Feb. 10, 2004 -- The amount of active ingredient in several brands of St. John's wort varies greatly, new research shows.
This new caution adds to building evidence about the potential risks of taking St. John's wort along with other medications. In 2000, the FDA issued an advisory urging physicians to caution patients that use of the herbal remedy could reduce the effectiveness of certain drugs, including many used to treat heart disease, depression, seizures, cancer, and to prevent organ rejection.
Studies have shown that the Hypericum plant, also known as St. John's wort, has mild antidepressant effects. Standardized formulations are supposed to contain 0.3% hypericin, the plant extract. However, few published studies have examined commercially available products for the amounts of hypericin and pseudohypericin -- both active compounds in St. John's wort that have been shown to fight depression and viral syndromes.
In this study, researchers measured contents of five products available over-the-counter in the U.S.
"We found that all five products had relatively low hypericin contents," writes lead researcher Zhao-Jun Wang, with the National Chun-Hsing University in Taiwan.
The amount of hypericin in one product was 39% of the amount stated on the label, and the other four products contained from 2% to 22% of the stated amount.
As for pseudohypericin content, none of the products claimed to contain this, yet this compound was found in the samples tested.
Another concern: "It is worth noting that the contents of hypericin and pseudohypericin may be different from batch to batch," writes Wang.
SOURCE: Wang, Z. Journal of the Science of Food and Agriculture, February 2004. WebMD Medical News: "St. John's Wort Affects Other Drugs."