Chemistry of shilajit, an immunomodulatory Ayurvedic rasayan

The chemical polemics in the reported literature on shilajit are resolved. This study shows that humification of latex and resin-bearing plants is responsible for the major organic mass (80-85%) of shilajit. The low mol. w t . chemical markers (&lo%) , viz. aucuparins, oxygenated dibenzo-K -pyrones and triterpenic acids of the tirucallane type (free and conjugated), occurring in the core structure of shilajit humus, are the major active constituents of Himalayan shilajit. The therapeutic effects of shilajit are the consequences of hormonal control and regulation of immunity. INTRODUCTION Shilajit is a blackish-brown exudation, from steep rocks of different formations, commonly found in the Himalayas, at altitudes between 1000-5000 m, from Arunachal Pradesh in the East to Kashmir in the West. It is also found in other countries, e.g. Afganisthan (Hindukush), Bhutan, China, Nepal, Pakistan, Tibet (Himalayan belt) and the USSR (Tien Shan,Ural). Shilajit is believed to arrest aging and produce rejuvenation (ref. 11, -two important attributes of a rasayan (refs. 2 , 3 ) . Considerable controversy had existed in the reported literature (ref. 3) when we initiated our study on the nature and chemical constituents of shilajit about fourteen years ago. It was variously described, as a bitumen or mineral resin varying greatly in consistency from a free-flowing liquid to a hard brittle solid; a plant fossil exposed by a elevation of the Himalayas; a substance of mixed animal and plant origin (refs. 3 , 4 ) . Twelve years after the publication of the circumstantial evidence for the contribution of plants in shilajit formation (ref.51, we obtained further direct evidence regarding the chemical character of shilajit (refs. 6,7). It would now require summation of our earlier findings for resolving the chemical polemics (refs. 3 , 4 ) on this subject and to report our recent findings, from analyses of shilajit from different regions, to show the generality of our conclusion. The first major advance in our understanding of the chemical character of shilajit was the observation that shilajit, from different regions, contained a large variety of organic compounds that can be broadly grouped into humic and non-humic substances (refs. 6,7). The non-humic substances, in soil-sediment humus (ref. 81, are low mol. w t . organic compounds that are characterizable by chemical and spectroscopic methods. The humic substances, by contrast, do not exhibit any specific physical and chemical characteristics (e.g. sharp m.p., consistent elemental composition, consistent pH, well-defined IR and NMR spectra), normally exhibited by characterizable organic compounds. Humic substances are produced by interaction of plants, algae, mosses, and microorganisms. The phytochemistry of vegetation around shilajit-bearing rocks, therefore, constituted an important part of our investigation. The coamon plant sources of humus, in mountain soils, are the perennial grasses and legumes, which possess finely branched root systems capable of regeneration. Other important sources of humus are the litter and latex of plants. Variation in the quality of shilajit humus (both chemical and biological) is, therefore, conceivable. The other factors that cause variations in shilajit humus are: (i) altitude and the nature of shilajit-bearing rocks; (ii) atmospheric conditions (e.g. alternate wetting and drying); (iii) pH and moisture content of the rock source; and (iv) activity of the rhizospheric microorganisms and their exo-enzymes. The stability of the humus reserve depends on one or more of these factors. Shilajit samples collected from different places, as expected, exhibit variations in chemical characteristics and bioactivities. Furthermore, the hazards of collection of shilajit and the scanty amount generally available in any one locale prompt unscrupulous traders to .adulterate it with rock soil, plant debris and quercus gums. It was, therefore, thought imperative to determine certain standards of shilajit on the basis of bioactivity-directed investigation of its chemical constituents.