The U.S. Pharmacopeia recently published its recommendation in the Pharmacopeial Forum
as a way of testing several marker substances in St. John's wort products.
The U.S. Pharmacopeia prefers HPLC to ultraviolet (UV) method tests (also referred to as
spectrophotometric methods) because HPLC is a more discriminating,
pharmaceutical-standard testing procedure. HPLC allows for quantitation of several marker
substances such as hypericin, pseudohypericin, and hyperforin while UV methods are unable
to separate key ingredients from product excipients.
The issue of St. John's wort testing received national attention in an article that appeared in the
Los Angeles Times, in which the dietary supplement industry was criticized for a lack of
quality control. The paper conducted a check of hypericin levels in 10 brands of St. John's wort
products, but used a UV method to perform the test, causing disputes from industry members
who said this was not the preferred way to perform the tests.
The National Nutritional Foods Association's TruLabel Random Testing Program used HPLC to
test the products featured in the Los Angeles Times article. The NNFA determined that the
L.A. Times reported to have lower than claimed levels of hypericin actually had 100% potency