Evaluation of the potential to increase the recovery of phenolic compounds with antioxidant and antidiabetic activities from mango leaves by fermentation pre-treatment and ultrasound-assisted extraction via sonotrode

This study focused on enhancing phenolic compounds recovery from mango leaves by using two non-thermal methods: lactic acid bacteria fermentation and ultrasound-assisted extraction via sonotrode. Optimal ultrasound conditions were established using a Box-Behnken model and response surface methodology. The established conditions showed higher phenolic content extraction if compared with ultrasonic bath and Soxhlet (1.5 and 2 times, respectively). Fermentation with different lactic acid bacteria strains allowed determining 58 polar compounds through HPLC-ESI-TOF-MS, including 11 compounds tentatively identified for the first time in mango leaves. Combining both techniques significantly increased total phenolic compounds from 20 % to 52 %, except with La. plantarum CECT 9567-C4. Antioxidant activity improved significatively by up to 7 % post-fermentation with La. plantarum CECT 748 T. Additionally, Le. brevis CECT 5354 and La. plantarum CECT 9567-C4 also showed enhanced α-amylase inhibition, suggesting antidiabetic potential. Thus, fermentation pretreatment with selected bacteria is able to produced phenolic-rich extracts with enhanced antioxidant and antidiabetic activity from mango leaves. Further techno-economic and in vivo analyses will be necessary to confirm these preliminary data. • 58 phenolic compounds identified by HPLC–ESI-TOF-MS analysis. • 11 phenolic compounds were tentatively identified for the first time. • Sonotrode is able to improve the phenolic extraction 2 and 1.5 times comparing with Soxhlet and US bath. • Combined fermentation and ultrasound techniques boost phenolic content by up to 52 %. • LAB fermentation enhances antioxidant and antidiabetic activities.