Applying Molecular Networking for the Detection of Natural Sources and Analogues of the Selective Gq Protein Inhibitor FR900359

Abstract

The cyclic depsipeptide FR900359 (FR), isolated from the traditional Chinese medicine plant Ardisia crenata, is a potent Gq protein inhibitor and thus a valuable tool to study Gq-mediated signaling of G protein-coupled receptors. Two new FR analogues (3 and 4) were isolated from A. crenata together with the known analogues 1 and 2. The structures of compounds 3 and 4 were established by NMR spectroscopic data and MS-based molecular networking followed by in-depth LCMS analysis. The latter approach led to the annotation of further FR analogues 5-9. Comparative bioactivity tests of compounds 1-4 along with the parent molecule FR showed high-affinity binding to Gq proteins in the low nanomolar range (IC = 2.3-16.8 nM) for all analogues as well as equipotent inhibition of Gq signaling, which gives important SAR insights into this valuable natural product. Additionally, FR was detected from leaves of five other Ardisia species, among them the non-nodulated leaves of Ardisia lucida, implying a much broader distribution of FR than originally anticipated.

Cell‐permeable high‐affinity tracers for Gq proteins provide structural insights, reveal distinct binding kinetics and identify small molecule inhibitors

“…(Taniguchi et al, ), while FR was isolated from the plant Ardisia crenata Sims and is produced by the bacterial endophyte Candidatus Burkholderia crenata that is present as a symbiont in the leaves of the plant (Crüsemann et al, ; Fujioka, Koda, & Morimoto, ). A few analogues of FR have also been isolated, however, in tiny amounts (Crüsemann et al, ; Reher et al, ). Recently, the total syntheses of 1 and 2 and some analogues were described, but they represent labour‐intensive procedures providing only small amounts of the products; all of the synthesized analogues showed moderate potency or were inactive (Xiong et al, ; Zhang et al, ).…”

Recent achievements in developing selective Gq inhibitors

“…Neither of these two analogs exhibited potent G q inhibition (Figure ), indicating the important pharmacological role of the hydroxyl group in β‐HyLeu‐1 and the double bond in N ‐MeDha, which was consistent with the results from YM‐254890 and analogs (Figure A). In contrast, two other FR900359 analogs, FR‐1 ( 54 , also known as AC‐1, Figure ) and FR‐2 ( 34 , also known as YM‐27 and AC‐0, Figure ), displayed selective and comparable G q inhibition to FR900359 (Figures and ) and isolation from A. crenata together with FR900359, while analog 54 was obtained by isolation together with FR900359 from A. crenata …”

“…In contrast, two other FR900359 analogs, FR‐1 ( 54 , also known as AC‐1, Figure ) and FR‐2 ( 34 , also known as YM‐27 and AC‐0, Figure ), displayed selective and comparable G q inhibition to FR900359 (Figures and ) and isolation from A. crenata together with FR900359, while analog 54 was obtained by isolation together with FR900359 from A. crenata Figure ) and FR‐4 ( 56 , Figure ), were obtained in a 3:1 mixture by isolation from A. crenata and biologically evaluated without further purification.…”

“…Equipotent analogs are highlighted (pink).The chemical structures were determined by X‐ray crystallographic analysis, mass spectrometry, one‐ and two‐dimensional nuclear magnetic resonance (NMR) spectrum analysis, liquid chromatography‐mass spectrometry (LC‐MS), extracted ion chromatograms, high‐performance liquid chromatography (HPLC), high‐resolution mass spectroscopy (HRMS), amino acid analysis and optical rotation. The FR‐3/FR‐4 were obtained and used as a 3:1 mixture (0.5 mg, 0.0001% yield) to evaluate their G q ‐inhibiting properties for inhibition of carbachol‐induced IP 1 production in CHO cells that stably express the M 1 muscarinic receptor, and exhibited almost equipotent to FR900359 [Color figure can be viewed at wileyonlinelibrary.com]…”

“…Meanwhile, two new analogs, FR‐3 ( 55 , also known as Sameuramide A isolated from a didemnid ascidian, Figure ) and FR‐4 ( 56 , Figure ), were obtained in a 3:1 mixture by isolation from A. crenata and biologically evaluated without further purification. The mixture showed almost equipotent inhibition of G q signaling to FR9000359 …”