Calorilvietric Investigation Of The Action Of Propolis On Bacterial Growth And Metabolism

Power-time (P-t) curves were established by growing Micrococcus /uteus in a flowrncalorimetric system using different inoculum densities to see if inoculum size affectsrncalorimetric experiments. The P-t curves obtained for the lower inoculum densities used werernthe same in several aspects except length of the calorimetric lag phase. Spectrophotometricrnand polarographic experiments were done simultaneously with the calorimetric experimentsrnto see if results from the latter are true pictures of metabolic events in the fermenter orrnexperimental artifacts introduced due to separation of fermenter from the calorimeter. Resultsrnfrom experiments with the different methods showed the same pattern indicating thatrnseparation of fermenter from the calorimeter does not introduce error at the pumping rate usedrn(100 mL 11• 1). Extraction of propolis was done with 70% methanol as a solvent. The yield ofrnextraction was 21 % (w/w) for all propolis samples used. Addition of water to the ethanolrnsolution of extract of propolis (EEP) resulted in precipitation of the water insolublerncomponents and hence separation of the water soluble from the water insoluble components.rnThe proportion of water soluble components was very low in propolis sample 3 (prop3).rnCalorimetric experiments with propolis were done by incorporating increasingrnconcentrations of tincture at different phases of the P-t cun•e and different propolis samplesrnat the mid exponential phase of the P-t curve for comparison of their effect. It was found thatrneffect of propolis can be detected at all phases of growth. However, comparison ofrnantibacterial activities for the different concentrations of propolis used was not possible at thernlag phase. Variation in activity was observed among the different propolis samples in their effectrnon the drop of the P-t curve which is directly proportional to the amount of cells killed orrninactivated, and the time needed for the resumption of growth after the curve has fallen offrnto a minimum value. Though incorporation of tincture resulted in a drop of the P-t curverncomparable to other propolis samples, growth was resumed sooner suggesting lowerrninhibitory effect on the survivors. But propolis sample 2 (prop2) possesses higher killing andrninhibitory effect on the survivors.rnFor all propolis samples used the strength of antibacterial activity, based on drop ofrnthe P-t curve and subsequent effect. could be ordered as follows: EEP > water insolublerncomponent > water soluble component. For some propolis samples the effect of EEP wasrngreater than even the sum of two of its components at a ce11ain concentration. It was thereforerndeduced that the water soluble and insoluble components exhibit synergistic interactions inrnEEP.rnThe calorimetric method was found out to be slightly less sensitive to detect effect ofrnlower concentrations of propolis than the agar well diffusion assay method. However, thernfom1er method had a very short assay time and clearly demonstrated that the mechanism ofrnaction of propolis is bactericidic.

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