ABSTRACT
In traditional setting, Alstoniaboonei
is used for the treatment of different ailments, this has been
attributed to its rich phytochemical and antioxidant properties.The
objective of the study was to evaluate the phytochemical properties and
antioxidant activity of the methanol, ethanol and hexane extracts of Alstoniaboonei
leaves. Qualitative analysis of phytochemical constituents such as
tannins, saponins, cardiac glycosides flavonoids and phenols were
carried out. Quantitative analysis of total phenolics, saponins and
flavonoids was performed by well-known test protocol. Antioxidant
activity reveals the presence of reactive oxygen species which helps to
scavenge free radicals that are present in the body. The in vitro
antioxidant activity was studied by diphenyl-2-picryl-hydrazyl (DPPH),
ferric reducing antioxidant power (FRAP), reducing power (RP) and
ferrous ion metal chelating. Results obtained for phytochemical studies
revealed that flavonoids were highest in ethanol extract(101.6±1.35)
while hexane extract (56.6±1.510) had the lowest content. Also phenol
was highest in methanol extract (262±4.93) and lowest in ethanol extract
(172.7±1.66). Result for total tannins (271±6) and proanthocyanidin
(200.7±2.19) indicates that methanol and ethanol extract had the
highest amount while hexane extract had and the lowest amount. IC5o values obtained by DPPH for ethanol extracts of Alstoniaboonei
(2.362µg/ml), when compared with other extracts, and was significantly
(P>0.05) lower than that of the standard vitamin C (12.81µg/ml).
Also, the ethanol extract(0.026µg/ml) showed low IC50 value
for ferrous ion metal chelating ability when compared with other
extract, but this value was non significantly(P>0.05) lower than the
standard(4.11µg/ml). Therefore, Alstoniaboonei has a great
potential for use as a natural source of antioxidant and also help in
the treatment of various ailments, or against free radical damage.