Quantification of antioxidants and antioxidant capacities of Lebanese composite dishes.

Abstract

Thirty-two Lebanese composite dishes were prepared according to procedures commonly followed in the Middle East and their contents of extractable polyphenols (EPP) were quantified by the Folin-Ciocalteu procedure on the aqueous-organic extracts. The non-extractable proanthocyanidins (NEPA), in the residues after extraction, were measured colorimetrically. Moreover, the antioxidant capacities (AC) of the dishes were assessed by the trolox equivalent antioxidant capacity (TEAC) and the ferric reducing ability of plasma (FRAP) assays. The total EPP contents of the analyzed dishes ranged between 10.96 and 455.80 gallic acid equivalents-100g fresh weight (FW). The values of non-extractable proanthocyanidins (NEPA) ranged from 15.20 to 2103.29 mg-100g FW. It was noted that NEPA was found at higher levels than EPP in the analyzed dishes. The antioxidant capacity of the samples as determined by FRAP was in the range of 0.04 and 3.19 mmol Fe (II)-kg FW and the TEAC from 0.15 to 14.8 mmol-kg FW. The vegetable-based dishes (List the dishes here) contributed most to the dietary antioxidant capacity (DAC) using ABTS assay (50.45percent) while the stuffed vegetable-based dishes showed the highest contribution (34.60 percent), among the tested groups, using the FRAP assay. Significant correlation was found between the FRAP value and the EPP content thereby suggesting phenolic compounds could be one of the major constituents responsible for the reducing ability of these dishes. Furthermore, a weak correlation was found between FRAP and ABTS signifying that the compounds capable of reducing oxidants could be different from those scavenging free radicals in the studied dishes. This study has shown that the NEPA fraction contributes significantly to the total antioxidant intake. The generated data will have a pivotal role in assessing the antioxidant quality of Lebanese, and related Mediterranean, diets and in identifying dietary items with high AC for improving the dietary antioxidant intakes of populations.