Olusegun Ekundayo

Antimicrobial activity of the essential oils of five Eucalyptus species growing in Nigeria

At 5 mg/ml concentration, the volatile oils from the leaves of five Eucalyptus spp growing in Nigeria exhibited considerable antibacterial activity against Gram-positive and Gram-negative microorganisms and antifungal activity against C. albicans.

A Review of the Volatiles of the Annonaceae

ABSTRACT The Annonaceae is a tropical to subtropical plant family distributed from Africa, Asia, Central and South America to Australia. It consists of numerous fruit trees (custard apple—Annona atemoya, soursop—A. muricata), plants whose dried fruit are used as condiments (Ethiopian pepper—Xylopia aethiopica, Calabash nutmeg—Monodora myristica and one well-known fragrant flower (ylang ylang—Cananga odorata). The volatile composition of these and numerous other species found in 17 different genera are reviewed. More than 200 volatiles have been identified in these essential oils. These compounds are basically mono- and sesquiterpenoids. Typical constituents include α- and β-pinene, myrcene, p-cymene, limonene, linalool, and 1,8-cineole. The sesquiterpenoids represented the most common group of components. Prenyl indoles, a rare nitro-ethane and a sesquiterpenoid of a novel skeletal type also have been encountered.

Antimicrobial activity of the essential oil of Hyptis suaveolens leaves

The essential oil of Hyptis suaveolens leaves showed antibacterial activity at 5 mg/ml concentration against two gram-positive and four gram-negative bacteria.

Larvicidal activity of turmerone-rich essential oils of Curcuma longa leaf and rhizome from Nigeria on Anopheles gambiae

Abstract The essential oils from the leaves and rhizomes of Curcuma longa. L. (Zingiberaceae) were subjected to larvicidal toxicity studies on Anopheles gambiae., the malaria vector. The leaf essential oils were obtained by hydrodistillation and analyzed by gas chromatography–mass spectrometry, respectively. The rhizome oil was much more toxic to the mosquito larvae, exhibiting 100% mortality at 0.125 mg/mL with an LC50 of 0.017 mg/mL. The leaf had absolute mortality at 0.500 mg/mL with an LC50 of 0.029 mg/mL. The observed toxicities were also found to be concentration dependent. The oils were found to be composed mainly of turmerones, with the major components in the leaf volatile oil being ar-turmerone (63.4%), α-turmerone (13.7%), and β-turmerone (12.6%). ar-Turmerone (44.4%), β-turmerone (26.5%), and α-turmerone (20.8% were the main components in the rhizome. Both oils displayed overwhelming activities compared with the reference compound N,N-Diethyl-m-toluamid (DEET) which had an LC50 value of 1.09 mg/mL. The turmerone composition, especially the combination of α-turmerone and β-turmerome constituents in the oils, may be responsible for the observed larvicidal toxicities of both essential oils. The essential oils from the leaf and rhizome of this plant may find use as a source of malaria vector control agents.

Essential oil constituents of Aframomum melegueta (Roscoe) K. Schum. seeds (alligator pepper) from Nigeria

The composition of the essential oil isolated from the seeds of Aframomum melegueta (Roscoe) K. Schum. by hydrodistillation was characterized by means of gas chromatography (GC) and gas chromatography–mass spectrometry (GC–MS). A total of 27 compounds constituting 98.6% of the volatile oil were identified. Two sesquiterpene hydrocarbons: humulene and caryophyllene made up 82.6% of the volatile oil, whilst their oxides amounted to a further 9.0%. Seventeen other mono- and sesquiterpenes accounted for only 1% of the volatile oil. Five non-terpenoids were detected in trace amounts only (<0.2%). Of the 27 constituents identified, 12 are reported as components of A. melegueta for the first time. Copyright

The antimicrobial activity of roots of Jatropha podagrica (Hook).

Hexane, chloroform and methanol extracts of the rootwood and rootbarks of Jatropha podagrica were studied for their antimicrobial activity against 18 organisms. All the extracts exhibited some broad spectrum antibacterial activity, at a concentration of 20 mg/mL. The hexane extracts were generally more active than the chloroform and methanol extracts. The hexane extract of the yellow rootbark was the most active of all the extracts and its activity was comparable to that of gentamycin but better with regard to the control of S. aureus and B. cereus. Three of the extracts, hexane extract of the yellow rootbark and hexane and methanol extracts of the rootwood showed moderate antifungal activity against the yeast fungus, Candida albicans. Copyright

Essential oil constituents of Hyptis suaveolens (L.) Poit. (Bush tea) leaves from Nigeria.

