Anti-inflammatory Thiazine Alkaloids Isolated from the New Zealand Ascidian Aplidium sp.:  Inhibitors of the Neutrophil Respiratory Burst in a Model of Gouty Arthritis

Abstract

Ascidiathiazones A (3) and B (4), two new tricyclic thiazine-containing quinolinequinone alkaloids, were isolated from the New Zealand ascidian Aplidium species. Both compounds inhibited the in vitro production of superoxide by PMA-stimulated human neutrophils in a dose-dependent manner with IC50 1.55 +/- 0.32 and 0.44 +/- 0.09 microM, respectively. In vivo inhibition of superoxide production by peritoneal neutrophils in a murine model of gout was observed for both compounds with oral doses of 25.6 micromol/kg. Ascidiathiazone A (3) was synthesized in four steps from 8-hydroxyquinoline-2-carboxylic acid.

Discovery and Evaluation of Thiazinoquinones as Anti-Protozoal Agents

“…A second series of hits identified in this screening program were ascidiathiazone A ( 2 ), also previously reported by us as an anti-inflammatory alkaloid from a New Zealand ascidian, and synthetic analogues 3 and 4 [16]. The anti-protozoal evaluation of 2 (Table 1, entry 1) established the natural product to be a moderately potent in vitro growth inhibitor of P. falciparum K1 strain (IC 50 3.3 μM) and Trypanosoma brucei rhodesiense (IC 50 3.1 μM) while being effectively inactive towards T. cruzi and Leishmania donovani and exhibiting low levels of cytotoxicity against a mammalian cell-line (L6, IC 50 170 μM).…”

“…Previous studies by ourselves [16,19] and others [20,21] have found that hypotaurine addition to quinones typically yields a mixture of regio-isomeric thiazine adducts. In the present study, we found that slow addition of a dilute solution of hypotaurine in MeCN/EtOH at room temperature afforded, after filtration and washing, analogues 7a – 7j in yields of 14%, 27%, 57%, 17%, 49%, 57%, 29%, 29%, 26% and 20%, respectively.…”

“…Efforts to directly prepare amide derivatives of 2 by reaction of the synthesized natural product [16] with various amines in the presence of peptide coupling reagents, led to the formation of complex product mixtures and low yields (data not shown). Instead we made use of a longer four step reaction sequence (Scheme 1).…”

“…In the present study, we found that slow addition of a dilute solution of hypotaurine in MeCN/EtOH at room temperature afforded, after filtration and washing, analogues 7a – 7j in yields of 14%, 27%, 57%, 17%, 49%, 57%, 29%, 29%, 26% and 20%, respectively. The regio-isomeric identity of the product in each case was established by 2D-NMR data, particularly HMBC experiments optimized for 8.3 and 2.0 Hz, which showed correlations from H-9 to quinone C-10 (8.3 Hz) and from NH-4 to quinone C-5 (2.0 Hz) [16]. Reaction of each of 7a – 7j with 2 N NaOH in DMF for 2 h [16] afforded the desired hydrolysed and autoxidised Δ 2(3) -thiazine analogues 8a – 8i and 8k in variable yield (30%–83%).…”

Alpha-amylase inhibitory activities of ascidians in the treatment of diabetes mellitus

“…The extraction of samples was carried out using the standard method (Pearce et al, 2007). were kept in ice chest at 5°C and immediately transported to laboratory.…”