Effects of surfactant micelles on solubilization and DPPH radical scavenging activity of Rutin Oyais Ahmad Chat, Muzaffar Hussain Najar, Mohammad Amin Mir, Ghulam Mohammad Rather ⇑ , Aijaz Ahmad Dar ⇑ Department of Chemistry, University of Kashmir, Srinagar-190006, J&K, India article info Article history: Received 17 August 2010 Accepted 16 November 2010 Available online 20 November 2010 Keywords: Radical scavenging activity Rutin Micelles DPPH Solubilization abstract The interaction of the antioxidant Rutin with the radical DPPH (2,2-diphenyl-1-picrylhydrazyl) in pres- ence of cationic (CTAB, TTAB, DTAB), non-ionic (Brij78, Brij58, Brij35), anionic (SDS) and mixed surfactant systems (CTAB-Brij58, DTAB-Brij35, SDS-Brij35) has been followed by spectrophotometric and tensio- metric methods to evaluate the DPPH radical scavenging activity (RSA) of Rutin in these model self- assembled structures. The results show that the solubilization capacity of various single surfactant sys- tems for both DPPH as well as Rutin followed the order cationics > non-ionics > anionic. The radical scav- enging activity of Rutin in the solubilized form was higher within ionic micelles than in non-ionic micelles. However, the antioxidant exhibited enhanced activity for the radical in mixed cationic–non- ionic micelles compared with any of the single component micelles. In contrast, anionic–non-ionic mixed micelles modulated the activity of Rutin in-between that seen for pure anionic and non-ionic micelles only. Ó 2010 Elsevier Inc. All rights reserved. 1. Introduction Redox reactions represent an essential part of aerobic life and cell metabolism. Oxygen uptake inherent to aerobic systems pro- duces Reactive Oxygen Species (ROS) like H 2 O 2 , 1 O 2 ,O Å 2 , OH Å , ROO Å and nitric oxide which have been linked with aging and many degenerative diseases such as cancer, inflammation, immune sys- tem decline, cardiovascular diseases, neurological disorders and atherosclerosis [1–3]. Flavonoids, a group of naturally occurring benzo-c-pyrone derivatives, have been reported to possess multitude of biological properties and proven to be strong antioxidants and free radical scavengers [4–7]. Rutin (Scheme 1), a kind of flavonol glycoside, shows various pharmaceutical effects like antihypertensive, anti- inflammatory, antihemorrahagic etc. that have been attributed partly to its ability to scavenge free radicals [8]. It has been reported that such activity of polyphenols is highly sensitive to the environmental factors like solvent polarity, use of micellar media etc. [8–10]. Interest in understanding the parameters that influence the activity of antioxidants in complex or multiphase systems is increasing as actual food products are multicomponent matrices [11–15]. As per Frankel [16], interfacial phenomena are key to better understanding of antioxidant action in heterogeneous foods and biological systems. Micelles and other disperse systems have been extensively used for modeling the effects of heterogeneous environments on reaction dynamics and mechanism, and complex behavior encountered in food and biological assemblies [17–20]. Solubilization of antioxidants in different phases and environs of micelles results in different physicochemical interactions com- pared to homogeneous systems thereby strongly influencing their activity [21–23]. The knowledge of partition coefficient is of crucial importance for understanding such differences in antioxidant activity in various micellar media and establishing the location of antioxidants within the micelles [14–24]. Interaction of different antioxidants with variously architec- tured surfactants in aqueous media and the consequent influence on their antioxidant activity has been the subject of a number of studies [8,9,25–30]. Heins et al. [9] reported that the antioxidant activity of phenolic compounds depends upon their interaction site at the interface of the micellar systems. The occupation of different environments by the radical and the antioxidant serves as a phys- ical barrier to the action of antioxidants. Thus, solubilization of Ru- tin within CTAB micelles makes it difficult to quench hydroxyl radical [8]. On the other hand concentration of radical and the anti- oxidant in the same environment will enhance the antioxidant activity as has been reported for Quercetin in CTAB micelles [29]. Studies have also revealed that the reaction between Puerarin and DPPH in Triton X-100 micelles is much faster than in semi- aqueous solutions [30]. 0021-9797/$ - see front matter Ó 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.jcis.2010.11.044 ⇑ Corresponding authors. Fax: +91 194 2421357/2425195. E-mail addresses: gmrather2002@yahoo.com (G.M. Rather), aijaz_n5@yahoo. co.in (A.A. Dar). Journal of Colloid and Interface Science 355 (2011) 140–149 Contents lists available at ScienceDirect Journal of Colloid and Interface Science www.elsevier.com/locate/jcis