Labels standardise hypericin; hyperforin is what predicted the effect
Across six preparations, how far St John's Wort sped up drug clearance tracked their hyperforin content closely and their hypericin content not at all. Hyperforin is not standardised.
What the study found
Products are standardised on the constituent that does not matter
Across six preparations, how far St John's Wort sped up drug clearance tracked their hyperforin content closely and their hypericin content not at all. Hypericin is what labels standardise, commonly at 0.3 percent. Hyperforin, the one that actually predicted it, is not standardised.
The caveat · A slope, with no safe cut-off
Forty-two men across six arms leaves about seven per arm, so each arm's estimate is imprecise. The preparations were picked to span the hyperforin range rather than to represent what sits on a shelf. Every arm showed some induction, including the near-hyperforin-free one, so this is a slope rather than a safe threshold.