Solid-state fermentation as a pre-treatment method for the extraction of bioactive compounds from pomegranate ( Punica granatum L.) and jatoba<acute accent> peel ( Hymenaea courbaril L.)

The present study aimed to extract antioxidant polyphenolic compounds from pomegranate peel (PPF) and jatoba<acute accent> peel (JPF) flours with initial moisture (IM) of 50% or 80% by solid-state fermentation (SSF) using the fungus Aspergillus niger, followed by extraction by maceration with hydroalcoholic solution. Bioactive compounds as p-coumaric acid, gallic acid, ellagic acid and isoquercetin, quercetin, 4-hydroxymethyl-benzoic acid and protocatechuic acid were identified and quantified by liquid chromatography-electrospray ionisation-mass spectrometry (LC-ESI-MS/MS) system. After 24h of PPF (50% IM) fermentation, the total flavonoid content (TFC) and antioxidant activity by ABTS increased 81% (from 737.3 to 1337.1 mg QCT/100 g d.b.) and 36% (from 532.3 to 721.7 mu mol Trolox/g of flour), respectively. Also in this time, the isoquercetin concentration in PPF increased to 164% (from 3.26 to 8.61 mg/L). For JPF, the fermentation did not promote a significant increase in TPC and TFC. On the other hand, increased concentrations of 40% (from 0.10 to 0.14 mg/L) and 64% (from 0.11 to 0.18 mg/L) of 4-hydroxymethyl-benzoic acid and protocatechuic acid, respectively were obtained after 96 and 24 h of JPF (80% IM) fermentation, respectively. Isoquercetin in PPF and quercetin in JPF exhibited the strongest correlation (r = 0.94 for ABTS and r = 0.95 for DPPH, respectively) with antioxidant activity of the extracts. SSF is efficient as a pre-treatment process to obtain bioactive extracts from pomegranate and jatoba<acute accent> peels, which have potential applications in the food, pharmaceutical and cosmetic fields.