They explained that the SFE allowed a wide range of chemicals to be isolated, while hydro-distillation was limited to volatile compounds and Soxhlet extraction was limited to high molecular compounds. Vági et al. [24] have also compared the extracts from marjoram using SC-CO2 (50 C and 45 MPa), ethanol Soxhlet extraction and hydro-distillation and the oil yields were 3.8 g/ 100 g, 9.1 g/100 g, and 0.8 ml/100 g, respectively. However, the SFE comprised 21% essential oil, while the alcoholic extract contained only 9% volatile oil substance. Zhao and Zhang [25] also compared the supercritical fluid extraction of M. oleifera leaves oil with the Soxhlet hexane extraction. The yield of the SFE process (the highest yield was 6.3%) was lower than that of the Soxhlet hexane extraction (9.3%).