Abstract
The aim of this study was to investigate the antioxidant activity of hexane extracts from leaves of Piper auritum (HS). Eight complementary in vitro test methods were used, including inhibition of DPPH· radicals, nitric oxide, superoxide anion, ion-chelating, ABTS, oxygen radical absorbance capacity, β-carotene bleaching and peroxy radical scavenging. The results indicated that HS possesses high antioxidant activity. To add to these finding we tested the effect against oxidative stress in liver, pancreas and kidney in diabetic rats. Low levels of SOD, CAT, GPx and GSH in diabetic rats were reverted to near normal values after treatment with HS. These results suggest that P. auritum prevents oxidative stress, acting as a suppressor of liver cell damage. Given the link between glycation and oxidation, we proposed that HS might possess significant in vitro antiglycation activity. Our data confirmed the inhibitory effect of HS on bovine serum albumin, serum glycosylated protein, glycation of LDL, and glycation hemoglobin. The effect of HS on diabetic renal damage was investigated using streptozotocin-induced diabetic rats. The oral administration of HS at a dose of 200 and 400 mg/kg body weight/day for 28 days significantly reduced advanced glycation endproduct (AGE) formation, elevated renal glucose and thiobarbituric acid-reactive substance levels in the kidneys of diabetic rats. This implies that HS would alleviate the oxidative stress under diabetes through the inhibition of lipid peroxidation. These findings indicate that oxidative stress is increased in the diabetic rat kidney and that HS can prevent renal damage associated with diabetes by attenuating the oxidative stress.
Highlights
Reactive oxygen species (ROS) are generated in all living organisms mainly during mitochondrial metabolism [1]
Molecules 2012, 17 formation, elevated renal glucose and thiobarbituric acid-reactive substance levels in the kidneys of diabetic rats. This implies that HS would alleviate the oxidative stress under diabetes through the inhibition of lipid peroxidation. These findings indicate that oxidative stress is increased in the diabetic rat kidney and that HS can prevent renal damage associated with diabetes by attenuating the oxidative stress
The total phenolic content in HS in leaves was rather low, i.e., 0.3% (w/w), so the strong antioxidant activity of the hexane extract appears to be related to its content of hydrophobic compounds, there is no correlation with total phenolic content in HS
Summary
Reactive oxygen species (ROS) are generated in all living organisms mainly during mitochondrial metabolism [1]. Excessive amounts of ROS may overwhelm natural antioxidant defenses promoting DNA, lipid and protein oxidative damage and oxidative stress, which may lead to cell injury and death [2]. The negative effects of oxidative stress may be mitigated by the consumption of antioxidants. Antioxidants are compounds that can delay or inhibit the oxidation of lipids and other molecules, and by doing so inhibit the initiation and propagation of oxidative chain reactions. They act by one or more of the following mechanisms: reducing activity, free radicalscavenging, potential complexation of pro-oxidant metals and quenching of singlet oxygen. There has been a renewed interest in finding natural antioxidants from plant materials
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