Usman Lamidi Ajao

@unilorin.edu.ng

Professor, Chemistry, Physical Sciences
University of Ilorin



                       

https://researchid.co/ajike_23

RESEARCH, TEACHING, or OTHER INTERESTS

Chemistry, Organic Chemistry

32

Scopus Publications

Scopus Publications

  • Effect of Time of Harvest on the Chemical Composition and Antioxidant Potential of Leaf Essential Oil of Syzygium guineense Growing in North Central Nigeria (Willd.) Dc. Var.
    Ajao Lamidi Usman, Ridwan Olanrewaju Ismaeel, and Alfanla Kamaldeen Musa

    Sociedad Quimica de Mexico, A.C.
    Abstract. The use of synthetic antioxidants to ameliorate oxidative stress goes with side effects. Some plants are known to be sources of natural antioxidants and, hence, could be used as alternatives to synthetic antioxidants without side effects. Meanwhile, the presence of the phytochemicals that exhibit antioxidant activity in plants depends on environmental conditions that vary with the time of harvest of plant materials. This study, therefore, investigated the effect of time of harvest on the chemical composition and antioxidant potential of leaf essential oil of Syzygium guineense native to North central Nigeria. To accomplish these, pulverized (500 g) leaves of S. guineense harvested in the morning and afternoon were separately hydrodistilled and yielded 0.25 ± 0.002 % (w/w) and 0.27 ± 0.003 % (w/w) of essential oils. Characterization of the oils using GC-MS revealed the presence of twenty-two and twenty-three compounds in the oils from morning and afternoon harvests. The most abundant compound in the oils was β-bergamotene (30.1 % and 27.3 %). D-limonene (2.9 % and 5.6 %), β-ocimene (4.2 % and 10.2 %), α-santalene (7.4 % and 7.7 %), α-cedrene (8.6 % and 9.0 %), β-farnesene (9.1 % and 10.2 %) and calamenene (7.1 % and 5.2 %) were detected in significant quantities in the oils. DPPH radial scavenging assay was used to evaluate the antioxidant activity of the oils with butylated hydroxyl toluene (BHT) as standard. The oils exhibited antioxidant activity with IC50 of 41.92 μg/mL and 33.12 μg/mL for the oils from morning and afternoon harvests. Although the oils exhibited lower antioxidant activity than the standard (IC50 of 28.63 μg/mL), but the oils could be used to ameliorate oxidative stress after clinical trials.


  • PHYTOCHEMICAL PROFILE, ANTIOXIDANT AND ANTIDIABETIC POTENTIAL OF ESSENTIAL OIL FROM FRESH AND DRIED LEAVES OF Eucalyptus globulus
    L. A. Usman, O. S. Oguntoye, and R. O. Ismaeel

    SciELO Agencia Nacional de Investigacion y Desarrollo (ANID)
    Pathogenesis of type 2 diabetes has been linked to oxidative stress. Synthetic drugs in use for the management of the stress and type 2 diabetes are expensive and their usage are associated with side effects. Some essential oils exhibited antioxidant and antidiabetic properties devoid of the side effects. Their activities are attributed to the type of phytochemicals whose presence in the oils of the fresh and dried samples are determined by environmental factors. This study therefore aimed at monitoring the effect of air-drying at ambient temperature on the phytochemical profile, antidiabetic and antioxidant potentials of leaf essential oils of E. globulus. To achieve this, 500 g of fresh and dried leaves of E. globulus were separately pulverized and hydrodistilled for three hours. The leaves yielded oils in the range of 0.22–0.55% (w/w). GC and GC–MS analyses of the oils revealed predominance of α-phellandrene (4.6–10.5%), D-limonene (18.5%), β-myrcene (20.8%), m-cymene (5.0-29.8%), terpinen-4-ol (0.4-4.7%), globulol (3.1-10.5%) and spathulenol (4.9-18.8%). The antioxidant activity of the oils was determined by DPPH and FRAP assays using ascorbic acid as standard. α-Amylase and α-glucosidase inhibitory assays were used to determine the antidiabetic potential of the oils using acarbose as standard. The oils exhibited antioxidant and antidiabetic activities that compared favourably with the standards. Meanwhile, the oil obtained from the leaves air-dried for three days showed the highest activities with competitive mode of α-amylase and α-glucosidase inhibitions. The oil could serve as alternative for the management of oxidative stress and type 2 diabetes.


