Genetic and phytochemical assessment for identification of Mucuna plants and Kwao Khruea herbs

Abstract

The genus Mucuna belongs to the Fabaceae family. The taxonomy of the plants in this genus is confused with several synonyms at the species and the morphological features of some species are often similar. All parts of the plants have medicinal properties. The seeds have been employed as a source of L-Dopa, a neurotransmitter precursor which provides an effective remedy for the treatment of Parkinson’s disease. There are thirteen species of Mucuna found in Thailand report. Most of them were used as folk medicine. Although the plants in this genus are known as source of L-Dopa, each species has been used in different properties. Six Mucuna plants, M. gigantea, M. interrupta, M. macrocarpa, M. monosperma, M. pruriens, and M. warburgii, were used in this study. According to the similar morphological features, the authentication of Mucuna plants is quite difficult, especially when they are in the form of powders. The tuberous root of M. macrocarpa was commonly known as “Black Kwao Khruea”. The other two Kwao Khruea, White (Pueraria candollei) and Red (Butea superba) Kwao Khruea, also belong to the Fabaceae family. The tuberous root of White Kwao Khruea shows oestrogenic effects in the females, whereas Red and Black Kwao Khruea show androgenic effects in males. However, the identification of these roots bearing the name “Kwao Khruea” and have similar features might cause problems in the crude drug market. Quality control for safety and efficacy of medicinal plants and herbal products is necessary. In this study, genetic assessment combining with phytochemical assessment was used to identify Mucuna plants and Kwao Khruea herbs. For genetic assessment, the multiplex PCR was developed for species identification based on ITS region. For phytochemical assessment, TLC densitometric method was used for comparative L-Dopa content. In addition, PCR-RFLP using restriction enzymes DdeI and TaqI was utilised to differentiate White, Red, and Black Kwao Khruea based on matK gene. This technique was also conducted to authenticate crude drugs sold as various types of Kwao Khruea in the crude drug markets. For rapid detection and highly sensitive, cycleaved PCR was also performed to discriminate these Kwao Khruea species. Moreover, the specificity of this technique was confirmed by its ability to distinguish M. macrocarpa from five related Mucuna plants. The results from these studies indicated that the combination of genetic and phytochemical assessment would be useful for the identification and discrimination of Mucuna plants and Kwao Khruea herbs.