Natural products for drug development and other value-added products

   Traditional medicine has been an integral part of Thai society for centuries. The Ministry of Public Health includes Thai medicinal plants in its list of essential drugs for the primary health care system of the nation. It is generally accepted that therapeutic efficacy and safety must be proven, not only for modern drugs, but also for herbal medicines. With herbal medicines, variations in the levels of active ingredients have been well documented and can account for lack of therapeutic effectiveness and occurrence of side effects. Currently, the research activities of the Laboratory of Pharmacology on natural products involve the development of rapid analytical methods for extraction, identification, and quantification of the phytochemicals from selected Thai medicinal plants. This includes the assessment of variation among plant materials and the standardization of the plant extracts. We have developed High Performance Liquid Chromatography (HPLC) techniques for simultaneous determination of these phytochemicals from many plants. High quality concentrated plant extracts are produced by different techniques, e.g. by freeze drying, spray drying or supercritical fluid extraction. Fingerprints of all phytochemicals present in the plants will be used for the quality control of these plant extracts. The major active compounds present in standardized extracts are also separated and purified to use as reference standards for quality control and pharmacological studies. In addition, as these medicinal plants are normally produced in dried-leaf form or whole plant, they can be easily contaminated with heavy metals and microorganisms from the environment (soil, water, or air) during growing and/or the manufacturing processes when the ready-to-use products are produced. Additional sources of heavy metal contamination are rainfall, atmospheric dust, plant protective agents, and fertilizers. Therefore, determination of some toxic metals such as cadmium, lead, arsenic, and mercury in medicinal plant products should be part of the quality control process to ensure the purity, safety and efficacy of these products.
Our current research in the laboratory also studies the determination of some toxic metals contaminated in natural products available in Thai markets (both local and imported products).Furthermore, pharmacological and toxicological studies of pure active compounds are also being carried out. The pharmacological studies focus on the cardiovascular system, respiratory system, neuronal and immune systems; neurodegenerative disease, diabetes, etc., as well as anti-malarial, anti-oxidant, and anti-cancer activities of the plant extracts and their active compounds. These studies will be carried out both in vitro and in vivo. The studies will have the potential to lead to major discoveries in the development of modern drugs and nutraceutical products for the benefit of human health. The medicinal plants that are currently studied in the Laboratory of Pharmacology are Andrographis paniculata, (A. paniculata), Dimocarpus longan (D. longan; longan), Sesamum indicum, Zingiber officinale, Oryza sativa (rice), and Gynostemma pentaphyllum (G. pentaphyllum). A. paniculata has been widely used in Thailand and is in the Thai Herbal Pharmacopeia as an herbal drug for the treatment of common cold symptoms and non-infectious diarrhea.
In collaboration with the Laboratory of Natural Products we found that several pure compounds of A. paniculata in exhibit antiplatelet aggregation, antihypertensive action, and anticancer activities. D

. longan (longan) has been studied in our laboratory for more than a decade. We are the first group in Thailand to explore the value-added potential of longan seed, and several pharmacological activities have been found for example antioxidant, antityrosinase, antiinflammatory and antifungal activities. In collaboration with Kasetsart University, we have conducted field research on sesame to develop shatter resistant sesame varieties that prevent seed loss during harvesting and have a high yield of sesame lignans which possess estrogenic/ antiestrogenic activities. In addition, these standardized plant extracts may be used as value-added ingredients in various food products such as fruit drinks, and cooked or canned foods, to enhance their nutritional values and promote good health. The spray-dried longan seed extract developed by the laboratory is used as an active ingredient in some cosmetic products such as herbal hand liquid soap and also in oral care products (e.g. mouthwash). In addition, the process for the preparation of concentrated G. pentaphyllum extract has been registered with Food and Drug Administration of Thailand for the production of this extract as an instant herbal tea. At present, we are in the process of applying for an FDA registration number for food.
Since 2000, our laboratory has also introduced good agricultural practice for medicinal plant cultivations at Tubtim Siam 05, Srakraew province which is the community development program of The Chulabhorn Research Institute (CRI). At present, this community grows selected medicinal plants supplying about 80% of the raw plants materials for the production of herbal drugs at Wang Nam Yen Hospital, Srakraew province, and also supporting for research activities of CRI. Adequate supply of good quality of medicinal plants is one of the key factors in herbal drugs development.