  • Chemical Composition of Root Essential oil of Peperomia pellucida (L.) Kunth. Grown in Nigeria
    L.A. Usman and R.O. Ismaeel

    Informa UK Limited
    Abstract Essential oil from leaf, root, and stem of Peperomia pellucida native to different countries have been isolated and characterized. Variations in the chemical composition of the essential oil from the same part of the plant were established. Meanwhile, the root essential oil of P. pellucida native to Nigeria has not been studied. This work aimed at characterizing the root essential oil of P. pellucida growing in Nigeria. To achieve this, pulverized roots (500 g) of P. pellucida were hydrodistilled and yielded 0.03±0.12 % (w/w) of essential oil. Analysis of the essential oil using GC and GC/MS showed the presence of twenty-three chemical compounds. The essential oil was predominated by sesquiterpenoids, which constituted 87.5 % of the oil. Monoterpenoids constituted 2.9 % of the oil. β-fernesene (22.2 %) was the most predominant compound in the essential oil. Other principal constituents of the oil were; β-bisabolene (14.8 %), β-bergamotene (10.7 %), 1,4- cadinadiene (7.4 %), α-copaene (6.6 %) and isosativene (6.5 %). Terpinen-4-ol (2.3 %) was the major monoterpenoid in the oil, while neryl acetate (0.6 %) existed in appreciable quantity. The predominance of β- fernesene in the oil implied that the oil was of β-farnesene chemotype.

  • Effect of Seasonal Variation on Chemical Composition, Antidiabetic and Antioxidant Potentials of Leaf Essential Oil of Eucalyptus globulus L.
    L.A. Usman, O.S. Oguntoye, and R.O. Ismaeel

    Informa UK Limited
    Abstract This study investigated the effect of seasonal variation on the chemical composition, antioxidant and antidiabetic activities of essential oil from leaves of Eucalyptus globulus. Pulverized leaves (500 g) of E. globulus from dry and rainy season harvests afforded 0.54 and 0.43 % (w/w) of essential oils respectively when subjected to hydrodistillation. GC and GC/MS analyses revealed the presence of forty-five and thirty-three compounds that represented 95.4 and 98.4 % of the oils obtained from leaves harvested during the dry and rainy seasons. The principal constituents of the essential oils were; D-limonene, m-cymene, o-cymene, 6-camphenol, terpinen-4-ol, globulol, diosphenol and spathulenol. The oils showed scavenging activity for DPPH radical with IC50 of 20.15 (dry) and 11.23 μL/mL (rainy). The essential oils showed significant reducing powers of 356.46±0.88 (dry) and 394.34±0.95 (rainy) FRAP equivalent. The oils inhibited the activity of α-amylase with IC50 of 8.37 (dry) and 6.78 (rainy) μg/mL. The IC50 for the α-glucosidase inhibition of the oils were 6.19 (dry) and 7.20 (rainy) μg/mL. The antioxidant and antidiabetic activities of the oils compared favourably with the standards used for the study. Hence, the essential oils can serve as an alternative to synthetic drugs to ameliorate oxidative stress and management of type 2 diabetes.

