Garlic's ability to prevent <it>in vitro </it>Cu²⁺-induced lipoprotein oxidation in human serum is preserved in heated garlic: effect unrelated to Cu²⁺-chelation

• Main Authors: Menjívar Marta, Barbachano-Esparza Laura, Albarrán Gabriela, Gil-Ortiz Mariana, Pedraza-Chaverrí José, Medina-Campos Omar N
• Format: Article
• Language: English
• Published: BMC 2004-09-01
• Series: Nutrition Journal
• Online Access: http://www.nutritionj.com/content/3/1/10
• ISSN: 1475-2891

<p>Abstract</p> <p>Background</p> <p>It has been shown that several extracts and compounds derived from garlic are able to inhibit Cu²⁺-induced low density lipoprotein oxidation. In this work we explored if the ability of aqueous garlic extract to prevent <it>in vitro </it>Cu²⁺-induced lipoprotein oxidation in human serum is affected by heating (a) aqueous garlic extracts or (b) garlic cloves. In the first case, aqueous extract of raw garlic and garlic powder were studied. In the second case, aqueous extract of boiled garlic cloves, microwave-treated garlic cloves, and pickled garlic were studied. It was also studied if the above mentioned preparations were able to chelate Cu²⁺.</p> <p>Methods</p> <p>Cu²⁺-induced lipoprotein oxidation in human serum was followed by the formation of conjugated dienes at 234 nm and 37°C by 240 min in a phosphate buffer 20 mM, pH 7.4. Blood serum and CuSO₄were added to a final concentration of 0.67% and 0.0125 mM, respectively. The lag time and the area under the curve from the oxidation curves were obtained. The Cu²⁺-chelating properties of garlic extracts were assessed using an approach based upon restoring the activity of xanthine oxidase inhibited in the presence of 0.050 mM Cu²⁺. The activity of xanthine oxidase was assessed by monitoring the production of superoxide anion at 560 nm and the formation of uric acid at 295 nm. Data were compared by parametric or non-parametric analysis of variance followed by a post hoc test.</p> <p>Results</p> <p>Extracts from garlic powder and raw garlic inhibited in a dose-dependent way Cu²⁺-induced lipoprotein oxidation. The heating of garlic extracts or garlic cloves was unable to alter significantly the increase in lag time and the decrease in the area under the curve observed with the unheated garlic extracts or raw garlic. In addition, it was found that the garlic extracts were unable to chelate Cu²⁺.</p> <p>Conclusions</p> <p>(a) the heating of aqueous extracts of raw garlic or garlic powder or the heating of garlic cloves by boiling, microwave or pickling do not affect garlic's ability to inhibit Cu²⁺-induced lipoprotein oxidation in human serum, and (b) this ability is not secondary to Cu²⁺-chelation.</p>