Félicien Avlessi

Variability in the Chemical Compositions of the Essential Oils of Five Ocimum Species from Tropical African Area

Abstract As part of our research on aromatic plants from Africa, we have analyzed, via GC and CG/MS, the essential oils from fresh leaves of five Ocimum species from tropical Africa: Ocimum basilicum L., O. gratissimum L., O. americanum L. (syn: O. canum Sims), O. lamiifolium Hochst. ex Benth. and O. minimum L. The chemical compositions of O. basilicum, O. gratissimum and O. minimum essential oils could be related to some chemotypes already defined for these three species: linalool- or methyl chavicol-types for the first species, thymol- or eugenol- or ocimenes/far- nesenes-types for the second one; finally, a high content of methyl chavicol (34.3%) and linalool (17.8%) was found in O. minimum oil, similar to that already described for a Brazilian species. On the other hand, an essential oil dominated by 1,8-cineole was described for the first time for a sample of O. americanum. Finally, the oil of O. lamiifolium, which was rich in sabinene, is chemically described for the first time.

Chemical composition and insecticidal activity of plant essential oils from Benin against Anopheles gambiae (Giles)

BackgroundInsecticide resistance in sub-Saharan Africa and especially in Benin is a major public health issue hindering the control of the malaria vectors. Each Anopheles species has developed a resistance to one or several classes of the insecticides currently in use in the field. Therefore, it is urgent to find alternative compounds to conquer the vector. In this study, the efficacies of essential oils of nine plant species, which are traditionally used to avoid mosquito bites in Benin, were investigated.MethodsEssential oils of nine plant species were extracted by hydrodistillation, and their chemical compositions were identified by GC-MS. These oils were tested on susceptible “kisumu” and resistant “ladji- Cotonou” strains of Anopheles gambiae, following WHO test procedures for insecticide resistance monitoring in malaria vector mosquitoes.ResultsDifferent chemical compositions were obtained from the essential oils of the plant species. The major constituents identified were as follows: neral and geranial for Cymbopogon citratus, Z-carveol, E-p-mentha-1(7),8-dien-2-ol and E-p-mentha-2,8-dienol for Cymbopogon giganteus, piperitone for Cymbopogon schoenanthus, citronellal and citronellol for Eucalyptus citriodora, p-cymene, caryophyllene oxide and spathulenol for Eucalyptus tereticornis, 3-tetradecanone for Cochlospermum tinctorium and Cochlospermum planchonii, methyl salicylate for Securidaca longepedunculata and ascaridole for Chenopodium ambrosioides. The diagnostic dose was 0.77% for C. citratus, 2.80% for E. tereticornis, 3.37% for E. citriodora, 4.26% for C. ambrosioides, 5.48% for C. schoenanthus and 7.36% for C. giganteus. The highest diagnostic doses were obtained with S. longepedunculata (9.84%), C. tinctorium (11.56%) and C. planchonii (15.22%), compared to permethrin 0.75%. A. gambiae cotonou, which is resistant to pyrethroids, showed significant tolerance to essential oils from C. tinctorium and S. longepedunculata as expected but was highly susceptible to all the other essential oils at the diagnostic dose.ConclusionsC. citratus, E. tereticornis, E. citriodora, C. ambrosioides and C. schoenanthus are potential promising plant sources for alternative compounds to pyrethroids, for the control of the Anopheles malaria vector in Benin. The efficacy of their essential oils is possibly based on their chemical compositions in which major and/or minor compounds have reported insecticidal activities on various pests and disease vectors such as Anopheles.

Aromatic Plants of Tropical West Africa. Part XIV. Chemical and Biological Investigation of Lippia multiflora Mold. Essential Oil from Benina

Abstract The essential oil of the leaves of Lippia multiflora collected in Benin was obtained by hydrodistillation and analyzed by capillary GC and GC/MS. Thirty-six components, representing 96.5% of oil were identified. The sample consisted mainly of monoterpenes. The major constituents were 1,8-cineole (39.9%), sabinene (11.1%), linalool (10.9%) and α-terpineol (10%). The antioxidant and antiradical activities of the oil was found to be low comparatively to that of butylated hydroxytoluene (BHT).

