Characterizing the phenolic constituents of baobab (Adansonia digitata) fruit shell by LC-MS/QTOF and their in vitro biological activities

Baobab (Adansonia digitata) fruit is a part of the baobab tree, a revered multi-purpose tree native to Africa with a myriad of potentials in providing shelter, food, medicine, clothing and as a valuable source of natural antioxidants. A massive quantity of baobab fruit shells (BFS) is generated as a waste from the baobab fruit processing representing significant economic and environmental challenges at the same time an opportunity for its valorization and commercial utilization. The present study explored the potentials of BFS as a source of phenolic compounds. For this purpose, the phenolic constituents of BFS were identified by LC-MS/QTOF analysis. Also, the Total Phenolic Chromatographic Index (TPCI), TPC, TFC, and antioxidant capacity were compared with the baobab seeds and pulp. The antidiabetic potential through a-amylase and a-glucosidase inhibitory activities was also compared with that of acarbose. The LC-MS/QTOF analysis led to the identification of 45 compounds, including quercetin, kaempferol, proanthocyanidins, phenolic acids and their derivatives, several of which had never been reported in baobab fruit. Moreover, the BFS showed higher TPC, TFC, and antioxidant capacity than the baobab seeds and pulp and inhibited a-amylase and a-glucosidase enzymes activities with much higher potency than acarbose. This research demonstrated the promising potentials of BFS as a good source of phenolic compounds that can further be utilized for food and pharmaceutical applications. (C) 2019 Published by Elsevier B.V.