Protective effect of tetrahydroquinolines from the edible insect allomyrina dichotoma on LPS-induced vascular inflammatory responses

The larva of Allomyrina dichotoma (family Scarabaeidae) is an edible insect that is registered in the Korean Food Standards Codex as a food resource. The chemical study on the larvae of A. dichotoma resulted in the isolation of three new tetrahydroquinolines, allomyrinaines A–C (1–3), one new dopamine derivative, allomyrinamide A (4), and four known compounds (5–8). The structures were elucidated on the basis of 1D and 2D nuclear magnetic resonance (NMR) and MS spectroscopic data analysis. Allomyrinaines A–C (1–3) possessed three stereogenic centers at C-2, C-3, and C-4, whose relative configurations were determined by analyses of the coupling constants and the nuclear Overhauser enhancement spectroscopy (NOESY) data, as well as DP4+ calculation. The anti-inflammatory effects of compounds 1–4 were evaluated in human endothelial cells. Allomyrinaines A–C (1–3) could stabilize vascular barrier integrity on lipopolysaccharide (LPS)-induced vascular inflammation via inhibition of the nuclear factor-κB (NF-κB) pathway. The physiologically relevant concentration was confirmed by Q-TOF-MS-based quantitative analysis on allomyrinaines A–C in crude extract. This study suggests that allomyrinaines A–C (1–3) are bioactive constituents of A. dichotoma to treat vascular inflammatory disorder.