Physicochemical Variability and Biodiesel Potential of Seed Oils of Two Hibiscus sabdariffa L. Phenotypes.

Considerable interest is being focused on vegetable oils as fuel. Due to their characteristics being close to diesel and their renewable potential, studies recommend their use for agricultural applications. Hibiscus sabdariffa var. sabdariffa is widely studied for the nutritional properties of its calyces. Although the seeds of this species are known to be rich in fatty acids, their use is little known in Benin Republic. Similarly, a few studies have attempted to characterize the seeds of the green phenotype of this plant species. By following standard methods, the fatty acid profiles of oils extracted from the seeds of the two varieties (red phenotype, sabdariffa (HSS), and green phenotype, altissima (HSA)) of H. sabdariffa L. were established. A comparative study of their physicochemical properties was also performed to highlight their potential use as fuel. It follows that HSS seed oil is yellow while HSA seed oil is dark green. For the two varieties, values obtained for the kinematic viscosity (∼4 mm2/s), cetane number (∼55), and density (0.87 g/cm3) are in accordance with the U.S. and European standards. However, it is observed that HSA oil is significantly more acidic (23.10 ± 0.22 for HSS vs 18.20 ± 0.40 mg KOH/g oil for HSS) with a higher peroxide value (HSA: 0.280 ± 0.002 vs HSS: 0.140 ± 0.001). The major fatty acids are the following: palmitic (HSA: 27.09 vs HSS: 25.48%), oleic (HSA: 31.81 vs HSS: 35.21%), and linoleic (HSA: 31.43 vs HSS: 29.70%) acids. These fatty acid profiles give to the two oils calorific values (∼39.45 MJ/kg) lower than that of diesel but good oxidative stability and cold filter plugging. The two oils could be used as fuel oil, after their transesterification to improve their properties.

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

This 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.

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

BACKGROUND: Insecticide 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. METHODS: Essential 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. RESULTS: Different 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. CONCLUSIONS: C. 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.

In vitro biological effects of two anti-diabetic medicinal plants used in Benin as folk medicine.

BACKGROUND: Extracts from Polygonum senegalensis (Polygonaceae) and Pseudocedrela kotschyi (Meliaceae) are two important traditionally used medicinal plants in rural Benin to treat many diseases and notably type 2 diabetes. The aim of the study was to investigate the α-glucosidase inhibition, antioxidant and antibacterial activities of those plants extract: Polygonum senegalensis leaves, and Pseudocedrela kotschyi root. METHODS: Hydro-alcoholic (50%) extracts were analyzed for their phytochemical content and tested for their inhibition potency on α-glucosidase from Saccharomyces cerevisiae. Antioxidant activities were assessed using the DPPH, ORAC, FRAP and DCFH-DA (cell based) assay. Finally, the antibacterial activity was evaluated using MIC determination on four Gram-positive cocci (Bacillus subtilis, Clostridium difficile, Enterococcus faecalis, Staphylococcus aureus), three Gram-negative bacilli (Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae), and the yeast Candida albicans. RESULTS: Each extract presented significant α-glucosidase inhibition and antioxidant activities. Polygonum senegalensis leaf extracts were the most active in each in vitro assay with an IC50 = 1.5 µg/ml for α-glucosidase inhibition and an IC50 = 6.8 µg/ml for DPPH scavenging, - 4.5 µmol Fe II/g of dry matter - 9366 µmol Trolox / g DW - for FRAP and ORAC values, respectively. IC50 = 2.3 µg GA / ml for DCFH-DA assay. Concerning its antibacterial activity, a growth inhibitory effect was observed only against three Gram negative bacilli: B. subtilis, E. faecalis, S. aureus and the yeast C. albicans at high concentration. CONCLUSION: The results showed that the semi alcoholic extract of the two studied plants possess α-glucosidase inhibitory activity, antioxidant potency, and low antibacterial effect.

Potential of the bush mint, Hyptis suaveolens essential oil for personal protection against mosquito biting.

We studied the potential of the essential oil extract from the bush mint, Hyptis suaveolens, for use against mosquito biting under both laboratory and field conditions. In the laboratory, the repellency of various concentrations (1-6%) of the essential oil was assessed against Anopheles gambiae, based on a 15-min landing and biting on treated forearms of volunteers. In the laboratory, the percentage of mosquitoes landing on the forearm was 42, 33, 23, 23, 9, and 2 for 1%, 2%, 3%, 4%, 5%, and 6% essential oil concentration, respectively; and 92 and 91 for the solvent (isopropanol) and untreated control, respectively. The percentage of mosquitoes taking a blood meal was 22, 12, 13, 12, 5, and 3 for 1%, 2%, 3%, 4%, 5%, and 6% essential oil, respectively; and 52 and 51 for the solvent and control, respectively. In the field, the 6% essential oil repelled all mosquitoes immediately postapplication; this activity declined to 75% after 5 h. The repellent action of the 8% essential oil concentration was higher, 97% after 5 h. Based on these data, the essential oil of H. suaveolens appears to be a good candidate for use in the integrated management of mosquito vectors of disease.