Nepalese traditional medicine and symptoms related to Parkinson׳s disease and other disorders: Patterns of the usage of plant resources along the Himalayan altitudinal range

Abstract

Ethnopharmacological relevance

Nepal is a hotspot for cultural and biological diversities. The tremendous diversity of ecosystems and climates and the blend of medicinal practices inherited from Ayurvedic and Traditional Tibetan Medicine are well suited to a study aimed at discovering information about medicinal plants to treat Parkinson’s disease (PD). In addition, this study across Nepal’s altitudinal range is relevant to understanding how cultural and ecological environments influence local traditional medicines. The aim of the study is to document the uses of medicinal plants in three different eco-geographical areas of Nepal (Chitwan–Panchase–Mustang) to treat symptoms related to PD. A second goal is to analyze the impact of culture and environment on the evolution of traditional medicine.

Materials and methods

The study was conducted in five communities located in three different eco-geographical environments and at altitudes ranging from 300 m to 3700 m. We interviewed a total of 56 participants (local people, folk, Ayurvedic and Amchi healers) across the three research areas. We conducted open-ended interviews to document the uses of medicinal plants to treat PD-related symptoms. Information provided by the interviewees suggested that the medicinal plants are also used to treat symptoms related to other disorders. We determined the informant consensus factor as well as the importance of specific plant species to (i) identify plants that are the best candidates to be analyzed experimentally for their potential to treat PD and (ii) perform a cross-cultural comparison of the three areas of study.

Results

This study reports the local uses of 35 different plant species along the Chitwan–Panchase–Mustang altitudinal range. We identify a total of eight plant species that were used in all three research areas, and more specifically one species used to treat PD-like symptoms. We identify a potential dual protective activity of medicinal plants used to treat PD-related symptoms as recent literature suggests that these plants also have anti-cancer properties. In addition, we document that the presence of Ayurvedic healers could influence local practices and that local practices could influence local Ayurvedic practices.

Conclusions

This study documents the uses of medicinal plants to treat symptoms related to PD and other disorders across the Chitwan–Panchase–Mustang altitudinal range. PD is a neurodegenerative disease affecting a growing number of people worldwide. No cures are available to slow the death of the neurons, and there is a critical need to work towards innovative therapeutic strategies. We identify medicinal plants based on traditional practices to help develop a cure for PD. The three areas of study were chosen for their ecological and cultural diversities, and two of these are included in conservation programs (Panchase Protected Forest and Annapurna Conservation Area). The documentation of community–natural resource relationships is another step in the preservation of traditional practices and local biodiversity and a reflection of communities’ rights in the design of conservation programs.

Introduction

Parkinson’s disease (PD) is the second most prevalent neurodegenerative disease with 5% of the population being affected by age 85 (Dauer and Przedborski, 2003, Dawson and Dawson, 2003, Shulman et al., 2011). The disease involves a loss of dopaminergic neurons from the substantia nigra in the midbrain, and this loss of neurons is largely responsible for symptoms such as the inability to initiate movement, resting tremor and reduced balance (Massano and Bhatia, 2012). Pathological molecular events underlying neurodegeneration in PD include oxidative stress (Wang et al., 2006, Sanders and Timothy Greenamyre, 2013), loss of mitochondrial function (Betarbet et al., 2000, Banerjee et al., 2009, Youle and van der Bliek, 2012), aggregation of the pre-synaptic protein alpha-synuclein (Spillantini et al., 1997, Dawson et al., 2010, Rochet et al., 2012), and neuroinflammation (Block et al., 2007). Current therapeutic strategies for PD only alleviate symptoms and do not reverse the neuronal death (Jankovic and Poewe, 2012). Accordingly, we propose to use an ethnopharmacological approach to identify medicinal plants with the potential to lower the risk of PD and slow the disease progress.

Nepal is a hotspot of cultural and ecological diversity. This small country of 147,181 km² is located between India and China, two highly advanced centers of traditional medicine. Over the ages, Nepal has been influenced by these two cultural centers, and as a result traditional medicinal approaches in this country are now characterized by a unique blend of Ayurvedic, Tibetan and local folk medicines with their own unique evolutionary history (Phoboo et al., 2008). More than 80% of the Nepalese rural population depends on traditional medicine as the primary source of health care (Phoboo et al., 2008). Nepal has a tremendous plant diversity and displays a striking variation in microclimates and climates ranging from tropical to alpine over a distance of only 150 km (Bhattarai and Vetaas, 2003). Floristically, Nepal is a transition zone between the Western and Eastern Himalayas, thus providing a unique blend of plant species, a large number of which are endemic. A total of 118 ecosystems distributed across five physiographic zones were identified (Shengji, 1996), and more than 6000 vascular plants have been documented so far (about 1.5 times as many as in France) (Press et al., 2000). Furthermore, numerous communities with diverse cultural elements (e.g. 100 spoken dialects (Ghimire, 2008)) evolved independently in Nepal and developed a broad range of uses for medicinal plants. In this context, we studied three natural areas with distinct eco-geographical characteristics, namely the Panchase, Chitwan and Lower Mustang regions.

The Panchase region is located in the districts of Kaski, Parbat and Syangja and encompasses an area of 54.7 km². This region is characterized by subtropical and temperate vegetation and is a hotspot for biological diversity (Bhattarai et al., 2011). More than 589 flowering plant species have been documented in the Panchase region, and here the orchid diversity is exceptional. In the Panchase region, 113 species of orchids have been identified (27% of the orchid species identified in Nepal), out of which two are endemic (Panisea panchaseensis and Eria pokharensia) (Subedi et al., 2011, Kunwar and Acharya, 2013). The Panchase Protected Forest Program is a community-based project initiated to preserve the land, plant and wildlife biodiversity from overexploitation and degradation (Upadhyay, 2012). This report is the first documentation of local medicinal practices to treat PD in Panchase, and it complements ongoing conservation work in this area (Kunwar and Acharya, 2013). Our research highlights the relation of local communities with their natural resources, a critical process for the proper conservation of biodiversity in relation to indigenous rights (IUCN, 2004, Bajracharya et al., 2006).

The Chitwan district has a surface area of about 2218 km² (Neupane and Shresta, 2009) and is located in the Indo-Gangetic plain of Nepal, or Terai (flat plains). The climate is subtropical, and there is heavy rainfall during the monsoon season, with an annual precipitation of 2214 mm recorded at Rampur station (Neupane and Shrestha, 2009). As a result, the vegetation in this region is characterized by deciduous tropical forests.

Lastly, the Mustang district is divided into the Lower and Upper Mustang regions and encompasses a region of 3,639 km². The Lower Mustang region spans an altitudinal range of 2000–3700 m and is characterized by an extreme bio-climatic gradient, from deciduous oak and pine forests to steppe formations (Fort, 1987). Overall, the Mustang district has a windy and dry climate with less than 200 mm of rain annually (NTNC, 2008). The Highlands of Nepal (>3000 m) are characterized by a reduced diversity of flora but a higher proportion of endemic species (MoFSC, 2002), and it is therefore critical to preserve and document local medicinal practices.

Diverse research strategies are needed to find a cure for PD. Nepal’s tremendous plant diversity and striking variation in climates and local culture provide a unique opportunity to obtain new insight into effective herbal remedies and to understand the role of vegetal and cultural environments in the evolution of medicinal practices. To capitalize on this opportunity, we conducted an ethnopharmacological study in which local people and traditional healers in the Panchase, Chitwan and Mustang regions were interviewed to document the use of local plants to treat PD-related symptoms. Our study revealed a number of candidate neuroprotective plant specimens that warrant further investigation in experimental models of PD and other disorders.