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Lapachol is a natural naphthoquinone with a range of biological effects, including anticancer activity. Microbial transformations of lapachol can lead to the formation of new biologically active compounds. In addition, fungi can produce secondary metabolites that are also important for drug discovery. The goal of this study was to evaluate the ability of filamentous fungi to biotransform lapachol into biologically active compounds and identify secondary metabolites produced in the presence of lapachol. Seven out of nine strains of filamentous fungi tested exhibited the ability to biotransform or biodegrade lapachol. The bioactive derivatives norlapachol and isolapachol were identified among biotransformation products. Moreover, lapachol stimulated the production of pyrrolo-[1,2- a ] pyrazine-1,4-dione, hexahydro-3-(2-methylpropyl) and phenol-2,4-bis-(1,1-dimethylethyl), secondary metabolites already known to have antimicrobial and antioxidant activities. These results open the perspective of using these strains of filamentous fungi for lapachol biotransformation and efficient production of several biologically active compounds.

Background and Objectives: β-Lapachone is a drug candidate in phase II clinical trials for treatment of solid tumors. The therapeutic efficacy of β-lapachone is closely related to its metabolism, since this o-naphthoquinone produces cytotoxic effect after intracellular bioreduction by reactive oxygen species formation. The aim of this study was to produce β-lapachone human blood phase I metabolites to evaluate their cytotoxic activities., Methods: The biotransformation of β-lapachone was performed using Mucor rouxii NRRL 1894 and Papulaspora immersa SS13. The metabolites were isolated and their chemical structures determined from spectrometric and spectroscopic data. Cell cytotoxicity assays were carried out with β-lapachone and its metabolites using the neoplastic cell line SKBR-3 derived from human breast cancer and normal human fibroblast cell line GM07492-A., Results: Microbial transformation of β-lapachone by filamentous fungi resulted in the production of five metabolites identical to those found during human blood metabolism, a novel metabolite and a product stated before only in a synthetic procedure. The analysis of the results showed that β-lapachone metabolites were not cytotoxic for the neoplastic cell line SKBR-3 derived from human breast cancer and the normal human fibroblast cell line GM07492-A. The cytotoxic activity assay against the neoplastic cell line SKBR-3 revealed that the lowest half-maximal inhibitory concentration (IC 50 ) values of these β-lapachone metabolites were 33- to 52-fold greater than IC 50 values of β-lapachone., Conclusions: The cytotoxic activity of β-lapachone in vivo may be reduced due to its swift conversion in blood.