Effects of steam explosion pretreatment on the physicochemical properties, phenolic profile and its antioxidant activities of Baphicacanthus cusia (Nees) Bremek. leaves

The intention of this work is to explore the effects of steam explosion (SE) pretreatment on physical properties, phenolic components and antioxidant activities of Baphicacanthus cusia (Nees) Bremek (BCB) Leaves. Under optimal SE condition of 1.3 MPa for 30s, a significant 74.52 % increase in total phenolic content and 38.16–109.14 % rise in antioxidant activities were achieved. According to Fick's second law, the increase in SE intensity improved the diffusion efficiency of phenolics, increasing the rate constant from 2.79 × 10 −2 min −1 to 21.85 × 10 −2 min −1 . In addition, 9 main phenolic components of BCB leaves extracts were further identified by HPLC-IT-TOF-MS 2 , and the effects of SE treatment on their contents were analyzed. The results suggested SE process enhanced the dissolution of phenolics and caused the degradation of primary flavonoid glycosides into aglycones. Moreover, SE also induced the isomerization of chlorogenic acid into neochlorogenic acid. This study will help to advance the high-value development and application of phenolics in BCB leaves. • Steam explosion (SE) pretreatment was firstly performed for Baphicacanthus cusia (Nees) Bremek. leaves. • Highest phenolics extraction (155.71 mg/g) was observed at 1.3 MPa for 30s. • Antioxidant activities were increased by 38.16–109.14 % with optimization. • 9 phenolic components were identified by HPLC-IT-TOF-MS 2 . • SE promoted the isomerization of chlorogenic acid and the formation of flavonoid aglycones.