Acetylcholinesterase-Inhibiting Activity of Pyrrole Derivatives from a Novel Marine Gliding Bacterium, Rapidithrix thailandica

Abstract

Acetylcholinesterase-inhibiting activity of marinoquinoline A (1), a new pyrroloquinoline from a novel species of a marine gliding bacterium Rapidithrix thailandica, was assessed (IC 50 4.9 μM). Two related pyrrole derivatives, 3-(2'-aminophenyl)-pyrrole (3) and 2,2-dimethyl-pyrrolo-1,2-dihydroquinoline (4), were also isolated from two other strains of R. thailandica. The isolation of 3 from a natural source is reported here for the first time. Compound 4 was proposed to be an isolation artifact derived from 3.The two isolated compounds were virtually inactive in the acetylcholinesterase-inhibitory assay (enzyme inhibition < 30% at 0.1 g L -1 ).

Previously Uncultured Marine Bacteria Linked to Novel Alkaloid Production

“…We also report the isolation of marinoquinolines G-I (5-7), three new metabolites related to the previously described marinoquinoline A (10) (Sangnoi et al, 2008). Marinoquinoline A (10) was originally isolated from Rapidithrix thailandica, also a member of the phylum Bacteroidetes.…”

Total Synthesis of Marinoquinoline A Using a Palladium(0)‐Catalyzed Ullmann Cross‐Coupling Reaction

“…The residue was purified by chromatography on a silica gel column (methanol/chloroform 1.5:10) and concentration of the appropriate fractions afforded a white solid. Recrystallization (acetone/chloroform/hexane) of this material gave 1 [1,2,4,7] (28 mg, 85 %) as a white crystalline solid. R f = 0.5 (ethyl acetate/hexane/methanol 7:2:1); m.p.…”

“…In 2008 Plubrukarn and co-workers reported [1] the isolation of marinoquinoline A (1) from a previously unknown marine gliding bacterium, Rapidithrix thailandica TISTR 1742, associated with seaweed collected from Yong Ling beach on the coast of Southern Thailand. Its structure, which embodies a 3H-pyrroloA C H T U N G T R E N N U N G [2,3-c]quinolone ring system, was established by single-crystal X-ray analysis [2] and the compound itself was shown to have acetylcholinesterase-inhibiting activity (IC 50 = 4.9 mm against Torpedo californica AChE).…”

“…Its structure, which embodies a 3H-pyrroloA C H T U N G T R E N N U N G [2,3-c]quinolone ring system, was established by single-crystal X-ray analysis [2] and the compound itself was shown to have acetylcholinesterase-inhibiting activity (IC 50 = 4.9 mm against Torpedo californica AChE). [1,3] In 2011 Müller and co-workers reported [4] the isolation of heterocycle 1 (Scheme 1) and five related compounds, marinoquinolines B-F (2-6, respectively), from the gliding bacterium Ohtaekwangia kribbensis (PWU 25), which was obtained from a soil sample collected in Uttar Pradesh, India. Compounds 1-6, which only differ in the nature of the substituent attached at the C2 position on the 3H-pyrroloA C H T U N G T R E N N U N G [2,3-c]quinolone framework, have weak antibacterial and antifungal activities but moderate cytotoxic effects against four mammalian cell lines (including three cancer cell lines) with IC 50 values in the range of 0.3-8.0 mg mL À1 .…”

A Radical-Mediated Approach to the Total Synthesis of Fluorinated Marinoquinoline A and Related Tricyclic and Tetracyclic Congeners

“…3 Five further derivatives, marinoquinolines B-F (1b-f) were reported in 2011. 4 These compounds all exhibited moderate cytotoxicity against three cancer cell lines and promising activities against the tropical parasite Plasmodium falciparumK1 (IC 50 = 1.7-15 μM).…”