  • Chemical Composition and Antioxidant Potential of Fruit Essential Oil of Laggera pterodonta (DC.) Benth Grown in North Central, Nigeria
    L.A. Usman and R.O. Ismaeel

    Informa UK Limited
    Abstract This study aimed at isolating, characterizing and evaluating the antioxidant potential of fruit essential oil of Laggera pterodonta native to Nigeria. Pulverized fruits (500 g) of L. pterodonta were hydrodistilled for 3 hours and yielded 0.07±0.02 % (w/w) of essential oil. The oil was analyzed using GC and GC-MS. The analyses revealed the predominance of sesquiterpenoids (92.7 %), while monoterpenoids constituted 1.5 % of the oil. The major compounds in the oil were α-bergamotene (29.3 %), β-bisabolene (16.9 %), α-copaene (8.8 %) and α-bisabolol (6.0 %). Terpinen-4-ol (0.5 %) and α-terpineole (1.0 %) were the only monoterpenoids detected in the oil. The antioxidant activity of the oil was determined using 2,2-diphenyl- 1-picryl hydrazyl (DPPH) radical scavenging assay. The oil exhibited antioxidant activity by scavenging DPPH radicals with IC50 of 6.05 μL/mL. The activity of the oil was higher than the activity of ascorbic acid with IC50 of 12.84 μl/ml used as standard. Therefore, the oil could serve as an alternative to synthetic drugs for the amelioration of oxidative stress.


  • Antidiabetic Potentials of Citrus aurantifolia Leaf Essential Oil
    Fatima Ibrahim, Lamidi Usman, Jubril Akolade, Oluwafemi Idowu, Azeemat Abdulazeez, and Aliyu Amuzat

    Georg Thieme Verlag KG
    Abstract Citrus aurantifolia leaf essential oil was extracted via hydrodistillation, chemical composition of the oil was analyzed using gas chromatography-mass spectrometry and its antidiabetic potentials was assessed in alloxan-induced hyperglycaemic rats using metformin as the reference drug for comparison. Chemical analysis showed that D-limonene (57.84%) was the major constituent of the oil. Other notable compounds identified were neral (7.81%), linalool (4.75%), sulcatone (3.48%) and isogeraniol (3.48%). Intraperitoneal administration of C. aurantifolia oil (100 mg/Kg b.wt.) to hyperglycaemic rats for 14 days caused significant reduction in fasting blood and hepatic glucose, whereas hepatic concentration of glycogen was significantly increased. Also, improvement in dyslipidaemia was observed in C. aurantifolia essential oil-treated hyperglycaemic rats; serum concentration of total cholesterol, triacylglycerol and low density lipoprotein-cholesterol were significantly reduced and high density lipoprotein-cholesterol was increased, resulting in decreased predisposition of rats to cardiac risks. Antihyperglycaemic potential of administration of the oil was lower but compared favourably with the oral antihyperglycaemic agent used as reference antidiabetic drug. Overall, data from this study showed that essential oil from the leaf of C. aurantifolia grown in North-Central Nigeria is a D-limonene chemotype. The oil showed considerable glucose lowering effect as well as the potential to ameliorate hyperglycaemia-induced dyslipidaemic complications in alloxanized rats.

  • Effect on germination and nutrient composition of storing cowpea [Vigna unguiculata (L.) Walp.] seeds in a hermetic atmosphere modified with essential oil vapour from leaves of sweet basil [Ocimum basilicum (L.)]


  • Evaluation of selected Nigerian medicinal plants for in vitro antiprotozoal activity
    Stephen O. Oguntoye, Oluwasesan M. Bello, Pius S. Fasinu, Ikhlas A. Khan, Zulfiqur Ali, Shabana I. Khan, and Lamidi A. Usman

    Bentham Science Publishers Ltd.

  • Assessment of selected medicinal plants indigenous to West Africa for antiprotozoal activity
    O.M. Bello, A.A. Zaki, S.I. Khan, P.S. Fasinu, Z. Ali, I.A. Khan, L.A. Usman, and O.S. Oguntoye

    Elsevier BV

  • Preservation of smoked African catfish, clarias gariepinus burchell against dermestes maculatus de geer (Coleoptera: Dermestidae) using neem seed oil-iodized salt mixtures


  • Chemical Composition and Antibacterial Activity of Fruit Essential Oil of Xylopia aethiopica D. Grown in Nigeria
    L.A. Usman, J.O. Akolade, B.O. Odebisi, and B. Olanipekun

