Olive Leaves Extract Lab Report

The olive leaves extracts used in this work were prepared by extraction of dried (60°C) and grinded olive leaves (particle size fraction < 1 mm) collected in Krasregia (Slovenia) in spring 2012. Extractions were done with water and mixtures of water/organic solvents (50:50, vol %) at various sample-to-solvent ratios [g mL-1] (Table 1) in flasks equipped with condenser. Temperature has been maintained by water bath at 80°C (for water) and at 60°C (for mixtures water/organic solvents). The extraction time was 2 hours. Ethanol and acetone were used as organic solvents in mixtures with water. After extraction, olive leaves particles were removed by filtration. The extracts were evaporated to dryness at reduced pressure at 40°C and stored in glass

The most widely used method for decreasing the polarity and increasing the volatility is silylation[10]. This means that all the alcohol groups in sugar structure are protected with non-polar trimethylsilyl (- Si(CH3)3or TMS) group. For optimization of silylation process, different silylation reagents, different reaction times and different temperatures were checked. Based on literature data BSTFA silylating potential is similar to that of MSTFA and both reagents should react similar as donors for TMS groups[10], but our results did not confirm this fact. In experiments were BSTFA and BSTFA + 1% TMCS in pyridine proved as less suitable for derivatization of the compounds. Nevertheless, the derivatising yield was very low and a precipitate was formed in the reaction vial. After silylation using mentioned reagents, with or without prior oximation, at least five peaks appeared in chromatograms for glucose-TMS derivative. These drawbacks were not removed either by changing the temperatures or reaction times. Also peak-area ratios were continuously changing. Therefore, in later experiments the known powerful silylation reagent, MSTFA, was used. Using MSTFA the best results were obtained. Only MSTFA provided complete silylation and, with or without prior oximation, gave as expected one sharp peak for mannitol, and not more than two peaks for glucose in all chromatograms (Figures 1 and 2). The two peaks for TMS glucose were actually α- and β-glucopyranose-TMS isomers. Using MSTFA peak-area ratios for both isomers were constant for whole concentration range. In addition, heating enhanced the derivatisation yield, but the maximum temperature was 80 °C. At higher temperatures (110 °C) a degradation of the compounds occurred as on the chromatograms for single compound multiple peaks appeared. Finally, the reaction time was also optimised, from 30 to 120 min, and maximum