Check valve and non-oxygen microwave assisted extraction of Chinese herbs: study of a novel technique for extraction of essential oils

Abstract

A novel green extraction technique of check valve & non-oxygen microwave assisted extraction (CVNO-MAE) for essential oils extraction was established. CVNO-MAE is a combination of microwave heating, vacuum pump and check valve, performed at anaerobic environment without added any solvent or water. CVNO-MAE has been compared with a conventional technique, solvent free microwave extraction (SFME), for the extraction of essential oils from two Chinese herbs: Curcuma phaeocaulis and Mentha haplocalyx. GC-MS analyses of the oils revealed the presence of 36 and 37 compounds in the essential oils of C. phaeocaulis and M. haplocalyx, respectively. There was an obvious difference in the quality of essential oils obtained by the two kinds of extraction methods. The CVNO-MAE method yielded an essential oil of C. phaeocaulis with lower amounts of oxygenated compounds (45.53%) than SFME (62.38%). Higher amounts of oxygenated compounds (89.57%) were present in the M. haplocalyx essential oil of SFME in comparison with CVNO-MAE (82.74%). CVNO-MAE is a fast low temperature extraction method carried in under pressure, appears as a good alternative for the extraction of essential oils from Chinese herbs and a green technology.