Combined Analysis of Metabolomics and Biochemical Changes Reveals the Nutritional and Functional Characteristics of Red Palm Weevil IRhynchophus ferrugineus/I Larvae at Different Developmental Stages

Edible insects have emerged as a highly sustainable alternative to animal protein, while the potential and value of many insect metabolites have not been fully explored and exploited. Among them, the red palm weevil (RPW) Rhynchophus ferrugineus Olivier (Curculionidae: Coleoptera), especially its larvae, has a long history of consumption and a large scale of breeding, but there is relatively little information available regarding its metabolic and biochemical information at different growth stages, which limits the further development of feeding and processing industries. This study aims to explore the changes in conventional nutrient, mineral compositions, and the characteristics of the metabolomics of RPW larvae at the early, middle, and old developmental stages. Results showed that the red palm weevil larvae are rich in proteins and lipids, with oleic acid and palmitic acid being the main fatty acids, and early larvae possess the highest protein, ash, and total phenolic content. A total of 424 metabolites such as lipids, organic acids, organic heterocyclic compounds and so on were detected from the RPW larvae. The Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis results indicated the ATP-binding cassette (ABC) transporter, the citric acid cycle, aminoacyl-tRNA biosynthesis and the mTOR pathway have significant effects during the three developmental stages. Moreover, early larvae showed better antioxidant activities in vitro compared to that of larvae at the middle and older stages. These provides scientific evidence and valuable information for the resource utilization of red palm weevil larvae. In this study, the changes in the conventional nutrient and mineral compositions as well as the metabolomics characteristics of the red palm weevil (RPW) Rhynchophus ferrugineus Olivier (Curculionidae: Coleoptera) larvae at early (EL), middle (ML) and old (OL) developmental stages were investigated. Results showed that the EL and ML had the highest content of protein (53.87 g/100 g dw) and fat (67.95 g/100 g), respectively, and three kinds of RPW larvae were all found to be rich in unsaturated fatty acids (52.17–53.12%), potassium (5707.12–15,865.04 mg/kg) and phosphorus (2123.87–7728.31 mg/kg). In addition, their protein contained 17 amino acids with the largest proportion of glutamate. A total of 424 metabolites mainly including lipids and lipid-like molecules, organic acids and their derivatives, organic heterocycle compounds, alkaloids and their deriv