Improved procedure for the quality control of Hypericum perforatum L.

A new, fast and reliable procedure for the quantification of the major compounds of Hypericum perforatum L. has been developed. Four naphthodianthrones (protopseudohypericin, pseudohypericin, protohypericin, hypericin) and two phloroglucinols (hyperforin, adhyperforin) were assayed by HPLC using a short (17 min) linear gradient, with hypericin and hyperforin as external standards. Extraction of dried plant material with methanol in the dark at room temperature for 2 h led to a complete recovery of phloroglucinols but only a partial recovery of the naphthodianthrone derivatives. Treatment of plant material with water:ethanol (40:60, v/v) in a water bath shaker at 80 degrees C led to the total extraction of hypericins, but a 10% loss of total hyperforins was also observed. The two extraction methods, applied successively to the same sample, allowed the complete extraction of all compounds of interest. A 5 min exposure of the crude extract of H. perforatum to sunlight (1 E/m2) induced a 96% loss of hyperforins, whereas the dry plant material lost only 20% of hyperforins after 2 h exposure to sunlight (24 E/m2).