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Evaluation of Solvent-Free Microwave Extraction Conditions on Essential Oils from Allium cepa Through Chemometric Analysis

[ Vol. 14 , Issue. 6 ]


Rabia Ikram*, Kah Hin Low*, Najihah Binti Hashim, Waqas Ahmad and Muhammad Nazil Afiq bin Nasharuddin   Pages 646 - 653 ( 8 )


Background: The feasibility of applying methods or the extraction of Allium cepa essential oils using solvent-free microwave extraction (SFME) has been compared to hydro-distillation (HD) process. Parameters of extraction were investigated using a rational design of experiment screening.

Objective: To screen the important factors that may influence the quantity and/or quality of the extracts derived from Allium cepa.

Method: A no. of 13 experiments were performed based on the screening process. The key parameters, such as power (350/500 W), size of the sample (chopped/sliced), quantity (500/1000 g), time of extraction (25/50 min.) and water ratio (20/50 mL) were selected based on the limitation of the instrument. The essential oils derived from Allium cepa were characterized by GC-MS analysis.

Results: The commonly collected constituents via SFME and HD are 3,4-Dimethylthiophene, Disulfide, methyl propyl, Dithiolane, 2,4-Dimethyl-5,6-dithia-2,7-nonadienal, 4,6-Diethyl-1,2,3,5- tetrathiolane, 5,7-Diethyl-1,2,3,4,6-pentathiepane (sulfur-containing compounds) and Methoxyacetic acid, cyclopentyl ester, 2-Propenoic acid, 2-methyl-, octyl ester (fatty acid esters).

Conclusion: A pragmatic relationship between the variations of extraction parameters has been studied. Results suggested and verified that among the factors, Power and time of extraction influence the process of extraction significantly.


Allium cepa, hydro-distillation, principal component analysis, solvent-free microwave extraction, essential oils, chemometric analysis.


Department of Chemistry, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Department of Chemistry, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Department of Pharmacy, Faculty of Medicine, University of Malaya, 50603, Kuala Lumpur, Institute of Chemical Sciences, University of Peshawar, 25120, Peshawar, Centre for Natural Products and Drug Discovery, Wellness Research Cluster, University of Malaya, 50603, Kuala Lumpur

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