Phenolic content, antioxidant activity and antiamylolytic activity of extracts obtained from bioprocessed pineapple and guava wastes

the relationship between phenolic content, antioxidant and antiamylolytic activities was investigated in rhizopus oligosporus-mediated solid-state bioprocessing of pineapple and guava residues. two different treatments of fruit residues mixed with soy flour (5g of soy flour and 5g of fruit residue; 1g of soy flour and 9g of fruit residue) were inoculated and incubated at 22oc. phenol rich extracts (non-concentrated and concentrated 10-fold by boiling) from day 2 and 10 were tested for their ability to inhibit alpha-amylase. in order to correlate the enzymatic inhibition with phenolic-linked antioxidant activity of the extracts, samples were evaluated for total phenolic content and free radical scavenging. alpha-amylase inhibition was observed for all extracts, concentrated or not, with values ranging from 10.91% to 100% (complete inhibition). a direct correlation between the total phenolic content or the free radical scavenging activity and alpha-amylase inhibition was not found, demonstrating that such an inhibition could be caused by the presence of specific compounds, phenolic or not, rather than by the actual concentration of overall fruit phenolics.