    Informa UK Limited
    Abstract Qualitative and quantitative analyses of the chemical constituents of fruit essential oil of Xylopia aethiopica and its antibacterial activity were investigated. Pulverized fruit of X. aethiopica was hydrodistilled in a Clevenger type apparatus. The resulting oil was characterized by Gas chromatography-Mass spectrometry (GC-MS) and its antibacterial activity was evaluated using agar diffusion method. Hydro-distilled X. aethiopica fruits yielded 1.3% v/w of essential oil. Investigation by GC-MS revealed that bulk of the oil was constituted by hydrocarbon monoterpenes (44.0%). The major constituents of the oil were; Eugenol (12.2%), acetyleugenol (7.0%), 1,8-cineole (6.8%), sabinene (6.7%), cis-ocimene (6.2%), β-caryophyllene (5.6%), γ-terpinene (5.3%), α-pinene (4.3%), β-linalool (4.3%), α-terpineol (4.1%), pinocarveol (3.7%), terpinene-4acetate (3.6%), α-thugene (3.6%), β-phellandrene (3.5%) and benzylbenzoate (3.3%). The oil showed various degree of inhibitory effect against three gram positive bacteria; Streptococcus pyogenes, Staphylococcus aureus, Bacillus subtilis and four gram negative bacteria; Enterobacter aerogenes, Klebsiella pneumoniae, Escherichia coli, Serratia marcescens, while no activity was recorded against Proteus mirabilis. The calculated activity index compared favourably with the standard gentamycin antibiotic used as control. Data from this study showed that aromatic compounds predominates the fruit essential oil of X. aethiopica growing in North Central Nigeria and the oil is active against a broad spectrum of clinical bacterial isolates.

  • Toxicity and repellency of Hoslundia opposita Vahl (Lamiaceae) leaves' essential oil against rust-red flour beetle, Tribolium castaneum Herbst (Coleoptera: Tenebrionidae)
    Samuel Adelani Babarinde, Adeyemi Oluseye Akinyemi, Lamidi Ajao Usman, Adeola Foluke Odewole, Abraham Opeola Sangodele, Oluwaseun Olasupo Iyiola, and Oluwatoyin Deborah Olalere

    Informa UK Limited
    The insecticidal properties of Hoslundia opposita Vahl (Lamiaceae) leaves' essential oil (EO) against Tribolium castaneum were investigated using contact toxicity and repellency bioassays. Mortality progressed with exposure period and ranged from 61.13% observed at 24 h after treatment (HAT) to 88.86% at 168 HAT. The LT50 (lethal time for 50% of treated adults) of H. opposita EO against T. castaneum was 10.42 h. Application of EO at 20–30 μL/30 cm2 caused significantly (P < 0.05) higher percentage repellency than what was observed in control, 10 and 15 μL/30 cm2 at 1 and 3 HAT, with significant repellency at 24 HAT regardless of dosage. Repellency class increased with EO dosage, with class V observed at 30 μL/30 cm2, regardless of exposure duration. The RD50 (repellency dose for 50% of treated adults) of 15.88 and 13.37 μL/30 cm2 for 1 and 2 HAT, respectively, was significantly higher than 0.09 μL/30 cm2 at 24 HAT.

  • Antidiabetic potentials of essential oil extracted from the leaves of hoslundia opposita vahl.
    Jubril Olayinka Akolade, Lamidi Ajao Usman, Omoaruemike Ebele Okereke, and Nasir Olarewaju Muhammad

    Mary Ann Liebert Inc
    Abstract This study was aimed at assessing the potential of essential oil from the leaf of Hoslundia opposita in the treatment of diabetes. Forty-eight rats (Rattus norvegicus) were randomized into two groups; nondiabetic and diabetic groups, each with four subgroups. Animals in the diabetic group were induced with diabetes using a single dose of alloxan monohydrate, 160 mg/kg body weight (b. wt.). The rats were treated with 110 and 220 mg/kg b. wt. of the essential oil. All treatments were administered, intraperitoneally, once a day for 4 days. In the nondiabetic condition, there was no effect of the oil on fasting blood glucose (FBG) levels in rats. In diabetic rats, the oil caused a significant reduction in FBG levels. Treatment with 110 mg/kg b. wt. of the oil reduced FBG almost to the normoglycemic level by day 4 and the overall glucose excursion during a 3-h intraperitoneal glucose tolerance test approached the baseline level at 120 min. Also, hepatic glycogen was significantly higher, while the glu...

