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Int. J. Mol. Sci. 2018, 19(9), 2640; https://doi.org/10.3390/ijms19092640

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

1
School of Pharmacy, Sungkyunkwan University, Suwon 16419, Korea
2
College of Medicine, University of Ulsan, Seoul 05505, Korea
3
College of Pharmacy, Kangwon National University, Chuncheon 24341, Korea
4
College of Korean Medicine, Gachon University, Seongnam 13120, Korea
5
Leibniz Institute for Natural Product Research and Infection Biology e.V., Hans Knöll Institute (HKI), Beutenbergstrasse 11a, 07745 Jena, Germany
These authors contributed equally to this work.
*
Authors to whom correspondence should be addressed.
Received: 15 July 2018 / Revised: 25 August 2018 / Accepted: 31 August 2018 / Published: 6 September 2018
(This article belongs to the Special Issue Natural and Semi-Synthetic Small Molecules in Drug Discovery)
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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 (28), 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 18 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. View Full-Text
Keywords: fungus-growing termite; Streptomyces sp.; isoflavonoid; neuroprotective effect; glutamate fungus-growing termite; Streptomyces sp.; isoflavonoid; neuroprotective effect; glutamate
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Lee, S.R.; Song, J.H.; Song, J.-H.; Ko, H.-J.; Baek, J.Y.; Trinh, T.A.; Beemelmanns, C.; Yamabe, N.; Kim, K.H. Chemical Identification of Isoflavonoids from a Termite-Associated Streptomyces sp. RB1 and Their Neuroprotective Effects in Murine Hippocampal HT22 Cell Line. Int. J. Mol. Sci. 2018, 19, 2640.

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