Moses S. Owolabi

Evaluation of the Inhibition of Carbohydrate Hydrolyzing Enzymes, the Antioxidant Activity, and the Polyphenolic Content of Citrus limetta Peel Extract

Type 2 diabetes mellitus is one of the most frequent causes of death in Mexico, characterized by chronic hyperglycemia. One alternative strategy for this metabolic abnormality is inhibiting the enzymes responsible for the metabolism of carbohydrates. We evaluated whether the aqueous Citrus limetta peel extract could inhibit the metabolism of carbohydrates. We found that this extract inhibited primarily the enzyme α-amylase by 49.6% at a concentration of 20 mg/mL and to a lesser extent the enzyme α-glucosidase with an inhibition of 28.2% at the same concentration. This inhibition is likely due to the high polyphenol content in the Citrus limetta peel (19.1 mg GAE/g). Antioxidant activity of the Citrus limetta peel demonstrated dose-dependent antioxidant activity, varying from 6.5% at 1.125 mg/mL to 42.5% at 20 mg/mL. The study of these polyphenolic compounds having both antihyperglycemic and antioxidant activities may provide a new approach to the management of type 2 diabetes mellitus.

Insecticidal Activity and Chemical Composition of the Morinda lucida Essential Oil against Pulse Beetle Callosobruchus maculatus

Insecticidal activity of essential oil extracted from Morinda lucida was tested on pulse beetle Callosobruchus maculatus, which is a pest that causes serious damage to several pulses. The insecticidal activity was compared with two pesticides, Phostoxin and Primo-ban-20. 120 mixed sex adult C. maculatus were introduced, along with 30 g of cowpeas. Four concentrations (0.40, 0.20, 0.10, and 0.05 μg/mL) of the M. lucida essential oil, Phostoxin, and Primo-ban-20 were tested. Essential oil chemical composition was analyzed by GC-MS. M. lucida essential oil showed a high toxicological effect, producing 100% mortality after 72 hours at a dose of 0.20 μg/mL. M. lucida essential oil had a potent insecticidal activity (LC90 = 0.629 μg/mL) compared to both pesticides, Phostoxin (LC90 = 0.652 μg/mL) and Primo-ban-20 (LC90 = 0.726 μg/mL), at 24 h. The main compounds of the essential oil were the oxygenated monoterpenoids, 1,8-cineole (43.4%), and α-terpinyl acetate (14.5%), and the monoterpene hydrocarbons, mostly sabinene (8.2%) and β-pinene (4.0%). Results clearly indicate that M. lucida essential oil can be used as an effective alternative for pulse beetle C. maculatus control, and it could be tested against other pulse beetles affecting Asia and Africa and throughout the world, thereby reducing use of synthetic pesticides.

Cymbopogon citratus (DC) Stapf Volatile Oil from South - West, Nigeria

Abstract Chemical analysis of the volatile oil of Cymbopogon citratus and its antibacterial effects were investigated. Chemical analysis of the C. citratus oil was determined using Gas Chromatograph-Mass Spectrometry technique. Out of 47 peaks (representing 97.36 % of the total oil), 37 constituents were identified representing 90.86 % of the total oil constituents. The major constituents were geranial (40.9 %), neral (29.7 %), myrcene (11.3 %), linalool (1.7 %) and geranylacetate (1.6 %). The oil was examined against six bacteria; Escherichia coli, Pseudomonas aeruginosa, Salmonella typhimurium, Klebsiella pneumonia, Serratia marcescens and Staphlycoccus aureus. It was found that C. citratus inhibited the growth of all tested microorganism.

Chemical Composition of the Seed Volatiles of Aframomum sceptrum (Oliv. & T. Hanb.) K. Schum. from Nigeria

Abstract The steam distilled volatile oil obtained from pulverized Aframomum sceptrum seeds was examined by gas chromatography-mass spectrometry (GC-MS). The major components were 1,8-cineole (81.9 %), α-terpineol (10.1 %) and β-pinene (4.8 %). The oil displayed no antibacterial activity against either Gram positive organisms such as Bacillus cereus, Staphylococcus aureus, or Gram negative organisms such as Escherichia coli, (MIC = 625 μg/mL).

