[ Research and Findings ]

Back to Nature – Medicinal of Nepal Point New Direction to Drug Discovery

by Dr Robin Mitra and Professor John Orbell School of Molecular Sciences, Victoria University, Australia

Professor Chris Gray and Dr Morley Muralitharan School of Life and Environmental Sciences, Deakin University, Australia Dr Stephen Chandler Florigene Pty Ltd

Medicinal plants have diverse therapeutic functions, and relatively low side effect. Researchers and scientists now recognize the vast potential of drug discovery and development in the rich varieties of medicinal plants in Nepal.

Differentiation and Diversity The kingdom of Nepal boasts of about 6000 to 7000 different species of plants that are distributed throughout the country and this vast diversity has been aptly attributed to the huge variation in altitude and the different habitats the plants tend to thrive in (Williams, 2005). Manandhar (1998) report indicated that there are about 800 species of medicinal plants in Nepal, 30% of which are recognized as ethnomedical contributions from the western regions of the country. Kunwar et al. (2006) stated that Nepal recognizes about 1624 species with medicinal as well as aromatic properties, Sri Lanka about 1400, India about 2500 and about 5000. The alpine flora from Nepal’s Himalayan region consists of 1227 species in 317 genera of which 114 from the sub-alpine zone and 45 from the alpine zone has been cataloged as plants with medicinal properties (Kunwar et al., 2006).

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Bridging the Disparity of Knowledge The core theme of the Nepali Nighantu is based on the practice and principles of traditional medicine and compiles a commentary on about 750 Nepali medicinal plants with annotations on their therapeutic merits (Kunwar et al., 2006). Although the use of medicinal plants is widespread in Nepal, however, Griggs et al. (2001) is of the opinion that very few species have been subjected to scientific investigations for their bioactive compounds and such, and apparently the paucity of documented studies on the healing properties of most plants of medicinal value is still a major failing. Most of the medicinal and aromatic plants that grow in alpine meadows and mountain pastures at high altitudes are initially collected by the herders (Oli et al., 2003) and are eventually traded in the local bazaars and bustling markets of Kathmandu. The distribution and uses of some of the most important plants that are commonly used in the traditional medicinal practice of Nepal are presented in this article.

Medicinal Plants and the Healing Properties Cassia fistula Linn (Rajbrik) of the family Leguminosae is a semi-wild Indian laburnum commonly known as “Golden Shower Tree” or “Indian Laburnum” and is distributed throughout Asia, , Mexico, China, West Indies, East Africa and Brazil (Duraipandiyan and Ignacimuthu 2007). The occurrence of C. fistula in the Dadeldhura district of Nepal and its potential as a herbal drug among the Raute tribe has been documented by Manandhar (1998). C. fistula is also mentioned in the Ayurvedic system of medicine as a treatment for hematemesis (bloody vomitus), pruritus (itching), leucoderma (loss of pigment in areas of the skin) and diabetes (Bhakta et al., 2001). The antibacterial properties of C. fistula as revealed from the study by Duraipandiyan and Ignacimuthu (2007) rationalizes its use in traditional medicine as a cure for skin infection, fever and diarrhea. In addition, Duraipandiyan and Ignacimuthu (2007) concluded that the compound 4-hydroxy benzoic acid hydrate that was isolated from C. fistula possessed antidermatophytic activity and hence the plant had the potential to serve as a source of drugs against fungal infections.

Dioscorea bulbifera Linn (Ban tarul), known as “Air potato” or “Air Yam” in English, belongs to the family Dioscoreaceae and is an important aspect of the diets of the people inhabiting the mid-hills and the Terai region of Nepal (Singh et al., 1979). Consumption of wild yam is generally popular among various tribes like the Chepangs, the Tharus, the Bantars, the Danuwars and the Tamangs, that inhabit the rural regions of Nepal (Bhandari et al., 2003). In Nepal, the roots of D. bulbifera are first cleaned, chewed raw and then swallowed as a treatment for pneumonia and throat problem (Shrestha and Dhillion, 2003). The root tubers of D. bulbifera are also used in Chinese medicine as a remedy for sore throat and struma (swelling of the thyroid gland) (Komori, 1997).

Mentha arvensis Linn (Babari), known as “wild mint” in English, is an aromatic herb belonging to the family Labiatae. The Mentha consists of more than 25 species of which M. arvensis, M. piperita, M. spicata and M.

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pulegium contain the essential oils consisting of monoterpenes like menthol, menthone, carvone and pulegone as the major constituents (Phatak and Heble, 2002). These oils are widely used in the food and pharmaceutical industries and also for flavor and/or fragrance formulations (Lawrence, 1992).

Picrorhiza scrophulariiflora (syn. Neopicrorhiza scrophulariiflora) Pennell (Kutki) belongs to the family Scrophulariaceae which is known as Kutki in the Nepalese language while the Sherpas call it Ho-dling (Bhattarai, 1989). From Smit et al. (2000) study, it was apparent that diethyl Soxhlet extract prepared from the dried of P. scrophulariiflora had the highest anti-inflammatory effect compared to all the other extracts. Prolonged administration of the extract orally inhibited carrageenan-induced paw edema in mice and also delayed prevalence of collagen-induced arthritis.

Stellera chamaejasme Linn (Dyaurali phool), known as Chinese Stellera in English, belongs to the genus of the family . S. chamaejasme is a popular medicinal plant not only in Nepal but also in China where it is widely distributed in the northern and western provinces as well as in the regions along the Yellow River (Peng et al., 2006). About 15g of the root is boiled in about 500 ml of water, strained and boiled again until it is reduced to about ¼ of the amount and then applied to treat aching joints in Nepal (Manandhar, 1995). The daphnane-type diterpene gnidimacrin, isolated from the roots of S. chamaejasme has been found to strongly inhibit cell growth of human leukemias, stomach cancers and non-small cell lung cancers in vitro (Yoshida et al., 1996).

Urtica dioica Linn (Sishnoo) is a plant belonging to the family Urticaceae that boasts of a long history as a herbal remedy and nutritious addition to the diet. Application of U. diocia as a medicinal plant has also been reported from Turkey (Kültür, 2007). The root juice is consumed as a treatment for fever or an infusion is prepared from the root and drunk as remedy for asthma in Nepal (Shrestha and Dhillion, 2003). U. diocia is used to relieve rheumatic pain. Rheumatoid arthritis is an autoimmune disease that is characterized by chronic inflammation, hyperproliferation of the synovial lining and cartilage destruction (Reihemann et al., 1999). The levels of cytokines such as tumor necrosis factor (TNF) are highly elevated in the synovial fluid (Reihemann et al., 1999) and TNF is a pivotal pathogenic factor in rheumatoid diseases (Elliott et al., 1994). U. diocia is used to treat excessive menstrual flow for which decoction prepared from the leaves, is drunk about four teaspoonfuls three times a day in Nepal (Joshi and Joshi, 2000).

Going Natural – The Future Trend In conclusion, scaffolds as basic library design – an integrated approach with structure-based approaches and classical medicinal chemistry will provide ingredients for the success of natural products and medicinal plants in Nepal and Asian biotechnology. Another approach will be the integration of natural products in the drug discovery process – pathway analysis, proteomics and chemical genomics. Natural products are regarded as privileged structures in the modern global pharmaceutical industry. We hope Nepal medicinal plants will contribute to the growing global pharmaceutical discovery and drug development. ■

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