Decomposition of cinnabarinic acid by hydrogen peroxide

Laccase-mediated synthesis of novel substituted phenoxazine chromophores featuring tuneable water solubility

Laccases are members of the blue copper oxidases family found in nature. They commonly oxidise a wide range of phenol and aniline derivatives, which in turn are involved in oxidative coupling reactions. Yet, laccases remain rarely described as biocatalysts in organic synthesis. This paper describes the chemical preparation of original sulfonated aminophenol substrates and their enzyme-mediated dimerisation into phenoxazine chromophores that feature tuneable water solubility as a function of the sulfonyl substituent. The scope and limitations of the biocatalysed synthetic process are outlined. Kinetic data were collected to evaluate the influence of physicochemical parameters. The structure of the novel phenoxazine dyes ("head-to-head" or "head-to-tail" dimer) was assessed by NMR spectroscopic analysis. Two crystalline compounds were analysed by X-ray diffraction. Such laccase-mediated synthesis (a green chemistry process) was proven to be more efficient than the chemical oxidation of o-aminophenols with silver oxide.

HPLC and NMR Studies of Phenoxazone Alkaloids from Pycnoporus Cinnabarinus

Crude extracts of the red-orange, bracket fungus Pycnoporus cinnabarinus, collected from five distinct Australian localities were subjected to a chemical and biological profiling study. Subsequent detailed investigation of two of these specimens resulted in the isolation of the new phenoxazone alkaloid, pycnoporin (8), together with cinnabarin (1), tramesanguin (2), and cinnabarinic acid (3). Ergosterol peroxide (11) was also identified from one of the specimens studied. Compounds 1-3 and 8 were elucidated by detailed spectroscopic analyzes, which included the application of elevated temperature-controlled NMR experiments. In addition to the isolation and characterization of 8, this study describes the first successful HPLC purification strategy and complete 2D NMR spectroscopic characterization of compounds 1-3. Also reported are the antioxidant and anti-inflammatory activities of the crude extracts of one of the P. cinnabarinus specimens. Compounds 1-3, 8 and 11 displayed varying degrees of antitumor activity while ergosterol peroxide (11) also showed slight antimicrobial and antiviral activities. This is the first report documenting the significant antitumor activity of cinnabarin (1).