Chemical Identification of Isoflavonoids from a Termite-Associated sp. RB1 and Their Neuroprotective Effects in Murine Hippocampal HT22 Cell Line.

Insect-associated bacteria have been recognized as a very promising natural resource for discovering bioactive secondary metabolites with diverse pharmacological effects. One new isoflavonoid glycoside, termisoflavone D (), together with seven known isoflavonoids (⁻), were identified from MeOH extracts of the fungus-growing termite-associated sp. RB1. The chemical structure of the new compound was elucidated using comprehensive spectroscopic methods including 1D and 2D NMR, along with LC/MS analysis. The existence of two rhamnose moieties in was determined with comparative NMR analysis, and the absolute configuration was elucidated using chemical reactions. The neuroprotective activities of compounds ⁻ were thoroughly investigated using the murine hippocampal HT22 cell line. Compound prevented glutamate-induced HT22 cell death by blocking intracellular reactive oxygen species (ROS) accumulation. The present study provides the first experimental evidence for the potential use of isoflavonoids from termite-associated bacteria as lead compounds that can prevent neuronal damage induced by glutamate.