Changes in phenolic and flavonoid profiles and antioxidant activity of mango peel during lactobacillus plantarum fermentation

Abstract

Mango peel contains phenolic and flavonoid compounds with potential as natural antioxidants. However, most of these compounds remain bound as glycosides, which may reduce their bioactivity, particularly their antioxidant capacity. One approach to increasing the phenolic and flavonoid content of mango peel is through biotransformation using lactic acid bacteria (LAB), including Lactobacillus plantarum. This study aimed to analyze changes in phenolic and flavonoid contents and the metabolite profile of mango peel, as well as to evaluate its antioxidant activity following biotransformation by L. plantarum. We carried out the biotransformation and harvested samples at 0 and 60 h. We extracted the fermented samples using ultrasound-assisted extraction (UAE) with methanol and concentrated the extract by evaporation to obtain a crude extract. We then analyzed the crude extract for total phenolic content, total flavonoid content, metabolite profile by HPLC, and antioxidant activity using the FRAP and ABTS assays. The results showed that biotransformation increased total phenolic content by 4.8% and total flavonoid content by 18.84%, although the latter increase was not statistically significant. HPLC characterization supported these changes, revealing new peaks and changes in peak intensity following biotransformation. The increase in total phenolic and flavonoid contents was accompanied by enhanced antioxidant activity, as indicated by the increased reduction of Fe3+ to Fe2+ in FRAP assay and the improved scavenging activity against ABTS•+ radicals, reflected by a decrease in the IC50 value.