2. IN SILICO STUDY TOWARDS UNDERSTANDING THE STABILITY AND REACTIVITY OF JASMONIC ACID AND METHYL JASMONATE STEREOISOMERS FOR PLANT DEFENSE PROCESS by RUMA GANGULY AND SAILESH K. MEHTA
The stereoisomers of Jasmonic acid and its derivative Methyl Jasmonate are known in the literature. The reactivity of these compounds varies with the substitutions at their chiral centers. Reports on the stability of such stereoisomers and their reactivity are scarce in the literature. We report the stability of the isomers of Jasmonic acid and its derivative Methyl Jasmonate computationally using Semi-empirical and DFT methods. The computed results suggest that there is predominance of trans- isomer in terms of energy and stability in unsubstituted Jasmonic acid and trans-isomer in plants seem to react with the specific receptor molecule. The unsubstituted Methyl Jasmonate cis-isomer is found to be stable compared to the trans-isomer and the energy difference between cis-isomer and trans- isomer is within the range of ~2.0 KJ/mol in the gas phase and aqueous medium. The experimental reports reveal that there is presence of 5-10% cis-isomers in the equilibrated mixture. Therefore, it appears that the activity of unsubstituted Methyl Jasmonate presumably governed by the presence of its cis- and trans- forms to interact with respective/specific receptor. The bioassay for the induction of genes encoding Jasmonate inducible proteins(JIPs) in barley by Waard et al. (1997) reported that the cis- /trans mixture of 3-Me-Methyl Jasmonate is inactive and the steric effect caused by presence of the bulky methyl group at C-3 position as the reason behind the inactivity. In our computational results, we have seen increase in the atomic distance between the side chains in trans-isomers in both Jasmonic acid and in Methyl Jasmonate after the addition of the methyl group at C-3 position of the cyclopentanone ring. This influences the volume of the molecules and hinders interaction with the specific receptor in receptor binding.
KEY WORDS: In Silico Study, Jasmonic acid, Methyl Jasmonate Stereoisomers, Plant Defense.