A mycotoxin produced by Penicillium viridicatum and related species — a quinoline alkaloid contaminant of stored cereals and grains. Viridicatin arises when Penicillium-dominated mould flora colonizes damp grain, often alongside ochratoxin A and citrinin from the same species complex. Toxicological data are limited compared with regulated mycotoxins, but its presence marks grain that has undergone significant mould spoilage and is likely to carry multiple toxins. Control follows standard practice — dry grain promptly, maintain cool dry storage, and divert visibly mouldy lots from the food chain. Viridicatin is a reminder of the long tail of unregulated fungal metabolites in cereals.