Characterization of antimicrobial leaf extracts by fourier transform infrared (FTIR) spectroscopy

All plants have different biological properties since they contain complex structures having different components. Leafs exhibit varying antimicrobial and antioxidant properties. In this thesis, different extracts of plants with antimicrobial activity like myrtle, laurel, hawthorn, linden, garlic, berry, olive, lemon balm and avocado leaf were prepared using different solvents (water, ethanol and ethanol/water). Bioactive properties such astotal phenolic content, antioxidant capacity and antimicrobial activity were determined and Fourier Transform Infrared Spectroscopy (FTIR) was used as a fast and precise method to characterize common macromolecular structures found in extracts. The highest total phenolic contentwas determined as 414.80 mg gallic acid / g KM in the ethanol extract of the myrtle leaf, the highest antioxidant capacity was assessed bythe ABTS method and the free radical (DPPH) scavenging antioxidant activity methods in the ethanol:water(%50:%50, v:v) extract of the lemon balm leaf (99.64% - 93.83%). Antimicrobial activity of the leaves were tested with agar well diffusion method Hawthorn leaf ethanol extract was found to be the extract exhibiting the most inhibitory effect on Escherichia coli (E.coli). In this study, ethanol extract of lemon balm leaf was determined to have the highest inhibitory effect on Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa). FTIR analyses of the leaves revealed that the leaves extracted with ethanol and ethanol:water (%50:%50, v:v)had similar spectra. Keywords:FTIR, antimicrobial activity, antioxidant capacity, total phenolic content