François Xavier Etoa

Bio: François Xavier Etoa is an academic researcher from University of Yaoundé I. The author has contributed to research in topics: Essential oil & Carvacrol. The author has an hindex of 5, co-authored 10 publications receiving 209 citations.

Carotenoid contents during ripening of banana hybrids and cultivars grown in Cameroon

Abstract: Introduction. Bananas and plantains (Musa spp.) are staple foods in Cameroon and surrounding countries. Strategies based on the utilization of cultural and locally consu- med foods are essential for the identification of solutions for the reduction of micronutrient malnutrition. Materials and methods. To assess the nutritional content of some varieties in order to assist the selection of new Musa hybrids, the carotenoid contents of 19 Musa culti- vars and hybrids from the CARBAP (Douala, Cameroon) germplasm were determined at three ripening stages. Frozen pulps were analyzed for their β-carotene, α-carotene and lutein con- tents using the HPLC method. The retinol activity equivalents (RAE)·100 g -1 fresh weight were calculated for four representative Musa types. Results and discussion. Significant differen- ces were observed between Musa cultivars according to their genotype. Plantain type (Mbouroukou n°1) and Musa hybrid (CRBP 755) exhibited the highest levels of RAE ((148 and 70) RAE·100 g -1 ) compared with dessert bananas (16 RAE·100 g -1 ). During ripening, the concentrations of these carotenoids increased or decreased significantly (α = 0.05%) accor- ding to the Musa type analyzed. The high β- and α-carotene as well as lutein contents of these Musa sp. could contribute to the nutritional status of people consuming these banana varieties in West and Central Africa and enhance their use in Musa breeding programs. Cameroon / Musa / fruits / ripening / developmental stages / carotenoids

Processing and food uses of bananas and plantains in Cameroon

Abstract: Introduction . In Southern Cameroon, bananas and plantains (Musa ) play an important role in the population’s diet. There are many food uses of these crops relative to the eating habits of consumers. Our study was carried out in order to list the varieties of bananas and plantains mostly used by housewives and restaurant dealers and to describe the various culinary preparations used for their transformation. Methods . The processing and culinary methods of bananas and plantains, including the estimation as well as the measurement of the quantities of ingredients used, and the traditional utilisations of these foodstuffs, were investigated in two Cameroonian towns (Bafoussam and Yaounde). Results . Some culinary preparations using different varieties are common in Southern Cameroon such as roasted or fried plantain, plantain chips, boiled plantain or banana and pounded plantain. They are eaten with various sauces, vegetables and other food complements. Other preparations found in these regions include stuffed plantain or banana, plantain or banana porridges and traditional recipes called kondre and malaxe. Preparation of chips, fried and roasted plantain are mainly carried out by women and young boys on the streets in an effort to diversify sources of income. These various transformation and uses of bananas and plantains contribute to the reduction of post–harvest losses as well as the valorisation of these perishable food stuffs. Conclusion . The evaluation of their nutrient composition (macro- and micronutrients) as well as the effects of culinary preparations and the bio-availability of those nutrients are being conducted at the CARBAP Post–Harvest Technology Laboratory in order to appreciate their contribution in the fight against malnutrition in some regions of Cameroon.

Effect of Fractioning on Antibacterial Activity of Enantia chlorantha Oliver (Annonaceae) Methanol Extract and Mode of Action.

Abstract: Infectious diseases caused by bacteria constitute the main cause of morbidity and mortality throughout the world and mainly in developing countries. In this work, the influence of fractioning and the mode of action of stem barks methanol extract of Enantia chlorantha were investigated. The aim was to optimize the antibacterial activity of the methanol extract. The extract was prepared by maceration of barks powder in methanol. Fractioning was done using increasing solvents polarity. Standard phytochemical methods were used for phytochemical screening. Minimum Inhibitory Concentrations (MIC) and Minimum Bactericidal Concentration (MBC) of the methanol extract and fractions were determined using broth microdilution method. The studied mode of action of both methanol extract and n-butanol fraction included antibiofilm activity, H+-ATPase-mediated proton pumping assay, salt tolerance, and cells cycle. The methanol extract of E. chlorantha stem barks was found to be active on all the bacteria tested (32 ≤ MIC ≤ 512 μg/mL), its activity being significant (MIC < 100 μg/ml) out of 5 of the 28 clinical isolates used. Salmonella enterica serovar paratyphi A was the most sensitive (32 μg/mL). Compared to the extract and other fractions, the n-butanol fraction was found to be more active (32 ≤ MIC ≤ 256). Significant antibacterial activity of this fraction was observed out of 10 of the 28 bacterial isolates and 3 out of 7 bacterial strains. Lowest MIC values (32 μg/ml) of this fraction were obtained with Escherichia coli (136), Pseudomonas aeruginosa (CIP 76110), and Salmonella enterica serovar typhi 9. The methanol extract of E. chlorantha and its n-butanol fraction revealed several modes of action including the prolongation of the latency phase of the bacterial growth, the inhibition of the pump with protons H+ - ATPases bacterial, the loss of the salt tolerance of the Staphylococcus aureus, and inhibition of the formation of the bacterial biofilm. The present results showed that the n-butanol fraction of the methanol stem barks extract of E. chlorantha possess the essential antibacterial components and could best be used to fight against bacterial infections as compared to methanol extract.

