Extraction of the Volatile Oils of Dictyopteris membranacea Batters 1902 by Focused Microwave-assisted Hydrodistillation and Supercritical Carbon Dioxide: Empirical Kinetic Modelling Approach, Apparent Solubility and Rate Constants

N. Riad, N. Bouzidi, M. R. Zahi, O. Touafek, Y. Daghbouche, L. Piovetti and M. El Hattab

Abstract
Supercritical carbon dioxide extraction (SCCO2) and focused microwave-assisted hydrodistillation (FMAHD) were used comparatively to isolate the volatile oils of the brown alga Dictyopteris membranacea from the crude ether extract. The volatiles fractions were analysed by GC/MS, the major compounds were: dictyopterene A, 6-butyl-1,4-cycloheptadiene, 1-undecen-3-one, 1,4-undecadien-3-one, (3-oxoundec-4-enyl) sulphur, tetradecanoic acid, hexadecanoic acid, 3-hexyl-4,5-dithiacycloheptanone, and albicanol. A kinetics study of the extraction of the volatile fractions obtained by the two processes was carried out, an external calibration allowed to quantify the content of the main metabolites. Empirical models were applied to adjust the experimental kinetics values but also to determine the values of apparent solubilities for SCCO2 and the rate constants for FMAHD. The results obtained revealed that the SCCO2 process was characterized by the coexistence of three distinct phases. For FMAHD, the extraction mechanism included two steps.

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Keywords
Dictyopteris membranacea, volatile oil, SCCO2, FMAHD, modeling, apparent solubility