Browsing by Author "Olanipekun B. E."

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    Effect of harvesting time on phytochemical profile and antioxidant activity of essential oil from Citrus medica leaves
    (College of Natural Sciences, Al-Hikmah University, Ilorin, 2017) Usman L. A.; Ologunja S. O.; Ismaeel R. O.; Akolade J. O.; Olanipekun B. E.
    Leaves (500 g) of Citrus medica L. harvested at interval of three hours from 7.00 am to 7.00 pm on a day during dry season were separately hydrodistilled for three hours. Oil yields from the leaves ranged from 0.22 - 0.34%. GC and GC-MS analyses revealed the predominant of monoterpenoids (50.5 - 70.3%) in theoils. The percentage composition of sesquiterpenoids was in the range of 29.7 - 29.5%. The principal constituents of the oils were; ocimene (4.1 - 5.6%), D-limonene (13.5 - 19.8%), terpinene (10.8 - 17.9%), linalool (3.8 - 4.0%), citronellal (2.7 - 7.5%), terpinen-4-ol (1.2 - 8.7%), citronelol (10.1 - 13.7%), linalyanthranilate (2.5 - 9.3%), elemene (3.0 - 6.4%), bergamotene (4.1 - 6.6%), humulene (1.2 - 2.8%), caryophyllene (7.9 - 16.5%), bisabolene (3.6 - 5.2%). The oils were of D-limonene and terpinene chemotypes. Antioxidant activity assay on the oils revealed that they were biochemically active against DPPH radicals. The activity was concentration dependent with the oil from 7am harvest having the highest activity and lowest EC50. Hence, the plant may be used as an alternative to synthetic antioxidants.
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    Effects of seasonal variation on chemical constituents and insecticidal activity of leaf essential oil of Citrus limonium
    (Nigerian Society of Biochemistry and Molecular Biology, Nigeria, 2015) Usman L. A.; Olanipekun B. E.; Ismaeel R. O.; Oguntoye O. S.; Ojumoola, A. O.
    Leaves (500g) of Citrus limonium harvested in the morning (7.00 am) during dry and rainy seasons were separately hydrodistilled and yielded 0.46 and 0.30 % (w/w) of essential oils. GC and GC-MS analysis revealed that the oils obtained from dry and rainy season harvests were predominated by monoterpenoids (84.2% and 77.2%). The most abundant constituent of the oils from dry and rainy season harvests was; limonene (17.9% and 15.3%). Other principal constituents of the oils were; ȕ-pinene (8.0% and 1.5%), terpinolene (7.0% and 7.1%), citronellal (12.9% and 8.3%), carveol (8.0% and 9.0%), neral (7.9% and 8.5%). citronellol (4.4% and 5.9%) and ȕ-caryophyllene (3.3% and 5.2%). Contact toxicity bioassay was used to investigate the insecticidal activity of the oils against Callosobruchus maculatus. Irrespective of the season of harvest the oils were active against the insect. Interestingly, oils from the two harvests had comparable activity against the adult C. maculatus. Hence, seasonal variation has no significant effect on insecticidal activity of the oil on the postharvest insect pest.