Marinoquinolines A−F, Pyrroloquinolines from Ohtaekwangia kribbensis (Bacteroidetes)

Abstract

Marinoquinoline A (1) was isolated from the gliding bacterium Ohtaekwangia kribbensis together with the novel marinoquinolines B-F (2-6). Their structures were elucidated from NMR and HRESIMS data. The pyrroloquinolines showed weak antibacterial and antifungal activities and moderate cytotoxicity against four growing mammalian cell lines with IC(50) values ranging from 0.3 to 8.0 μg/mL. In a screening against tropical parasites marinoquinolines A-F (1-6) showed activity against Plasmodium falciparum K1 with IC(50) values between 1.7 and 15 μM.

Hymenosetin, a 3-decalinoyltetramic acid antibiotic from cultures of the ash dieback pathogen, Hymenoscyphus pseudoalbidus

“…Minimum inhibitory concentrations (MIC) were determined in a serial dilution assay carried out in a similar manner as previously described (Okanya et al, 2011;Surup et al, 2013) using various test organisms for antibacterial and antifungal activities (Table 3). The assays were conducted in 96-well microtiter plates in EBS-medium (0.5 % casein peptone, 0.5 % glucose, 0.1 % meat extract, 0.1 % yeast extract, 50mM HEPES [11.9 g/L], pH 7.0) for bacteria and MYC-medium (Okanya et al, 2011) for yeasts and filamentous fungi.…”

“…The assays were conducted in 96-well microtiter plates in EBS-medium (0.5 % casein peptone, 0.5 % glucose, 0.1 % meat extract, 0.1 % yeast extract, 50mM HEPES [11.9 g/L], pH 7.0) for bacteria and MYC-medium (Okanya et al, 2011) for yeasts and filamentous fungi. Depending on the activity, the starting concentration of 2 as well as of the reference drugs varied from 67 to 6.7 µg/ml.…”

“…The in vitro cytotoxicity assay with the established mouse fibroblast cell line L929 was performed as reported by Okanya et al (2011). The IC 50 value of hymenosetin (2) was determined to be 8 µg/ml.…”

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

“…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 .…”

New Developments in the Mechanism of Drug Action and Toxicity of Conjugated Imines and Iminiums, including Related Alkaloids

“…Synthetic pyrroloquinolines (52) showed a wide range of biological activity, such as DNA intercalation and antileukemic properties [32]. Pyrroloquinolines (53) isolated from gliding bacterium Ohtaekwangia kribbensis showed antibacterial, antifungal and moderate cytotoxicity against growing mammalian cell lines [33]. Ammosamide alkaloids (54), isolated from the marine Strepmyces strain CNR-698, were found to inhibit quinone reductase 2 [34].…”