Gaetan Richard

(Trans)esterification of mannose catalyzed by lipase B from Candida antarctica in an improved reaction medium using co-solvents and molecular sieve

Four co-solvents (dimethylformamide [DMF], formamide, dimethyl sulfoxide [DMSO], and pyridine) were tested with tert-butanol (tBut) to optimize the initial rate (v0) and yield of mannosyl myristate synthesis by esterification catalyzed by immobilized lipase B from Candida antarctica. Ten percent by volume of DMSO resulted in the best improvement of v0 and 48-hr yield (respectively 115% and 13% relative gain compared to pure tBut). Use of molecular sieve (5% w/v) enhances the 48-hr yield (55% in tBut/DMSO [9:1, v/v]). Transesterification in tBut/DMSO (9:1, v/v) with vinyl myristate leads to further improvement of v0 and 48-hr yield: a relative gain of 85% and 65%, respectively, without sieve and 25% and 10%, respectively, with sieve, compared to esterification. No difference in v0 and 48-hr yield is observed when transesterification is carried out with or without sieve.

Phytotoxic activity and chemical composition of Cassia absus seeds and aerial parts

Abstract The present study was conducted to assess the phytotoxic potential and the phytochemical composition of Cassia absus. Aqueous extracts caused significant reduction in root growth of Lactuca sativa. Seed extract was more effective than aerial part extract. Successive extractions of this plant were performed using solvents with increasing polarities. The methanolic seed extract exerted strong phytotoxic effect on seedling growth, followed by petroleum ether extract of the aerial part. The phytochemical investigation showed that among the organic extracts, methanol extracts of seeds and aerial parts contained the highest amounts of total phenolics and proanthocyanidins. Seeds were rich in linoleic acid followed by palmitic acids. Palmitic, stearic and arachidic acids were the major fatty acids in aerial parts. HPLC-DAD analysis of the methanolic extracts revealed the presence of luteolin in C. absus aerial parts.

Hepatoprotective and antidiabetic activities of Fraxinus angustifolia Vahl extracts in animal models: characterization by high performance liquid chromatography analysis.

BACKGROUND/AIM The present study was designed to explore antidiabetic and hepatoprotective potentials of Fraxinus angustifolia leaf (FAL) and bark (FAB) extracts in vivo. MATERIALS AND METHODS Streptozotocin (STZ)-induced diabetic rats, pretreated with the extracts (25 and 50 mg/kg), were monitored for fasting blood glucose (FBG) levels. Hepatoprotective potential was examined after injection of an excessive dose of paracetamol (10 g/60 kg) by analysis of biochemical parameters (transaminases, bilirubin), malondialdehyde (MDA) levels, and histological sections. high performance liquid chromatography analysis was also performed for partial characterization. RESULTS A considerable hypoglycemic effect was noticed 2 h after the STZ-induction, with a higher efficiency (P < 0.05) for FAL (68%) as compared with FAB (57%). A significant (P < 0.05) reduction in MDA was observed for paracetamol-fed mice pretreated with FAL (50 mg/kg), FAB (50 mg/kg), or both (25 mg/kg each) extracts, and the MDA levels for the three conditions were 0.290 ± 0.034, 0.340 ± 0.038, and 0.25 ± 0.058 nmoles/mg of liver tissue, respectively). Hence, simultaneous treatment provided a better protection. Histological observations confirmed the higher hepatoprotective potential of FAL over FAB extracts. CONCLUSION The obtained results indicate the possibility of pharmacological exploitation of F. angustifolia extracts in the treatment of diabetes and associated liver diseases.

Biochemical composition of Tunisian Nigella sativa L. at different growth stages and assessment of the phytotoxic potential of its organic fractions

Abstract The present study was conducted to study some biochemical characteristics of Tunisian Nigella sativa at different developmental stages of plant growth (vegetative, flowering and fruiting stages) and to screen the chemical constituents and the phytotoxic activity of their organic extracts on lettuce (Lactuca sativa L.). The GC–MS analysis of petroleum ether fractions revealed that N. sativa seeds were rich in linoleic acid (58% of total fatty acids), oleic acid (22% of total fatty acids) and palmitic acid (12% of total fatty acids). The fatty acid composition of aerial parts showed an increase in the level of saturated fatty acids accompanied by a concomitant decrease of polyunsaturated fatty acids levels during the developmental stage. The phytochemical investigation showed that among the organic extracts, the methanolic extract from aerial parts harvested at the fruiting stage contained the highest amounts of phenolic and flavonoid compounds. The phytotoxic study revealed that N. sativa negatively affected the growth of lettuce plants. This effect was largely dependent on the developmental stage at which material was collected and the nature of extracting solvent. The methanolic extract of aerial parts harvested at the vegetative stage was the most active on seedling growth of lettuce.