Digestive stability and absorption of green tea polyphenols: Influence of acid and xylitol addition Soon-Mi Shim a, ⁎, Sang-Ho Yoo a , Chan-Su Ra b , Young-Kyung Kim b , Jin-Oh Chung b , Sang-Jun Lee b, ⁎ a Department of Food Science & Technology and Carbohydrate Bioproduct Research Center, Sejong University, 98 Gunja-dong, Gwangjin-gu, Seoul, 143-747, Republic of Korea b Health Science Research Institute, AmorePacific R&D Center, Yongin-si, Gyeonggi-do 446-729, Republic of Korea abstract article info Article history: Received 10 August 2011 Accepted 12 October 2011 Keywords: Catechin Digestive stability Intestinal uptake Vitamin C Xylitol The objective of this study was to determine the effect of sugar substitute and acid on digestive stability and intestinal uptake of catechins in Ready-To-Drink (RTD) green tea. Green tea extracts formulated with pre- scribed amounts of sucrose (200, 500, and 1000 mg), glucose (280, 700, and 1400 mg), and xylitol (200, 500, and 1000 mg) in combination with citric acid (10 mg) or vitamin C (10 mg) were subjected to an in vitro digestion model coupled with Caco-2 cells. Green tea extracts only showed a poor digestive recovery (5.3%) of total catechins and EGC and EGCG significantly decreased with the digestive recovery of 4.6% and 6.1%, respectively. However, measured amount of EGC, EGCG, or ECG in digestive fluids and caco-2 human intestinal cell significantly increased by adding citric acid or vitamin C. There was remarkable increase of di- gestive recovery of total catechins in green tea with xylitol/citric acid and xylitol/vitamin C by 1.7–2.5 times and 3 times, respectively, with different amounts of xylitol. It was also determined that intestinal uptake of total catechins significantly increased 6 and 11 times in green tea with xylitol/citric acid and xylitol/vitamin C, respectively, compared to green tea only. © 2011 Elsevier Ltd. All rights reserved. 1. Introduction Green tea made with dried leaves of Camellia sinensis has become associated with many cultures in Asia, the Middle East, and the West. Over the past decades, green tea has been brought to scientific stud- ies to investigate its biological effects including antioxidative and anticarcinogenic functions due to various polyphenols (Morita, Kirkpatrick, Tamaki, & Chengelis, 2009; Morita, Knapp, Tamaki, & Stump, 2009; Ogura, Ikeda, Yuki, & Morita, 2008). The major poly- phenols found in green tea are catechins consisting of (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epigallocatechin-gallate (EGCG), and (-)-epicatechin-gallate (ECG). Their health benefits have been reported as protecting from oxidative stress and reducing the risk of cardiovascular disease and certain types of cancers (Green, Murphy, Schulz, Watkins, & Ferruzzi, 2007; Neilson, Song, Sapper, Bomser, & Ferruzzi, 2010). However, the bioavailability of these catechins is very low due to low digestive stability and poor intestinal absorption (Green, Murphy, Schulz, Watkins, & Ferruzzi, 2007; Peters, Green, Janle, & Ferruzzi, 2010). For instance, it was reported that more than 80% of the total catechins were degraded in simulated human digestive conditions (Green, Murphy, Schulz, Watkins, & Ferruzzi, 2007). The small intestinal condition of having slightly alkali pH and the presence of reactive oxygen species made green tea catechins unstable compared to gastric fluid (Record, & Lane, 2001). Ready-to-drink (RTD) green tea is sold in a prepared form and ready for consumption. Commercial RTD green tea is typically pre- pared with citric acid or vitamin C, starch, and sugar in order to adjust taste and stabilize beverage formulations (Green, Murphy, Schulz, Watkins, & Ferruzzi, 2007). Supplementation of citric acid or vitamin C in RTD green tea has been shown to be effective in enhancing taste as well as inhibiting oxidation (Chen, Zu, Wong, Zhang, & Chung, 1998). Recently, it was also found that the addition of vitamin C and sucrose may improve catechin solubility thereby enhancing bioaccessibility of catechins in simulated human digestive condition and accumulation of catechins by human intestinal cells (Green, Murphy, Schulz, Watkins, & Ferruzzi, 2007; Peters, Green, Janle, & Ferruzzi, 2010). However, the addition of sucrose in RTD green tea could bring concern on adverse health effect by an over-intake of su- crose. The World Health Organization (WHO) recommended that added sugar should be no more than 10% of dietary energy (Malik et al., 2006) and yet, a commercial sweetened RTD green tea bever- age is typically formulated with a high level of sucrose (e.g., it com- posed of 95% of sugar, in extreme case), the use of non-caloric and calorie less sweeteners instead of sucrose is required for the formu- lation of RTD green tea beverages. Xylitol, pentose-sugar alcohol, is me- tabolized very slowly resulting in keeping blood insulin levels low (Islam, 2011). It also supplies less energy than other sugars (Shafer, Levine, Marlette, & Morley, 1987). Food Research International 45 (2012) 204–210 ⁎ Corresponding author at: Dept of Food Science and Technology, Sejong University, Gwangjin-Gu, Seoul 143-737, Republic of Korea. Tel.: +82 2 3408 3229; fax: +82 2 3408 4319. E-mail address: soonmishim@sejong.ac.kr (S.-M. Shim). 0963-9969/$ – see front matter © 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodres.2011.10.016 Contents lists available at SciVerse ScienceDirect Food Research International journal homepage: www.elsevier.com/locate/foodres