Evaluation of total phenolic and flavonoid compounds of Lavandula angustifolia and Melissa officialis and their antibacterial properties using different solvents and extraction methods

Secondary metabolites of plants such as phenols and flavonoids can neutralize free radicals and antioxidant and cytotoxic activities of plants are related to their polyphenolic compounds. Antibiotic resistance has become a major problem in the treatment of infectious diseases and led to the usage of medicinal plants. The purpose of the current study was to investigate the total phenolic and flavonoid compounds of Lavandula angustifolia and Melissa officialis, and evaluate their antibacterial effects on Staphylococcus aureus and Escherichia coli. Two extraction method of lyophilization and the water bath method were used in the extraction of Lavandula angustifolia and Melissa officialis.  Folin-ciocalteu and aluminum chloride methods were used for the determination of total phenolic and flavonoid compounds and microdilution broth and disc diffusion methods were used for the evaluation of the antibacterial effect. The results showed that the total phenolic compounds of Lavandula angustifolia with the amount of 24 ± 0.04 mg /g DW using the lyophilization method and methanol solvent and the total flavonoid compounds of Lavandula angustifolia with the amount of 17.85 ± 0.011 mg /g DW using leophilization and ethanol solvent were the highest amounts among others. Methanol extract of Lavandula angustifolia was the most effective extract with a 9.5 and 7.5 mm zone of inhibition and on Escherichia coli and Staphylococcus aureus respectively. It can be concluded that Lavandula angustifolia and Melissa officialis contain phenolic and flavonoid compounds that can be used as medicinal plants in the treatment of infectious diseases caused by Staphylococcus aureus and Escherichia.