Abstract:
This thesis describes the isolation and structure elucidation of secondary metabolites from
four plants Bridelia verrucosa, B. stipularis, B. tomentosa (Family: Phyllanthaceae) and
Erythrina fusca (Family: Fabaceae) as well as biological studies of the extractives from these
plants along with E. variegata (Family: Fabaceae). A total of nineteen compounds were
isolated of which three appear to be new. The structures of the isolated compounds were
elucidated mainly by spectroscopic studies including high field NMR.
The stem bark of B. verrucosa afforded eight compounds viz. glochidonol (BVSP-1, 46),
brassicasterol (BVSP-2, 47), friedelin (BVSP-4, 48); 5β-24S-ethylcholestan-3β-ol (BVSP-6,
49); stigmasterol (BVSP-34, 50); 5,5'-dihydroxysesamine (BVBC-2, 51), 3-ketoleanane (53)
and pinoresinol (BVS-65, 54). Except stigmasterol (50) and pinoresinol (54) this is the first
report of the isolation of compounds 46-49, 53 and 54 from the genus Bridelia and 51 has
been identified as a new natural product. Phytochemical investigations of methanolic extract
of the stem bark of B. stipularis provided two triterpenes namely, glut-5(6)-en-3-one (BS-01,
55), glut-5(6)-en-3α-ol (BS-06, 56) and a cholestane type compound (22E)-7-hydroxy-28methylcholesta-4,22-dien-3-one
(BS-11,
57).
All
these
are
the
first
report
of
their
occurrence
from
B. stipularis while (22E)-7-hydroxy-28-methylcholesta-4,22-dien-3-one is a new
compound. On the other hand, phytochemical investigation of methanol extract of the stem
bark of B. tomentosa yielded friedoolean-5(6),14(15)-dien-3-one (BT-1, 58), β-taraxerol (BT6,
59), D
-stigmasterone (BT-8, 60) and lupeol (BT-14, 61). This is the first report of their
occurrence from this plant and friedoolean-5(6),14(15)-dien-3-one (58) is a novel compound.
The carbon tetrachloride soluble fractions of a methanol extract of the stem bark of E. fusca
provided three flavonoids namely, shinpterocarpin (EF-7, 62), lupinifolin (EF-8, 63) and 3,9dihydroxy-4-(3,3-dimethylallyl)[6aR,11aR]-pterocarpan
(64) and a steroid, β-sitosterol (EF38,
65).
All
these
are
the
first
report
except
65
from
E.
fusca.
The
crude extracts and organic soluble material of the investigated plants and some purified
compounds were screened for their antimicrobial activity against a wide range of Grampositive
and Gram-negative microorganisms and fungi by the standardized disc diffusion
method. Kanamycin and Griseofulvin were used as reference drugs for the test.
