The Food Safety and Technology Research Centre under the Department of Applied Biology and Chemical Technology of The Hong Kong Polytechnic University (PolyU) has developed a new method for rapid authentication of Chinese herbal medicines, including Ganoderma (known as Lingzhi in Chinese), and Gastrodiae Rhizoma (known as Tianma in Chinese). The new method is quick and simple, which takes around 10 minutes to analyse one raw sample, achieving various ends including authentication of genuine and counterfeit species, classification of wild types and cultivated types, as well as differentiation of geographical origins. This method can be further applied to other herbal medicines.
Lingzhi and Tianma are two of the most popular and valuable Chinese medicines. Due to their high commercial values, problem of counterfeiting, adulterating and confusing Lingzhi and Tianma species is not uncommon in the market. Conventionally, fingerprint chromatography is adopted to authenticate and differentiate the species as it can provide comprehensive chemical composition of a sample. However, it is a labor-intensive and time-consuming method as it takes several hours to undergo the sample preparation and separation process for one sample.
Recently, the PolyU research team adopts the direct ionization mass spectrometry (DI-MS) method to detect the major active components of Lingzhi (ganoderic acids) and Tianma (gastrodin, parishin B/parishin C/and parishin). By directly applying a high voltage on a small piece of raw sample with its surface loaded with solvents, spray ionization could be induced at the tip of the sample to generate corresponding mass spectra within minutes, as if they are fingerprints which helps identification. The presence of major active components in the DI-MS spectra authenticates genuine samples from counterfeit ones. Moreover, with Principal Component Analysis (PCA), a commonly used dataset analytic tool, wild and cultivated types can be classified, while geographical origins could be differentiated.
There are approximately 80 Lingzhi species while only two of them, known as Chizhi and Zizhi in Chinese, are described in Chinese Pharmacopeia. Some other Lingzhi species which have similar appearances are commonly found to be confused with the official species. On the other hand, Tianma is easily confused with two counterfeit species, namely Cacalia davidii (Franch.) Hand.-Mazz. and Canna edulis Ker.
Both wild Lingzhi and Tianma are very rare and cultivation has become the major source. In general, wild types have higher contents of major active components and thus better curative effect. Samples originated from different geographical locations also have variations in components due to varying cultivation conditions.
The method developed by PolyU is simple, rapid, reproducible and can be easily adopted by researchers in relevant fields as no additional specialized device is required. It has the potential to be further expanded for analysis of other herbal medicines, for example, Heshouwu and Wuweizi, and therefore is expected to bring positive impact on the Chinese herbal medicine industry.
The research findings were published on Analytica Chimica Acta, a leading journal in analytical science.