Chemistry of Shilajit

By: Shibnath Ghosal

Pure & Appl. Chern., Vol. 62, No. 7, pp. 1285-1288, 1990.
Printed in Great Britain.
@ 1990 IUPAC
Chemistry of shilajit, an immunomodulatory
Ayurvedic rasayan
Shibnath Ghosal
Department of Pharmaceutics, Banaras Hindu University, Varanasi-5, India

Abstract - 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. wt.
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. wt. 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.
1285 1286 S. GHOSAL
CHEMISTRY OF SOURCE MATERIALS OF SHlLAJlT
During our bioactivity-directed investigation of shilajit samples, from different
countries, some striking similarities were observed in respect of their contained low mol.
wt. bioactive compounds. Several phenylpropanoid-acetate-derived aucuparins, oxygenated
biphenylcarboxylates, isolated and characterized as their permethylated derivatives (1-3)
(ref. 7), and oxygenated dibenzo-or' -pyrones (3-5) (refs. 6,7) were found to occur
ubiquitously, albeit in different amounts, in all authentic samples of shilajit. We also
located some of the living plant ancestors of these compounds.
Over eighty different plant species were reported (ref. 9) in and around the shilajit
rocks in Kumaon itself. One species which was consistently found to be present in
shilajit-bearing rocks, throughout the Eastern and the Western Himalayas, was a rich latex
producing plant, Euphorbia royleana Boiss. (Euphorbiaceae). Some other latex and resin
producing common species, in these regions, are the legumes, e.g. Trifolium, (family,
Anacardiaceae) , Ficus (Moraceae) , and Juniperus (Cuprassaceae) . - T. ripens (Leguminosae), collected from different places in the Himalayan belt, yielded
several phenylpropanoid-acetate-derived metabolites including (1) to (2). E. royleana
(latex and debris), putrefied by shilajit rhizospheric microorganisms, yieldez the three
other important shila jit marker compounds (5-5) along with several other equivalent
metabolites. A conceptual model for the genesis of (1) to (51, involving an intermediate
(I), was envisaged (ref. 10). Another key intermediate (i), isolated from a free-flowing
(premature) sample of shilajit, provided strong circumstantial evidence in support of the
aforesaid biogenetic route (ref. 10). The reactive intermediate (8) was autoxidized, in
presence of light and air, to give a mixture of (6) and (57, presumably via the
endo-peroxide (2).
Continuing the phytochemical investigation, we have now isolated and characterized from
-- R. cotinus and E. succedanea (Anacardiaceae), several phenolic lipids of the type (2) and
triterpenoids (both free and conjugated,- oligoglycosides) of the tirucallane types
(11-12). Enzymatic hydrolysis of a major triterpenoid saponin fraction, with
hesperidinase, followed by column chromatography (Si gel using n-BuOH saturated with
water) of the sapogenin fraction afforded a mixture of 24(Z)-3/j-hydroxytirucalla- 7,24-
dien-26-oic acid (ga) and 24(2)-3p -hydroxytirucalla-8,24-dien-26-oic acid (gal. From
the aqueous hydrolysate, L-arabinose, L-rhamnose, D-xylose and D-glucose were isolated, as
their alditol acetates, and identified by GLC. In case of shilajit, from different
regions, both E- and Z-isomers of the triterpenoid sapogenins (Ga-b) and (ga-b) and the
phenolic constituents were isolated and characterized. The structures of these compounds
were established by comprehensive spectroscopic analyses, crucial chemical transformations
and synthesis, where possible. Pharmacological and immunological screening of these
compounds, individually and in combination, established their significant contribution to
the therapeutic efficacy of shilajit. Among the other organic compounds contributing to
the bioactivity of shilajit, humic and fulvic acids, from shilajit humus, are noteworthy.
However, the main task that confronts researchers in this field (study of humus) today is
to decipher the complexity of the building units of humus and their allignments, after
polycondensation, in the core structures of humic substances.
HUMIC SUBSTANCES FROM SHlLAJlT
Scanning electron microscopy and viscosity measurements of humic acids (HAS) and fulvic
acids (FAs), from shilajit, suggested for the FAs a relatively open, flexible structure
punctured by voids (micropores) of different diameters, at different pH. FAs from
biologically equiactive shilajit samples exhibited a number of similarities in respect of:
(i) elemental and micronutrient (trace metal ions) compositions; (ii) aromatic and
aliphatic carbon ratio; (iii) absorbance ratio at 465/665 nm (E-4/E-6); (iv) viscosity
and particle size; and (v) PMR and CMR spectra.
Relatively mild degradation of shilajit-HAS, by boiling with water, yielded several
aliphatic ('2-16 to C-20) and phenolic acids together with common sugars, glucose,
arabinose, rhamnose and xylose. These compounds were, presumably, loosely held in the
core structures of shilajit HAs either by weak bonding or by adsorptionJintercalation in
