Seven New Alkaloids Isolated from Marine Flavobacterium Tenacibaculum discolor sv11

Abstract

Marine flavobacterium Tenacibaculum discolor sv11 has been proven to be a promising producer of bioactive nitrogen-containing heterocycles. A chemical investigation of T. discolor sv11 revealed seven new heterocycles, including the six new imidazolium-containing alkaloids discolins C-H (1–6) and one pyridinium-containing alkaloid dispyridine A (7). The molecular structure of each compound was elucidated by analysis of NMR and HR-ESI-MS data. Furthermore, enzymatic decarboxylation of tryptophan and tyrosine to tryptamine and tyramine catalyzed by the decarboxylase DisA was investigated using in vivo and in vitro experiments. The antimicrobial activity of the isolated compounds (1–7) was evaluated. Discolin C and E (1 and 3) exhibited moderate activity against Gram-positive Bacillus subtilis DSM10, Mycobacterium smegmatis ATCC607, Listeria monocytogenes DSM20600 and Staphylococcus aureus ATCC25923, with MIC values ranging from 4 μg/mL to 32 μg/mL.

New Imidazolium Alkaloids with Broad Spectrum of Action from the Marine Bacterium Shewanella aquimarina

“…A comprehensive analysis of the HRMS/MS spectra of the [M+H] + ions corresponding to blue nodes in the molecular network ( Figure 1 ) revealed that the F2 fraction also contained putative novel PEA and TYM alkaloids bearing an imidazolium ring, which were tentatively named as shewazoles ( 13 – 37 , Table 3 ). Indeed, these compounds share almost the same fragmentation pathways with discolins F-H from the marine flavobacterium Tenacibaculum discolor sv11 [ 48 ].…”

“…In addition, the formation of the cognate δ ions, i.e., [C 8 H 9 ] + and/or [C 8 H 9 O] + , occurs during fragmentation of shewazoles, thus confirming the presence of PEA and/or TYM, as already observed for shewamidines ( Figure 4 and Figure 5 ). Sequential losses of two styrene/hydroxystyrene molecules (C 8 H 8 /C 8 H 8 O) from the [M+H] + ions generate the ε fragment ion corresponding to the central imidazolium core ( Figure 4 , fragmentation α + ε), as shown for discolins [ 48 ]. The presence of the imidazolium ring is also suggested by the homolytic scission reaction leading to formation of the radical cation ζ from the fragment ion α ( Figure 4 and Figure 5 ).…”

“…These fragmentation pathways were supposed to produce azirine cations as described in Figure 4 [ 51 ]. Notably, neutral loss of R 1 CN generates a more abundant ion as compared to R 2 CN and R 3 CN losses according to MS/MS spectra recorded for discolins [ 48 ]. Therefore, this observation was used to assign the position of the R 1 substituent group.…”

Marine natural products

“…2 A red alga-derived Tenacibaculum discolor yielded eight imidazolium alkaloids discolins A–H 181– 188 , together with two 1,2,3,5-alkylated pyridinium structures dispyridine A 189 and dispyridine 190 , 1 H -pyrrolo[3,2- b ]pyridinium alkaloids dispyrrolopyridines A 191 and B 192 , and the dispyrrole 193 . 56,57 Notably, dispyrrolopyridine A 191 showed potent antibacterial activity, moderate antifungal activity, and weak nematocidal activity. Hydroxamate-containing siderophores, tenacibactins K–M 194 – 196 were isolated from a coral-derived Tenacibaculum sp., with 196 showing moderate activity against rat embryonic fibroblasts and the P388 murine leukemia cell line.…”

Synthesis and Antibacterial Studies of Phenethylamine Alkaloid Natural Products Along with Their Analogues: Discolin A, B, E and Bacillimidazole B

“…Out of these, 8 are from the discolin family and show activity against Gram-positive Bacillus subtilis DSM10, Mycobacterium smegmatis ATCC607, Listeria monocytogenes DSM20600, and Staphylococcus aureus ATCC25923, with MIC values ranging from 4 μg/mL to 64 μg/mL. 11 12 In 2023 Song Lim Ham et al discovered imidazolium antibiotic bacillimidazole G from the probiotic Bacillus licheniformis having the same molecular structure as discolin E, which shows MIC values of 0.7–2.6 μg/mL against human pathogenic Gram-positive and Gram-negative bacteria including methicillin-resistant Staphylococcus aureus (MRSA) and Lipopolysaccharide (LPS) lacking Acinetobacter baumannii ΔlpxC . 13 Some PEA-containing alkaloids are also isolated by Jia-Xuan Yan and co-workers from marine sponges associated with bacillus, bacillimidazole family, which show antimicrobial activities.…”