Contents lists available at ScienceDirect Food Research International journal homepage: www.elsevier.com/locate/foodres In vitro and in vivo assessment of anti-hyperglycemic and antioxidant effects of Oak leaves (Quercus convallata and Quercus arizonica) infusions and fermented beverages Claudia I. Gamboa-Gómez a,b , Luis E. Simental-Mendía b , Rubén F. González-Laredo a , Esteban J. Alcantar-Orozco a , Victor H. Monserrat-Juarez a , Julio C. Ramírez-España a , Jose Alberto Gallegos-Infante a , Martha R. Moreno-Jiménez a , Nuria E. Rocha-Guzmán a,⁎ a Instituto Tecnológico de Durango, Felipe Pescador 1830 Ote., 34080 Durango, Dgo., Mexico b Biomedical Research Unit Mexican Social Security Institute, 34067 Durango, Mexico ARTICLE INFO Keywords: Fermented beverages Kombucha Anti-hyperglycemic activity Antioxidant activity Oak leaves ABSTRACT The aim of this study was to evaluate the anti-hyperglycemic and antioxidant effects of oak leaves infusions and fermented beverages from Quercus convallata and Q. arizonica in vitro and in vivo. Female C57BL/6 mice fed with high saturated fat and fructose diet-induced obesity were treated with oak leaves beverages (200 μL/per day equivalent to 15 mg of lyophilized sample/Kg of body weight for infusions and 31 mg of lyophilized sample/Kg of body weight for fermented beverages) for 3 months and an oral glucose tolerance test (OGTT) was performed. Blood plasma was obtained for determination of glucose, lipid profile, and oxidative stress markers (ABTS, nitric oxide, and ORAC assays). Insulin resistance was estimated using the product of triglycerides and glucose (TyG). Oak leaves infusions and fermented beverages exhibited exerted inhibition of α-amylase (8–15% and 5–9%, respectively) and α-glucosidase (98% and 99%, respectively) enzymes. After OGTT, the groups treated with either oak leaves infusions or fermented beverages showed lower glucose levels compared with the obesity control group (18%) and a similar glucose tolerance to healthy control group. On long-term evaluation, inter- vention groups showed a significant reduction in fasting glucose concentrations (41–50% for oak leaves infu- sions and 52–66% for fermented beverages) and TyG index (4.2–4.6% for oak leaves infusions and 5.9–7.5% for fermented beverages) compared with the obese control group. Oak leaves infusions and fermented beverages had antioxidant potential in vitro and scavenging activity for radicals such as peroxyl and peroxynitrite anions. Our results suggest anti-hyperglycemic and antioxidant effects of beverages prepared with leaves of Quercus species in vitro and in vivo. 1. Introduction Obesity is a highly prevalent metabolic disorder characterized by an excess of visceral adiposity. Furthermore, it has been associated with dyslipidemia, hyperglycemia, insulin resistance, and oxidative stress through several mechanisms, leading to metabolic syndrome (Alberti et al., 2009). Regard, oxidative stress is an imbalance of reactive oxygen species (ROS) and antioxidant defenses. The cells are protected against the excess of ROS by antioxidant enzymes (e.g. catalase, glutathione peroxidase (GPX), superoxide dismutase (SOD), and other anti- oxidants). However, when ROS overwhelms antioxidant capacity, the cell functions are affected by this imbalance (Matsuda & Shimomura, 2013). On over-nutrition condition, a large amount of glucose is oxidized during the tricarboxylic cycle, leading to an increased production of electron donors in the mitochondrial electron transport chain. Thus, the process of electron donation to molecular oxygen promotes the pro- duction of superoxide ions (Brownlee, 2005). In addition, an excess of free fatty acids increases the oxidation level in the mitochondria. Both, β-oxidation of fatty acids and oxidation of free fatty acids-derived acetyl CoA by the tricarboxylic cycle, produce the same electron donors (NADH and FADH2) as in glucose oxidation; thus, an increased free fatty acid oxidation results in mitochondrial overproduction of ROS (Brownlee, 2005). Several studies have reported a correlation between ROS and glu- cose metabolism disturbances, such as hyperglycemia and insulin http://dx.doi.org/10.1016/j.foodres.2017.09.040 Received 6 June 2017; Received in revised form 14 September 2017; Accepted 17 September 2017 ⁎ Corresponding author. E-mail address: nrocha@itdurango.edu.mx (N.E. Rocha-Guzmán). Abbreviations: QC i , Quercus convallata infusion; QC k , Quercus convallata fermented beverage; QA i , Quercus arizonica infusion; QA k , Quercus arizonica fermented beverage Food Research International 102 (2017) 690–699 Available online 23 September 2017 0963-9969/ © 2017 Elsevier Ltd. All rights reserved. T