Context Biotransformation systems are profitable tools for structural modification of bioactive natural compounds into valuable biologically active terpenoids. Objective This study determines the biological effect of (R)-(+)-limonene and (À)-a-pinene, and their oxygenated derivatives, (a) perillyl alcohol and (S)-(+)-and (R)-(À)-carvone enantiomers and (b) linalool, trans-verbenol and verbenone, respectively, on human colon tumour cells and normal colonic epithelium. Materials and methods Biotransformation procedures and in vitro cell culture tests were used in this work. Cells were incubated for 24 h with terpenes at concentrations of 5-500 mg/mL for NR, MTT, DPPH, and NO assays. IL-6 was determined by ELISA with/without 2 h pre-activation with 10 mg/mL LPS. Results trans-Verbenol and perillyl alcohol, obtained via biotransformation, produced in vitro effect against tumour cells at lower concentrations (IC 50 value ¼ 77.8 and 98.8 mg/mL, respectively) than their monoterpene precursors, (R)-(+)-limonene (IC 50 value ¼ 171.4 mg/mL) and (À)-a-pinene (IC 50 value ¼ 206.3 mg/mL). They also showed lower cytotoxicity against normal cells (IC 50 4500 and4200 mg/mL, respectively). (S)-(+)-Carvone was 59.4% and 27.1% more toxic to tumour and normal cells, respectively, than the (R)-(À)-enantiomer. (R)-(+)-limonene derivatives decreased IL-6 production from normal cells in media with or without LPS (30.2% and 13.9%, respectively), while (À)-a-pinene derivatives induced IL-6 (verbenone had the strongest effect, 60.2% and 29.1% above control, respectively). None of the terpenes had antioxidative activity below 500 mg/mL. Discussion and conclusions Bioactivity against tumour cells decreased in the following order: alcohols4ketones4hydrocarbons. (R)-(+)-limonene, (À)-a-pinene, and their derivatives expressed diverse activity towards normal and tumour cells with noticeable enantiomeric differences.
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