Amount of active ingredient in some St John's wort products may not match claims on product's label
Some commercial products of St John's wort (Hypericum perforatum) contain much higher or much lower amounts of active ingredient than stated on the label, say researchers from Taiwan.
Professor Miao-Lin Hu and colleagues from the National Chung-Sing University
examined five St John’s wort products purchased from Californian
health food stores. They used liquid chromatography methods to measure
the amounts of hypericin and pseudohypericin, the two active ingredients
of St John’s wort, contained in each product.
Despite none of the products listing pseudohypericin as an ingredient,
it was present in all of them in higher quantities than hypericin. The
actual amounts of hypericin ranged from 1.7 to 38.5 per cent of the stated
amount. When the total hypericin content was measured, the amounts ranged
from 2.9 to 114 per cent of the stated amount.
The study is published online in
the Journal of the Science of Food and Agriculture, a journal of the
Society of Chemical Industry.
Commenting on the study, Jonathan Berman, of the health and safety group
at the SCI, said: “Inaccurate labelling has at least one of two
effects. The first is potentially to lead to an incorrect dose when the
label is complied with. The second is the potential to degrade the perceived
significance of the label information among other dispensing practitioners,
or patients.” This perception could then carry over to other drugs,
he added.
A spokesman for the Medicines and Healthcare products Regulatory Agency
told The Journal that there is evidence that some unlicensed herbal medicines
available in the UK are manufactured to poor quality standards. He said: “Under
the current UK regulatory arrangements it is difficult for the public
to identify which products are made to good standards and which are prone
to the kind of problems identified in the research.”
He added that the proposed European Directive on Traditional Herbal Medicinal
Products would apply to manufactured over-the-counter herbal remedies.
This will set clear standards for quality, manufacturing and labelling
information. |
The
Pharmaceutical Journal