Effect of fractioning on antibacterial activity of n-butanol fraction from Enantia chlorantha stem bark methanol extract

Abstract: Enantia chlorantha is a plant belonging to Annonaceae Family. The Barks and leaves are used traditionally to treat infectious diseases. Earlier studies highlighted the antibacterial activity of stem barks methanol extract. This study is thus aimed at investigating the effect of fractionation on antibacterial activity of its n-butanol fraction. The extract of E. chlorantha stem barks was obtained by maceration in methanol and then subjected to a liquid/liquid partition by successive depletion with solvents of increasing polarity. The n-butanol fraction was fractionated by adsorption chromatography on silica gel. A product was isolated from the dichloromethane/methanol (2%) fraction and the structure was determined on the basis of spectroscopic data; Proton Nuclear Magnetic Resonance (1H NMR), Carbon-13 Nuclear Magnetic Resonance (13C NMR), Heteronuclear Multiple Bond Correlation (HMBC), H-correlation spectroscopy (H-COSY), attached proton test (APT), heteronuclear multiple quantum coherence (HSQC). The antibacterial activity was evaluated by broth microdilution method against six reference strains and eight clinical bacterial strains. The n-butanol fraction was found to be active with MIC values ranging from 32 to 256 μg/mL. The FA sub-fraction was more efficient among the eight sub-fractions, the n-butanol fraction and comparable to Chloramphenicol used as reference antibiotic. The product obtained was elucidated as palmitin. The antibacterial activity of the latter was comparable to that of Chloramphenicol on one reference strain and 4 of the 6 clinical strains. The FA sub-fraction had better antibacterial activity than the n-butanol fraction and other sub-fractions, and possibly palmitin was the active substance responsible for the antibacterial activity of E. chlorantha.

Potential of Cameroonian plants and derived products against microbial infections: a review.

Abstract: In Cameroon, infectious diseases are amongst the most commonly notified diseases and largest cause of mortality. Many plants are used locally in traditional medicine for their treatment. The aim of the present review is to summarize currently available evidence and knowledge concerning Cameroonian plants used to treat bacterial and fungal infections, and the efficacy of plant-derived extracts and compounds. The traditional uses of plants in the treatment of infectious diseases have been collected and tabulated. The antimicrobial activity of the extracts and the chemical constituents of most of these plants are summarized in this report. Plants used traditionally in Cameroonian medicine, with laboratory work on any part or products, have been documented. Numerous extracts and compounds have been tested for antimycobacterial, antibacterial and antifungal efficacy and some of them were significantly active. Most of the bioactive compounds isolated were phenolics and alkaloids. In conclusion, many plant species are used in traditional medicine in Cameroon to treat infectious diseases, and several interesting openings have originated for further inquiry following IN VITRO antimicrobial activity evaluation. However, much work is still to be done to standardize methods and cut-off points for describing the antimicrobial activity, and on the study of the mechanisms of action.

Composition and antioxidant activity of the essential oils of Xylopia aethiopica (Dun) A. Rich. (Annonaceae) leaves, stem bark, root bark, and fresh and dried fruits, growing in Ghana.

Abstract: The chemical composition of the essential oils obtained from the leaves, the barks of the stem and the root, as well as from the fresh and dried fruits of Xylopia aethiopica, growing in Ghana, was investigated by gas chromatography/mass spectrometry analyses. Kovats indices, mass spectra, and standard compounds were used to identify a total of 93 individual compounds. The monoterpene hydrocarbons formed the main portion in all studied samples. β-Pinene was predominant in all cases, while trans-m-mentha-1(7),8-diene was the main compound in the essential oils of the leaves and the barks of roots and stems. Their potential antioxidant activity was also investigated and found to be significant in scavenging superoxide anion radical. Keywords: Xylopia aethiopica; Ghana; volatile constituents; leaves; fruits; stem bark; root bark

Natural Product Interventions for Chemotherapy and Radiotherapy-Induced Side Effects.

