柠檬提取物对变形链球菌乳酸脱氢酶和蔗糖酶活性的影响

目的 观察柠檬提取物对变形链球菌(Streptococcus mutans,Sm)乳酸脱氢酶、蔗糖酶活性的影响,探讨柠檬酸提取物抑制Sm致龋活力的相关机制.方法 采用二倍稀释法,用含2%蔗糖的胰蛋白胨大豆肉汤将柠檬提取物的抑菌浓度稀释为0.64、0.32、0.16、0.08及0.04 g/L共5个质量浓度的溶液(5个实验组),以胰蛋白胨大豆肉汤液体培养基作为空白对照组.加入Sm菌液,厌氧培养6、18、24及48 h,采用还原性辅酶Ⅰ氧化法测定乳酸脱氢酶活性、用pH计测定培养液的pH变化值(△pH),同时采用3,5-二硝基水杨酸显色法测定蔗糖酶的活性.结果 随着柠檬提取物浓度的升高(0.04～0.64 g/L),乳酸脱氢酶、蔗糖酶活性和△pH均逐渐降低(P＜0.01):加入Sm厌氧培养24 h后,Sm乳酸脱氢酶活性从(0.8025±0.0913)×103 U/L降至(0.2099±0.0283)×103 U/L,Sm蔗糖酶活性从(-0.0107±0.0003)×103U/L降至(-0.0078±0.0002)×103 U/L,Sm △pH从2.8067±0.0404降至2.5033±0.0416(24 h).各实验组之间及与空白对照组之间差异有统计学意义(P＜0.01);柠檬提取物对Sm产酸的抑制作用与对乳酸脱氢酶活性的抑制作用之间呈正相关(r=0.8120～0.9918,P＜0.01).结论 低于抑菌浓度的柠檬提取物对Sm乳酸脱氢酶活性和蔗糖酶活性及产酸能力都具有显著抑制作用,作用强度具有浓度依赖性,对对数期细菌抑制作用强于其他生长周期,具有防龋药物的潜能.

Effects of lemon peel extracts on lactate dehydrogenase and sucrase activity of Streptococcus mutans

Objective To investigate the effect of lemon peel extracts(LPE) on the activity of lactate dehydrogenase and sucrase of Streptococcus mutans (Sm). Methods After serial dilution with trypticase soy broth (TSB) medium containing 2% glucose, LPE was used as the experimental group, and TSB without LPE as the control group. Sm was added to each group,which was then cultured for 6,18,24 and 48 hours in the anaerobic tank. The activity of lactate dehydrogenase (LDH) was measured with the method of oxidation of reduction coenzyme I and the pH value of the culture solution was also detected. The activity of the sucrose was determined with the method of coloration of 3,5-dinitrosalicylic acid. Results The activity of LDH, sucraae and the changes of solution pH were decreased with the increase of the concentration of LPE (P ＜ 0. 01 ). The activity of LDH were declined from (0. 8025 ± 0. 0913 ) × 103 U/L to (0. 2099 ±0. 0283) × 103 U/L; the activity of sucrase were declined from ( -0. 0107 ±0. 0003) × 103 U/L to ( -0.0078 ±0.0002) × 103 U/L; the△pH were declined from(2.8067 ±0.0404) to (2.5033 ±0. 0416) (24 h results). The differences were significant between experimental groups and the control group (P ＜ 0. 01 ), and there were also significant differences among experimental groups with different LPE concentration( P ＜0. 01 ). The inhibitory effect of acid generation and lactate dehydrogenas' activity of Sm were positively correlated ( P ＜ 0. 01 ). Conclusions LPE can inhibit the activity of lactate dehydrogenase,sucrase and the acid production capacity of the Sm in a dose dependent manner. The inhibitory effects in logarithmic phase is stronger than that in other phases of growth cycle.