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).