GC-MS Analysis of Chemical Composition and Determination of Antimicrobial Activity of Laurel Leaf Extracts Prepared by Different Methods and Solvents

This study aimed to investigate the chemical composition and antimicrobial activity of laurel leaf extracts obtained using different methods and solvents. Extraction was performed using the Soxhlet, ultrasound-assisted, and orbital shaker methods with water, ethanol, methanol, ethyl acetate, acetone, hexane and chloroform. The chemical compositions of the extracts were analyzed with a gas chromatograph coupled to a mass spectrometer and a flame ionization detector (GC-MS-FID). The GC-MS-FID results were compared to data of the Wiley and National Institute of Standards and Technology (NIST) libraries to identify the chemical composition of the analytes. The antimicrobial activities of the extracts against Staphylococcus aureus NCTC10788, Bacillus cereus NCTC7464, Salmonella typhi NCTC11994, Listeria monocytogenes ATCC11994 and Escherichia coli NCTC2001 were determined with in-house disc diffusion testing. The highest efficiency was achieved using the Soxhlet method and methanol (49.11%). Among the solvents tested, hexane, and among the methods used, ultrasound-assisted extraction exhibited the lowest efficiency (P<0.05). The extracts showed a stronger inhibitory effect on Grampositive bacteria (P<0.05). The highest level of antimicrobial activity was achieved against S. aureus with the use of the stock solution concentrations of the extracts obtained with the combined use of the ultrasound-assisted method and the solvents ethanol, ethyl acetate, acetone and hexane. The bacteria most resistant to almost all concentrations of the laurel leaf extracts were S. typhi, E. coli and L. monocytogenes. The method and solvent for extraction should be chosen carefully, depending on the targeted molecules and desired activity.