title: Optimization of the isolation and quantitation of kahweol and cafestol in green coffee oil.
abstract: Kahweol and cafestol are two diterpenes that exist mainly as esters of fatty acids in green coffee oil. To recover them under their free form they have to be either saponified or trans-esterified. These two compounds are well known to be sensitive to heat, and reagents, therefore experimental conditions used in the transesterification reaction are critical. In this paper, a Doehlert experimental design plan is used to optimize the transesterification conditions using some key variables such as the temperature of the reaction, the reagent base concentration and the duration of the reaction. Therefore, the optimal parameters determined from the Doehlert design are equal to 70 °C, temperature of the reaction; 1.25 mol L(-1) concentration of the reagent base; and 60 min reaction time. The contour plots show that the extracted quantity of kahweol and cafestol can depend greatly from the experimental conditions. After transesterification, the free form of the diterpernes is extracted from the lipid fraction using liquid-liquid extraction and analyzed using GC-FID without prior derivatization. The amount of kahweol and cafestol obtained from green coffee oil obtained by cold mechanical press of Catuai coffee bean is equal to 33.2±2.2 and 24.3±2.4 g kg(-1)oil, respectively. In an attempt to streamline the process, the transesterification reaction is performed in an in-flow chemistry reactor using the optimal conditions obtained with the Doehlert experimental design. The amount of kahweol and cafestol obtained from the same green coffee oil is equal to 43.5 and 30.072 g kg(-1)oil, respectively. Results are slightly higher compared to the ones obtained with the batch procedure. This can be explained by a better mixing of the coffee oil with the reagents and a faster transesterification reaction.
authors.affiliation: Institut de Chimie Organique et Analytique (ICOA), Université d'Orléans-CNRS, Rue de Chartres BP 6759, 45067 Orléans cedex 2, France. Electronic address: Agnes.chartier@univ-orleans.fr.
authors.forename: Agnes
authors.initials: A
authors.lastname: Chartier
authors.forename: Mathieu
authors.initials: M
authors.lastname: Beaumesnil
authors.forename: Alessandra Lopes
authors.initials: AL
authors.lastname: de Oliveira
authors.forename: Claire
authors.initials: C
authors.lastname: Elfakir
authors.forename: Stephane
authors.initials: S
authors.lastname: Bostyn
mesh_terms: D002849:Chromatography, Gas; D040503:Coffea / Q000737:chemistry*; D004224:Diterpenes / Q000302:isolation & purification*; D004952:Esters; D005163:Factor Analysis, Statistical; D059625:Liquid-Liquid Extraction / Q000379:methods; D013058:Mass Spectrometry; D010938:Plant Oils / Q000737:chemistry*; D013696:Temperature
chemical_list: D004224:Diterpenes; D004952:Esters; D010938:Plant Oils; C053401:kahweol; C053400:cafestol
keywords: Cafestol; Doehlert design; Flow chemistry; Kahweol; Quantification; Transesterification