Antioxidant activity of inclusion complexes of tea catechins with β-cyclodextrins by ORAC assays C. Folch-Cano a , C. Jullian b , H. Speisky c , C. Olea-Azar a, ⁎ a Departamento de Química Inorgánica y Analítica, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Casilla 233, Santiago 1, Chile b Departamento de Química Orgánica y Fisicoquímica, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Casilla 233, Santiago 1, Chile c Laboratorio de Antioxidantes, Instituto de Nutrición y Tecnología de los Alimentos, Universidad de Chile, Casilla 138-11, Santiago, Chile abstract article info Article history: Received 11 March 2010 Accepted 8 June 2010 Keywords: Antioxidants Tea catechins ORAC-FL ORAC-PGR β-cyclodextrins Inclusion complexes of native and two derivatizated β-cyclodextrins with some tea catechins (TCs) like catechin (C), epigallocatechin gallate (EGCG) and gallocatechin gallate (GCG). The stoichiometry of TC complexes was determined and in all cases was 1:1. Stability constants were determined and their antioxidant capacity against reactive oxygen species (ROS) studied by means of the ORAC-fluorescein (ORAC-FL) and the ORAC-pyrogallol red (ORAC-PGR) assay. The antioxidant capacity of these TC in aqueous solution in the absence and presence of βCDs was studied using Multi-Detection Microplate Reader. The antioxidant reactivity mainly depends of the inclusion modes of the TC in the βCDs cavity. The difference between ORAC-PGR values for the same TC show that the inclusion structures should be different, maybe leading the same number of hydrogen atoms exposed (ORAC-FL values) outside or in the borders of βCDs cavity. © 2010 Elsevier Ltd. All rights reserved. 1. Introduction Cyclodextrins (CDs) are cyclic oligosaccharides composed of glucopyranose units and can be represented as a truncated cone structure with a hydrophobic cavity (Szejtli, 1998). The cavity is relatively hydrophobic, while the external faces are hydrophilic (Li & Purdy, 1992). The most extraordinary characteristic of a cyclodextrin is its ability to form inclusion complexes with a variety of compounds, i.e., by trapping foreign molecules (guest) in its cavity (host). Generally, hydrophobic molecules or those with hydrophobic resi- dues have the highest affinity with the CD cavity in aqueous solution, and it is well established that the ability of β-cyclodextrin (βCD) to enhance drug stability and solubility depends on formation of inclusion complexes (Szejtli, 1994). Unmodified or unsubstituted βCD, i.e., those with no substituent on the glucopyranose unit, have poor water solubility and are parenterally unsafe due to nephrotox- icity. Therefore, several synthetically modified and relatively safe βCD have been made and used in parenteral formulations, such as hydroxypropyl-β-cyclodextrin (HPβCD) (Shuang, Pan, Guo, Cai, & Liu, 1997) and Heptakis-2,6-O-di methyl-β-cyclodextrin (DMβCD). The molecular encapsulation of drugs and food ingredients with CDs improves the stability of flavours, vitamins, colourants and unsatured fats, etc., both in a physical and chemical sense, leading to extended product shelf-life. (Brewster & Loftsson, 2007; Szente & Szejtli, 2004; Szente & Szejtli, 2005). HPβCD has been shown to be well tolerated in humans, with the main adverse event being diarrhea and there have been no reported adverse events on kidney function. In fact, is an alternative to βCD, with improved water solubility and may be more toxicologically benign (Gould & Scott, 2005). Tea is a beverage made from the leaves of Camellia sinensis species of the Theaceae family. This beverage is one of the most ancient and, next to water, the most widely consumed liquid in the world. Tea leaves are primarily manufactured as green, black, or oolong, with black tea representing approximately 80% of tea products consumed. Green tea is the non-oxidized/non-fermented product and contains several polyphenolic components such as catechin (C), epicatechin (EC), epicatechin gallate (ECG), epigallocatechin (EGC), epigalloca- techin gallate (EGCG) and gallocatechin gallate (GCG). EGCG is the major green tea catechin (TC) (N 40% dry weight) and is probably, the principal responsible of chemoprevention and cardiovascular diseases prevention due to its free radical scavenging and antioxidant activities (Chemoprevention Branch and Agent Development Committee, 1996). Regular intake of tea is associated with an improved antioxidant status in vivo that may contribute to lowering the risk of certain types of cancer, coronary heart disease, atherosclerosis, stroke (Hong, Smith, Ho, August, & Yang, 2001; Sano et al., 2004; Uesato et al., 2001; Vinson, Teufel, & Wu, 2004), reduced mutagenicity (Gupta, Sahaa, & Giri, 2002) and inflammation (Katiyar, Matsui, Elmets, & Muktar, 1999), protection against neurodegenerative diseases (Choi et al., 2000; Choi et al., 2001; Datla et al., 2004) and increasing insulin sensitivity (Wu, Juan, Ho, Hsu, & Hwang, 2004). Research on the Food Research International 43 (2010) 2039–2044 ⁎ Corresponding author. Tel.: +56 2 9782844; fax: +56 2 7370567. E-mail address: colea@uchile.cl (C. Olea-Azar). 0963-9969/$ – see front matter © 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodres.2010.06.006 Contents lists available at ScienceDirect Food Research International journal homepage: www.elsevier.com/locate/foodres