Thiocolchicine (10-methylthiocolchicine) is a semi-synthetic alkaloid with notable cytotoxic activity. Complexes of 10-methylthiocolchicine with Li+, Na+, K+, Rb+ and Cs+ monovalent cations of perchlorates and iodides have been obtained and characterized by spectroscopic methods, semi-empirical studies and molecular modelling. An explanation of the chemical nature of complexes formed between this alkaloid and monovalent metal cations of perchlorate and iodide salts which are present in human daily life is important. Their activities as cytotoxic and antifungal agents were also tested against the SKOV-3 cancer cell line and for eight selected microfungi species, respectively. Biological tests indicated no antifungal properties for 10-methylthiocolchicine. Complexation of 10-methylthiocolchicine with monovalent metal cations significantly improved the anticancer potency (~IC50 = 4 nM) against the SKOV-3 cancer cell line. © 2020 Elsevier Ltd