In recent years, emphasis has been placed on the use of natural materials in the control and treatment of various infections, as some chemically synthesized drugs have undesirable side effects. | R. SHARAFATI-CHALESHTORI, F. SHARAFATI-CHALESHTORI, M. RAFIEIAN Turk J Biol 35 (2011) 635-639 © TÜBİTAK doi: Biological characterization of Iranian walnut (Juglans regia) leaves Reza SHARAFATI-CHALESHTORI1, Farhad SHARAFATI-CHALESHTORI2, Mahmoud RAFIEIAN2 1 Department of Food Hygiene, Research and Science Branch, Islamic Azad University, Tehran - IRAN 2 Medical Plants Research Center, Shahrekord University of Medical Sciences, Shahrekord - IRAN Received: Abstract: In recent years, emphasis has been placed on the use of natural materials in the control and treatment of various infections, as some chemically synthesized drugs have undesirable side effects. In this study, the ethanol extract of Iranian walnut leaves was examined for antibacterial activities on Streptococcus mutans, Streptococcus salivarius, Streptococcus sanguinis, and Actinomyces viscosus using the microdilution method. Total phenols, flavonoids, and flavonols were also determined colorimetrically. The minimum inhibitory concentrations (MIC) for ethanolic extract ranged between and mg/mL and minimum bactericidal concentrations (MBC) ranged between and 250 mg/mL. Total phenols were 410 ± mg/g gallic acid equivalent, and total flavonols and flavonoids were 270 ± and 330 ± mg/g rutin equivalent, respectively. These findings show that Iranian walnut leaves have antibacterial effects on the 4 examined bacteria and may be a suitable alternative remedy for protection and treatment of dental plaque due to these microorganisms. Key words: Antimicrobial effects, Juglans regia, dental plaque, phenols, flavonoids, flavonols Introduction The genus Juglans (family Juglandaceae) comprises several species and is widely distributed throughout the world. Green walnuts, shells, kernels and seeds, bark, and leaves are used in the pharmaceutical and cosmetic industries (1,2). Leaves are easily available in abundant amounts. Walnut leaves are .