Adulteration of St. John's Wort products: How to identify quality problems

Hypericum perforatum L., known as St. John's Wort (SJW), is an important medicinal plant. Aside of being the most commonly used Herbal Medicinal Product for treating depression [1], products made with SJW powdered plant material and various extracts were the 9^th most sold botanical dietary supplement (DS) in the mass market channel in the USA in 2012 [2]. Due to the popularity of this botanical dietary supplement, there is a potential for economically driven adulteration of SJW products particularly with other Hypericum species [3].

Under U.S. Food and Drug Administration's cGMP, manufactrers of DS that are sold in the U.S. are required to identify and use an appropriate scientifically valid method for each established specification [4]. The goal of this work was to re-evalute the role that HPTLC could play in this context. Triggered by the fact that some SJW ingredients on the market have given unusual results (such as odd colors of solutions obtained during sample preparation), several commercial samples labeled to contain extracts of H. perforatum were analyzed by HPTLC using methodology from the USP [5], with additional detection under white light. Uncommon fingerprints were obtained for several products (Fig. 1b and 1c) suggesting presence of other species, degradation products, and/or polar additives, which however could not be detected with this method because they are at the application position. Therefore a new HPTLC method was developed that made it possible to identify these additives as a mixture of legal food colors in an amount between 0.84 and 1.04% (Fig. 1 d), which has been identified by scanning densitometry and confirmed by HPTLC-MS. By using the USP method with additional detection mode it was possible to identify 8 samples of SJW adulterated with dyes and six other samples with a flavonoid fingerprint different from that specified by USP from total of 37 samples of dry extracts, products and herb material analyzed.

Fig. 1: Image of the plate derivatized with NP and PEG reagents, under UV 366nm (A and B) and white light (C and D). Track 1: Hypericin; Track 2: USP Powdered SJW Extract; Track 3: SJW liquid extract; Track 4: SJW s1; Track 5: SJW s2; Track 6: SJW s3; Track 7: SJW s4.

Keywords: St. John's Wort, HPTLC, adulteration.

References:

[1] Klaus L, Michael B, Matthias E, Cynthia M. St John's wort for depression. Meta-analysis of randomised controlled trials. Brit J Psych 2005; 186: 99 – 100

[2] Mark B, Ashley L, Carla O, Mary EL. Herb supplement sales increase 4.5% in 2011. HerbalGram 2012; 95: 60 – 64

[3] Om PJ, Amit K, Pavan K, Niranjan KM. Adulteration and substitution in Indian medicinal plants: An overview. J Med Plants Stud 2013; 1: 127 – 132

[4] U.S. FDA. 21 CFR 111, the current good manufacturing practice in manufacturing, packaging, labeling, or holding operations for dietary supplements. Final rule. June 2007.

[5] USP St. John's Wort monographs. USP 38-NF32. 2015, 6207 – 6212. United States Pharmacopeial Convention, Rockville, MD.