M. Severin

Improvement of enzymatic synthesis yields of flavour acetates: The example of the isoamyl acetate

SummaryIsoamyl acetate synthesis was chosen as a model to improve flavour acetate yields by optimising the enzymatic reaction. Alcohol:acid molar ratio, temperature, water content and amount of enzyme effects were analyzed. The optimum values were respectively 4, 45°C, 0,1% (w/v) and 0,5 g. In these conditions, the synthesis yield reached 80 % after 24 h of reaction and was found 15 times greater than those already reported in the literature.

Biological activity of the shrubBoscia senegalensis (PERS.) LAM. ex Poir. (Capparaceae) on stored grain insects

Biological activity of leaves, fruits and extract of the African shrubBoscia senegalensis (PERS.) LAM. ex Poir. was evaluated against five stored-grain insects. When added to cowpeas at 2–4% (w/w), fresh ground fruits and leaves caused 80–100% mortality inCallosobruchus maculants (F.) adults and significantly reduced both emergence and damage of the F1 progeny. Acetone fruit extract exhibited a potent fumigant effect onProstephanus truncatusHorn, C.maculatus, andSitotroga cerealella OLIV.; with LT50 values of 3.8, 2.3, and below 1.5 hr, respectively. LC50 determination forB. senegalensis fruits and leaves as well as pure methylisothiocyanate (MITC) onTribolium castaneum HERBST,Sitophilus zeamais MOTSCH. andC. maculatus showed a differential response of the insects to plant parts or MITC. Quantitative dosage ofBoscia active components and LC50 values obtained for the plant tissues, compared to those of pure molecules, indicate that the biological activity ofB. senegalensis is due to the liberation of MITC from a glucosinolate precursor glucocapparin contained inBoscia fruits and leaves.

OPTIMIZATION OF LIPASE-CATALYZED SYNTHESIS OF CITRONELLYL ACETATE IN SOLVENT-FREE MEDIUM

SummaryCitronellol esterification catalyzed byCandida antarctica lipase is performed with high yields (74%) in a solvent-free medium. The use of dessicants gives a 10% yield enhancement and substrate excess consumption by adding calculated amounts of acetic acid lead to a 80% pure citronellyl acetate. Quantities up to 100 ml are treated with success.

Applications Of Chromatographic And Spectrometric Techniques To The Study Of Dexamethasone Related-Compounds

SummaryA methodology for the analysis of dexamethasone and related compounds is proposed. Nine corticoids (corticosteroids) have been separated by TLC and by normalphase HPLC. The optimization of the HPLC separation is performed on a diol column and with a n-hexane/isopropanol (80:20) mobile phase. Mass spectrometry is used to elucidate the nature of the compounds isolated from illicit drug formulations and to confirm the structure of synthesised derivatives from the parent dexamethasone.

Validation of a quantitative procedure for the extraction of sterols from edible oils using radiolabelled compounds

The work described in this paper is integrated in an analytical programme organised by the Community Bureau of Reference with the aim of developing reference materials certified for sterol content. Preliminary inter-comparison of methods showed that the level of agreement of the results was insufficient for certification purposes. Errors could occur in the different steps before the final determination by gas-liquid chromatography. It was, therefore, decided to validate a quantitative procedure for the isolation of sterols. A well defined saponification-extraction method was tested using labelled sterols ([3H]cholesterol and [3H]cholesteryl oleate) and radiochemical measurements. The study has shown that total cholesterol recovery reached 100.5 +/- 1.4%, that cholesteryl ester was saponified quantitatively and that there were no appreciable amounts of degradation products. The procedure has been used as the basis for the certification of three reference materials and it has been shown that the saponification and extraction procedure leads to the quantitative recovery of sterols regardless of the nature of the fatty material tested.

FAST ANALYSIS OF RAPESEED GLUCOSINOLATES BY NEAR-INFRARED REFLECTANCE SPECTROSCOPY

Industry and plant breeders require fast methods to analyze glucosinolates in rapeseed. We tested the potential of near infrared reflectance spectroscopy (NIRS) for this analysis and developed calibration equations on a large population of whole seeds. Reference methods used are high performance liquid chromatography (HPLC) and gas liquid chromatography (GLC) of desulphoglucosinolates, a glucose-release method after purification on an anion exchange column and a palladium test. In the range from 2 to 107 μM/g and after transformation of the data in first derivative, a correlation coefficient of 0.99 was observed, as well as standard errors of estimated values of 2.15, 2.52, 2.67 and 4.07 for samples analyzed by HPLC, GLC, glucose and the palladium test, respectively. With different wavelengths, a limited calibration test on seeds containing from 4 to 40 μM/g gives a standard error of 1.91 μM/g (HPLC).

