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Sanguinarine (Sang) is a natural alkaloid and distributed in several plants of Papaveraceae. The antitumor, antioxidant, antimicrobial and anti-inflammatory effects of Sang were extensively reported, but its speciality and mechanism against Lepidoptera insects were still unknown. In this study, detailed toxicological parameters of Sang against silkworms, Bombyx mori (B. mori), were determined by a toxicological test. Then, a nuclear magnetic resonance-based (NMR) metabolomics method was adopted to analyze the changes in hemolymph metabolites of silkworms after feeding Sang. The growth of fourth-instar larvae was significantly ceased by the oral administration of 0.05–0.3% Sang and vast deaths appeared in 0.3% Sang group on Day 4 and Day 5. The quantitative analysis of metabolites indicated that trehalose and citrate levels in hemolymph were increased after 24 h of feeding 0.3% Sang, whereas the concentrations of pyruvate, succinate, malate and fumarate were decreased. In addition, the enzymatic determination and reverse transcription quantitative PCR (RT-qPCR) showed that the trehalase (THL) activity and the transcriptional level of one gene coding THL were uniformly weakened by 0.3% Sang. One of the important mechanisms of Sang against silkworms might be interpreted as follows. Sang impaired trehalose hydrolysis, reduced THL activity and transcription, and led to the inhibition of energy metabolism, consequent antigrowth and high lethality in larvae of B. mori. Our findings offered new insights into the insecticidal effect of Sang from the perspective of energy metabolism and provided the basis for the application of Sang in the control of Lepidoptera pests. Unlabelled Image • The defensive roles of sanguinarine against the Lepidoptera insect were still unknown. • Sanguinarine significantly inhibited the growth of fourth-instar Bombyx mori larvae. • Sanguinarine targeted on trehalase and induced the systemic inhibition of energy metabolism in silkworms. • This study provided the basis for the application of Sang in the control of Lepidoptera pests. [ABSTRACT FROM AUTHOR]

Abstract 1-Deoxynojirimycin (DNJ) is a natural d -glucose analogue from mulberry with promising physiological activity in vivo. Up to the present, the antidiabetic effects of DNJ on lowering blood sugar and accelerating lipid metabolism in mammals were broadly reported, but the specific character of DNJ against insects was vastly ignored. In this study, a toxicological test of DNJ againgst eri-silkworm, Samia cynthia ricini was carried out to investigate the potential of DNJ in insect management. Further, a method of nuclear magnetic resonance (NMR) metabonomics and real-time qPCR (RT-qPCR) were performed to analyze the alteration in midgut of eri-silkworm caused by DNJ. The result of toxicology showed that 5% and 10% DNJ could significantly inhibit the development of third-instar larvae on day 1–5, and mass deaths happened in DNJ groups on day 3–5. The quantitative analysis of 1H NMR in fifth-instar larvae showed that trehalose level increased in midgut of 0, 6 and 12 h DNJ groups, while the concentrations of glucose, lactate, alanine, pyruvate, α-ketoglutarate and fumarate were reduced in varying degrees. Meanwhile, principal component analysis (PCA) indicated that there were significant differences in the metabolic profiles among 12 h DNJ groups and the control group. In addition, RT-qPCR results displayed that four genes coding α-glucosidase, trehalase (THL) and lactate dehydrogenase (LDH) were lowered in expression of 12 h DNJ groups. Simultaneously, THL activity was significantly lowerd in 12 h DNJ groups. These mutually corroborated results indicated that the backbone pathways of energy metabolism, including hydrolysis of trehalose and glycogens, glycolysis and tricarboxylic acid (TCA) cycle were significantly inhibited by DNJ. Thus, the specific mechanism of DNJ efficiently suppressing the growth and energy metabolism of eri-silkworm was explored in this study, providing the potential of DNJ as to the production of botanical insecticide. Graphical abstract Unlabelled Image Highlights • The defensive roles of DNJ against the herbivorous insect were still unknown. • DNJ could significantly inhibited the development of third-instar larvae of eri-silkworm. • DNJ induced metabonomic and transcriptional changes in midgut of fifth-instar eri-silkworm. • This study exerted a potential of DNJ in the production of botanical insecticide. [ABSTRACT FROM AUTHOR]