Effects of acidity and molecular size on bacteriostatic properties of beer hop derivates

Isohumulones exert bacteriostatic effects on most gram-positive bacteria. Hop compounds can cross cytoplasmic membranes in undissociated form, being dissociated internally. Transport pathway across cell membranes requires a reasonably hydrophobic solute of moderate size.Hydrophobicities of solutes can readily be determined by measuring partition coefficients, P.Therefore, in order to evaluate the antimicrobial activity of isohumulones and structurally similar molecules, a free energy correlation has been used which allows estimation of log P values. Moreover, the maximum molecular diameter of these molecules has been calculated by using an AM1 semiempirical calculation. A comparative analysis of the antimicrobial potential of the hop derived molecules which might be present in beer is then established.