Essential oil production by Anthemis nobilis L. tissue culture.

Summary The production of essential oil by tissue cultures of Anthemis nobilis L. including cell suspension, shoot and crown-gall cultures is reported. The biosynthetic capability of these different cultures was compared with that of plants grown in a field. The addition of crude polysaccharide fraction prepared from yeast extract and from the plant itself to shoot cultures affected the composition and total essential content (from 0.08 % to 0.30 % dry weight). The essential oil content of the crown-gall tissue of A. nobilis was 0.25 % of the dry weight and the composition of the essential oil was comparable to that of the flowers.

Edible fats and oils reference materials for sterols analysis with particular attention to cholesterol. Part 1. Investigation of some analytical aspects by experienced laboratories

The work reported here is integrated into a programme organized by the Community Bureau of Reference with the aim of developing edible oil reference materials (RMs) certified for cholesterol content. One vegetable oil (RM 162, a blend of soya and maize oils) and two animal fats (RM 163, a blend of pig and beef fats, and RM 164, an anhydrous milk fat) possessing, respectively, low, medium and high cholesterol contents were chosen for this purpose. The present paper summarizes the analytical conclusions resulting from three interlaboratory trials carried out to identify and correct for the major sources of random and systematic errors linked to the protocol and to the gas–liquid chromatographic analysis. Several improvements to the methodology, and recommendations, have been proposed for the determination of individual sterols within the certification exercise. The latter will be reported elsewhere.

Influence of a hormonal preparation containing glucocorticoids (dexamethasone esters), progestagen (chlormadinone acetate) and oestrogen (ethynyl oestradiol) on testosterone, insulin-like growth factor-1 (IGF-1), IGF binding proteins and spermatogenic cells in finishing bulls.

Growth-promoters are banned by the European Community, but different hormonal cocktails are still illegally used. This experiment was therefore conducted to evaluate the effects of one of the most currently used cocktails on some hormonal parameters and spermatogenesis in finishing bulls in an attempt to provide a suitable screening technique for their illegal use. Sixteen double-muscled Belgian White Blue finishing bulls (mean ivcight: 535 (s.d. 37) kg) were blocked into control (C; no. = 7) and treated (Dex; no. = 9) groups. Animals were treated i.m. with the hormonal preparation (dexamethasone isonicotinate and phosphate, chlormadinone acetate and ethinyl oestradiol) on day 0, day 15 and day 30. Animals were slaughtered on day 45. Three h before each treatment and just prior to slaughter, jugular blood samples were collected to monitor the testosterone (T) response to an i.v. injection of gonadotropin releasing hormone (GnRH) (0·5 fig GnRH per kg body weight). Testicular tissue was also collected at slaughter. Plasma T and insulin-like growth factor-1 (IGF-1) concentrations were measured by radioimmunoassay. IGF-binding proteins (IGFBPs) were evaluated using Western ligand blotting. Daily weight gains were lower in the control group (1·29 (s.d. 0·13) kg for C v. 1·60 (s.d. 0·39) kg for Dex) but the difference ivas not significant. After treatment, spermatogonia, spermatocytes, spermatids and spermatozoa disappeared from the testis and seminiferous tubules consisted only of Sertoli cells; these observations suggest that treated animals were sterile. Moreover, plasma T concentrations in response to GnRH stimulation were suppressed f P v.

Biological activity of Cassia occidentalis L. against Callosobruchus maculatus (F.) (Coleoptera: Bruchidae)

Abstract In developing countries, traditional control methods are commonly used against stored-product insects and mites. In Senegal, the leaves of Cassia occidentalis L. (Caesalpiniaceae) are used to protect cowpea seeds (Vigna unguiculata L. (Walpers)) against Callosobruchus maculatus (Coleoptera: Bruchidae). The biological activity of the leaves, the seeds and oil of C. occidentalis was evaluated in controlled conditions (28 ± 2°C, 45 ± 5% r.h.) against C. maculatus. At the rate of 10% (w/w), both fresh and dry leaves as well as whole and ground seeds had no contact toxicity on the cowpea beetle. In contrast, seed oil induced an increase in mortality of C. maculatus eggs and first larval instar at the concentration of 10 ml/kg cowpea. The basis of the ovicidal and larvicidal activities are discussed in this paper. Several trials using pure compounds have highlighted that several fatty acids (linoleic, oleic and stearic) are responsible for C. occidentalis toxicity. C. occidentalis seed oil did not reduce the oviposition of C. maculatus at 10 ml/kg seed.