High methoxyl pectin grafted onto gallic acid by one- and two-pot redox-pair procedures

The aim of this research was to graft gallic acid (GA) onto high methoxyl pectin (HMP) through the redox-pair of ascorbic acid (Aa) and hydrogen peroxide (H₂O₂) with one- and two-pot procedures. The effectiveness of the both procedures and the chemical, physical and antioxidant properties of the obtained HMP-GA were evaluated. HMP-GA_one-pot (23.3 ± 0.21 mg GA Equivalent (GAE)/g) and HMP-GA_two-pot (32.3 ± 0.52 mg GAE/g) were best obtained at H₂O₂/Aa molar ratio-HMP/GA weight ratio of 9.0-0.5 and 16.0-0.5, respectively. The UV-Vis and FT-IR spectra and along with their derivative and thermal gravimetric analyses, revealed differences between HMP-GA_one-pot and HMP-GA_two-pot. The latter exhibited a greater antioxidant capacity than the former in single electron transfer (ET), hydrogen atom transfer (HAT), and ET-HAT mixed assays. The chemical differences can be attributed to side reactions that may have interfered with the grafting reaction. Consequently, HMP-GA, possessing unique antioxidant and prebiotic properties, can be synthesized through redox-pair procedures.