Abstract
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 (1), together with seven known isoflavonoids (2–8), were identified from MeOH extracts of the fungus-growing termite-associated Streptomyces sp. RB1. The chemical structure of the new compound 1 was elucidated using comprehensive spectroscopic methods including 1D and 2D NMR, along with LC/MS analysis. The existence of two rhamnose moieties in 1 was determined with comparative NMR analysis, and the absolute configuration was elucidated using chemical reactions. The neuroprotective activities of compounds 1–8 were thoroughly investigated using the murine hippocampal HT22 cell line. Compound 5 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.
Highlights
Insects are one of the most eminently successful groups of animals and occupy almost every terrestrial environment
We used an LC/MS-guided isolation technique coupled to our house-built UV library of LC/MS to identify and separate isoflavonoids from the termite-associated Streptomyces sp
As previously reported by our group [9], several UV traces with the distinctive pattern of isoflavonoids were detected when MeOH extracts of Streptomyces sp
Summary
Insects are one of the most eminently successful groups of animals and occupy almost every terrestrial environment. Over millions of years of coevolution, symbiotic microbes have adapted to live in or on the insect community thereby producing biologically active metabolites important for microbial and insect survival. Insect-associated bacteria have been recognized as a very promising natural source for discovering novel bioactive secondary metabolites [3,4,5,6]. The high rediscovery rate of known natural products has diminished the enthusiasm to explore new natural products from historically important natural sources such as medicinal plants. We have a long-standing bacteria have been recognized as a very promising natural source for discovering novel bioactive secondary metabolites [3,4,5,6]. Je. nMtohl.uSscii.a2s0m18,t1o9,e2x6p40lore new natural products from historically important natural sources su2cohf 1a3s medicinal plants.
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