Cytotoxic and Antimicrobial Diterpenes Isolated from Hyptis dilatata

Abstract

Diterpenes 7-ethoxyrosmanol (1) and carnosol (2) were isolated and identified from the extracts of Hyptis dilatata collected in the Orinoco region, Colombia, used traditionally in this region for the treatment of wound infections of cattle. Their stereostructures were elucidated by 1D and 2D NMR experiments including 1H, 13C, COSY, HSQC, HMBC and NOESY. Although compound 1 has been reported previously, its NMR assignments were revised, completed and corrected. These compounds showed a specific antimicrobial activity against Gram (+) strains. The cytotoxic activity of compounds 1 and 2 was evaluated against a panel of three cancer cell lines (MCF7, HeLa and HT29) using curcumin as positive control. Carnosol (2) showed cytotoxic activity against all three cell lines having a similar response as the positive control with an IC50 approximately of 15-20 µg/mL in each case. On the other hand, 7-ethoxyrosmanol (1) showed lower activity than carnosol, with an IC50 approx. of 20-30 µg/mL for the three cancer cell lines. This is the first report on cytotoxic activity against MCF7, HeLa and HT29 cancer cell lines and the antimicrobial activity of compound 1, and the first report on cytotoxic activity against HeLa of compound 2. In addition, the main volatile components of the essential oil of H. dilatata which displayed quorum sensing inhibitory activity were identified by GC/MS analysis. Finally, these results let us to propose H. dilatata as a potential resource of antimicrobial and cytotoxic compounds. Keywords: 7-ethoxyrosmanol, antimicrobial activity, carnosol, cytotoxic activity, Hyptis dilatata, quorum sensing inhibition.