the identification of its constituents using electrochemical detection was developed. Effects of several important factors were investigated to acquire the optimum conditions. The working electrode was a 300 μm carbon disc electrode at a working potential of +0.90 V (vs. SCE). The analytes can be well separated within 20 min in a 75 cm length fused-sillica capillary at a separation of 16 kV in 50 mmol L−1 borate buffer (pH=9.0). The current response was linear over about three orders of magnitude with detection limits (S/N=3) ranging from 0.2 to 0.5 mg L−1 for all the analytes. The method was successfully used in the analysis of Hypericum perforatum with relatively simple extraction procedures, and the assay results were satisfactory.