title: Thermal degradation of allicin in garlic extracts and its implication on the inhibition of the in-vitro growth of Helicobacter pylori.
abstract: Allicin, the main active principle related to Allium sativum chemistry, is considered to be responsible for the bacteriostatic properties of garlic. The work described here has demonstrated the direct implication of the allicin present in solvent-free garlic extracts obtained with ethanol (ethanolic garlic extract, EGE) and acetone (acetonic garlic extract, AGE) in the inhibition of the in-vitro growth of Helicobacter pylori (Hp), the bacterium responsible for serious gastric diseases such as ulcers and even gastric cancer. The evolution of allicin concentration as a function of time and temperature has been the subject of a kinetic study. The reaction order, activation energy, and preexponential factor (in accordance with Arrhenius theory) have been determined for the decomposition process of allicin in these organic media. First-order decomposition, an activation energy of 97.4 kJ/mol, and an Arrhenius preexponential factor of 8.9 x 10(10) s(-1) have been determined for allicin in EGE. For allicin in AGE the kinetic order determined was 1.5, the activation energy 184.5 kJ/mol, and the preexponential factor 3.1 x 10(24) s(-1) (mg/L)(-0.5). The presence or absence of allicin in these garlic products was found to be crucial for the inhibition of the in-vitro growth of Hp, as demonstrated by microbiological analysis for AGE. A relationship has been identified between the effectiveness and durability of the anti-Hp properties shown by AGE and the allicin content of these products. The bacteriostatic properties were active for up to 10 months if the samples were maintained at 6 degrees C.
authors.affiliation: Departamento Ingeniería Química, Facultad de Ciencias Químicas, Universidad de Castilla-La Mancha, Avenida Camilo José Cela 10, 13004 Ciudad Real, Spain.
authors.forename: Pablo
authors.initials: P
authors.lastname: Cañizares
authors.forename: Ignacio
authors.initials: I
authors.lastname: Gracia
authors.forename: Luis A
authors.initials: LA
authors.lastname: Gómez
authors.forename: Antonio
authors.initials: A
authors.lastname: García
authors.forename: Carlos
authors.initials: C
authors.lastname: Martín De Argila
authors.forename: Daniel
authors.initials: D
authors.lastname: Boixeda
authors.forename: Luis
authors.initials: L
authors.lastname: de Rafael
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D001673:Biodegradation, Environmental; D002455:Cell Division / Q000187:drug effects; D004220:Disulfides; D004355:Drug Stability; D005737:Garlic / Q000737:chemistry*; D016480:Helicobacter pylori / Q000166:cytology / Q000187:drug effects*; D007700:Kinetics; D010936:Plant Extracts / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology*; D013441:Sulfinic Acids / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology*; D013696:Temperature
chemical_list: D000900:Anti-Bacterial Agents; D004220:Disulfides; D010936:Plant Extracts; D013441:Sulfinic Acids; C006452:allicin