Effect of rosmarinic acid and carnosic acid on AGEs formation in vitro Juanying Ou a,1 , Junqing Huang b,1 , Mingfu Wang a,⇑ , Shiyi Ou c,⇑ a Food and Nutritional Science Program, School of Biological Sciences, The University of Hong Kong, Hong Kong, China b Institute of Integrated Chinese and Western Medicine, Medical College of Jinan University, Guangzhou 510632, China c Department of Food Science and Engineering, Jinan University, Guangzhou 510632, China article info Article history: Received 9 August 2016 Received in revised form 10 November 2016 Accepted 11 November 2016 Available online 11 November 2016 Keywords: Rosemary extracts Advanced glycation end-products Dicarbonyl compounds Carboxymethyl lysine Carboxyethyl lysine abstract This work aimed to investigate the effect of the two main components of rosemary extracts, namely ros- marinic acid (RA) and carnosic acid (CA), on the formation of advanced glycation end-products (AGEs) in vitro. In the bovine serum albumin (BSA)/glucose model, addition of RA and CA at 400 lg/mL inhibited fluorescent AGEs by more than 90%, and carboxymethyl lysine (CML) and carboxyethyl lysine (CEL) by 82.7% and 75.2%, and 71.4% and 64.2%, respectively. Moreover, the addition of RA and CA at 400 lg/mL inhibited fluorescent AGEs by more than 90% both in the BSA/glyoxal (GO) and BSA/methylglyoxal (MGO) models, the formation of CML by 64.9% and 53.9% in BSA/GO model, and CEL by 28.9% and 24.3% in BSA/MGO model, respectively. RA and CA also significantly decreased the concentration of MGO and protein carbonylation. Ó 2016 Elsevier Ltd. All rights reserved. 1. Introduction Advanced glycation end-products (AGEs) are a group of hetero- geneous compounds formed from the non-enzymatic glycation of proteins, lipids and nucleic acid. These compounds can covalently cross-link with proteins (Van Puyvelde, Mets, Njemini, Beyer, & Bautmans, 2015; Zamora, Navarro, Aguilar, & Hidalgo, 2015). Based on their fluorescence properties and cross-linking structures, AGEs are divided into two types: fluorescent cross-linking AGEs and non-fluorescent non-cross-linking AGEs. The former includes arg- pyrimidine, 2-(2-furoyl)-4(5)-(2-furanyl)-1H imidazole, the gly- oxal–lysine and methylglyoxal–lysine dimers, fluorolink, pentosidine, pyrropyridine and vesperlysines A, B and C. The latter includes N e -(carboxymethyl) lysine (CML), N e -(carboxyethyl) lysine (CEL), pyrraline, 3-deoxyglucasone–imidazolones and methylglyoxal–imidazole ones (Wu, Huang, Lin, & Yen, 2011). AGEs are generated through a Maillard reaction. During the reac- tion, the carbonyl groups and free amino groups of proteins form Amadori products, which further produce various reactive dicarbonyl species, such as deoxyglucosones, glyoxal (GO) and methylglyoxal (MGO). MGO and GO are crucial intermediates for the formation of AGEs in vivo (Li, Zheng, Sang, & Lv, 2014). AGEs are known to contribute to diabetes, insulin resistance, Alzheimer’s disease, cancer growth, and degenerative bone disease. The inter- action between AGEs and their receptors (RAGE; receptor for AGEs) elicits oxidative stress, inflammatory reactions and thrombosis, thereby causing vascular aging and damage (Ho, Chang, Tong, & Yu, 2014; Sharma, Kaur, Thind, Singh, & Raina, 2015). AGEs can be produced in vivo and in food. Intake of food-derived AGEs have harmful effects on human health (Sharma et al., 2015). Intake of AGEs induces protein cross-linking and intracellular oxi- dant stress similar to their endogenous counterparts. Oral intake of AGEs-containing foods can induce type 1 diabetes mellitus in dif- ferent animal models and influence the effect of calorie restriction on oxidant stress, age-related diseases and life span (Sharma et al., 2015; Uribarri et al., 2015; Van Puyvelde et al., 2015). Therefore, inhibition of AGEs formation both in vivo and in food is important for the promotion of human health, especially for managing diabetes. Use of inhibitors is an effective approach to reduce AGEs forma- tion. Some synthetic compounds, such as aminoguanidine, show high inhibitory capacity against AGEs formation (Delgado- Andrade, 2016). However, this compound has been associated with several adverse effects in vivo and is not permitted for food appli- cations. Thus, the search for natural products that can inhibit AGEs formation has recently increased (Uribarri et al., 2015). Antioxi- dants, including plant extracts and their active ingredients, such http://dx.doi.org/10.1016/j.foodchem.2016.11.056 0308-8146/Ó 2016 Elsevier Ltd. All rights reserved. Abbreviations: AGEs, advanced glycation end-products; BSA, bovine serum albumin; CA, carnosic acid; CEL, N e -(carboxyethyl) lysine; CML, N e -(carboxymethyl) lysine; DNPH, 2,4-dinitrophenylhydrazine; GO, glyoxal; MGO, methylglyoxal; OPD, o-phenylenediamine; PBS, phosphate buffer saline; RA, rosmarinic acid. ⇑ Corresponding authors. E-mail addresses: mfwang@hku.hk (M. Wang), tosy@jnu.edu.cn (S. Ou). 1 Juanying Ou and Junqing Huang contributed equally to this work. Food Chemistry 221 (2017) 1057–1061 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem