Antimicrobial Activities of Sesquiterpene-Rich Essential Oils of Two Medicinal Plants, Lannea egregia and Emilia sonchifolia, from Nigeria.

Lannea egregia (Anacardiaceae) and Emilia sonchifolia (Asteraceae) are plants used in traditional medicine in southwestern Nigeria. The essential oils from the leaves of L. egregia and E. sonchifolia were obtained by hydrodistillation and analyzed by gas chromatography-mass spectrometry. Both essential oils were dominated by sesquiterpenoids. The major components in L. egregia leaf essential oil were α-panasinsen (34.90%), (E)-caryophyllene (12.25%), α-copaene (11.39%), and selina-4,11-diene (9.29%), while E. sonchifolia essential oil was rich in γ-himachalene (25.16%), (E)-caryophyllene (15.72%), and γ-gurjunene (8.58%). The essential oils were screened for antimicrobial activity against a panel of bacteria and fungi and displayed minimum inhibitory concentrations ranging from 156 µg/mL to 625 µg/mL. Based on these results, either L. egregia or E. sonchifolia essential oil may be recommended for exploration as complementary antibacterial or antifungal agents.

Composition of the Essential Oil and Insecticidal Activity of Launaea taraxacifolia (Willd.) Amin ex C. Jeffrey Growing in Nigeria.

The rice weevil (Sitophilus oryzae) is a pest of stored grain products such as rice, wheat, and corn. Essential oils represent a green environmentally-friendly alternative to synthetic pesticides for controlling stored-product insect pests. Launaea taraxacifolia is a leafy vegetable plant found in several parts of Nigeria. The leaves are eaten either fresh as a salad or cooked as a sauce. The essential oil obtained from fresh leaves of L. taraxacifolia was obtained by hydrodistillation and analyzed by gas chromatography/mass spectrometry (GC-MS). Twenty-nine compounds were identified, accounting for 100% of the oil composition. The major component classes were monoterpene hydrocarbons (78.1%), followed by oxygenated monoterpenoids (16.2%), sesquiterpene hydrocarbons (2.1%), oxygenated sesquiterpenoids (0.3%), and non-terpenoid derivatives (3.3%). The leaf essential oil was dominated by monoterpene hydrocarbons including limonene (48.8%), sabinene (18.8%), and (E)-ß-ocimene (4.6%), along with the monoterpenoid aldehyde citronellal (11.0%). The contact insecticidal activity of L. taraxacifolia essential oil against Sitophilus oryzae was carried out; median lethal concentration (LC50) values of topical exposure of L. taraxacifolia essential oil were assessed over a 120-h period. The LC50 values ranged from 54.38 µL/mL (24 h) to 10.10 µL/mL (120 h). The insecticidal activity of the L. taraxacifolia essential oil can be attributed to major components limonene (48.8%), sabinene (18.8%), and citronellal (11.0%), as well as potential synergistic action of the essential oil components. This result showed L. taraxacifolia essential oil may be considered as a useful alternative to synthetic insecticides.

Compositional analysis of the essential oil of Boswellia dalzielii frankincense from West Africa reveals two major chemotypes.

Frankincense, an oleoresin produced by Boswellia species, has historical medicinal and religious significance, and is today used extensively for its essential oil. Boswellia dalzielii, a species found in West Africa, is one of the few frankincense species for which there is no information on the oleoresin essential oil. In order to correct this deficiency, the chemical compositions of the essential oil hydrodistilled from 21 samples of oleoresin taken directly from B. dalzielii trees in northern Nigeria, were analyzed by gas chromatography - mass spectrometry as well as chiral gas chromatography. In addition, a hierarchical cluster analysis was performed on the essential oil compositions from the 21 oleoresin samples from northern Nigeria as well as two samples from Ghana. The essential oil fractions obtained by hydrodistillation of B. dalzielii oleoresins were dominated by α-pinene (21.7-76.6%), followed by α-thujene (2.0-17.6%), myrcene (up to 35.2%), p-cymene (0.3-15.6%), and limonene (1.1-32.9%). The levorotatory enantiomers predominated for the monoterpenes with 98.1 ±â€¯1.5% (-)-α-thujene, 99.2 ±â€¯0.5% (-)-α-pinene, and 96.8 ±â€¯1.4% (-)-ß-pinene. Limonene showed the largest variation in enantiomeric distribution [67.3 ±â€¯12.1% (-)-limonene]. The cluster analysis revealed two major chemotypes, one dominated by α-pinene and one much rarer chemotype rich in myrcene.

The volatile constituents of Parquetina nigrescens from southwestern Nigeria.

The leaf essential oil of Parquetina nigrescens collected from Badary, Nigeria, was obtained by hydrodistillation and analyzed by gas chromatography - mass spectrometry. The essential oil had a simple composition with only five identified components. The oil was dominated by citral (35.0% neral and 53.7% geranial). The high concentration of citral in the essential oil likely contributes to the ethnomedicinal utility and bioactivities associated with this medicinal plant.

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 ß-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.

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.

Essential oil composition and insecticidal activity of Blumea perrottetiana growing in southwestern Nigeria.

The essential oil from the aerial parts of Blumea perrottetiana was obtained by hydrodistillation and analyzed by GC-MS. The volatile oil is dominated by 2,5-dimethoxy-p-cymene (30.0%) and 1,8-cineole (11.0%) with lesser amounts of sabinene (8.1%), delta-cadinene (5.3%) and (E)-caryophyllene (3.9%). The essential oil demonstrated notable insecticidal activity against the red flour beetle, Tribolium castaneum, consistent with traditional uses of the plant as an insecticide and anthelmintic.

The effect of essential oil formulations for potato sprout suppression.

The concerns over safety and environmental impact of synthetic pesticides such as chlorpropham (CIPC) has stimulated interest in finding environmentally benign, natural sprout suppressants, including essential oils. The effects of Chenopodium ambrosioides and Lippia multiflora essential oils on sprout growth and decay of stored potatoes has been investigated. Formulations of essential oils with alumina, bentonite, or kaolin, both with and without Triton X-100 additive, were tested. These formulations have been compared to the pulverized plant materials themselves as well as wick-volatilized essential oils. The results showed that the tested oils possess compositions that make them suitable for application as sprout suppressants. Additionally, the formulation seems to be able to reduce the volatility of the essential oil and artificially extend dormancy of stored potatoes.

Volatile constituents and antibacterial screening of the essential oil of Chenopodium ambrosioides L. growing in Nigeria.

The essential oil of the aerial parts of Chenopodium ambrosioides L. has been isolated by hydrodistillation and analyzed using GC-MS. The major components were found to be alpha-terpinene (63.1%), p-cymene (26.4%) and ascaridole (3.9%). The oil displayed no antibacterial activity against either Gram-positive bacteria Bacillus cereus or Staphylococcus aureus, or the Gram-negative bacterium Escherichia coli (MIC=1250 microg/mL). A cluster analysis of C. ambrosioides essential oils reveals at least seven distinct chemotypes: ascaridole, alpha-terpinene, alpha-pinene, p-cymene, carvacrol, alpha-terpinyl acetate, and limonene.