Abstract: Cancer is the second leading cause of death in the world. Chemotherapy and radiotherapy are the common cancer treatments. However, the development of adverse effects resulting from chemotherapy and radiotherapy hinders the clinical use, and negatively reduces the quality of life in cancer patients. Natural products including crude extracts, bioactive components-enriched fractions and pure compounds prepared from herbs as well as herbal formulas have been proved to prevent and treat cancer. Of significant interest, some natural products can reduce chemotherapy and radiotherapy-induced oral mucositis, gastrointestinal toxicity, hepatotoxicity, nephrotoxicity, hematopoietic system injury, cardiotoxicity, and neurotoxicity. This review focuses in detail on the effectiveness of these natural products, and describes the possible mechanisms of the actions in reducing chemotherapy and radiotherapy-induced side effects. Recent advances in the efficacy of natural dietary supplements to counteract these side effects are highlighted. In addition, we draw particular attention to gut microbiotan in the context of prebiotic potential of natural products for the protection against cancer therapy-induced toxicities. We conclude that some natural products are potential therapeutic perspective for the prevention and treatment of chemotherapy and radiotherapy-induced side effects. Further studies are required to validate the efficacy of natural products in cancer patients, and elucidate potential underlying mechanisms.

Degradation of β-carotene during fruit and vegetable processing or storage: reaction mechanisms and kinetic aspects: a review

Abstract: Introduction. Food processing significantly lowers the quality of fruits and vegetables, which is a major concern for the food industry. Micronutrients are particularly affected, and among them β -carotene, which exhibits very interesting sensory, nutritional and biological properties. The literature concerning β -carotene degradation is extensive, but the conclusions are very different as a function of the biological, chemical and food transformation points of view. This paper proposes a synthesis of complementary approaches in the study of β -carotene during food transformation and storage. Degradation reactions. Degradation compounds are numerous, including isomers, epoxides, apocarotenones, apocarotenals and short-chain cleavage products, among them some flavour compounds. A detailed reaction scheme of isomerisation and autoxidation of β -carotene could be deduced from the literature data. The main pathways are well documented, but the global reaction scheme is still incomplete. Furthermore, most of the mechanistic studies are carried out in model systems, thus data may misrepresent β -carotene behaviour in real food products. Kinetics during processing and storage. The determination of degradation kinetics permits the identification of the fastest reactions, i.e. , generally those with the greatest impact, and also the quantification of the effect of the factors which can lower β -carotene content. Temperature, occurrence of oxygen, food composition and food structure are shown to affect the β -carotene loss rate significantly. However, the methodologies used to obtain the kinetic parameters are of major importance, and finally, most of the results found in the literature are specific to a study and difficult to generalise. Discussion and conclusion. Mechanistic and kinetic approaches each provide interesting data to improve understanding and monitoring of β -carotene. The combination of all this data, together with thermodynamic and analytical considerations, permits the building of observable reaction schemes which can further be transcribed through mathematical models. By this multidisciplinary approach, scarcely used for the time being, knowledge could be capitalised and useful tools could be developed to improve β -carotene retention during food processing and storage. (Resume d'auteur)

Antibacterial activities of selected Cameroonian spices and their synergistic effects with antibiotics against multidrug-resistant phenotypes

Abstract: The emergence of multi-drug resistant (MDR) phenotypes is a major public health problem today in the treatment of bacterial infections. The present study was designed to evaluate the antibacterial activities of the methanol extracts of eleven Cameroonian spices on a panel of twenty nine Gram negative bacteria including MDR strains. The phytochemical analysis of the extracts was carried out by standard tests meanwhile the liquid micro-broth dilution was used for all antimicrobial assays. Phytochemical analysis showed the presence of alkaloids, phenols and tannins in all plants extracts. The results of the antibacterial assays indicated that all tested extracts exert antibacterial activities, with the minimum inhibitory concentration (MIC) values varying from 32 to 1024 μg/ml. The extracts from Dichrostachys glomerata, Beilschmiedia cinnamomea, Aframomum citratum, Piper capense, Echinops giganteus, Fagara xanthoxyloides and Olax subscorpioidea were the most active. In the presence of efflux pump inhibitor, PAsN, the activity of the extract from D. glomerata significantly increased on 69.2% of the tested MDR bacteria. At MIC/5, synergistic effects were noted with the extract of D. glomerata on 75% of the tested bacteria for chloramphenicol (CHL), tetracycline (TET) and norfloxacin (NOR). With B. cinnamomea synergy were observed on 62.5% of the studied MDR bacteria with CHL, cefepime (FEP), NOR and ciprofloxacin (CIP) and 75% with erythromycin (ERY). The overall results provide information for the possible use of the studied extracts of the spices in the control of bacterial infections involving MDR phenotypes.