A Comparative Study on The In Vitro Antioxidant and Antimicrobial Potentials of Three Endemic Ononis L. Species From Turkey

Objectives In this study, the antioxidant capacity, antimicrobial activity and phenolic contents of aerial parts and roots extracts of three endemic Ononis L. (Leguminosae) species (O. sessilifolia Bornm., O. basiadnata Hub. & Mor., O. macrosperma Hub. & Mor.) were investigated for the first time. Materials and Methods The phenolic contents of the extracts [water and ethanol (EtOH)] and fractions [dichloromethane, EtOAc and n-butanol] were determined using Folin-Ciocalteu's phenol reagent. Also, their antioxidant capacities were studied using qualitative DPPH˙ (1,1-diphenyl-2-picrylhdrazyl radical) and TBA assays. The antimicrobial activity of these extracts and fractions compared with standard antibiotics were studied using disc diffusion assays against various Gram-positive and Gram-negative bacteria and fungi. Results The total phenolic contents of the water extracts were found to range between 14.78-80.33 mg/g, and the EtOH extracts ranged from 67.19-145.33 mg/g. EtOAc fractions of the three species were rich in terms of total phenolic contents when compared with other extracts (242.56-620.89 mg/g). The most significant results in the TBA assays were obtained in EtOH extracts of O. macrosperma (IC50=0.13±0.17 µg/mL), O. sessilifolia (IC50=1.41±0.58 µg/mL) and root (IC50=1.96±0.39 µg/mL). Conclusion EtOAc fractions rich in phenolic content were also found to be the most effective in antioxidant activity assays. Although all water extracts had no antimicrobial activity, EtOH extracts and n-butanol fractions showed generally moderate activity against bacteria. Some EtOAc fractions except for O. sessilifolia showed less activity against Escherichia coli, Staphylococcus aureus, MRSA and Candida albicans.