Analysis of the hypericin and pseudohypericin content of commercially available St John's Wort preparations

The use of herbal medications and supplements has been growing worldwide with over four billion dollars a year spent on alternative medicines in the United States. St John's wort herbal preparations are generally standardized to "total hypericins" as a means of illustrating a degree of quality control to the consumer. This standardization has been based on a nonspecific method that overestimates and sums the two major naphthodianthrone compounds (hypericin and pseudohypericin) that are found in these products.

To use a more specific and sensitive method to accurately determine the total hypericin content (sum of hypericin and pseudohypericin) in commercially available St John's wort herbal preparations.

The current standard method for determining the naphthodianthrone content is a spectrophotometric method specified in the United States Pharmacopeia. Compounds other than hypericin and pseudohypericin can contribute falsely to the naphthodianthrone concentration, reducing this methods specificity.

Fifty-four commercially available St John's wort products were purchased in Canada and the United States.

A specific and sensitive liquid chromatographic method with fluorescent detection was used to specifically quantify the hypericin and pseudohypericin content in commercially purchased St John's wort products.

Analysis revealed large variations in total naphthodianthrone content, with the percentage of label claim varying from 0% to 108.62% for capsules, and from 31.34% to 80.18% for tablets. The content of tinctures varied from zero to 118.58 microg/ml. Only two products were observed to have a total naphthodianthrone concentrations within 10% of their label claim.

When the active or marker compounds in an herbal or alternative medicine have been identified, standardization is an important step to ensure consistency from batch to batch. However, consistency is not apparent between brands and most products have inaccurate label claims. On average, most labels overestimate the hypericin and pseudohypericin content by a factor of almost two.