The &amp;lt;i&amp;gt;in Vitro&amp;lt;/i&amp;gt; Antioxidant Capacities of Hydroalcoholic Extracts from Roots and Leaves of &amp;lt;i&amp;gt;Smallanthus sonchifolius&amp;lt;/i&amp;gt; (Yacon) Do Not Correlate with Their &amp;lt;i&amp;gt;in Vivo&amp;lt;/i&amp;gt; Antioxidant Action in Diabetic Rats

Anacharis Babeto De Sá-Nakanishi,Andreia Assunção Soares,Jurandir Fernando Comar,Rosane Marina Peralta,Mariana Marques Nogueira Wendt,Ciomar Aparecida Bersani Amado,Sandra Da Silva Silveira,Júlia Rosa Moreira,Adelar Bracht,Ana Carla Broetto Biazon,Cristiane Vizioli Castro Ghizoni

doi:10.4236/jbm.2016.42003

Abstract

Leaf and root extracts of Smallanthus sonchifolius (yacon), have antihyper-glycemic activity and antioxidant properties. The present study aims to compare the in vivo hepatic antioxidant activity of hydroalcoholic extracts of yacon leaves and roots in rats with streptozotocin-induced diabetes in terms of their in vitro antioxidant capacity. Rats were treated during 14 days with 1060 mg·Kg-1 root extract or 400 mg·Kg-1 leaf extract. The latter was richer in phenolics and possessed a much higher in vitro antioxidant activity. Both extracts prevented hyperglycemia in diabetic rats. The liver of diabetic rats presented increased levels of protein carbonyls and ROS and decreased activities of antioxidant enzymes. Treatment with both root and leaf extracts restored the protein carbonyl levels to normality. The root extract also restored the ROS levels to normality, but the leaf extract was not effective. The root extract was also more effective in restoring the activity of at least two important antioxidant enzymes (glucose 6-phosphate dehydrogenase and glutathione peroxidase). In terms of the antioxidant load (which was 17 times lower in the root extract treatment), the in vivo action of the root extract was more effective than the leaf extract in reducing the hepatic oxidative stress that accompanies diabetes.

Highlights

Diabetes mellitus is a syndrome of multiple etiology that occurs due to the lack of insulin and/or to the inability of the cells to properly respond to it
Total phenolic compounds and the antioxidant activity in vitro (DPPH assay) of the hydroalcoholic extracts were evaluated in order to compare the antioxidant potential of the root extracts with those of the leaf extracts and to compare them with other types of yacon extracts
The antioxidant activity of the extracts was explored by measuring their capacity of inhibiting reactive oxygen species (ROS) generation in rat liver mitochondria, which constitute a true biological system as opposed to the chemical DPPH assay

Summary

Introduction

Diabetes mellitus is a syndrome of multiple etiology that occurs due to the lack of insulin and/or to the inability of the cells to properly respond to it. The main feature of chronic diabetes is hyperglycemia, often accompanied by dyslipidemia and endothelial dysfunction [1]. These abnormalities are associated with the development of macro- and microvascular complications such as atherosclerosis, retinopathy, nephropathy and neuropathy. The exact mechanisms underlying the development and progression of diabetes mellitus and its complications are not clear. There is growing evidence that the excessive generation of reactive oxygen species (ROS), associated to a diminished capacity of the antioxidant system, causes oxidative stress in a variety of tissues, as already demonstrated for both patients and experimental diabetic animals [1]-[3]. One of the main goals of research in recent years has been to find therapies capable of attenuating the oxidative stress associated to diabetes [4]

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