Study On Quantitative Structure-Property/Activity Relationship Of Hydroxybenzoate Group

Hydroxybenzoate group is the very impotant preservatives, which are widelyused in medicine, foods and cosmetics. To investigate the behaviors ofchromatographic separation and antimicrobial activities, to search the key factorsaffecting chromatographic separation and antimicrobial activities, and to provideguidance for the development of new preservatives and optimization ofchromatographic separation conditions effectly, three Quantitative Structure-RtentionRelationship （QSRR） models and two Quantitative Structure-Activity（minimuminhibition concentration and antimicrobial half life） Relationship （QSAR） models for25hydroxybenzoate group were founded in this paper.Firstly,10quantum chemistry parameters and8molecular connectivity indiceswhich characterize the structure information of25hydroxybenzoate group werecalculated by the method of DFT/B3LYP/6-31G（d） in Gaussian09and the topologytheory. Then the retention time on three stationary phases were determined, the QSRRmodel of hydroxybenzoate group on three chromatographic columns(C₁₈、SE-30、OV-17) were set up as follows.On the non-polar coloumns of C₁₈and SE-30, the major factors affectingchromatographic separation are related to¹X_p^v、³X_p^v indices and EHOMOwhich reflectthe number of molecular branches and characterize the electronic information ofmolecular structure respectively. It was indicated that the chromatographic separation is greatly affected by the number of molecular branches and electron structure.¹X_p^v、³X_p^v are highly correlated with the dispersion forces, so, the retention time isdependent on dispersion forces between moleculars on the type of non-polar coloumn.However, on the milddle-polar coloumn of OV-17, the chromatographic separation isrelated not only to¹X_p^v、³X_p^v but also to polarizability（р）, which indicate that theretention time is greatly influenced by the pramaters representing the polar ofmolecular on the strongly polar of OV-17.Secondly, the minimum inhibition concentration（MIC） and antimicrobial half life(t_0.5) inhibiting escherichia coli were determined. By combining the Electron-cloudand the energy of frontier molecular orbital（FMOs）,25hydroxybenzoate groupcompounds antimicrobial activities were discussed. It was shown that the main groupswhich determined the antimicrobial activities are α,β-unsaturated carbonyl group andphenolic hydroxyl group. The model of QSAR can well predict the MIC and t_0.5in therange of atomic number(the number of C among1-4on the ester chain of MIC, and1-3of t_0.5).The QSAR equation show that MIC and t_0.5have good relationship with theindices of3v45c, vpc, v3p, EHOMOand ELUMO. vcindex reflects the space of themolecular chain,4v5pcand vpindices indicate the lipid solubility fragment and thelipophilicity fragment that around of functional group respectively, EHOMOand ELUMOreflects the ability of electrondonating and electronacceptor between the reactionprocess of compounds and microorganism. More over, when the atomic number of Cis between1-4, the compounds of hydroxybenzoate group antimicrobial activitiesincrease with the increase of the esterification degree and the length of ester group,when the number of C more than five there is a general decreasing trend forantimicrobial activities. The t_0.5will increase with the growth of ester group, but it willbecome short under the condition of MIC when the atomic number of C more thanfour.