Variation diurne de la composition chimique et influence sur les propriétés antimicrobiennes de l’huile essentielle de Ocimum canum Sims cultivé au Bénin

L’huile essentielle de Ocimum canum Sims (Lamiaceae) obtenue par hydrodiffusion à différents moments de la journée a été analysée par GC/FID et GC/SM puis testée sur différentes bactéries par la microtechnique de dilution. Le rendement et la composition chimique de l’huile varient selon le temps et l’ensoleillement. Abondant le matin à 7 heures (1,71±0,01%), le rendement décroît progressivement avec l’augmentation des rayons solaires, jusqu’à son minimum à 13 heures (1,35±0,01%) quand le soleil est au zénith, avant de croître à nouveau à sa valeur la plus élevée (1,78±0,02% à 19 h) au couché du soleil. Plus de 54 composés représentant près de 98% des hydrodiffusats, ont été identifiés dans les différents échantillons. Les principaux sont : α-thujène (5,56 à 7,85%), β-myrcene (2 à 6,94%), δ-3-carène (3,07 à 4,84%), p-cymène (14,61 à 22,8%), g-terpinène (6,05 à 10,7%), carvacrol (7,94 à 30,8%), β-caryophyllène (0,15 à 18,86%) et β- sélinène (2,74 à 14,41%). Les taux de certains constituants comme β-caryophyllène et β-sélinène croissent avec l’ensoleillement contrairement à ceux du carvacrol, p-cymène. Cette variation diurne perturbe la synergie d’action des constituants de l’huile qui présentent une forte activité inhibitrice (0,38 à 7,19 mg/ml) sur Staphylococcus aureus ATCC 25923, Enterococcus faecalis ATCC 29212, Escherichia coli ATCC 25923, Acinetobacter baumannii ATCC 19609 et Staphylococcus aureus résistante 1199B NorA. Les huiles obtenues à 7 heures et 19 heures sont les plus efficaces à faible concentration (0,38 à 2,88 mg/ml). Pour la première fois, l'interaction est démontrée entre variation diurne de la composition chimique et propriétés antimicrobiennes de l'huile essentielle de Ocimum canum Sims du Bénin.Keywords: Ocimum americanum, composés volatils, Chémotype à carvacrol Variation diurne-Activité antibactérienn

2,7-dihydroapogeissoschizine from root bark of strychnos Gossweileri

In this paper, we describe the isolation and structural determination of 2,7-dihydroxyapogeissoschizine, a new alkaloid from the root bark of Strychnos gossweileri. Elucidation of its structure is based mainly on 1D and 2D NMR studies; its conformation was optimized by energy minimization. This type of skeleton is related to geissoschizine but with the notable diffrence that the 1 and 17 positions are joined giving an additional fused ring. Such a seven-membered ring has ,to our knowledge, only been observed in apogeissoschizine, obtained after chemical tratment of two alkaloids ( geissospermine and geissoschizine). 2,7-dihydroxyapogeissoschizine is therefore, the first natural product possessing this skeleton. According to a preliminary test, this new alkaloid shows low toxicity to B16 melanoma cells, but not for non-cancer 3T3 fibroblasts cultured in vitro.THese results have to be confirmed by further tests

South American Strychnos Species. Ethnobotany (except Curare) and Alkaloid Screening

The ethnobotanical uses of South American species of Strychnos L. (Loganiaceae) are reviewed, with the exception of their major role in the preparation of curare, which will be dealt with in detail elsewhere. Medicinal uses are less common than is the case with the African and Asian species of the genus. About 140 samples, mostly of leaves, belonging to 53 species, have been screened for alkaloids. As with species from other parts of the world, the stem bark and root bark tend to be a richer source than leaves. Nor-harman is present in extracts from S. barnhartiana leaves. Pyridino-indolo-quinolizidinone (angustine-type) bases are also found in several species. The occurrence and pharmacology of the (non-curarizing) alkaloids known to be present in South American Strychnos species is reviewed

Activités antibactérienne in vitro de Cassia alata, Lantana camara et Mitracarpus scaber sur Dermatophilus Congolensis isolé au Bénin

