Marco Pelillo

Analysis of green tea catechins: comparative study between HPLC and HPCE

Abstract A comparison between a borate–phosphate–SDS based MEKC and an RP-HPLC method for the separation of seven tea catechins and gallic acid in a green tea extract is here proposed. Under optimised conditions, HPCE offered several advantages respect to time of analysis (compounds were separated within 4.5 min), sensitivity (HPCE LODs were about 20–100 times lower than HPLC ones) and solvent consumption. HPCE displayed excellent migration time repeatability (RSD% on MT

Preliminary investigation into development of HPLC with UV and MS-electrospray detection for the analysis of tea catechins

Abstract There is an increasing interest in the biological and technological role of natural antioxidants present in green tea extracts. This is due to the inhibition of the oxidative process showed by tea catechins, which is higher than those of synthetic antioxidants (such as BHT) and other vegetal extracts (rosemary, oregano, grape seeds). In a first step of the work a rapid reversed phase HPLC method for the determination of catechins in green tea extracts, using a binary gradient system, was developed. Commercial green tea extracts were analyzed and the different catechins quantified. EGCG ((−)-epigallocatechin-3-gallate) and EGC ((−)-epigallocatechin) were proposed as index of the antioxidant quality of tea extracts. Subsequentely, the previous chromatographic method was applied on a HPLC–MS system in order to verify the accuracy of some HPLC-DAD results and compare the two detection modes, on such a polyphenolic mixture. The use of mass spectrometry detection in quantification of catechins ensured an higher specificity of the method and a constant qualitative control of the identity of chromatographic peaks thanks to the concurrent acquisition of more than one mass signal (as M+1 and M+Na pseudomolecular peaks).

Calculation of the molar absorptivity of polyphenols by using liquid chromatography with diode array detection: the case of carnosic acid.

Antioxidant activity of vegetable extracts is related to the nature and the amount of active components, mainly polyphenols; therefore, a correct quantification of these molecules should be required to define their concentration in such kind of vegetable extracts. A fast and accurate method to calculate molar absorption coefficients (epsilon), by using HPLC, has been tested on standard polyphenols and caffeine, and should be widely adapted for standardless quantitative analysis. Molar absorptivity (epsilon) of carnosic acid (CA) was determined from 200 to 300 nm, by the proposed method and those values were compared to tert-butyl-hydroxytoluene (BHT) ones for further comparative quantification.

Fast separation and determination of carnosic acid and rosmarinic acid in different rosemary (Rosmarinus officinalis) extracts by capillary zone electrophoresis with ultra violet-diode array detection

SummaryCarnosol, carnosic acid, rosmarinic acid and other not identified phenolic compounds were separated by capillary zone electrophoresis (CZE) using a 40-cm long capillary and a 20 mM tetraborate buffer (pH 9.0), within 3 min. A UV-diode array detector was employed to collect spectra of phenolic compounds. The effect of some separation parameters on peak resolution and migration time of phenolic species present in a refined rosemary extract was studied. The repeatability of the method was also investigated: the intraday relative standard deviation on total peak area was less than 4%, while the intraday relative standard deviation on migration time was less than 0.6%. Moreover the CZE method showed good sensitivity (0.0007 μg mL1 for carnosic acid and rosmarinic acid). Carnosic acid and rosmarinic acid have been quantified in different commercial extracts of rosemary. Finally, the optimized method was also applied to evaluate the recovery of these two compounds when different organic solvents were employed during the extraction procedure.

Mass spectral fragmentations of cholesterol acetate oxidation products

In this work, electron-impact mass spectroscopy (EI-MS) was employed on a wide range of sterol compounds in order to study their behaviour with regard to their functional groups. In particular, some specific mechanisms of fragmentation occurring in these substrates (i.e. retro-Diels-Alder reaction, neutral molecules eliminations, specific hydrogen migrations) were investigated. Loss of the alkyl side chain and of the D ring were observed in all cases. Finally, a classification of sterols on the basis of characteristic mass spectral fragments is suggested, and further applications to substrates with functional groups on positions other than the A and B rings is proposed.