Abstract The essential oil of the leaves of Hyptis suaveolens (L.) Poit. from Nigeria was isolated by hydrodistillation. The oil was analyzed by GC and GC/MS. Of the 49 components which were detected, 39 amounting to 89.5% were identified. The dominant components were sabinene (16.5%), trans-a-bergamotene and β-caryophyllene (19.8%), terpinen-4-ol (9.6%) and β-pinene (8.6%).

Chemical composition, antimicrobial, and cytotoxicity studies on S. erianthum and S. macranthum essential oils.

Context: Solanum erianthum D. Don and Solanum macranthum Dunal (Solanaceae) are widely used in traditional medicine. The leaves act as an abortifacient and in particular to treat leucorrhoea, sores, and skin irritations. Objective: This study was undertaken to characterize the volatile constituents of the leaf and fruit essential oils of S. erianthum and S. macranthum; their antimicrobial and in vitro cytotoxic bioassay against human breast and prostate tumor cells. Methods: The volatile oils were obtained by hydrodistillation and analyzed for their constituents by gas chromatography-mass spectrometry (GC-MS). Minimum Inhibitory Concentrations (MIC) were determined using the microbroth dilution technique while the cytotoxic potentials were evaluated using the Cell Titre 96(R) AQueous Non-Radioactive Cell Proliferation Assay method. Results: Solanum erianthum essential oils were characterized by the abundance of α-terpinolene (17.8%), α-phellandrene (17.5%), p-cymene (15.7%) and β-pinene (11.7%) in the leaves; α-humulene (23.1%), humulene epoxide II (20.0%), caryophyllene oxide (16.5%), methyl salicylate (11.8%) and β-caryophyllene (10.9%) in the fruits. The leaf oil of S. macranthum consisted of (E)-phytol (29.0%), pentadecanal (28.1%) and pentadecane (7.7%) while the major fruit oil constituents were α-humulene (36.5%), β-caryophyllene (17.8%), ethyl palmitate (9.4%), and methyl salicylate (8.2%). Solanum erianthum leaf volatile oil demonstrated potent inhibitory activity against Hs 578T and PC-3 human breast and prostate tumor cells respectively. In addition, the Solanum essential oils exhibited significant antimicrobial activity (19.5–625 µg/mL) on pathogens employed in the assay. Conclusion: The Solanum essential oils possess strong antimicrobial activity in addition to the potent cytotoxic potential of S. erianthum leaf oil against Hs 578T and PC-3 cells.

epi-Cubebanes from Solidago canadensis.

GC-MS of the essential oil prepared by hydrodistillation of the green parts of a specimen of Solidago canadensis collected near Katowice, Poland, revealed two new sesquiterpene hydrocarbons. Their EI mass spectra resembled the mass spectrum of beta-ylangene (1) but the retention indices of the new compounds differed markedly from this known compound. After isolation of the new compounds by preparative GC their investigation by one- and two-dimensional NMR techniques resulted in the identification of 6-epi-alpha-cubebene (2) (minor constituent, 1.5%) and 6-epi-beta-cubebene (3) (major constituent, 20.5%).

Assessing anthropogenic contamination in surface sediments of Niger Delta, Nigeria with fecal sterols and n-alkanes as indicators

The occurrence of sterols and n-alkanes in surface sediments from rivers and canals in the Niger Delta, Nigeria, determined with a gas chromatography-mass spectrometry method, was used to assess the impacts of anthropogenic activities in the area. The concentrations of total sterols (∑₈Sterol) and n-alkanes (∑₂₈n-alkane) in the sediments ranged from 133 to 2040 ng/g and 474 to 79,200 ng/g, respectively. An evaluation of the source diagnostic indices indicated that petroleum related sources (petrogenic) were the main contributor of n-alkanes in the samples, with minor contribution from higher plants waxes (biogenic), while the sterols were mainly of biogenic origin. The ratio of α-cholestanone/(α-cholestanone+β-cholestanone), a commonly used source diagnostic index, implicated no fecal contamination in most of the sediment samples under investigation. These results have established the occurrence of anthropogenic contamination in Niger Delta sediments with significant contributions from petrogenic sources.