Antioxidants properties of food ingredients measured by different in vitro analytical approaches

Several epidemiological studies indicate that foods containing antioxidant compounds can play an important role on human health. Indeed, they may contribute in reducing the risk of chronic diseases such as cancer, inflammation, heart diseases and aging-related disorders, caused by free radicals. These are highly unstable molecules that may oxidize nucleic acids, proteins, lipids or DNA and can initiate degenerative diseases. Antioxidant compounds inhibit or quench free radical reactions by accepting or donating electrons to eliminate the unpaired condition of the radical. Among others, grapes (Vitis vinifera L.) and green tea (Camellia sinensis L.) are considered a good source of compounds with considerable antioxidant activity. However, the claimed antioxidant activity of a food or food supplements should be confirmed by analytical tests, but due to the complexity of foods and botanical ingredients (the so called "matrix effect"), the assessment of this property is often considered too expensive and complex by food industry. The aim of this study was to set-up and compare different in vitro analytical approaches suitable for the evaluation of the antioxidant activity of samples containing Vitis vinifera and Camellia sinensis. Two spectrophotometric assays were used to evaluate the total antioxidant activity associated to the samples included in the study and were based on the use of two specific radicals: 1) 2,2-azinobis-(3-ethylbenzothiazoline-6-sulphonate) radical (ABTS ̇+), 2) 1,1-diphenyl-2-picrylhydrazyl radical (DPPH ̇). The results were expressed as equivalent of gallic acid (EAG) in mg/g. A novel chromatographic approach, based on the use of High Performance Thin Layer Chromatography (HPTLC) was also applied, allowing to obtain the semi-quantitative measure of antioxidant activity associated with any specific compound in the samples analyzed. Both chromatographic and spectrophotometric assays were reliable and the results obtained comparable. The positive results of the study suggest a possible application of methods here described to obtain a rapid in vitro evaluation of the biological activity of food.