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There are many antioxidant compounds in mango peel and seed, and they could be used as a natural and very inexpensive alternative to synthetic food additives. However, the conditions in which the antioxidants are extracted must be optimized. This work proves that conditions such as extraction solvent or temperature have a crucial impact on obtaining extracts rich in antioxidants from mango biowastes.

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The oxidation of tryptophan (Trp) residues, mediated by peroxyl radicals (ROO.), follows a complex mechanism involving free radical intermediates, and short chain reactions. The reactivity of Trp towards ROO. should be strongly affected by its inclusion in peptides and proteins. To examine the latter, we investigated (by fluorescence) the kinetic of the consumption of free, peptide-and protein-Trp residues towards AAPH (2,2'-azobis(2-amidinopropane) dihydrochloride)-derived free radicals. Interestingly, the initial consumption rates (R-i) were only slightly influenced by the inclusion of Trp in small peptides and proteins (human serum albumin and human superoxide dismutase). Depending on the Trp concentration, the R-i versus Trp concentration ([Trp]) plots showed three regions. At low Trp concentrations (1-10 mu M), a linear dependence was observed between R-i and [Trp]; at intermediate Trp concentrations (10-50 mu M), the values of R-i were nearly constant; and at high Trp concentrations (50 mu M to 1 mM), a slower increase of R-i than expected for chain reactions. Similar behavior was detected for all three systems (free Trp, and Trp in peptides and proteins). For the first time we are showing that alkoxyl radicals, formed from self-reaction of ROO., are responsible of the Trp oxidation at low concentrations, while at high Trp concentrations, a mixture of peroxyl and alkoxyl radicals are involved in the oxidation of Trp residuesFondecyt 1141142 3140307 Novo Nordisk Foundation NNF13OC000429

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