Antimicrobial effect of flavonoid from leaves extracts of Asphodeline anatolica E. Tuzlaci from Turkey

Introduction. Plant products have been shown to possess antimicrobial activity against multi-drug resistant strains (Lemos de Azevedo Maia et. al., Molecules, 2011). The genus Asphodeline (Liliaceae) is represented in Turkey by 20 taxa which are traditionally used for medicinal purpose in Anatolia region (Zengin & Aktumsek, Afr J Tradit Complement Altern Med, 2014). Methanol, acetone and aqueous extracts of leaves of Asphodeline anatolica E. Tuzlaci were examined for their antimicrobial activities and flavonoid constituents. Materials and Methods. The broth microdilution method was used to determine the Minimal Inhibitory Concentration (MIC) and the Minimal Bactericidal Concentration (MBC) of the A. anatolica extracts against twenty Gram-positive and Gram-negative bacteria, including MDR strains, and four yeasts. Characterization of the flavonoids content in the A. anatolica acetone, methanol and aqueous extracts was accomplished by HPLC-DAD-ESI-MS. Results. The acetone and methanol extracts showed higher efficacy towards Gram-positive bacteria than Gram-negative bacteria, but they had no activity against the yeasts tested. Particularly, the acetone extract showed the higher bacteriostatic activity (MIC: 31.25-125.00 µg mL-1 against Staphylococcus aureus ATCC 6538P and clinical isolates methicillin-resistant S. aureus (MRSA) (8 strains); 62.50-125.00 µg mL-1 against Listeria monocytogenes ATCC 13932 and L. monocytogenes isolated from food (8); 500.00 µg mL-1 against Pseudomons aeruginosa ATCC 9027 than methanol extract (MIC: 125.00-500.00 µg mL-1 against S. aureus ATCC 6538P and clinical isolates MRSA (8); 250.00 µg mL-1 against S. epidermidis ATCC 35984. Water extract showed no activity against all the tested microorganisms. Polyphenols were present both in acetone and methanol extracts but absent in aqueous extract. The phytochemical analysis of flavonoids revealed the presence as the main constituents of cirsimaritin (24.43 mg/g), diosmin (19.55 mg/g) and kaempferol-glucoside (8.93 mg/g) in acetone extracts and rutin (43.92 mg/g), diosmin (19.85 mg/g ), cirsimaritin (16.53 mg/g) and catechin 3-O-gallate (17.89 mg/g) in methanol extracts. Discussion and Conclusions. The data obtained demonstrate a direct relationship between the flavonoids content of the leaves extracts and the antimicrobial effect for the first time. The more antimicrobial activity of acetone extract could be due to different flavonoid content and composition than in methanol extract. The bioactivity of an individual component can change in the presence of other component within the extract combinations, corresponding to a synergic effect. However, in order to prove this, it would be necessary to separate the fractions for each peak and test them separately.