Evaluation of antioxidant activities of various solvent extracts of Carissa opaca fruits Sumaira Sahreen, Muhammad Rashid Khan * , Rahmat Ali Khan Department of Biochemistry, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad 4400, Pakistan article info Article history: Received 3 December 2009 Received in revised form 1 February 2010 Accepted 30 March 2010 Keywords: Carissa opaca Antioxidant activity Solvent extraction Phenolics DPPH Fruit abstract The chloroform and aqueous fractions of Carissa opaca fruit, a traditional medicinal fruit in Pakistan pos- sessed a high amount of total phenolic and flavonoid contents as compare to other solvent fractions with potent antioxidant activities in scavenging DPPH, superoxides, hydroxyl, hydrogen peroxide, ABTS radi- cals, and had strong iron chelating activity. On the other hand, the ethyl acetate fraction showed the high- est inhibition of b-carotene linoleic acid peroxidation and phosphomolybdate assay. A high correlation coefficient existed between EC 50 values of DPPH, superoxides, hydroxyl, hydrogen peroxide, ABTS radi- cals, total phenolics and flavonoids, but a non significant correlation was found in the case of iron chelat- ers, b-carotene and phosphomolybdate assay. This study verified that the chloroform and aqueous fractions have strong antioxidant activities which were correlated with its high level of phenolics and flavonoids. These fractions can be used as a source of potential antioxidant or functional food material. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Free radicals, chemical reactions, and several redox reactions of various compounds may cause protein oxidation, DNA damage, and lipid peroxidation in living cells (Morissey & O’Brien, 1998). In- creased consumption of whole grains, fruits, and vegetables is re- lated to a reduced risk of chronic diseases, diabetes, cancer, cardiovascular and neurodegenerative diseases such as Alzhei- mer’s disease (Kaur & Kapoor, 2001). Different fruits exhibit differ- ent antioxidant capacities according to their polyphenol content, vitamin C, E, carotenoids and flavonoids (Saura-Calixto & Goni, 2006). Polyphenols are common constituents of the human diet, with fruits and vegetables being the major dietary source of these bioac- tive compounds. The possible health benefits of polyphenol con- sumption have been suggested to derive from their antioxidant properties Evidence for their role in the prevention of degenerative diseases is emerging. There are huge varieties of antioxidants con- tained in fruits. Several methods have been developed to estimate the antioxidant capacity of different plant materials (Guo et al., 2003). Phenolic compounds are ubiquitous in plants, and when plant foods are consumed, these phytochemicals contribute to the intake of natural antioxidants in the human diets and has to be resolved to obtain the optimum antioxidant efficiency. The scientific basis for the statement that plants and their active constituents play an important role in the prevention of chronic and degenerative diseases is continuously advancing. In fact, the origin of many therapeutic substances is due to secondary metab- olism in the plant (Maganha et al., 2010). Carissa opaca is an evergreen shrub which can grow up to 3.5 m tall, branches glabrous or puberulous, leaves glabrous, opposite and ovate, spines arising between the petiole, hard and sharp, 2.5–3.5 cm long. Flowers white, corolla tube slender 8–12 mm long. Fruit berry some what ellipsoid, dark purple when ripe, with milky juice, edible. The plant is distributed in drier parts of India and Pakistan (from Punjab-Himalayas up to 6000 ft, in Murree) Burma and Sri Lanka (Nazimuddin & Qaiser, 1983). The whole plant is commonly used as a treatment in worm infested sores of animals, fly repellent, stimulants and in asthma (Jabeen, Khan, Ahmad, Zafar, & Ahmad, 2009). Researchers have reported that fruits and leaves are used for the treatment of jaundice and hepa- titis (Abbasi et al., 2009). Adhikari, Babu, Saklani, and Rawat (2007) reported that the fruit is a purgative, used in fever cough and diarrhea. Recently, researchers have sought to isolate powerful and non- toxic natural antioxidants from edible plants not only to prevent autoxidation and lipid peroxidation, but also to replace synthetic antioxidants. The fruit of C. opaca has been more often used as a food than for medicinal purpose, which attracted our curiosity to investigate the antioxidant activity of the fruit. To our knowledge, there is no report in the literature on the antioxidant potential of C. opaca fruit. The main objectives of this study were (i) to determine the phenolic content and antioxidant capacity of fruit and (ii) to examine the efficiency of different solvents for the extraction of phenolics. 0308-8146/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2010.03.120 * Corresponding author. Tel.: +92 51 90643086; fax: +92 51 9205753. E-mail address: mrkhanqau@yahoo.com (M.R. Khan). Food Chemistry 122 (2010) 1205–1211 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem