ISSN: 2410-9649 Abate et al / Chemistry International 3(3) (2017) 277-287 iscientic.org. 277 www.bosaljournals/chemint/ editorci@bosaljournals.com Article type: Research article Article history: Received October 2016 Accepted January 2017 July 2017 Issue Keywords: P. lanceolata Free radicals Antioxidant activity Total polyphenol content Total flavonoid content Antimicrobial activity In this study, three different antioxidant activity quantification methods: 2,2- diphenyl-1-picrylhydrazyl radical scavenging (DPPH), reducing power, FRAP and peroxide value determination including total phenolic, TP, total flavonoid, TF assays of crude leaf extracts of Plantago lanceolata were carried out. The extracts showed significant activities in all antioxidant assays in a concentration dependent manner. The crude extracts were found to possess higher ferric reducing activity ranging from 336.58±0.052 mgAAE/100g (90% methanol) to 172.94±0.032 mgAAE/100g (petroleum ether) and DPPH activity varied from 90.6% (90% methanol) to 36.04% (petroleum ether). Strong correlation of TPC with AEACDPPH and AEACFRAP (R 2 = 0.9033 and R 2 = 0.8538 respectively) implied that compounds in the extract were proficient to scavenge the DPPH free radical and reducing ferric ions into ferrous ions. Moreover, peroxide values of the extracts were obtained and varied from 19.8 meq/kg (90% methanol) to 379 meq/kg(petroleum ether) and 3.1meq/kg (90% methanol) to 119 meq/kg (petroleum ether) at 70 o C and room temperature respectively. Therefore, P. lanceolata leaf extracts as compared to the control showed effective activity in delaying oxidation of the oil. Antimicrobial capacity evaluation of crude extracts against different gram-positive and gram-negative organisms was also evaluated and a higher degree of antimicrobial activity was observed of crude extracts with MIC and MBC values in the range of 6.25 to 25% were also observed for the crude extracts. © 2017 International Scientific Organization: All rights reserved. Capsule Summary: Antimicrobial and antioxidant activities of the Plantago lanceolata leaves extracts have been examined using different test systems. The extracts showed effective activity in delaying oxidation of the oil as compared to the control. Antimicrobial capacity evaluation of the crude extract against different gram-positive and gram-negative organisms demonstrated significant activity with mean zone of inhibition up to 26 mm. Cite This Article As: L. Abate, A. Abebe and A. Mekonnen. Studies on antioxidant and antibacterial activities of crude extracts of Plantago lanceolata leaves. Chemistry International 3(3) (2017) 277-287. INTRODUCTION A free radical is any species capable of independent existence that contains one or more unpaired electrons (Halliwell, 2000). Free radicals are well documented for playing a dual role in our body as both deleterious and beneficial species. In low/moderate concentrations free radicals are involved in normal physiological functions but excess production of free Chemistry International 3(3) (2017) 277-287 Studies on antioxidant and antibacterial activities of crude extracts of Plantago lanceolata leaves Limenew Abate, Atakilt Abebe ,* and Alemayehu Mekonnen Bahir Dar University, Bahir Dar, Ethiopia *Corresponding author’s E. mail: atakiltabebe1@gmail.com ARTICLE INFO ABSTRACT