The methylprolithospermate (MPL) molecule is a biological which was recently synthesized from salvia yunnanensis CH Wright by Yu et al [1]. It contains antioxidant activity, anti-inflammatory activity, antimicrobial activity, antidiabetic activity, anticancer activity, antiplatelet activity, etc [2,3]. Three thermodynamic cycles were required for the estimation of MPL’s pKa by the means of DFT at the level of B3LYP/6-311++G(d,p)//6-31+G(d). The sites of interest are the functional groups -OH and -COOH, located at four sites in MPL. In these thermodynamic cycles, water molecules were held as monomers in one hand (monomer cycles), and cluster on the other hand (cluster cycles). The isodesmic scheme was used as benchmark method and yielded pKa1 = 5.0 ± 0.5, pKa2 = 7.3 ± 01, pKa3 = 8.7 ± 0.1, and pKa4 = 14.6. The findings show that monomer cycles produce very good results for the three cycles at carboxylic site (pKa1) depending on the size of water molecule. Cluster cycles are excellent in one case of thermodynamic cycle.

Olivier Holtomo has completed his PhD at the age of 34 years from Douala University in Cameroon. He has been working in computational chemistry and physical chemistry. He is Lecturer in the Department of Physics and Head of Service of Cooperation at the University of Maroua. He has published 16 papers in reputed journals.