Ethnobotany and Antibacterial Activities of Selected Medicinal Plants of Nepal Himalaya

Abstract

This study aims to explore medicinal plants from Manang and Mustang districts and examine their antibacterial activity in vitro against different strains of microorganisms. Field information was gathered by direct observation of locals through semi-structured interviews and information regarding the bioassay test was obtained through laboratory research. A total of 157 ethnomedicinal plant species belonging to 56 families and 114 genera are reported from the study area. These 157 locally used medicinal plants treat 150 ailments. This study found that many different parts of medicinal plant species are used as medicine. It would follow that the most commonly used plant parts have been selected because they contain more active principles in the form of biologically active secondary metabolites in comparison to the least commonly used parts. Of 157 medicinal plants documented, 88 plants were used for multiple uses, such as for food, fence and fuelwood, ritual and religious, and others. Several medicinal plants, i.e., Allium species, Hippophae species, etc., with multiple uses have great medicinal value and high market price even in Kathmandu and Pokhara. Even though the market price of these species has been increasing steadily, the local consumption has not yet decreased. Therefore further bioprospecting research on these species could help with the conservation and management of these local resources as well perhaps benefits the local people economically. In vitro antibacterial assays of 92 extracts from 79 ethnomedicinal plants used to treat diseases potentially caused by bacteria were examined. Overall, 73 % of plant extracts showed activity against Gram-positive Staphylococcus aureus, and Bacillus subtilis, and 69 % showed activity against Gram-negative Escherichia coli, and Pseudomonas aeruginosa. Although the nature and number of active antibacterial principles involved in each extracts are not clear, the broad spectrum of activity of several plants is promising. Thirty-three selected plant species were extracted with methanol, dichloromethane and hexane, resulting in a crude separation of the chemical components into groups of varying polarity. The minimum inhibitory concentration (MIC) of these extracts against the same bacterial species was obtained, and gives insight into the chemical nature of the biologically active constituents. The strong activity of the highly non-polar hexane extracts (shown by the low MIC values) indicates that the bioactive chemical(s) of those plant species was best extracted in non-polar solvent, and therefore was likely to be non-polar as well. Altogether 39 medicinal plants were prioritized and categorised as high, moderate or low priority in Manang and Mustang districts. Among the 39 prioritized species selected, 8 species were high priority, 29 were moderate priority, and 7 species were low priority. Bulk amounts of medicinal plant trade is seen from Manang and Mustang and if the process of trading of important medicinal plants continues on this scale for several years, species such as Cordyceps sinensis, Dactylorhiza hatagirea, etc, will become increasingly rare. Therefore I suggest immediate steps of cultivation of these species in the barren lands and use of sustainable harvesting approaches which may be helpful to conserve these species as well as othere wild plant resources in their natural habitats. In conclusion, this survey has shown that the local populations of Manang and Mustang districts have a wide knowledge on the use of wild plants for various purposes, including medicinal, food, fuelwood, fence, fodder, timber, household article, ritual, religious, etc. The present laboratory work lends support to the claims by traditional medicinal healers regarding the biological usefulness of the above plants. The antibacterial activities of the plants often explain their use by the local community