page_title: Caloboletus calopus
section_title: Biochemistry
hierarchical_section_title: Caloboletus calopus / Biochemistry
context_page_description: Caloboletus calopus, commonly known as the bitter beech bolete or scarlet-stemmed bolete, is a fungus of the bolete family, found in Asia, Northern Europe and North America. Appearing in coniferous and deciduous woodland in summer and autumn, the stout fruit bodies are attractively coloured, with a beige to olive cap up to 15 cm across, yellow pores, and a reddish stipe up to 15 cm long and 5 cm wide. The pale yellow flesh stains blue when broken or bruised.
  Christiaan Persoon first described Boletus calopus in 1801. Modern molecular phylogenetics showed that it was only distantly related to the type species of Boletus and required placement in a new genus; Caloboletus was erected in 2014, with C. calopus designated as the type species. Although Caloboletus calopus is not typically considered edible due to an intensely bitter taste that does not disappear with cooking, there are reports of it being consumed in eastern Europe. Its red stipe distinguishes it from edible species, such as Boletus edulis.
context_section_description: Although it is an attractive-looking bolete, Caloboletus calopus is not considered edible on account of its very bitter taste, which does not disappear upon cooking. There are reports of it being eaten in far eastern Russia and Ukraine. The bitter taste is largely due to the compounds calopin and a δ-lactone derivative, O-acetylcyclocalopin A. These compounds contains a structural motif known as a 3-methylcatechol unit, which is rare in natural products. A total synthesis of calopin was reported in 2003.
  The pulvinic acid derivatives atromentic acid, variegatic acid, and xerocomic acid are present in B. calopus mushrooms. These compounds inhibit cytochrome P450—major enzymes involved in drug metabolism and bioactivation.  Other compounds found in the fruit bodies include calopin B, and the sesquiterpenoid compounds cyclopinol and boletunones A and B. The latter two highly oxygenated compounds have significant free-radical scavenging activity in vitro. The compounds 3-octanone (47.0% of total volatile  compounds), 3-octanol (27.0%), 1-octen-3-ol (15.0%), and limonene (3.6%) are the predominant volatile components that give the fruit body its odour.
caption: Structure of calopin.[37]