-M. Cardot  Professor, Univ Clermont 1, UFR Pharmacie, ERT-CIDAM, Biopharmaceutical Department, Clermont- Ferrand, F-63001 France; e-mail: j-michel.cardot@u-clermont1.fr. Correspondence to: J-M Cardot, Biopharmaceutical Department, 28 Place H. Dunant, BP 38, 63001 Clermont-Ferrand, France.