Aromatic Plants of Tropical West Africa. Part XV. Chemical and Biological Evaluation of Leaf Essential Oil of Commiphora africana from Benin

Abstract The essential oil from leaves of Commiphora africana collected in Benin was analyzed by capillary GC and GC/MS. The essential oil was characterized by a majority of sesquiterpenoid constituents with bisabolane skeleton among them bisabolone (38.4%) and β-sesquiphellandrene (19.1%) were the most abundant. The radical scavenging activity of the oil was found to be low comparatively to that of butylated hydroxytoluene (BHT).

Chemical and Biological Investigation on Volatile Constituents of Pentadesma butyracea Sabine (Clusiaceae) From Benin

Abstract The essential oils obtained by hydrodistillation of leaves, bark and roots of Pentadesma butyracea collected in Natitingou (Benin) were investigated by capillary GC and GC/MS. Twenty-eight components, representing 97–99% of oils, were identified. The samples were exclusively sesquiterpenic, dominated in all cases by β-caryophyllene (58.0–75.0%) and α-humulene (10.1–14.2%); the leaf oil was characterized by a high content of α-copaene (14.2%). Finally, no significant antiradical activity (DPPH method) or inhibitory effect on the soybeen lipoxygenase activity could be observed.

Chemical Composition and Insecticidal and Repellent Effect of Essential Oils of Two Premna Species against Sitotroga cerealella

This work aims to study for the first time the chemical composition and evaluate insecticidal and repellent effects of essential oils of Premna angolensis and Premna quadrifolia leaves, against Sitotroga cerealella, an insect pest of rice stocks as alternatives to synthetic pesticides. The GC-MS analysis showed that essential oil of P. angolensis contains 29 compounds representing 96.1% of the oil and 42 compounds corresponding to 91% for the essential oil of P. quadrifolia. The main constituents regardless of the species were β-caryophyllene (13.1%), (E)-β-caryophyllene (13.5%), octen-3-ol (3.2%–28%), phytol (3.7%–4.9%), β-elemene (1.4%–21%), globulol (11.2%), germacrene-D (8.9%), α-humulene (2.9%–6.4%), α-pinene (5%), sabinene (3.7%), δ-cadinene (0.4%–3.3%), and linalool (3.3%). The results of laboratory tests showed that both essential oils have insecticidal and repellent effects on S. cerealella. Presenting the results, the damage caused by the adults and larvae of S. cerealella was evaluated by calculating the percentage of grains attacked and weight loss thereof. The results suggest that volatile extracts of P. angolensis and P. quadrifolia can be used as alternatives to synthetic chemicals in paddy protection against S. cerealella.

Aeollanthus pubescens Benth. from Benin: A Potential Source of Essential Oil with High Antiradical Efficiency

The chemical composition of the essential oils obtained by hydrodistillation from leaves of three samples of Aeollanthus pubescens Benth. (Lamiaceae) growing wild in Benin were analyzed by GC and GC-MS. To date the biological functions of A. pubescens essential oils have not been demonstrated scientifically even if this plant is traditionally used by local population in alimentary and medicine. We investigated the chemical composition of A. pubescens essential oils and their antiradical and anti-inflammatory activities. Twenty four compounds were identified and quantified in the essential oils, the major compounds being thymol (63.6 %; 9.5 %; 63.4 %), carvacrol (3.1 %; 51.1 %; 2.1 %), thymyl acetate (9.8 %; 0.8 %; 10.2 %), carvacryl acetate (0.8 %; 6.1 %; 0.7 %), p-cymene (5.6 %; 9.0 %; 5.5 %) and γ-terpinene (6.4 %; 11.2 %; 6.6 %). The antiradical activity of these oils was found to be high and a low anti-inflammatory activity was observed. Fractionation of a thymol rich sample allowed the identification of the bioactive fractions and their contribution to the efficiency of the whole extract. This study suggests that A. pubescens essential oils may be useful in the food industry where the antioxidants are used to retard the degradation of fatty substances, but also in cosmetics or in the field of herbal medicine, where the radical species are associated with the concept of antiaging.