Determination of antioxidant and antimicrobial activity of sweetgum (Liquidambar orientalis) leaf, a medicinal plant

Abstract In the study, sweetgum tree (Liquidambar orientalis), which is an endemic species that grows in Mugla, Köyceğiz and is applied for medicinal purposes among the public, its leaves was examined. The antioxidant ability of the extract obtained from dried plant leaves has been evaluated using a variety of methods which are Total Phenolic Substance, Total Flavonoid, FRAP, CUPRAC, DPPH, and ABTS+. Simultaneously, the antimicrobial activity of the plant extract was examined using disk diffusion and microdilution methods to determine the minimum inhibitor concentration (MIC). While the total phenolic content of Liquidambar orientalis extract was 96.34 mg GAE/g, the total amount of flavonoid was 2.15 mg QE/g. When the results of the antioxidant analysis were examined, it was observed that it had a good level of antioxidant activity with the results of 49.25 ± 0.54 mmol TEAC/g according to the CUPRAC method, 39.83 ± 0.25 µmol Fe/g according to the FRAP method, 80.34 μg/mL according to the DPPH method and 51.20 μg/mL according to the ABTS+ method. As a result of the antimicrobial analysis, it was indicated that L. orientalis extract was more effective on Staphylococcus aureus (S. aureus), which is a gram-positive bacterium and causes a wide variety of clinical diseases. Even, L. orientalis extract with an MIC value of 10 mg/mL has been found to have a higher antibacterial effect than Amoxicillin+Clavulanic acid, which is used as a standard drug in that field. This research is significant because it is the first to report the determination of all biological activities for L. orientalis, including total polyphenols, flavonoid contents, antioxidant content, and antimicrobial activity.