提取方法对百里香精油化学成分和抗氧化活性的影响

本文分别采用水蒸气蒸馏法（SD）、同时蒸馏萃取法（SDE）、冷等离子体辅助提取法（CPAE）从百里香叶片中提取精油，通过气相色谱-质谱联用（GC-MS）分析了三种精油中的挥发性成分，测定其精油中的总酚、总黄酮、花青素含量，通过DPPH?、ABTS+?、总抗氧化能力三个抗氧化指标评估了其体外抗氧化性，并将精油中的主要活性成分与抗氧化能力进行相关性分析，比较得出得率更高、抗氧化性更好的提取方法。结果表明，不同提取方法在精油得率上有显著性差异（P<0.05），SDE法的精油得率最高，达到了1.30%。经GC-MS分析，三种精油共检出了36种组分，主要成分均为2-茨醇（32.194%~32.515%）、香芹酚（17.265%~19.998%）、百里香酚（13.031%~15.202%）和α-松油醇（11.296%~12.012%），其中，SDE法和CPAE法比SD法制备得到的精油在以上活性成分上含量更高。在总酚、总黄酮、花青素的测定结果中，SDE法制备得到的精油中总酚和花青素含量更高，分别为133.67±0.20 mg GA/g EO、0.32±0.02 mg/g EO，CPAE法制得的精油总黄酮含量最高，达到了54.82 mg Rutin/g EO。在体外抗氧化性实验中，三种精油在实验浓度范围内对各项抗氧化指标都表现出较强的抗氧化性和明显的量效关系，其中，SDE法获得的精油对于自由基的清除效果更佳，在最高实验浓度下清除率均在96%以上。通过抗氧化相关性分析发现，百里香精油的抗氧化活性与酚类等物质的含量密切相关。综上，从各项实验结果来看，SDE法是一种更为可取的提取百里香精油的方法。

Effect of Extraction Methods on Chemical Constituents and Antioxidant Activity of Essential Oil from Thymus vulgaris L.

The essential oils from Thymus vulgaris L. were extracted by using different methods of stream distillation (SD), simultaneous distillation extraction (SDE), and cold plasma assisted extraction (CPAE) separately, then the volatile components in the essential oils were identified by GC-MS. The contents of total phenols, flavonoids and anthocyanins in essential oil were determined. Its antioxidant activity in vitro was evaluated by three antioxidant indexes: DPPH?, ABTS+? and total antioxidant capacity, and the correlation between the main active components in essential oil and antioxidant capacity was analyzed. Therefore, the extraction method with higher rate and better antioxidant capacity was obtained. The results showed that different extraction methods had significant difference in yield (P<0.05). And the SDE method had the highest yield, reaching 1.30%. By GC-MS analysis, 36 components of the three essential oils were detected. The main volatile components were borneol (32.194%~32.515%), carvacrol (17.265%~19.998%), thymol (13.031%%~15.202%), α-terpinol (11.296%~12.012%). The SDE and CPAE methods had higher contents of main active ingredients than SD method. In the determination results of total phenols, total flavonoids and anthocyanins, the contents of total phenols and anthocyanins in the essential oil prepared by SDE method were 133.67±0.20 mg GA/g EO and 0.32±0.02 mg/g EO, respectively. The contents of total flavonoids in the essential oil prepared by CPAE method were the highest, reaching 54.82 mg Rutin/g EO. In vitro antioxidant experiments, the three essential oils showed strong antioxidant activity and obvious dose-effect relationship to various antioxidant indexes within the experimental concentration range. Among them, the essential oil obtained by SDE method had better scavenging effect on free radicals, and the scavenging rate was above 96% at the highest experimental concentration. Correlation analysis showed that the antioxidant activity of the essential oils were closely related to the content of phenols and other main substances. In conclusion, according to the experimental results, the SDE method is a more desirable method for the extraction of essential oils from Thymus vulgaris L..