Flavin-dependent halogenase involved in the biosynthesis of melleolides, a range of antifungal and phytotoxic polyketide derivatives composed of an orsellinic acid (OA) moiety esterified to various sesquiterpene alcohols. The halogenase catalyzes the transfer of a single chlorine atom to the melleolide backbone, resulting in a 6'-chloromelleolide product. The enzyme acts on free substrate and does not depend on carrier-protein-dependent acceptor molecules. Can also catalyze the transfer of a single bromine atom to the melleolide backbone in vitro. chloride + FADH2 + melleolide F + O2 = 6'-chloromelleolide F + FAD + H(+) + 2 H2O bromide + FADH2 + melleolide F + O2 = 6'-bromomelleolide F + FAD + 2 H2O Melleolide sesquiterpene aryl esters are cytotoxic secondary products with anti-cancer potential (PubMed:21376582, PubMed:26952552). Armillaridin shows therapeutic and radiosensitizing effects on human esophageal cancer cells (PubMed:23864890). Armillaridin induces autophagy-associated cell death in human chronic myelogenous leukemia as well as of hepatocellular carcinoma cells (PubMed:27592257, PubMed:31488037). Armillaridin can also inhibit the differentiation and activation of human macrophages and thus might have potential to be developed as a biological response modifier for inflammatory diseases (PubMed:25746621). Armillaria species are both devastating forest pathogens and some of the largest and oldest terrestrial organisms on Earth (PubMed:31746694) (Probable). They forage for hosts and achieve immense colony sizes via rhizomorphs, root-like multicellular structures of clonal dispersal (Probable). Belongs to the flavin-dependent halogenase family.