title: [Effects of lemon peel extracts on lactate dehydrogenase and sucrase activity of Streptococcus mutans].
abstract: 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 coenzymeIand 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, sucrase 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) × 10(3) U/L to (0.2099 ± 0.0283) × 10(3) U/L; the activity of sucrase were declined from (-0.0107 ± 0.0003) × 10(3) U/L to (-0.0078 ± 0.0002) × 10(3) U/L; the ΔpH 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.
authors.affiliation: Department of Preventive Dentistry, Tianjin Medical University Dental Hospital, Tianjin, 300070, China. zxy_tj@sohu.com
authors.forename: Xiang-yu
authors.initials: XY
authors.lastname: Zhang
authors.forename: Zhi-fen
authors.initials: ZF
authors.lastname: Yu
authors.forename: Da-zhao
authors.initials: DZ
authors.lastname: Wang
authors.forename: Ying
authors.initials: Y
authors.lastname: Liu
authors.forename: Mao-ding
authors.initials: MD
authors.lastname: Guo
mesh_terms: D002957:Citrus / Q000737:chemistry*; D005947:Glucose; D007770:L-Lactate Dehydrogenase / Q000378:metabolism*; D019344:Lactic Acid; D010936:Plant Extracts / Q000494:pharmacology; D013295:Streptococcus mutans / Q000201:enzymology*; D013393:Sucrase / Q000378:metabolism*
chemical_list: D010936:Plant Extracts; D019344:Lactic Acid; D007770:L-Lactate Dehydrogenase; D013393:Sucrase; D005947:Glucose