ABSTRACT
There are about 500,000 species of plants growing on the earth and it is estimated that
at least 5000 different chemical compounds of secondary metabolites are present in a
single species of plant. It is apparent that the secondary metabolites of plant origin con-
stitute a tremendous resource for exploring useful drugs. In plants, the primary metabo-
lites, including proteins, lipids, nucleic acids, enzymes, and coenzymes, etc., come from
the metabolism of carbohydrates with the incorporation of nitrogen and mineral ele-
ments. By utilizing primary metabolites and numerous infinite molecules, plants syn-
thesize the secondary metabolites for the purpose of survival and well-being.