  • Haematological parameters of alloxan-induced diabetic rats treated with leaf essential oil of Hoslundia opposita (Vahl)


  • A review on conversion of triglycerides to on-specification diesel fuels without additional inputs
    Olusola O. James, Sudip Maity, M. Adediran Mesubi, Lamidi A. Usman, Kolawole O. Ajanaku, Tolu O. Siyanbola, Satanand Sahu, and Rashmi Chaubey

    Hindawi Limited
    Dependence on fossil fuels for global energy supply has continued to generate concerns about climate change and sustainable development. It has motivated the search for carbon‐neutral alternative resources for the production of transportation fuels to replace crude oil. Although biodiesels have recently emerged as a close substitute to petrol diesel, their use in compression ignition engines designed to run on petro‐diesel fuels are linked to adverse effects on the engines' performance and life span. This informed efforts at upgrading biodiesel or direct conversion of triglycerides to hydrocarbon mixtures that are identical or similar to that of petro‐diesel through hydrodeoxygenation. Moreover, it seems that commercial methods for the conversion of triglycerides to diesel fuels depends on inputs (methanol and hydrogen) derived from fossil fuels. However, it will be desirable to do so without inputs from fossil fuels. Hence, reaction paths for direct conversion of triglycerides to on‐specification hydrocarbons fuels without hydrogen gas input are discussed and suggested strategies are in cognisance of green chemistry principles. Copyright © 2012 John Wiley & Sons, Ltd.

  • Bioactivity of rhizome essential oils from two varieties of Cyperus articulatus (L.) grown in Nigeria, using brine shrimp (Artemia salina) lethality tests


  • Bioactive Steroid from the Root Bark of Psorospermum corymbiferum
    MF Zubair, IA Oladosu, NO Olawore, LA Usman, CO Fakunle, AA Hamid, and MS Ali

    Elsevier BV

  • Effect of oral administration of ethanolic leaf extract of acanthospermum hispidium DC from Nigeria on some selected rat kidney enzyme activities


  • Chemical constituents and anti-inflammatory activity of leaf essential oil of Nigerian grown Chenopodium album L


  • Towards the conversion of carbohydrate biomass feedstocks to biofuels via hydroxylmethylfurfural
    Olusola O. James, Sudip Maity, Lamidi Ajao Usman, Kolawole O. Ajanaku, Olayinka O. Ajani, Tolu O. Siyanbola, Satanand Sahu, and Rashmi Chaubey

    Royal Society of Chemistry (RSC)
    This review appraises the chemical conversion processes recently reported for the production of hydroxylmethylfurfural (HMF), a key biorefining intermediate, from carbohydrate biomass feedstocks. Catalytic sites or groups required for the efficient and selective conversion of hexose substrates to HMF are examined. The principle of concerted catalysis was used to rationalise the dehydration of fructose and glucose to HMF in non-aqueous media. A survey of reported reaction routes to diesel-range biofuel intermediates from HMF or furfural is presented and self-condensation reaction routes for linking two or more HMF and furfural units together toward obtaining kerosene and diesel-range biofuel intermediates are highlighted. The reaction routes include: benzoin condensation, condensation of furfuryl alcohols, hetero Diels–Alder reaction and ketonisation reaction. These reaction routes are yet to be exploited despite their potential for obtaining kerosene and diesel-range biofuel intermediates exclusively from furfural or hydroxylmethylfurfural.

  • Chemical constituents of leaf essential oil of north-central nigerian grown Vitex Agnus-castus


  • Environmental and health risk of bush burning


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