Biochemistry

The in vitro Free Radical Scavenging Activity of aqueous, ethanol, ethylacetate and n-hexane extracts of leaves of
Datura stramonium and Ocimum gratissimum were investigated. Due to the fact that Free radicals are implicated in many
diseases including diabetes mellitus, arthritis, cancer, ageing. etc. In the treatment of these diseases, antioxidant therapy has
gained utmost importance. The phytochemical analysis was carried out by standard methods and the antioxidant activity of the
various extracts were measured on the basis of the free radical scavenging activity of the extract on stable 1, 1-diphenyl
2-picrylhyorazyl (DPPH) at varying concentrations of the plant extracts (20, 40, 60, 80 and 100 μg/ml) and absorbance was
measured at 517nm using UV-Vis spectrophotometer. The results indicated that alkaloids, flavonoids, terpenoids, steroids and
tannins were present in D. stramonium ethanol leaf extract while alkaloids, flavonoids, terpenoids and steroids were present in O.
gratissimum n-Hexane leaf extract. The percentage inhibition of the solvent extracts at 100 μg/ml - aqueous (30.77 %), ethanol
(74.90 %), ethylacetate (49.94 %) and n-hexane (69.90 %) for D. stramonium while for O. gratissimum - aqueous (45.84 %),
ethanol (49.47 %), ethylacetate (63.94 %) and n-hexane (91.14 %). Of all the extracts, n-hexane leave extract of O. gratissimum
exhibited the highest free radical scavenging activity with IC50 0.21 μg/ml compared to ethanol leave extracts of D. stramonium
with IC50 0.29 μg/ml. This study revealed that n-hexane leaf extract of Ocimum gratissimum had a more potent antioxidant
activity compared to the ethanol leaf extract of D. stramonium which had moderate antioxidant activity. Both plants extracts had
no significant difference when compared with ascorbic acid standard (0.19 μg/ml) at (P≤.05). The phytochemical profile of the
plants might be responsible for their high antioxidant activity, thus justifying wide use of O. gratissimum in diet which could
provide a source of high dietary antioxidants and D. stramonium in ethno-botanical applications.

Purification and structural identificationof the mosquito larvicidal compounds present in Ocimum gratissimum leaf extracts
against Culex quinquefasciatus mosquito larvae. The larvicidal potential of the aqueous, ethanol, ethtylacetate, n-hexane and purified
fractions of O. gratissimum were tested against the early fourth and third instars larvae of C.quinquefasciatus Mosquito species.
Larvicidal toxicity assay were performed using different concentrations and larval mortality was observed after 12 hr, 24 hr and 48 hr of
treatment respectively. Thin layer and Column chromatography were used to purify the fraction with the highest larvicidal activity while
FTIR and GC-MS were used for structural identification of the phytoconstituents. The result of phytochemical studies revealed the
presence of sterols, flavonoids, alkaloids and saponins in O. gratissimum n-Hexane extract. The effective larvicidal activity was observed
in O. gratissimum n-hexane extract against C. quinquefasciatus mosquito larvae with percentage mortality of 96% at 25ppm after 24hr
whereas LC50 and LC90 2.57 and 2.52ppm respectively. Following the bioactivity-guided fractionation,the active constituent was found in
Fraction three of O. gratissimum n-Hexane extract(F3) with percentage mortality of 100% at 100ppm after 24hr whereas LC50 and LC90
of (1.28 and 4.28ppm) respectively.Isolated from O. gratissimum n-Hexane fraction(F3) was characterized as caryophylleneoxide in
band C by spectroscopic analyses. The Lethal concentration LC50 of the isolated caryophylleneoxide was 2.21ppm and with percentage
mortality of 100%. These work showed that Caryophyllene oxides might be a potent larvicidal agent for mosquito control.