Chemical Composition of Essential Oil from the Leaves of Clerodendrum polycephalum Baker growing in Nigeria

Abstract The essential oil obtained from the hydrodistillation of the leaf of Clerodendrum polycephalum Baker collected from Badagary, Nigeria was analyzed by gas chromatography-flame ionization detector (GC-FID) and gas chromatography-mass spectrometry (GC-MS). Forty compounds, representing 97.2 % of the total oil contents were identified in the essential oil. Sesquiterpene hydrocarbons (74.1 %) and oxygenated sesquiterpene (11.9 %) are main classes of compounds present in the oil. Monoterpene compounds totalling 10.6 % of the oil contents were also identified in the oil. The main constituents of the oil were β-caryophyllene (28.9 %), α-muurolene (9.0 %) and β-pinene (8.6 %). There were significant amounts of 1,5,9,9-tetramethyl-Z,Z,Z,Z-cycloundecatriene (7.4 %), 9-epi-(E)-caryophyllene (5.6 %) and (E)-nerolidol (5.5 %). The present study represents the first report on the chemical constituents of the volatile oil of Clerodendrum polycephalum.

Chemical Composition, Antibacterial Activity, and Brine Shrimp Lethality Test of Essential Oil from the Leaves of Eugenia natalitia

Eugenia natalitia Sond. (Myrtaceae) is a shrub or small to medium-sized tree (ca. 5–10 m in height) found in coastal and montane evergreen forests of Southern Africa [1, 2]. It is a glabrous shrub or small tree, hairless throughout, copiously finely gland-dotted with opposite leaves. The authors are unaware of any literature reports on the biological potentials the plants might have exhibited or any chemical constituents it possesses. This paper reports the volatile compounds identified in the essential oil of the aerial part of E. natalitia from South Africa. Previous studies on the essential oil components of this plant species have been reported [3]. Fresh leaves of E. natalitia were collected beside the Botanical Garden, Department of Botany, University of Zululand, KwaDlangezwa, KwaZulu-Natal, South Africa, in March 2008. It was identified by Mrs. N. R. Ntuli of the same department. A voucher specimen [LAWAL, OA-25 (ZULU)] was deposited in the Herbarium of the University. The air-dried and pulverized leaves (500 g) of E. natalitia were hydrodistilled in a Clevenger-type apparatus according to the British Pharmacopoeia specifications [4] for 3 h. Gas chromatography (GC) analysis was carried out on a Hewlett Packard HP 6820 gas chromatograph equipped with an FID detector and HP-5MS column (30 m 0.25 mm ID, film thickness 0.25 m), and the split ratio was 1:25. The oven temperature was programmed from 50 C (after 2 min) to 240 C at 5 C/min, and the final temperature was held for 10 min. Injection and detector temperatures were 200 C and 240 C, respectively. Hydrogen was the carrier gas (1 mL/min). Gas chromatography-mass spectrometry (GC-MS) analyses of the oil was performed on a Hewlett Packard gas chromatograph HP 6890 interfaced with a Hewlett Packard 5973 mass spectrometer system equipped with an HP 5-MS capillary column (30 m 0.25 mm ID, film thickness 0.25 m). The oven temperature was programmed from 70–240 C at the rate of 5 C/min. The ion source was set at 240 C, and electron ionization at 70 eV. Helium was used as the carrier gas at a flow rate of 1 mL/min. Scanning range was 35 to 425 amu; 1.0 L of diluted oil in hexane was injected into the GC/MS. The components of the oil were identified based on a comparison of their retention indices and mass spectra with known standards and with the Wiley library mass spectra database for the GC/MS system and published data [5, 6]. The essential oil of E. natalitia was tested for its antibacterial potential by the agar disc diffusion method according to an established procedures [7, 8]. The brine shrimp (Artemia salina) lethality test of the essential oil was carried out according to the previously described procedures [9, 10]. Data are presented as mean ± standard error of the mean (SEM). The level of statistical significance was taken at 5% confidence level. A pale yellow oil in a yield of 0.17% (v/w), based on dry weight, was obtained from the hydrodistillation of E. natalitia. Seventeen components accounting for 95.9% of the total oil content were identified by GC/MS (Table 1).

The Leaf Essential Oil of Momordica charantia from Nigeria is Dominated by Geijerene and Pregeijerene

The leaf essential oil of Momordica charantia was obtained by hydrodistillation and analyzed by gas chromatography- mass spectrometry. The leaf oil was rich in geijerene (11.2 %), pregeijerene (27.1 %), α-pinene (14.0 %), β-pinene (7.1 %), (E)-caryophyllene (4.6 %), and germacrene D (8.6 %); remarkably different from previous reports of this plant.

Volatile Components from the Stem Bark of Vitellaria paradoxa

Abstract The volatile oil from the stem bark of Vitellaria paradoxa (shea) has been obtained by hydrodistillation and analyzed by GC-MS. The oil is characterized by a high concentration of germacrene D (21.8 %), with smaller quantities of linalool (6.5 %), (E)-caryophyllene (6.3 %), (E)-phytol (4.9 %), and β-elemene (3.8 %). The V. paradoxa bark oil was screened for antibacterial activity but was inactive (MIC ≥ 625 μg/mL).