Ingredient authentication of commercial Xihuangcao herbal tea by a microscopic technique combined with UPLC-ESI-QTOF-MS/MS

Herbal tea is a widely consumed beverage in the world and numerous materials can be used as its ingredients. As they are not regarded as drugs, the ingredients in tea are proposed to be safe. To ensure the safe use and quality of herbal tea, an easy and practical method should be created to identify the ingredients in commercial herbal tea. In this study, a combined method, which uses a microscopic technique and UPLC-ESI-QTOF-MS/MS analysis, was applied in the identification of a commercial Xihuangcao herbal tea bag containing multiple herbs. Three original plants of Xihuangcao were first collected and studied as reference materials, and the ingredients in eight Xihuangcao herbal tea samples were identified via microscopy. The herbs that appeared in high frequency were further verified by UPLC-ESI-QTOF-MS with representative peaks in the extracted ion chromatograms. Result showed that Xihuangcao could be found in 7 out of 8 batches of tea bags, of which Isodon serra was the major species. Some herbs that are not listed as ingredients were also found in the samples. This is the first study that uses a combined microscopic and mass spectrometric method to identify mixed herbal tea samples with unknown ingredients, which proved to be a fast, accurate and practical method that can be applied in routine laboratories.