Effects of pH and temperature on the stability of sesquiterpene lactones

As part of a series of our research on sesquiterpene lactones, we report here on the stability of different sesquiterpene lactones, isolated from the species Anthemis melanolepis [1] and Centaurea spinosa [2], under various pH and temperature conditions. The stability of five sesquiterpene lactones bearing or not a side chain was calculated at pH 5.5, 7.4 (buffer solutions) and RPMI 5% and at temperatures 25 0 C and 37 0 C for 96 hours. Sesquiterpene lactones bearing a side chain lost this side chain at pH 7.4 and 37 0 C, while they were stable at pH 5.5. Sesquiterpene lactones not bearing a side chain seemed to be stable at all conditions. The structure of the products was elucidated by spectroscopic methods, particularly high-field NMR spectroscopy ( 1 H-NMR). These results reveal novel stability requirements during the in vitro cytotoxic and cytostatic tests of sesquiterpene lactones and may contribute to a better understanding of the stability of these natural products. Acknowledgements: This project is co-financed within Op. Education by the ESF (European Social Fund) and National Resources. References: 1. Saroglou V. et al. (2007) Helv. Chem. Acta 90:171–175. 2. Saroglou, V. et al. (2005)J. Nat. Prod. 68:1404–1407.