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Volume 2
J Chem Tech App 2018, Volume 2
BIOASSAY-DIRECTED ISOLATION OF HYPOTENSIVE ALKALOIDS FROM
HOLARRHENA PUBESCENS
Khalid Aftab
University of Karachi, Pakistan
H
olarrhena pubescens
belongs to the family Apocynacea, commonly known as “kurchi” is highly reputed in traditional medicine
as a remedy for amoebic dysentery and other intestinal ailment. Bioassay-directed fractionation by chromatographic meth-
ods the ethanolic extract of
Holarrhena pubescens
resulted in the isolation of steroidal alkaloids i.e. Holamide and Pubscinine.
Holamide showed a three proton doublet at 1.45 (J=6.56 Hz) and two AB doubles at 3.17 and 3.00 each for on proton (J=12.06
Hz) in the 1H NMR spectrum suggested that it belongs to conanine series of alkaloid (A class of compound with the steroid nu-
cleus and a five members heterocyclic ring with nitrogen). In contrast Pubscinine showed one methyl at 1.28 while the doublet is
missing a three proton singlet was observed at 2.28 due to a vinylic methyl indicated a double bond in the 18,20 – epimino ring of
the conanine series of alkaloids. In anaesthetized rats, the Holamide and Pubscinine caused a fall in blood pressure in a dose-de-
pendent manner. Pretreatment of animals Atropine completely abolished the hypotensive response of Acetycholine; whereas
hypotensive effect of Holamide and Pubscinine were not modified by Atropine. Similarly Acetylcholine produced contractile
effect in guinea-pig ileum, which was antagonized by atropine, however both (Holamide and Pubscinine) failed to produced any
stimulant response on guinea-pig ileum. These data indicate that the steroidal alkaloids i.e. Holamide and Pubscinine from
Hol-
arrhena pubescens
mediated hypotensive response through a mechanism different to that of Acetycholine.