Glycerol for improving solubility and evaluation of antimicrobial activity for natural products

With this study, we aimed to improve solubility and provide enhanced evaluation of antimicrobial activity with the addition of glycerol as a co-solvent with DMSO. The antimicrobial activities of glycerol and DMSO were evaluated against Staphylococcus aureus, and glycerol was found to be cause less growth inhibition. Compounds with poor water solubility were selected for biological screening and solubility testing. The glycerol/DMSO solution improved the time to solubilize (at 10mM) in ten out of the twenty-one tested compounds. Apparent assay solubility was assessed using turbidity measurements with a spectrophotometer at 600 nm. Notable improvement in solubility (where less light was blocked by lack of particulate matter) was observed for six compounds with glycerol/DMSO in media. To gauge our spectrophotometric analysis of solubility, we subjected six compounds to analysis with liquid-chromatography coupled to mass spectrometry. These analyses confirmed the solubility results obtained spectrophotometrically. Improved bioactivity with glycerol/DMSO/media against S. aureus was observed for four of the seven active compounds, resulting in minimum inhibitory concentrations (MIC) less than that of our standard water/DMSO/media solution. This study provides a rapid and effective way of assessing solubility in standard antimicrobial assay conditions and offers new solutions for improving solubility in-vitro by employing glycerol as a co-solvent.