Advanced multidimensional quality evaluation of encapsulated peppermint oil products in various formulas.

We investigated the actual label indications and quality of encapsulated peppermint oil (PO) products marketed as medicinal products for irritable bowel syndrome (IBS) or health food. Quality was multidimensionally evaluated with regard to the original plant source, content of PO and components of safety concern, and formulation. The original plant source was evaluated with reference to the criteria specified in the British and European pharmacopoeias and advanced GC-MS profiling tests, combined with simple discriminant analysis of the major 4 components (menthol, menthone, menthofuran, and isomenthone), which enabled evaluation of the various PO product formulations. 10 samples of 8 medicinal products and 40 samples of health food products were tested. Results showed that 2 medicinal products and 18 health food products were suspected of using material similar to mentha oil, which is frequently confused with PO. Menthol quantitative analysis showed that one medicinal product and 6 health food products contained different amounts of PO content from the indicated amounts. Further, one medicinal product and one health food product contained high levels of components of safety concern. Formulation quality was evaluated by the disintegration test, which found that 3 medicinal products and 15 health food products were not compliant. These results suggest that the quality of some PO products is inadequate. In particular, all health food products labeled with health claims related to IBS had problems in their quality or evidence of health claims.