Bikaverin is a reddish pigment produced by different fungal species, most of them from the genus Fusarium, with
antibiotic properties against certain protozoa and fungi. Chemically,
bikaverin is a
polyketide with a tetracyclic benzoxanthone structure, resulting from the activity of a specific class I multifunctional
polyketide synthase and subsequent group modifications introduced by a
monooxygenase and an O-
methyltransferase. In some fungi,
bikaverin is found with smaller amounts of a precursor molecule, called norbikaverin. Production of these metabolites by different fungal species depends on culture conditions, but it is mainly affected by
nitrogen availability and pH. Regulation of the pathway has been investigated in special detail in the
gibberellin-producing fungus Fusarium fujikuroi, whose genes and
enzymes responsible for
bikaverin production have been recently characterized. In this fungus, the synthesis is induced by
nitrogen starvation and acidic pH, and it is favored by other factors, such as aeration,
sulfate and
phosphate starvation, or
sucrose availability. Some of these inducing agents increase
mRNA levels of the enzymatic genes, organized in a coregulated cluster. The
biological properties of
bikaverin include antitumoral activity against different
cancer cell lines. The diverse
biological activities and the increasing information on the biochemical and genetic basis of its production make
bikaverin a metabolite of increasing biotechnological interest.