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The preliminary phytochemical analysis of the aqueous ethanolic
extract of the bark of Thespesia populnea (L.) revealed the presence of alkaloids,
unsaturated sterols, triterpenes, flavonoids and the absence of anthraquinones. The
froth test indicated the presence of saponins. Most importantly this study revealed
the presence of proanthocyanidins which has not been reported before. In the present
study, ethyl acetate and aqueous soluble proanthocyanidin fractions (EASPA and
AQSPA respectively) were extracted and purified by chromatography on Sephadex
LH-20. Prussian blue test and acid catalyzed cleavage test revealed that
proanthocyanidins have been successfully separated from non-proanthocyanidin
phenolics. The yields of purified EASPA and AQSPA fractions were 0.081% and
0.72% (by weight) of the fresh bark. Acid catalyzed cleavage followed by TLC
studies of both EASPA and AQSPA fractions showed the presence of two
anthocyanidins, cyanidin and delphinidin, suggesting that they are composed of
(epi)catechin and (epi)gallocatechin units with (epi)catechin being more abundant
compared to the other. This was further confirmed by 13C NMR spectroscopic
studies. In addition, 13C NMR spectroscopic studies revealed (epi)catechin to be the
epi-isomer. The preliminary antioxidant activity of purified EASPA and AQSPA
fractions was determined using the DPPH assay. The IC50 values of EASPA and
AQSPA (0.0725 mg/mL and 0.0781 mg/mL respectively) were clearly lower than
that of ascorbic acid (0.125 mg/mL), which is an established standard used in
antioxidant studies. Thus, proanthocyanidin samples appear to possess better
antioxidant capacity than ascorbic acid. In addition, EASPA and AQSPA fractions
were shown to mediate cytotoxic activity against MCF 7 cells through SRB assay.
