Study On Extraction, Refining And Physical Modification Of Litsea Cubeba Essential Oil

Litsea cubeba is endemic plant resource in our country, however, utilization ratio of Litsea cubeba is lower. The extraction, purification and chemical composition analysis of Litsea cubeba essential oil, inclusion of citral and β-CD derivatives, and preparation of essential oil-β-CD complex were studied. In the present work, the main results were listed as followings.(1)Extraction process and dynamic model of Litsea cubeba essential oilExtraction processes of Litsea cubeba essential oil extracted by SD, UMASD and MASD were optimized. The extraction yield of Litsea cubeba essential oil for SD was 3.06% under optimization conditions of extraction time of 4 hours, liquid-solid ratio of 20:1 mL·g-1. The optimum conditions of UMASD were microwave power of 100W, liquid-solid ratio of 20:1 mL·g-1 and extraction time of 2 hours, and extraction yield of Litsea cubeba essential oil was 3.22%. The extraction yield of Litsea cubeba essential oil for MASD was 3.07% under optimization conditions of microwave power of 100 W, liquid-solid ratio of 20:1 mL·g-1 and extraction time of 2 hours.Based on the theory of mass transfer, The dynamic model of Litsea cubeba essential oil extracted by SD, UMASD and MASD were Vt=0.87081(1-e-0.00362t), Vt=0.63924(1-e-0.01304t) and Vt=0.64022(1-e-0.01157t), respectively. The correlation coefficients of three dynamic model were more than 0.995, and the variances were less than 0.002.(2) Chemical composition analysis of Litsea cubeba essential oilThe effects of extraction methods, preservation time, localities and different parts of Litsea cubeba on chemical compositions of essential oil were systematically investigated. The chemical compositions of Litsea cubeba essential oil extracted by different methods were same, however, their content was different. The citral content of essential oil extracted from fresh fruit was far higher than that of dried fruit, and the quality of essential oil obtained from fresh fruit was better than that of dried fruit. The chemical compositions of essential oil obtained from different regions were significant differences, which was relevant to Litsea cubeba variety, geography and climate conditions. The chemical compositions of essential oil extracted from different parts of Litsea cubeba were significant differences.(3)Purification process of citral from Litsea cubeba essential oilHigh purity citral was prepared from Litsea cubeba essential oil by addition and hydrolysis reaction, and purification process was obtained. When catalyst was not added, the optimum conditions were reaction time of 6 hours and reaction temperature of 10℃, and purify and yield of citral were 95.40% and 86.86%, respectively. When RM-β-CD was used as catalyst, the optimum conditions were reaction time of 3.33 hours, catalyst dosage of 0.050%(mol%) and reaction temperature of 15.52℃ by single factor experiment and Box-Behnken experiment design, and purify and yield of citral were 96.70% and 85.80%, respectively.(4)Inclusion of citral and β-cyclodextrin derivativesThe stoichiometric ratio in citral-β-CD derivatives complexes and formation constants were studied by spectrophotometry, and thermodynamics parameters were calculated. The 1:1 complex between citral and β-CD derivatives was formed. The formation constants of citral-p-CD derivatives complexes decreased with the increase of temperature. The formation constant of citral-β-CD complex was less than those of citral-RM-β-CD complex and citral-HP-β-CD complex under same temperature. The thermodynamics parameters showed that the formation of complexes was spontaneous and exothermic process, and the main driving force was enthalpy (AH0).(5)Preparation and properities of Litsea cubeba essential oil-β-CD complexThe optimum process of Litsea cubeba essential oil-β-CD complex was obtained by orthogonal experiment. The optimum conditions were oil-solid ratio of 1:6, inclusion temperature of 30℃ and inclusion time of 1.5 hours, and the inclusion rate of essential oil and yield of complex were 71.15% and 89.31%, repectively. Complex was confirmed by UV, IR, X-RD and SEM. The thermal stability and photostability of Litsea cubeba essential oil-β-CD complex were improved.