Karel Stránský

Solubility of two vegetable oils in supercritical CO2

Abstract Dynamic method was applied to measure the solubility of oils from seed of Ribes nigrum (blackcurrant) and Vitis vinifera (grape-vine) in supercritical CO 2 at pressures up to 29 MPa. The solubility of blackcurrant seed oil, which had been refined prior to the measurement and therefore it contained only triglycerides, was measured at 40–60°C. It was correlated with CO 2 density and temperature by adjusting the constants of Adachi–Lu equation. The obtained equation is suitable for predicting the solubility of triglycerides of most vegetable oils. The solubility of grape seed oil, containing large percentage of free fatty acids, mono- and diglycerides, was measured at 40°C. It was twice as large as the solubility of refined blackcurrant seed oil, and it decreased after most of the free fatty acids had been extracted. A simplified stepwise model describing fractionation of the mixture during the solubility measurement was derived and applied to estimate the grape seed oil solubility and its changes.

Selective enzymic esterification of free fatty acids with n-butanol under microwave irradiation and under classical heating

Selective enzymic esterification of free fatty acids, obtained from blackcurrant oil by chemical saponification, with n-butanol using four immobilized lipases under microwave irradiation and under classical heating was studied. A positive effect of microwave irradiation on chemical yields of the products of the enzymic reactions and specificity of lipases were observed in comparison with a controlled heating in an incubator equipped with shaking (classical heating) applied during the identical enzyme-mediated processes. The maximum quantity of γ-linolenic acid (30%) was obtained with Lipozyme used as biocatalyst of the reaction under microwave irradiation. The maximum quantity of butyl γ-linolenate (20%) was obtained by a Pseudomonas cepacia lipase catalyzed esterification under classical heating.

Release of volatiles during the flowering period of Hydrosme rivieri (Araceae)

Abstract The release of volatile compounds from a flower of Hydrosme rivieri was recorded during the whole flowering period (7 days). The quantities of six odour components (dimethyl disulphide, dimethyl trisulphide, n -alkanes C 10 , C 11 , C 12 and C 13 ) forming the main part of emanating volatiles were plotted versus time. n -Alkanes started to emanate 3 days before the release of dimethyl disulphide and dimethyl trisulphide (the components with a rotting meat odour).

Lipase-mediated hydrolysis of blackcurrant oil

Four commercially available lipases, both free and immobilized, were tested for their ability to catalyze hydrolysis of blackcurrant (Ribes nigrum) oil using two different approaches. The lipase from Mucor miehei was studied free and immobilized in two different ways. The former series of enzymic reactions were performed in tap water at 40 degrees C, but the latter series of enzymic processes were carried out in mixtures of isooctane and phosphate buffer (in a typical 2/1 ratio of the components) at 30 degrees C. These conditions were optimized to increase and/or to maximize the yields of the products, which were priority targets in this study. A rate of hydrolysis and a selective preference of the hydrolytic enzymes towards fatty acids, with a special focus on enrichment of alpha-linolenic acid and/or gamma-linolenic acid, were studied. Higher rates of hydrolysis of the blackcurrant oil in the former series of reactions were observed with the immobilized lipase from Pseudomonas cepacia used as biocatalyst. In the latter approach, the most favorable results of the rate of hydrolysis of the target blackcurrant oil were achieved with the immobilized lipase from Mucor miehei employed as biocatalyst. Only three lipases, selected from a series of lipases tested during this investigation, displayed specificity towards alpha-linolenic acid and gamma-linolenic acid, i.e. the immobilized lipase from P. cepacia, lipase from M. miehei and lipase from P. fluorescens.

Unusual Fatty Acids in the Fat Body of the Early Nesting Bumblebee, Bombus pratorum

Unusual fatty acids with 24, 26, and 28 carbon atoms were found in triacylglycerols (TAGs) isolated from fat body tissue of bumblebee Bombus pratorum. The most abundant one was (Z,Z)-9,19-hexacosadienoic acid. Its structure was determined by mass spectrometry after derivatization with dimethyl disulfide and by infrared spectroscopy. ECL (equivalent chain length) values of its methyl ester were determined on both DB-1 and DB-WAX capillary columns. (Z,Z)-9,19-Hexacosadienoic acid is quite rare in nature. So far it has been identified only in marine sponges, and this work is the first evidence of its occurrence in a terrestrial organism. HPLC/MS analysis of the bumblebee TAGs showed that (Z,Z)-9,19-hexacosadienoic acid is present in one third of all TAG molecular species. As it was found in all sn-TAG positions, it is likely that (Z,Z)-9,19-hexacosadienoic acid is transported to tissues. Interestingly, labial gland secretion of B. pratorum was found to contain (Z,Z)-7,17-pentacosadiene, a hydrocarbon with markedly similar double bond positions and geometry. Possible biosynthetic relationships between these two compounds are discussed.

Nonsaponifiable lipid components of the pollen of elder (Sambucus nigra L.)

Pollen of the elder (Sambucus nigra L.) was extracted with chloroform-methanol. The extract was separated by column chromatography into the following groups of compounds: hydrocarbons (8.7%). polycyclic aromatic hydrocarbons (0.2%), complex esters (5.2%), triglycerides (18.7%), hydroxy esters (27.9%), free fatty acids and alcohols (16.8%), free sterols (6.8%), and triterpenic alcohols (4.0%). The nonsaponifiable components (hydrocarbons, fatty acids, alcohols, and sterols) were examined in detail using spectroscopic and chromatographic methods (IR spectroscopy, GC, and GC-MS). The identified compounds were characterized by their mass spectra and Kováts retention indices. The double bond positions and their configurations in unsaturated compounds are also reported.