their internal voids. The plant secondary metabolites which are trapped in the internal
voids of humic substances are spared from and resistant to common chemical and biological
decomposition. This is consistent with the observed ubiquitous occurrence of the
aucuparins and dibenzo--:-pyrones in the core of shilajit from different regions. During
systemic administration of shilajit, these constituents, even if,presentasminorentities,
elicit their potent biological effects and are, therefore, regarded as markers of shilajit.
According to accepted tenets, biogenesis of humus (ref. 8) involves a two-stage process:
(i) fragmentation of plant and microbial constituents into small molecules (monomers), and
(ii) heteropolycondensation of the monomers into high mol. wt. humus. Our results of Chemistry of shilajit 1287
investigation of shilajit HAS, however, suggested participation, at least in part, of some
plant-derived intact phenolic metabolites, viz. biphenyl carboxylates (and equivalents),
in their core structure. These phenolic moieties were transformed into polynuclear
aromatic hydrocarbons, phenanthrene, 2-methylphenanthrene and 2,3-benzofluorene, on Zn
dust distillation of shilajit HAS. The same degradation products were also obtained when
soil-sediment HAS were subjected to Zn dust distillation. Thus, some inherent structural
similarities were indicated for shilajit and other common HAS.
Variations in chemical characteristics and biological actions were observed in the humic
substances of shilajit itself having different consistencies, e.g. dark brittle (over
exposed), brown viscous (mature), and free-flowing liquid (premature shilajit). This may
be due to the fact that humus reserve is a complex mass whose complexity is determined by
the intensity of several factors: (a) the rate of formation of fresh humus; (b) adsorption
of plant root exudates and leached materials from debris of plants and microorganisms to
humus reserve; (c) the rate of decomposition of the caged and free low mol. wt. compounds;
and (d) the rate of decomposition of HAS and FAs into humin and other intractable products.
Hence the quality of humus, which primarily acts as the liposomic carrier of low mol. wt.
bioactive compounds of shilajit, would constitute an important determinant to the
therapeutic potential of shilajit. It was, therefore, thought necessary to determine the
biological activity profiles of the low mol. wt. organic compounds and the HAS and FAs of
shilajit, individually and in combinations, to evaluate their additive and synergistic
potential.
..
(1 1 R1=R4=H, R2=R3=OMe (4) R~=R~=H
(2) R1=RgR$H R4= C02Me (5 1 R1= Me, R2=H
(3) R1 =OMe,R2;R3=H,RkCO2Me (6) R1=H,R2=OH
9 &:
Ho 4 00
HO c15 H31 - n
C02 H
n = 0,2,4
1 2 (lla) R =C02H, R =Me
(llb) R’=Me, R2=C02H
(12a) R1 =C02H, R 2 =Me
(12b) R1 =Me, R2= C02H
BlOACTlVlTY OF SHlLAJlT AND ITS CONSTITUENTS
Clinical applications of shilajit in Ayurveda, as a rasayan, are well documented (refs.
1,3). However, no modern scientific study was carried out before on the mode of action of
shilajit. The effects of shilajit, as reported in the Ayurvedic literature, seem to
suggest its influence on endocrine, autonomic, and brain functional changes. The
discovery that these changes can be mediated by cytokines, released by activated
immunologic cells (ref. 11>, has opened up possibilities for similar mechanism of action 1288 S. GHOSAL
of shilajit. Certain combinations of the phenolic and triterpenoid constituents, and the
FAs of shilajit produced significant effects against restraint stress-induced ulcers (ref.
6). The mechanism of anti-ulcerogenic actions of shilajit and its constituents was also
evaluated (ref.6). This was based on their effects on mucin contents, and on the
concentrations of DNA and protein in the gastric juice. The combinations provided
significant resistance to mucosa against the effects of ulcerogens and also prevented the
shedding of mucosal cells. The anti-allergic action of these compounds was successfully
tested against antigen- and compound 48/80 (histamine releaser)- induced degranulation of
mast cells (ref. 12). The anti-stress activity of these compounds was suggested by their
augmentation of murine swimming endurance exercises. Shilajit and its combined
constituents also elicited and activated, in different degrees, murine peritoneal
macrophages and activated splenocytes of tumour-bearing animals at early and later stages
(unresponsive) of tumour growth (tested according to ref.13). Shilajit from USSR, and its
corresponding combined fractions, acted essentially as cell-growth factors in both normal
and tumour cells by maintaining membrane integrity. The results obtained till now are
sufficiently impressive to warrant expectation that more extensive and comprehensive
studies on shilajit and its constituents would validate the Ayurvedic rasayan, shilajit, as more effective than several currently available clinically efficacious immunomodulators
(refs. 14, 15).
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