br Conflicts of interest br

Conflicts of interest
Acknowledgements This work was sponsored by grants from Longyan University Scientific Research Fund for the Young Scholars (LQ2016010), Middle-aged and Young Teachers Education Research Projects of Fujian Province (JAT170569), Longyan University Scientific Research Fund for the Doctoral Young Scholars (LB2015004) and Longyan University Key Discipline Fund of Biological Engineering.
Introduction Diabetes mellitus is a chronic metabolic disease affecting 4% of the population worldwide (Chen, Magliano, & Zimmet, 2012). In particular, the rates of type 2 Dynorphin A and obesity have soared in both developed and developing countries (Jain & Saraf, 2010). Hyperglycemia in diabetes mellitus is considered the primary factor for the pathogenesis of long-term diabetic complications (American Diabetes Association, 2010). Sustained reductions in hyperglycemia can delay the development of long-term diabetic complications that are caused by microvascular damage without reducing the increased cardiovascular risk derived from macrovascular injury (Gleissner, Galkina, Nadler, & Ley, 2007; UK Prospective Diabetes Study (UKPDS) Group, 1998). Consequently, the emergence of these debilitating pathologies appears to be unavoidable in the majority of diabetic patients (Brownlee, 2005). During the past four decades, aldose reductase (AR, EC 1.1.1.21) has been widely investigated as an enzyme critically involved in the onset and progression of various pathologies associated with diabetes mellitus. AR is the pivotal enzyme in the polyol pathway that induces the diabetic complications. In recent years, important advances in understanding the physiological and pathological roles of AR demonstrated that this enzyme is involved in inflammatory signaling under both hyperglycemic and normoglycemic conditions. Accordingly, known AR inhibitors (ARIs) were shown to prevent cellular inflammatory events (Maccari & Ottanà, 2015). Furthermore, oxidative stress and free radicals are closely associated with induction of the diabetic state or aggravation of diabetic complications (Wiernsperger, 2003). Therefore, there is growing interest in the development of novel and effective ARIs, in particular those with antioxidant effects that may be useful for the amelioration of the related diseases. To date, a large variety of ARIs have been developed, such as epalrestat, tolrestat, zopolrestat, zenarestat, and quercetin (Alexiou et al., 2009, Costantino et al., 1997, Costantino et al., 1999, Costantino et al., 2000, Miyamoto, 2002, Suzen and Buyukbingol, 2003). However, their clinical applications were often hampered by adverse side effects. Although epalrestat showed a good clinical effect and is marketed in Japan and India, it was suggested that its efficacy should be monitored by further long-term comparative studies in different patient populations (Ramirez & Borja, 2008). Moreover, the concern of using synthetic antioxidants, such as butylated hydroxytoluene, is also increasing because of their potential carcinogenic effects (Wang, Hwang, & Lim, 2015a). Thus, there is growing interest in using food supplements to inhibit AR and oxidation because of their better safety profile and less frequent adverse effects. In Peru, there is wide biodiversity and about 5000 plant species are used for alimentation and medicines. Tea infusion is the most frequent form of food supplement used by Peruvians from ancient times for health protection and disease treatment. It can be said that tea infusion is a part of everyday life for Peruvians. Some infusion tea plants may serve as good source for the development of functional foods. Recently, there is growing interest in Peruvian plants by national governments and health providers. Three widely known plants are Uncaria tomentosa (cat’s claw), Phyllantus niruri (chanca pidera) and Lepidium meyenii (maca), which were already shown to have therapeutic or prophylactic potential. However, very few studies of Peruvian plants have been published compared with studies of plants from Asian countries, and no report has been published related to the AR inhibitory activity of Peruvian infusion tea plants.