Maan B. Rokaya

Rheum australe D. Don: A review of its botany, ethnobotany, phytochemistry and pharmacology

ETHNOPHARMACOLOGICAL RELEVANCE Rheum australe D. Don (Polygonaceae) has been commonly used in traditional medicine for a wide range of ailments related to the circulatory, digestive, endocrine, respiratory and skeletal systems as well as to infectious diseases. AIM OF THE REVIEW To provide the up-to-date information that is available on the botany, traditional uses, phytochemistry, pharmacology and toxicology of Rheum australe. Additionally, to highlight the possible uses of this species to treat different diseases and to provide a basis for future research. MATERIALS AND METHODS The present review covers the literature available from 1980 to 2011. The information was collected from scientific journals, books, theses and reports via a library and electronic search (Google Scholar, Web of Science and ScienceDirect). RESULTS Ethnomedical uses of Rheum australe have been recorded from China, India, Nepal and Pakistan for 57 different types of ailments. The phytochemical studies have shown the presence of many secondary metabolites belonging to anthraquinones, stilbenes, anthrones, oxantrone ethers and esters, chromones, flavonoids, carbohydrate, lignans, phenols and sterols. Crude extracts and isolated compounds from Rheum australe show a wide spectrum of pharmacological activities, such as antidiabetic, anti-inflammatory, antifungal, antimicrobial, antioxidant, anticancer, hepatoprotective and immune-enhancing activities, as well as a usefulness for improving renal function. CONCLUSION Rheum australe has been widely used source of medicine for years without any adverse effects. Many studies have provided evidence for various traditional uses. However, there is a need for additional studies of the isolated compounds to validate the traditional uses in human models. The present review on the botany, traditional uses, phytochemistry and toxicity has provided preliminary information for further studies and commercial exploitations of the plant.

Medicinal plants used by the Tamang community in the Makawanpur district of central Nepal

BackgroundWe can conserve cultural heritage and gain extensive knowledge of plant species with pharmacological potential to cure simple to life-threatening diseases by studying the use of plants in indigenous communities. Therefore, it is important to conduct ethnobotanical studies in indigenous communities and to validate the reported uses of plants by comparing ethnobotanical studies with phytochemical and pharmacological studies.Materials and methodsThis study was conducted in a Tamang community dwelling in the Makawanpur district of central Nepal. We used semi-structured and structured questionnaires during interviews to collect information. We compared use reports with available phytochemical and pharmacological studies for validation.ResultsA total of 161 plant species belonging to 86 families and 144 genera to cure 89 human ailments were documented. Although 68 plant species were cited as medicinal in previous studies, 55 different uses described by the Tamang people were not found in any of the compared studies. Traditional uses for 60 plant species were consistent with pharmacological and phytochemical studies.ConclusionsThe Tamang people in Makawanpur are rich in ethnopharmacological understanding. The present study highlights important medicinal plant species by validating their traditional uses. Different plant species can improve local economies through proper harvesting, adequate management and development of modern techniques to maximize their use.

Traditional uses of medicinal plants in gastrointestinal disorders in Nepal

ETHNOPHARMACOLOGICAL RELEVANCE Gastrointestinal disorders cause morbidity and can lead to mortality, especially in the developing world where sanitation is deficient. A large part of the human population relies on medicinal plants for treating various diseases, including gastrointestinal disorders. The present review summarizes the traditional uses of medicinal plants of Nepal used to treat gastrointestinal disorders, and evaluates their bio-efficacy based on a review of the available phytochemical and pharmacological literature. MATERIAL AND METHODS We searched different electronic databases and libraries for the literature on medicinal plants used in Nepal to treat gastrointestinal disorders. For each species, we also searched the literature for information on conservation status, as well as for phytochemical and pharmacological studies in support of the ethnobotanical information. We used principal component analysis to explore the relation among disorders and plant families, plant life forms, plant parts and preparation modes. We also performed permutation tests to determine if botanical families were used more often than expected considering their availability in the Nepali flora. RESULTS We documented a total of 947 species belonging to 158 families and 586 genera used to treat gastrointestinal disorders in Nepal. Diarrhea was the disorder treated by the highest number of species (348), followed by stomachache (340) and dysentery (307). Among the reported species, five were endemic to Nepal, whereas 16 orchid species were protected under CITES Appendices II and III. The randomization test showed that species belonging to 14 families were used less often than expected, whereas plants belonging to 25 families were used more often than expected. The PCA scatter plot showed distinct groups of gastrointestinal disorders treated with similar plant life forms, plant parts, and/or preparation modes. We found 763 phytochemical studies on 324 species and 654 pharmacological studies on 269 species. CONCLUSION We showed the diversity and importance of medicinal plants used to treat gastrointestinal disorders in the traditional health care system of Nepal. As such disorders are still causing several deaths each year, it is of the utmost importance to conduct phytochemical and pharmacological studies on the most promising species. It is also crucial to increase access to traditional medicine, especially in rural areas. Threatened species need special attention for traditional herbal medicine to be exploited sustainably.

