柠檬精油对表兄链球菌致龋毒力因子的影响

Effect of lemon essential oil on caries factors of Streptococcus sobrinus

目的探讨柠檬精油降低表兄链球菌（Streptococcus sobrinus，Ss）致龋力的相关机制。方法自行提取柠檬精油，纸片扩散法测定柠檬精油对Ss的最小抑菌浓度（minimal inhibitory concentration，MIC），将柠檬精油倍比稀释为小于MIC的4个质量浓度组（分别为0．281、0．563、1．125、2．250∥L实验组），以胰蛋白胨酵母液体培养基作为对照组。加入10^8 CFU／ml的Ss菌悬液，厌氧培养6、18、24、48h。Neson—Somogyi法测定各时间点的还原糖量，计算葡糖基转移酶（glucosyltmnsfemse，GTF）活性；乳酸一丙酮酸连续检测法测定各时间点乳酸脱氢酶（1actatedehydrogenase，LDH）活性；蒽酮法测定各时间点水不溶性多糖（waterinsolubleglucan，WIG）的含量；pH计测定培养液各时间点pH值，计算实验前和各时点的pH差值（ApH）。结果在同一时点随着柠檬精油质量浓度的升高，GTF、LDH活性、WIG含量及ApH值均逐渐降低，各实验组与对照组间差异均有统计学意义（P〈0．01），GTF、LDH、WIG及ApH的最高值均出现在对照组，分别为（6．71±0．61）mIU、（135．8±1．7）U／L、（47．15±5．12）mg／L及（2．67±0．01）；最低值均出现在最高质量浓度（2．250egL）实验组，分别为（0．39±0．07）mIU、（95．0±5．4）U／L、（2．44±0．38）mg／L及（0．61±0．01）。结论低于MIC的柠檬精油仍具有抑制SsGTF、LDH活性的作用，导致WIG合成减少，细菌产酸量降低。

Objective To investigate the mechanism of lemon peel essential oil （LPE） on the cariogenicity of Streptococcus sobrinus （Ss）. Methods LPE was extracted by the authors, and the minimum inhibition concentration （MIC） was measured by disc diffusion method. The LPE was used as the experimental group with concentrations ranging from 2. 250 g/L to 0. 281 g/L prepared with trypticase peptone yeast（TPY） culture medium, and TPY culture medium was used as the control group. Ss at the concentration of l0s CFU/ml was added to each group, and cultured for 6, 18, 24, 48 hours . Neson- Somogyi method was used to measure the content of reducing sugar, and glucosyltransferase （GTF）activity. The activity of lactate dehydrogenase （LDH）was measured by lactic acid and pyruvic acid continuous monitoring method. The content of water insoluble glucan （WIG） was measured by anthrone method, and the pH value of the culture solution was detected. The value of pH before the experiment and the time difference was alculated as A pH. Results At the same time point, the activity of GTF and LDH and the concentration of WIG and the value ApH decreased gradually with the increase of concentration of LPE. There were significant differences between each experimental group and control group （ P 〈 0. 01 ）. The control group had the maximum value, GTF： （6. 71 ± 0. 61 ） mIU, LDH： （ 135.8 ± 1.7） U/L, WIG： （47.15 ± 5.12） mg/L, ApH： （2. 67 ± 0. 01 ）. The highest drug concentration group had the minimum value ： GTF ： （0. 39 ± 0. 07 ） mlU, LDH ： （95.0 ± 5.4 ） U/L, WIG ： （ 2. 44 ± 0. 38 ） mg/L, A pH ： （ 0. 61 ± 0. 01 ）. Conclusions The LPE below the MIC could still inhibit the GTF, LDH activity and lead to the decrease of WIG and the acid production.