*Corresponding Author Address: Mr. Biruk Sintayehu Fanta (MSc. Assistant professor of Pharmacognosy), Department of Pharmacognosy, School of Pharmacy, College of Health Sciences, Mekelle University, P.O. Box: 1871, Mekelle, Ethiopia; Email: biruksintayehu2006@gmail.com World Journal of Pharmaceutical Sciences ISSN (Print): 2321-3310; ISSN (Online): 2321-3086 Published by Atom and Cell Publishers © All Rights Reserved Available online at: http://www.wjpsonline.org/ Original Article Appraisal of Radical Scavenging Activities and Phytochemical Constituents of the Aerial Part Extracts of Guizotia scabra (Vis.) Chiov Etsay Weldekidan 1 , Gomathi Periyasamy 1 , Biruk Sintayehu 1 *, Mebrahtom Gebrelibanos 1 , Abera Hadigu 2 , Raghavendra Yarlagadda 3 1 Department of Pharmacognosy, School of Pharmacy, College of Health Sciences, Mekelle University, P.O. Box 1871, Mekelle, Ethiopia 2 Department of Pharmacology and Toxicology, School of Pharmacy, College of Health Sciences, Mekelle University, P.O. Box 1871, Mekelle, Ethiopia 3 Jimma University, College of Public Health and Medical Sciences, Department of Pharmacy, Jimma, Ethiopia Received: 10-08-2016 / Revised: 30-08-2016 / Accepted: 06-09-2016 / Published: 30-09-2016 ABSTRACT Guizotia scabra (family Asteraceae) is a wild edible and medicinal plant native to Africa. It is widely used for treatment of myriads of diseases associated with oxidative stress, and this study aimed at evaluating the 1, 1- diphenyl-2-picrylhyorazyl (DPPH) radical scavenging activity and detecting major phytochemical constituents of extracts from the aerial part of G. scabra. The aqueous and 80% methanolic crude extracts prepared by decoction and by maceration, respectively as well as the different solvent fractions prepared from each of them showed considerable DPPH scavenging activity with IC50 ranging from 11.66-55.60 μg/ml. The n-butanol fraction prepared from the aqueous crude extract of the aerial part of G. scabra showed the most potent DPPH scavenging activity (IC50=11.66 μg/ml) next to ascorbic acid (IC50=1.23 μg/ml). Phytochemical screening on both the aqueous decoction and 80% methanol crude extracts showed the presence of polyphenols, flavonoids, saponins, and phytosteroids. In conclusion, the aerial part of G. scabra contains phytochemicals with marked radical scavenging activity that could at least partly justify the traditional use of the plant for treatment of different diseases associated with oxidative stress and its potential as source potent antioxidants. Key words: Free radicals, radical scavenging, DPPH, phytochemical screening, Guizotia scabra, aerial part INTRODUCTION Free radicals are very reactive atoms or molecules with lone pair of electrons in their outer most shell and they are known for playing a dual role as both detrimental and valuable species. Excessive free radicals can cause oxidative damage to biomolecules, such as lipids, proteins and deoxyribonucleic acid (DNA) eventually leading to numerous chronic diseases [1-5]. The questionable safety of synthetic antioxidants that are mainly used in food industries and the growing public desire in preventive medicine have increased the interest in the search for more effective, safer and cheaper antioxidants from natural sources that can be used as nutraceuticals in the prevention of chronic diseases and as preservatives in foods, cosmetic and pharmaceutical industries [6-8]. Guizotia scabra (Vis.) Chiov., family Asteraceae is a native plant of Africa which is found in Nigeria, Cameroon, Democratic Republic of Congo, Rwanda, Burundi, Sudan, Eritrea, Ethiopia, Kenya, Uganda, Tanzania, Malawi, Zambia, Zimbabwe and Mozambique [9]. Locally it is known as Meche (Amharic), Hadaa-udda (Oromic), and Nehuka (Tigrigna) languages. In Ethiopia and other parts of Africa the leaf and seed parts are edible and the different parts of the plant are used for treatment of myriads of diseases associated with oxidative stress [10-12]. In Harar, eastern parts of Ethiopia, the aqueous decoction of the dried leaf and aerial parts of the plant are used for treatment of gastrointestinal disorders, inflammation, diabetes, malaria and cancer while the flower is used for treatment of eczema. Previous pharmacological studies revealed the antiviral, antioxidant, anticomplement, and antibacterial activities of the plant [12-14]. Sesquiterpene lactone and flavonoid was isolated from the leaf part of the plant [15]. Though G. scabra is widely used for treatment of