Characterization of melanin extracted from apricot (Armeniaca sibirica) and its effect on hydrazine-induced rat hepatic injury

Abstract

Melanin is a complex, highly coloured natural antioxidant with potent biological activities and diverse applications. A potential source of melanin is the Siberian apricot (Armeniaca sibirica) whose kernel skin is currently a waste by-product. To explore its potential, melanin from apricot kernel skin was extracted. The molecular mass was determined by gel chromatography and its structure was examined by elemental analysis, UV-Vis, infrared, and solid-state nuclear magnetic resonance (13C-NMR) spectroscopy. In addition, its protective effect against hydrazineinduced hepatic injury in rats was evaluated. The results showed that melanin has < 5% sulphur (S) content, indicating that it consists mostly of eumelanin. Its UV-Vis, infrared and 13C-NMR spectra were very similar to those of synthetic melanin, although it had relatively high carboxylate, aliphatic, and phenol-skeleton content. Two distinct fractions (2.4±0.12 and 0. ±560.1 kDa) were detected. Injections of hydrazine at 65 mg/kg body-weight (b.wt.) doses resulted in significant (p < 0.01) increases in lipid peroxidation (malondialdehyde contents) in liver homogenates and serum alanine aminotransferase and aspartate aminotransferase activities (64%, 69%, and 98% increase relative to the controls, respectively). It also induced significant (p < 0.05 or 0.01) decreases in liver homogenate catalase, glutathione peroxidase, and superoxide dismutase activities and reduced glutathione content (48%, 28%, 7%, and 98% reduction, respectively). Administering melanin prior to hydrazine, at 10 mg/kg b.wt., strongly inhibited these changes and ameliorated histopathological hepatic injury. The results indicated that melanin alleviated hydrazine-induced liver injury by relieving oxidative stress, which may provide a novel protective strategy for protection against liver diseases.