Distribution Patterns of Medicinal Plants along an Elevational Gradient in Central Himalaya, Nepal

This study aimed to compare the distribution patterns and trends of plant parts used among different groups of medicinal plants, geographical regions, and between medicinal plants and all vascular plants. We used the published sources for elevation records of 2,331 medicinal plant species to interpolate presence between minimum and maximum elevations and estimated medicinal plant richness for each 100-m elevational band. Monte Carlo simulations were used to test whether differences in elevational distribution between different groups of medicinal plants were significant. Total number of medicinal plants as well as different groups showed unimodal relationship with elevation. The elevational distributions of medicinal plants significantly differ between regions and between medicinal plant groups. When comparing the richness of all medicinal plants to all vascular plants, Monte Carlo simulations indicated that the numbers of medicinal plants are higher than expected at low elevations. The highest richness of medicinal plants at low elevation could be possibly due to favorable environmental factors such as high temperature, rainfall, sunlight or due to higher density of human population and thus higher pressure on use of any plants in lower elevations.

Trade-off among different anti-herbivore defence strategies along an altitudinal gradient

We found that Salvia nubicola distributed along a broad altitudinal gradient developed a range of defence strategies against insect herbivores. The strategies, however, do not seem to be used simultaneously in all populations even though most of them are correlated with the altitudinal gradient along which herbivore pressure is decreasing. Our study thus shows the importance of simultaneous study of different defence strategies since understanding trade-offs among them could be necessary for detecting the mechanisms by which plants are able to cope with changes in plant-herbivore interactions as a consequence of future climate change.

Heterogeneous Landscapes on Steep Slopes at Low Altitudes as Hotspots of Bird Diversity in a Hilly Region of Nepal in the Central Himalayas.

Understanding factors determining the distribution of species is a key requirement for protecting diversity in a specific area. The aim of this study was to explore the factors affecting diversity and distribution of species of birds on different forested hills in central Nepal. The area is rich in species of birds. Because the area is characterized by steep gradients, we were also interested in the importance of altitude in determining the diversity and species composition of the bird communities. We assessed bird diversity and species composition based on point observations along a gradient of increasing altitude in two valleys (Kathmandu and Palung) in central Nepal. Data on environmental variables were also collected in order to identify the main determinants of bird diversity and species composition of the bird communities. We recorded 6522 individual birds belonging to 146 species, 77 genera and 23 families. Resident birds made up 80% (117 species) of the total dataset. The study supported the original expectation that altitude is a major determinant of species richness and composition of bird communities in the area. More diverse bird communities were found also in areas with steeper slopes. This together with the positive effect of greater heterogeneity suggests that forests on steep slopes intermixed with patches of open habitats on shallow soil at large spatial scales are more important for diverse bird communities than more disturbed habitats on shallow slopes. In addition, we demonstrated that while different habitat characteristics such as presence of forests edges and shrubs play an important role in driving species composition, but they do not affect species richness. This indicates that while habitat conditions are important determinants of the distribution of specific species, the number of niches is determined by large scale characteristics, such as landscape level habitat heterogeneity and altitude. Thus, to protect bird diversity in the mid-hills of central Nepal, we should maintain diverse local habitats (viz. forest, shrubs, open land, etc.) but also make sure the natural habitats on steeper slopes with large scale heterogeneity are maintained.

