Abstract:

In this work, we isolated melanin from the testae of wild apricots (MTWA) by ultrasonic-assisted extraction.
The optimization of the extraction process was carried out using by the combined use of one-factor-at-a-time method
and response surface analysis (RSA) with Box-Behnken experimental design. Then the antioxidant activities of MTWA
were analyzed including free radical scavenging capacity, metal ion-chelating capacity and lipid peroxidation inhibition.
The results showed that the optimal extraction conditions were determined as follows: NaOH concentration, 0.33 mol/L;
temperature, 63.07 ℃; time, 3 h; and solid-to-solvent ratio, 1:10 (g/mL). Under these conditions, the maximum yield of
MTWA of 4.14% was obtained. The in vitro antioxidant tests showed that MTWA had weaker 1,1-diphenyl-2-picrylhydrazyl
(DPPH) and 2,2’-azinobis-(3-ethylbenzthiazoline-6-sulphonate), radical scavenging activities and ferric reducing ability. However,
compared with synthetic melanin, MTWA had much stronger metal ion-chelating ability. MTWA also had stronger hydroxyl
radical-scavenging activity and provided significant inhibition of lipid peroxidation induced by H2O2 and Fe2+-VC.

Key words: ultrasnic-assisted extraction, wild apricot testae, melanin, response surface analysis, antioxidant activities