NOW has continued its programme of testing supplements sold on Amazon, this time on popular herb St John’s Wort.
Results revealed that every single product failed potency testing except for the NOW sample.
Several samples contained synthetic dyes, which are commonly used by bad actors to make low-quality or adulterated products appear authentic.
St John’s Wort (Hypericum perforatum) is used to support mood balance and emotional well-being.
The key active compounds, hypericin and pseudo hypericin, are responsible for its beneficial properties and are typically standardised to 0.3%.
Ensuring supplements contain genuine, properly standardised extract is essential for product quality and effectiveness.
NOW purchased two bottles of each St John’s Wort supplement (including NOW product) from Amazon.com in August 2025.
One bottle of each sample was tested in NOW’s state-of-the-art in-house labs.
To ensure accuracy and transparency, the other bottle was sent to Alkemist Labs, an ISO 17025-accredited independent laboratory specialising in botanical identification and testing.
Hypericin was quantified by High-Performance Liquid Chromatography (HPLC) using a validated reverse-phase method after irradiation with white light to ensure specificity.
Hypericin content was expressed as the sum of hypericin and pseudo-hypericin.
High-Performance Thin Layer Chromatography (HPTLC) was performed to confirm the product identity and detect common synthetic dyes, which artificially inflate hypericin readings in less specific testing methods.
NOW's testing found the following results:
- Out of 22 tested brands, only NOW met the label claim for total hypericin and contained no synthetic dyes
- Nine brands contained synthetic dyes
- Five brands had no detectable hypericin and none of the gummy brands had any detectable hypericin
- Non-standardised St. John’s Wort whole herb may have as low as 0.03% hypericin and of the six products containing the non-standardised material, all had less than this amount.
“We are accustomed to seeing abysmal test results in at least some of the brands we buy from Amazon for this testing programme, but this time we were shocked to find that they all failed and only NOW St. John’s Wort met the label claim for total hypericin and showed no evidence of dye adulteration,” said Katie Banaszewski, NOW Senior Director of Quality.
“What stands out most to me is the strong evidence that none of these brands used fit-for-purpose testing, if they tested at all."
"Our in-house analytical testing, paired with Alkemist Labs’ independent verification, underscores the importance of scientifically valid methods.”
Choosing the correct testing method for St. John’s Wort is critical.
Non-specific methods, such as simple colourimetric or spectrophotometric assays, can be fooled by synthetic dyes that mimic the red colour of hypericin.
These approaches may artificially inflate potency results, making products appear compliant when they are not.
In contrast, HPLC can separate and identify true hypericin compounds from adulterants, providing an accurate and reliable measure of product quality.
NOW’s and Alkemist’s testing both relied on chromatographic specificity, ensuring confidence in the findings.
NOW will continue to purchase and test products sold on major online platforms and publicly share the results to encourage higher quality standards across the supplement industry.