Antioxidant strength and efficacy of Rosemary, purple-fleshed sweet potatoes and water Hyacinth extracts in stabilizing Nile perch (Lates Niloticus) fish oils

Abstract

The Nile perch fish oils that are locally used in fish feed formulation are susceptible to peroxidation. This study carried out at National Crops Resources Research Institute (NaCRRI) aimed at unveiling the effectiveness of the plant based antioxidants in stabilizing Nile perch fish oils. During the study, Nile perch fish oils were treated with, Rosemary; water hyacinth; and purple-fleshed sweet potatoes (PFSP) extracts. Ethoxyquin was used to treat fish for comparison purposes with the plant-based extracts and the antioxidant potentials of both ethoxyquin and phytochemical plants were determined using five analytical methods. 1) Quantifying enzymatic and non-enzymatic antioxidants in selected plants used in stabilizing Nile perch fish oils. The study found out significant varying (Tukey’s test, p<0.05) concentrations of enzymatic and non- enzymatic antioxidant concentrations. Furthermore, the scavenging capacity, ranged from 15.92±0.51 (µg/g ASc.AE) in water hyacinth stem to 68.19±1.07 (µg/g ASc.AE) in PFSP. 2) Determining the antioxidant capacity of selected plants with selected determining methods. A multivariate analysis revealed a total variability of 95% of the five profiled antioxidant assays. More so, an increase in oxidation products was observed to be higher in the un-stabilized fish oil compared to the stabilized fish oil at room temperature and fresh oil at +4o C. 3) Determining oxidative stability of Nile perch fish oils treated with natural antioxidants. Overall, extracts from either Rosemary, or water hyacinth or purple-fleshed sweet potatoes stabilized Nile perch fish oils to some extent, with reduction in peroxide, MDA equivalent and p-anisidine values though with great variation in efficacy, at any ethoxyquin equivalent concentration levels. The findings of this study recommend Purple-fleshed sweet potatoes extract for use as a replacement for the synthetic antioxidants.