Diversity, distribution and host-species associations of epiphytic orchids in Nepal

Associations between epiphytes and their hosts are among the main factors affecting the biodiversity and distribution of epiphytes. While several previous studies explored the association between epiphyte diversity and host characteristics, very little is known about the generality of such associations at larger spatial scales. We aim to explore the associations between diversity and distribution of epiphytic orchids and host characteristics in different localities in Nepal. Epiphytic orchids and their hosts were recorded along the transects in total of 23,539 host individuals. To describe the diversity of orchids in the different localities, a rarefaction function was used. Univariate and multivariate analyses were carried out to explore the associations with locality, host characteristics, and their interactions with locality. In total, we recorded 141 species of orchids growing on 192 host species. The five localities significantly differed in orchid diversity and abundance. The number of orchid individuals per host species significantly increased with increasing number of host individuals. Species richness, abundances, occupancy of orchid species on host species and composition of orchids varied across the localities. Species richness and abundance was significantly higher on hosts in the higher strata and differed between families of host species. Abundance was higher on evergreen hosts. Composition of orchid communities are also associated with host characteristics, such as habit (shrub/tree/climber), bark texture, nature (deciduous/evergreen) and the plant families of host species. This study revealed a high diversity of epiphytic orchids in the localities studied and strong associations between the orchids and their hosts. Future studies looking at the relationships between epiphyte communities and host characteristics need to identify relationships at a wider scale in order to determine whether they are really general rather than site-specific.

Sustainable harvesting strategy of medicinal plant species in Nepal – results of a six-year study

Although many studies have demonstrated great variation in the life histories of various perennial plants between years and habitats, current studies on sustainable harvesting of medicinal plants have only lasted two to four years. We explored the effects of harvesting on the survival of populations of highly used perennial medicinal plants (Rheum acuminatum and R. australe) that are endemic to the Himalayan region. We collected data on recruitment, growth and survival in populations of R. acuminatum in open and forest habitats as well as R. australe in open habitats over six years in central Nepal. We used a matrix modelling approach to compare population growth and the effect of different harvesting regimes on population survival. Although the population dynamics among the studied Rheum species in the two habitat types and among various years of the study were relatively similar and stable, there were significant differences in sensitivity to harvesting. The results of our study suggest that harvesting of both species can be considered sustainable under certain conditions. Either selective (only vegetative or only flowering individuals) or rotational (once every five or more years) harvesting strategies should be adopted. Optimal management, however, partly differs between species and strongly depends on habitat conditions. The conclusions of this study could also be applied to other commonly harvested alpine and perennial medicinal plants in the Himalayan region.

Xanthones Content in Swertia multicaulis D. Don from Nepal

The medicinal plant Swertia multicaulis D. Don was collected in Rasuwa District (Nepal) and the xanthone content of its ethyl acetate extracts was studied. The total amount of xanthones in S. multicaulis determined by HPLC reaches almost 13 g of xanthones per 1 kg of dry matter. The identification of xanthones in S. multicaulis was achieved by a combination of HPLC, LC–MS and LC–NMR. The final assignment of the individual chemical structures was provided by NMR, supported by preparative HPLC. In eight chromatographic peaks, four major xanthones were identified—1,3-dihydroxy-5,8-dimethoxyxanthone, 1-hydroxy-3,5,8-trimethoxyxanthone, bellidifolin (1,5,8-tri-hydroxy-3-methoxyxanthone), and decussatin (1-hydroxy-3,7,8-trimethoxyxanthone).

Habitat Ecology of Ophiocordyceps sinensis in Western Nepal

As a valuable entomophagus fungus species, caterpillar fungus (Ophiocordyceps sinensis) is endemic to the alpine meadows of the Tibetan Plateau and adjoining Himalayas. However, little is known about its ecological niche and habitat. We investigated its associated plant species and habitat across different sites in Dolpa, west Nepal, and explored how associated plant species and soil characteristics affect its density and growth during the months of June and July in 2 consecutive years. Detrended correspondence analysis was used to capture the distribution pattern of plant species. Principal component analysis was applied to visualize the gradients of the soil data, and generalized linear models were employed to test the effects of nutrients and vegetation on the availability and size of caterpillar fungus. A total of 33 plant species were frequently associated with caterpillar fungus across the investigated sites. The abundance of the fungus was significantly affected by vegetation composition, whereas the individual fungal traits were independent of soil nutrients or vegetation composition. Therefore, it is essential to protect associated plant species to better conserve caterpillar fungus at high elevations.