Etudes chimiques et activités biologiques d'extraits de végétaux aromatiques d'origine béninoise

Ce travail rend compte des études chimiques et biologiques d'extraits volatils et non volatils de plantes aromatiques acclimatées au Bénin. La première partie passe en revue quelques généralités sur les huiles essentielles, les métabolites secondaires et les méthodes d'analyse chromatographique. Dans cette partie, quelques caractéristiques générales ont été décrites sur Candida albicans , le cancer et sur les déprédateurs respectifs du maïs et du niébé que sont le Prostephanus truncatus et Callosobruchus maculatus. La deuxième partie donne les résultats de l'analyse chimique des constituants volatils extraits de 20 espèces aromatiques appartenant à 10 familles botaniques collectées dans différentes régions du Bénin : les Anacardiaceae, Annonaceae, Asteraceae, Clusiaceae, Lamiaceae, Leguminosae-Papilionoideae, Myrtaceae, Poaceae, Verbenaceae et les Zingiberaceae. On trouve sur l'ensemble des échantillons investigués, les différentes structures rencontrées dans les huiles essentielles : terpènes, dérivés aromatiques et constituants aliphatiques. Une 3e partie décrit les résultats phytochimiques qui mettent en exergue les métabolites souvent rencontrées dans le règne végétal : les tanins, les alcaloïdes, les flavonoïdes, les stérols et triterpènes, etc..La 4e partie discute des résultats d'études biologiques. Différentes réactions liées au profil chimique de chacune des huiles essentielles testées ont été observées au cours de ces études biologiques. Les huiles essentielles d'Aeollanthus pubescens, de Xylopia aethiopica et de Cymbopogon giganteus ont été actives sur Candida albicans. Par ailleurs, l'activité d'autres huiles essentielles évaluées sur la cellule cancéreuse mammaire MCF-7 a révélé un potentiel anticancéreux des extraits volatils de Pentadesma butyracea, Siphonochilus aethiopicus, Xylopia aethiopica et de Ozoroa insignis. Dans le domaine de la protection des récoltes, les résultats de nos travaux ont montré respectivement les caractères insecticide, larvicide et ovicide des huiles essentielles de Pimenta racemosa, Chromolaena odorata, Lantana camara et du Psidium guajava sur Prostephanus truncatus d'une part puis des huiles essentielles de Cymbopogon giganteus et de Xylopia aethiopica sur Callosobruchus maculatus d'autre part. L'ensemble des résultats, tant sur le plan chimique que biologique met en évidence les potentialités de certaines espèces, pour une exploitation de leur extrait volatil à des fins thérapeutiques et dans la lutte post-récolteCLERMONT FD-BCIU Sci.et Tech. (630142101) / SudocSudocFranceF

CHEMICAL STUDY AND ANTIMICROBIAL ACTIVITIES OF VOLATILE EXTRACTS FROM FRESH LEAVES OF [i]CRASSOCEPHALUM RUBENS[/i] (JUSS

The present work has studied the chemical composition of the essential oil (EO) extracted from the fresh leaves of [i]C[/i][i]rassocephalum rubens[/i] and tested its efficacy against some pathogenic microorganisms isolated from common foods largely consumed, which had been incriminated as responsible of food infections and toxi-infections. The chemical composition of the essential oil extracted from the fresh leaves of [i]Crassocephalum rubens[/i], has revealed the presence of limonene (48.8� myrcene (30.7� E-(β)-ocimene (7.4�20and α-thujene (4.6�20as the main components. In addition some oxygenated components had been identified. They are linalool, terpinen-4-ol, p-cymen-8-ol, E-nerolidiol and E-bisabol-11-ol. The Minimal Inhibitory Concentration (MIC) determined on some bacteria Gram ([i]Staphylococcus aureus[/i], [i]Streptococcus faecalis[/i]), bacteria Gram- ([i]Escherichia coli[/i], [i]Salmonella typhi[/i]) and against a pathogenic yeast ([i]Candida albicans[/i]) vary from 0.54 mg/mL to 4.38 mg/mL. The two Gram are more sensitive to the EO activity while the two Gram- less sensitive and Candida albicans relatively resistant to the EO activity

INSECTICIDAL ACTIVITIES OF ESSENTIAL OILS EXTRACTED FROM THREE SPECIES OF POACEAE ON ANOPHELES GAMBIAE SPP, MAJOR VECTOR OF MALARIA

