Nutrient Profiling of Some Terrestrial Plant Leaves for Their Prospective Use as Nonconventional Ingredients in Carp Diets

Abstract

The present study was performed to investigate the basic chemical composition and nutritional value of 10 terrestrial plant leaves (viz. Mangifera indica, Litchi chinensis, Artocarpus heterophyllus, Ziziphus mauritiana, Albizia lebbeck, Tamarindus indica, Cicer arietinum, Bauhinia acuminata, Delonix regia and Peltophorum pterocarpum) abundant in tropical and subtropical environments. The leaf meals were evaluated comprehensively, encompassing proximate composition (% dry matter), amino acids, fatty acids, antinutritional factors (ANFs), antioxidants and antibacterial potential using established methodologies. The crude protein (CP) content of the leaves ranged from 10.92% to 20.74% (w/w), with the highest content observed in A. lebbeck leaves. The crude lipid (CL) and crude fibre (CF) contents varied between 1.23%–5.38% and 13.73%–24.63%, respectively (w/w). The protein-to-energy ratio (P/E) ranged between 32.32 and 60.70 mg/kcal, with significantly higher (p  < 0.05) P/E in A. lebbeck compared to the other leaves. Dominant fatty acids in the evaluated plant leaves included palmitic acid (C16:0), oleic acid (C18:1n9c) and linolenic acid (C18:3n3). Considerable amounts of essential amino acids (EAAs) and nonessential amino acids (NEAAs) were recorded in the plant leaves, with maximum quantities detected in A. lebbeck and A. heterophyllus, respectively. Notably, substantial amounts of mineral elements were also detected in the plant leaves. Z. mauritiana was identified as a rich source of iron (Fe), copper (Cu) and manganese (Mn), while the highest calcium (Ca), phosphorus (P) and magnesium (Mg) levels were recorded in A. heterophyllus. Furthermore, the aqueous extracts of the leaves exhibited antioxidant and antibacterial potentials, with the maximum activities for both observed in T. indica. Analyses of ANFs indicated the presence of trypsin inhibitor (TI) (1.62–3.69 mg/g), tannin (21.25–61.25 mg/g), phytic acid (1.74–5.42 mg/g), cellulose (14.53%–21.37%) and hemicellulose (5.48%–10.56%) in the leaves. The study conclusively proposes the utilization of leguminous plants, particularly A. lebbeck, B. acuminata and P. pterocarpum, as potential nonconventional ingredients after eliminating or deactivating the major ANFs. This information on nutrients and ANFs of the less explored terrestrial plant leaves can be used to optimize low-cost carp diet formulation to ensure the economic profitability of fish farmers in the region.