Free Radical-Scavenging and Oxidative Hepatic Injury-Alleviating Properties of Azadirachta Indica Seed Protein Isolate and Hydrolysates

The antioxidant and hepatoprotective activities of Azadirachta indica (neem) seed protein hydrolysates were investigated. Neem seed protein isolate (NSPI) was enzymatically hydrolyzed using pepsin, pancreatin, and trypsin. Oxidative hepatic injury (OHI) was induced using 0.1 mM FeSO4. Treatment was carried out through co-incubation of the oxidative hepatic tissues with NSPI and its hydrolysates. The tissues were analyzed for glutathione (GSH), nitric oxide (NO) and malondialdehyde (MDA) levels as well as catalase (CAT), superoxide (SOD) and acetylcholinesterase (AChE) activities. The pepsin hydrolysate (PNSPH) had a higher degree of hydrolysis (DH) and peptide yield compared to pancreatin and trypsin. The PNSPH had a more potent 2,2-diphenylpicrylhydrazyl (DPPH) and SOD scavenging activities than the other protein hydrolysates, whereas, it had a weak ferric reducing power (FRAP). The $\boldsymbol{2,2}^{\prime}-\mathbf{azino-bis}$ (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) scavenging activity of the pepsin, pancreatin, and trypsin hydrolysates were not significantly different from each other. Induction of OHI significantly $(\mathbf{p} < \boldsymbol{0.05})$ reduced GSH concentration, CAT, and SOD activities whereas the levels/activities of MDA, NO, and AChE increased. Treatment with NSPI and its hydrolysates with varying capacities, significantly reversed these levels/activities. The results implies that neem seed protein hydrolysates possess antioxidant activities and ameliorative effects against iron-induced oxidative hepatic injury by modulating oxidative imbalance and cholinergic activity. Hence, neem seed protein hydrolysates may be a potential nutraceutical in the control of oxidative stress and its related complications.