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H-, 13C-NMR) of this compound revealed that this compound was 7-[6-(b b-carboxyethyl)-5-isopropylidene-1,2-dimethylcyclo-hexylmethoxy]coumarin (galbanic acid), previously isolated from Ferula assa-foetida. In the presence of sub-inhibitory concentration of galbanic acid (100 m mg/ml) the MIC of penicillin G for S. aureus decreased from 64 to 1 (a sixteen four-fold decrease) and for cephalexin from 128 to 1 m mg/ml (a one hundred twenty eightfold decrease). The highest fold decrease in MIC was observed for cephalexin in combination of galbanic acid against test strain. These results signify that the low concentration of galbanic acid (100 m mg/ml) potentiates the antimicrobial action of penicillin G and cephalexin suggesting a possible utilization of these compounds in combination therapy against S. aureus.

In this study the enhancement effect of Sophora pachycarpa roots' acetone extract on the antibacterial activity of gentamycin was evaluated against Staphylococcus aureus. Disc diffusion and broth dilution methods were used to determine the antibacterial activity of gentamycin in the absence and presence of plant extract and its various fractions separated by TLC. A clinical isolate of S. aureus was used as test strain. The active component of the plant extract involved in enhancement of gentamycin's activity had R f = 0.72 on a TLC plate. The spectral data ( 1 H NMR, 13 C NMR) of this compound revealed that this compound was 5,7,2Ј,4Ј-tetrahydroxy-8-lavandulylflavanone (sophoraflavanone G), previously isolated from Sophora exigua. In the presence of 0.03 μg/ mL of sophoraflavanone G the MIC value of gentamycin for S. aureus decreased from 32 to 8 μg/mL (a fourfold decrease). These results signify that the ultra-low concentration of sophoraflavanone G potentiates the antimicrobial action of gentamycin suggesting a possible utilization of this compound in combination therapy against Staphylococcus aureus.

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