Abstract
Peppermint leaf, sage leaf, thyme herb, and their preparations are common components of herbal medicinal products (HMPs). According to the European Pharmacopoeia guidelines, the above-mentioned plant substances are standardized for the content of essential oils, omitting polyphenols, which also have a significant impact on their activities. The aim of this study was to evaluate the stability of the predominant polyphenols—rosmarinic acid, luteolin-7-O-β-glucuronide, and eriocitrin—in selected commercial liquid HMPs containing thyme, sage, and peppermint under long-term, intermediate, and accelerated testing conditions. Qualitative and quantitative analyses of these polyphenols were performed by the previously optimized and validated HPLC-DAD method. Rosmarinic acid stability was better in hydroethanolic than in an aqueous solution. The effect of the solvent on the stability of luteolin-7-O-β-glucuronide and eriocitrin could not be determined and requires further investigation. The present study is the first to analyze the stability of these compounds in commercial herbal medicinal products. The expiration dates proposed by the manufacturers of the tested HMPs did not guarantee stable levels of all analyzed polyphenols throughout the stated period. However, this study is preliminary and requires continuation on a larger number of medicinal products.
Highlights
Herbal medicinal products (HMPs) are medicines that contain herbal substances or herbal preparations as the only active ingredients [1]
The stability of rosmarinic acid and the predominant flavonoid compounds in five batches of liquid HMPs was analyzed under three different storage conditions—accelerated, intermediate, and long-term study
Both the conditions of the tests and their duration were under the European Medicines Agency (EMA) and the International Council for Harmonisation of technical requirements for pharmaceuticals for human use (ICH) guidelines
Summary
Herbal medicinal products (HMPs) are medicines that contain herbal substances or herbal preparations as the only active ingredients [1]. HMPs must fulfill restrictions regarding their characteristics, identification, and purity. An important part of the assessment of the quality of medicinal products, including herbal medicinal products, is the evaluation of their stability. Stability tests allow for the determination of the effects of environmental factors (e.g., temperature, humidity) on active ingredients and on a medicine’s quality, efficacy, and safety. Dried herbal materials—peppermint leaf, sage leaf, and thyme herb—as well as most of their preparations, under the guidelines of the European Pharmacopoeia (Ph. Eur), are standardized for the content of essential oils, with complete disregard for polyphenols, such as phenolic acids and flavonoids, no less relevant for their therapeutic effect [3]
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