In vitro bioaccessibility of phenolic compounds and alpha-glucosidase inhibition activity in yoghurts enriched with mango peel powder

This study investigated the potential health benefits and functional properties of mango peel powder (MPP) as a source of antioxidants and alpha-glucosidase inhibitors in yoghurts with probiotic bacteria. The study involved plain yoghurt (PY, control), yoghurt fortified with 2% mango peel powder (MY), and yoghurt fortified with 2% MPP and 1% of each probiotic culture of L. casei, L. rhamnosus, B. lactis (MPY). Bioactive potential and individual polyphenols in the products were analysed before and after in vitro gastrointestinal digestion. Results showed that both MY (0.26 ± 0.02 mg/g GAE) and MPY (0.28 ± 0.04 mg/g GAE) had significantly (p ≤ 0.05) higher phenolic contents than PY (0.17 ± 0.02 mg/g GAE). Among the 15 quantified phenolic compounds, quercetin-3-rhamnoside was highest in MPP (432.86 ± 11.02 mg/100g dry wt.), followed by MPY (47.97 ± 1.20) and MY (34.44 ± 2.76 mg/100g fresh wt.). The quantities of the major individual phenolic compounds declined significantly (p < 0.05) in MPP only after gastric digestion, while remained stable in MY and MPY. There were significant (p ≤ 0.05) increments in α-glucosidase inhibition activity (6.06% and 8.47%, in MY and MPY, respectively) post intestinal digestion. The LC-ESI-QTOF-MS/MS analysis of all the sample extracts (undigested and digested) identified a total of 108 phenolic metabolites including 33 phenolic acids, 42 flavonoids, 11 lignans, 3 alkylphenols, 4 coumarins, 3 tyrosols, 1 stilbene, 2 xanthones, 4 phenolic terpene, and 3 tyrosols, 2 hydroxybenzoketones, 1 hydroxybenzaldehyde and 2 other phenolic metabolites. This study provides scientific evidence for the utilization of MPP fortified yoghurts as functional food products.