Identification of Neuroprotective Spoxazomicin and Oxachelin Glycosides via Chemoenzymatic Glycosyl-Scanning - PubMed (original) (raw)

. 2017 Jan 27;80(1):12-18.

doi: 10.1021/acs.jnatprod.6b00949. Epub 2016 Dec 28.

Ryan R Hughes 1, Meredith A Saunders 1, Sherif I Elshahawi 1, Larissa V Ponomareva 1, Yinan Zhang 1, Sydney R Winchester 1, Samantha A Scott 1, Manjula Sunkara 1, Andrew J Morris 1, Mark A Prendergast 1, Khaled A Shaaban 1, Jon S Thorson 1

Affiliations

Identification of Neuroprotective Spoxazomicin and Oxachelin Glycosides via Chemoenzymatic Glycosyl-Scanning

Jianjun Zhang et al. J Nat Prod. 2017.

Abstract

The assessment of glycosyl-scanning to expand the molecular and functional diversity of metabolites from the underground coal mine fire-associated Streptomyces sp. RM-14-6 is reported. Using the engineered glycosyltransferase OleD Loki and a 2-chloro-4-nitrophenylglycoside-based screen, six metabolites were identified as substrates of OleD Loki, from which 12 corresponding metabolite glycosides were produced and characterized. This study highlights the first application of the 2-chloro-4-nitrophenylglycoside-based screen toward an unbiased set of unique microbial natural products and the first reported application of the 2-chloro-4-nitrophenylglycoside-based transglycosylation reaction for the corresponding preparative synthesis of target glycosides. Bioactivity analysis (including antibacterial, antifungal, anticancer, and EtOH damage neuroprotection assays) revealed glycosylation to attenuate the neuroprotective potency of 4, while glycosylation of the structurally related inactive spoxazomicin C (3) remarkably invoked neuroprotective activity.

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Conflict of interest statement

The authors declare the following competing financial interest(s): The authors report competing interests. JST is a co-founder of Centrose (Madison, WI).

Figures

Figure 1

Figure 1

General glycosyl-scanning scheme. In this strategy, activated 2-chloro-4-nitrophenylglycoside donors help drive the OleD Loki-catalyzed transglycosylation reaction toward desired product formation where the resulting production of colorimetric 2-chloro-4-nitrophenol affords a real-time indicator of sugar-nucleotide production and utilization as an indirect measure of target glycoside production.

Figure 2

Figure 2

Structures of validated OleD Loki substrates identified and corresponding glycosides generated via preparative OleD Loki-catalyzed chemoenzymatic synthesis.

Figure 3

Figure 3

OleD Loki-catalyzed colorimetric glycosyl-scanning results using 2-chloro-4-nitrophenyl-Glc (1) (A) or 2-chloro-4-nitrophenyl-GlcNH2 (2) (B) as donor for all Streptomyces sp. RM-14-6 metabolites confirmed to turnover based on LC-MS [positive control, 4-methylumbelliferone (4-MeU); negative control, no acceptor (DMSO)]. No turnover was observed with compounds 10–20 (Supporting Information, Figure S1). The turnover of compound 8 (the synthetic enantiomer of metabolite 7) was identical to 7.

Figure 4

Figure 4

EtOH damage neuroprotection assay (propidium iodide uptake in rat-derived organotypic hippocampal slice primary cell cultures). (A) DMSO control; (B) 48 h exposure to 100 mM EtOH; (C) 48 h exposure to 100 mM EtOH and 10 nM 3a; (D) 48 h exposure to 100 mM EtOH and 1 _μ_M 4a; (E) dose–response with 48 h exposure to EtOH (100 mM) in the absence or presence of 3a on propidium iodide uptake; (F) Ddose–response with 48 h exposure to EtOH (100 mM) in the absence or presence of 4a on propidium iodide uptake. *p < 0.001 vs control; **p < 0.001 vs EtOH.

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