L'activité antibactérienne in vitro des extraits aqueux et alcooliques de Cassia alata, de Lantana carnara et de Mitracarpus scaber a été comparée avec celle de l'oxytétracycline et de la pénicilline procaine sur une bactérie Gram-positif, Dermatophilus congolensis, agent de la dermatophilose bovine. Les extraits alcooliques bruts de C. alata, de L. camara et de M. scaber se sont révélés plus actifs sur D. congolensis que leurs extraits aqueux. Les zones d'inhibition à 500 mg/ml ont été de 14 à 20 mm et de 20 à 24 mm respectivement pour les extraits aqueux et alcooliques sur une souche isolée d'animaux infectés. Les deux extraits de M. scaber ont montré une activité antibactérienne plus élevée sur D. congolensis que ceux de C. alata et de L. carnara. L'activité antibactérienne des extraits alcooliques bruts de M. scaber in vitro sur D. congolensis, à 500 mg/ml, a été équivalente à celle de la pénicilline procaïne à la concentration de 800 mg/ml et environ 10 à 15 fois moindre que celle de l'oxytétracycline

Quantification of rotenone in seeds of different species of yam bean (Pachyrhizus sp.) by a SPE HPLC-UV method

This study describes the development of a validated method for the quantification of rotenone in yam bean. The milled seeds were submitted to a Soxhlet dichloromethane extraction which allowed extracting 90% of the seeds rotenone. Elimination of the lipids was obtained via solid phase extraction. Rotenone was eluted with dichloromethane/methanol and the solution dried under vacuum and solubilised directly in methanol before injection in HPLC. The whole process was realised as much as possible protected from light and at temperatures lower than 40°C which allowed high recovery rates of spiked rotenone. Total error was used as criterion for the validation process and accuracy profiles drawn. The method allows the quantification of rotenone in yam bean seeds from 0.07% up to 1.25% (w/w). This method was applied to the quantification of rotenone in the seeds of several accessions of Pachyrhizus erosus and P. ahipa. The results range from 1.13 to 2.76 mg/g dry material

A RAPID UHPLC-DAD-ESI-MSn METHOD FOR ANTHOCYANINS QUANTIFICATION FROM Euterpe oleracea FRUITS HARVESTED AT DIFFERENT TIMES

Euterpe oleracea is a palm tree widely distributed in northern South America. Its greatest occurrence and economic importance happens in the floodplains of the Amazonian delta. The fruits called açai are an interesting source of different anthocyanins. Lately they have gained popularity in North America and in the European countries in the food industry and in the health sector due to their extremely high antioxidant capacity and potential anti-inflammatory activities [1]. Some studies have characterized chemically açaí pulps and have reported anthocyanin profiles which differ both qualitatively and quantitatively. Among other reasons, these differences may be associated with the stages of ripening of the fruits, since açai fruits are generally harvested in different maturation stages. The evaluation of the anthocyanin profile of açai fruits during different maturation stages is thus important for the post-harvest industry. In addition a rapid separation by UHPLC and an unambiguous identification by MSn are very useful for an effective quality control of the fruits. Thus, the aim of this study was to characterize the anthocyanin profiles of açai fruits at different stages of maturity. The fruits were harvested during the peak harvesting season, between July and October 2009, in the floodplains of the eastern Amazonian region (State of Pará, Brazil). A protocol of solid-liquid extraction of phenolic compounds was developed. Characterisation of the anthocyanins present in the fruits of Euterpe oleracea was conducted by UHPLC–DAD–ESI–MSn analysis, in positive ionization mode. All identified compounds was separated in 10 minutes of a total run time of 21 min instead of 55 min in the previously developed HPLC method. Six anthocyanins were identified in the extracts namely: cyaniding-3-glucoside, cyaniding-3-rutinoside, pelargonidin-3-glucoside, peonidin-3-glucoside, peonidin-3-rutinoside and cyanidin. The first two compounds were the major constituents in all maturity stages, with similar proportions, except for the first maturity stage for which the anthocyanins were under the limit of quantification. However, in the last maturity stage, cyanidin-3-glucoside became less abundant than cyanidin-3-rutinoside. On the other hand, cyanidin decreased with maturation. For the other compounds, proportions were similar along maturation. Hence, this work was important as it provides valid information on variation of anthocyanin profiles of açai fruits during maturation. This may contribute to the selection of an optimal maturity stage for harvesting as well as it will allow a rapid quality control of the fruits. [1]: Heinrich, M., et al., Açai (Euterpe oleracea Mart.)- A phytochemical and pharmacological assessment of the species’ health claims. Phytochem. Lett. (2010), doi: 10.1016/j.phytol.2010.11.00