In this paper, the insecticidal activities on Anopheles gambiae spp of the essential oils (EO) extracted from the dry leaves of some species collected in Benin were studied. The essential oil yields are 2.8, 1.7 and 1.4�0respectively for Cymbopogon schoanenthus (L.) Spreng (CS), Cymbopogon citratus Stapf. (CC) and Cymbopogon giganteus (Hochst.) Chiov (CG). The GC/MS analysis showed that the EO of CS had a larger proportion in oxygenated monoterpenes (86.3�20whereas those of the sheets of CC and CG are relatively close proportions (85.5�0and 82.7�0respectively) with. The piperitone (68.5� 2-carene (11.5� and -eudesmol (4.6�20are the major components of the EO of CS while trans para-mentha-1(7),8-dien-2-ol (31.9� trans para-mentha-2,8-dien-1-ol (19.6� cis para-mentha-2,8-dien-1-ol (7.2� trans piperitol (6.3�20and limonene (6.3�20prevailed in the EO of CG. The EO of CC revealed a rich composition in geranial (41.3� neral (33� myrcene (10.4� and geraniol (6.6� The biological tests have shown that these three EO induced 100�0mortality of Anopheles gambiae to 1.1, 586.58 and 1549 µg•cm-2 respectively for CC, CS and CG. These effects are also illustrated by weak lethal concentration for 50�0anopheles population (CC: 0.306; CS: 152.453 and CG: 568.327 µg•cm-2) in the same order of reactivity. The EO of CC appeared most active on two stocks (sensitive and resistant) of Anopheles gambiae

CHEMICAL CHARACTERIZATION AND BIOLOGICAL ACTIVITIES OF EXTRACTS OFTHREE PLANTS USED IN TRADITIONAL MEDICINE IN BENIN: TECTONA GRANDIS, UVARIA CHAMEAE AND JUSTICIA SECUNDA

Objective: The present study was devoted to the chemical analysis of three plants (Tectona grandis, Uvaria chameae and Justicia secunda) usually used by traditional healers in Benin, for their curative properties in the treatment of certain diseases. Methods: After characterization of large chemical groups present in ethanolic extract of these plants, the total polyphenols were measured by the Folin method, the content of condensed tannins, total flavonoids, anthocyanins and anthocyanidins was evaluated by spectrophotometry. Results: The results show the presence of several secondary metabolites such as saponins, alkaloids, tannin, mucilages, anthraquinones, leucoanthocyanins, anthocyanins and triterpene in varying proportions in the three plants. The contents of condensed tannins, of anthocyanidins, total polyphenols and total flavonoids are respectively higher in the leaves (13.409 mg/g, 1.529 mg/g, 3.479 mg/g and 24.640 mg/g) than the bark of T.g (8.612 mg/g, 0 mg/g, 2.694 mg/g and 12.410 mg/g). As against, leaves of U.care richer in condensed tannins, flavonoids and total polyphenols (44.290 mg/g, 9.135 mg/g, 4.779 mg/g) than J.s (0 mg/g, 2.011 mg/g and 1.478 mg/g) unlike anthocyanidins. Of three plants studied, U.c was revealed the richest in polyphenolic compounds (condensed tannins, total polyphenols) and J.s was least rich. This content of polyphenolic compounds explain the antiradical activities observed; an CI50 of 0.700 mg/mL for U.c, 14.340 mg/mL for leaves of T.g, 24.790 mg/mL for bark of T.g and 46.500 mg/mL for leaves of J.s. Conclusion: This study contributes to increase those plants's phytochemical knowledge and allows having a better understanding of their pharmacological properties Keywords: Polyphenols, Antiradical activities, Solid phase micro extraction, Tectona grandis, Uvaria chameae, Justicia secunda

Comparative chemical study and cytotoxic activity of Uvariodendron angustifolium essential oils from Benin.

International audienceThis study aimed to compare the chemical composition of volatile extracts obtained by hydrodistillation of leaves, stems, bark and roots of Uvariodendron angustifolium (Engl. & Diels) R. E. Fries. The essential oils, obtained with yields between 0.12 and 0.66%, were analyzed by GC/FID and GC/MS. A great variability in the chemical composition was observed depending on the plant part treated. The essential oils obtained from leaves and stems contained mainly neral (29.7-30.5%) and geranial (42.9-47.3%), while methyl eugenol was the major component of the volatile extracts from bark (68.3%) and roots (85.3%). Interesting cytotoxic properties of these essential oils on human breast cancer cells MCF-7 were demonstrated