A major portion of drugs used in Ayurvedic system of medicine which has been practiced since the early human civilization in Indian subcontinent were of plant origin. It should be noted that 70% of the population in this region depends on Ayurveda for their medical treatment and 60% of the drug resources are obtained from the Himalayan region. Therefore, Nepal becomes a potential source of plant drug resource since it occupies a major portion of the Himalaya. In the present paper, in general a current status of medicinal plant resources of Himalayan region especially Nepal will be discussed. In addition to this, a typical example of antidiabetic activity of Shilajit will be taken for the discussion. Shilajit is one of the crucial elements in several formulations including those of Rasayana, a therapy in Ayurveda, which has been practiced in the prevention of ageing and mental disorder. Although, Shilajit is widely used for the treatment of diabetes, no satisfactory scientific reports are available up to now. The crude Shilajit in the market is a dark brown or black rock-like substance collected from the Himalayan region with a strong smell of cow's stale urine. In our studies, Shilajit (collected in the central Himalayan region) prevented the diabetes in nonobese diabetic (NOD) mice model. Shilajit also prevented the diabetes in the rats against the action of multiple low-dose (10 mg/kg, i.v., 5 times) of streptozotocin. On the other hand, Shilajit did not show antioxidative activity. The preventive action of Shilajit on diabetes is mainly focused on the Thl and Th2 cell activities, since Th2 cells activity was found to be significantly upregulated. Shilajit, however, showed a mild action in controlling the blood sugar level in young, old, and mild diabetic rats, but not in the severe diabetic rats. It also stimulated the nitric oxide production in macrophages. Based on these evidences, the antidiabetic activities of Shilajit appear to be immunomodulative probably by protecting or strengthening insulin-producing b-cells in the pancreas. Further systematic research on constituents of Shilajit and its quality evaluation is necessary to enable the use of natural medicines in the treatment of diabetes.

• Purusotam Basnet