Chemical modification of curcumin: Solubility and antioxidant capacity

Abstract

The aim of this study was to develop a chemical method for demythylation of curcumin. The methoxy groups reduced solubility and low bioavailability of curcumin. The treatment of curcumin with hydrogen bromide or choline chloride increased cucumin water solubility from 1 mg/mL to 30 or 25 mg/mL, respectively. 1HNMR spectra showed that the chemical shift of O-methoxy groups at 3.9 ppm disappeared upon chemical treatment of curcumin, and indicated that these groups were removed especially after hydrogen bromide treatment. The antioxidant activity of treated curcumin and untreated curcumin was measured using different in vitro assays (i.e., 1,1-diphenyl-2-picrylhydrazyl and 2,2’-azino-bis (3-ethylbenzo-thiazoline-6-sulfonic acid) radical scavenging, and phosphomolybdenum complex formation). A remarkable increase in 1,1-diphenyl-2-picrylhydrazyl and 2,2’-azino-bis (3-ethylbenzo-thiazoline-6-sulfonic acid) radical scavenging was observed as curcumin-hydrogen bromide > curcumin-Choline chloride > curcumin. The formation of phosphomolybdenum complex was found to increase in the order of curcumin-choline cloride > curcumin-hydrogen bromide > curcumin with EC50 30, 41, and 114 µg/mL, respectively. In conclusion, hydrogen bromide-treated curcumin could be used as potential antioxidant in new functional foods.