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. 2011 May;48(3):203-8.
doi: 10.3164/jcbn.10-84. Epub 2011 Apr 13.

Sweet Potato (Ipomoea Batatas L.) Leaves Suppressed Oxidation of Low Density Lipoprotein (LDL) in Vitro and in Human Subjects

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Free PMC article

Sweet Potato (Ipomoea Batatas L.) Leaves Suppressed Oxidation of Low Density Lipoprotein (LDL) in Vitro and in Human Subjects

Miu Nagai et al. J Clin Biochem Nutr. .
Free PMC article

Abstract

Sweet potato (Ipomoea batatas L.) leaves are consumed as vegetables around the world, especially in Southeast Asia. The aim of this study was to investigate the inhibitory effect of sweet potato leaves on low-density lipoprotein oxidation in vitro and in human subjects. We compared the antioxidant activity of 8 kinds of sweet potato leaves. Every sweet potato leaf had high radical scavenging activity and prolonged a lag time for starting low-density lipoprotein oxidation in vitro. We found that sweet potato leaves contained abundant polyphenol compounds and the radical scavenging activity and prolongation rate of lag time were highly correlated with total polyphenol content. We also confirmed that thiobarbituric acid reactive substances production was increased in endothelial cell-mediated low-density lipoprotein oxidation, which was decreased by treatment with sweet potato leaves. We further measured the low-density lipoprotein oxidizability in 13 healthy volunteers after their intake of 18 g of "Suioh", raw sweet potato leaves. "Suioh" prolonged a lag time for starting low-density lipoprotein oxidation and decreased low-density lipoprotein mobility. These results suggest that sweet potato leaves have antioxidant activity leading to the suppression of low-density lipoprotein oxidation.

Keywords: antioxidant activity; atherosclerosis; low-density lipoprotein; polyphenol; sweet potato leaves.

Figures

Fig. 1
Fig. 1
Relationship between DPPH radical scavenging activity and total polyphenol content of 8 kinds of sweet potato leaves. DPPH radical scavenging activity was expressed as ascorbic acid equivalent (A). Total polyphenol content was determined by Folin-Ciocalteu assay and expressed as chlorogenic acid equivalent (B). Values are means ± SD (n = 3). Different letters indicate statistically significance (p<0.05) among different groups by Fisher’s PLSD test after ANOVA. There was a significant positive correlation between total polyphenol content and DPPH radical scavenging activity (C).
Fig. 2
Fig. 2
Relationship between a lag time for starting LDL oxidation and total polyphenol content of 8 kinds of sweet potato leaves. LDL (70 µg/ml protein) was incubated with AMVN-CH3O (final concentration 400 µM) at 37°C in the absence or presence of sweet potato leaves extracts. The lag time for starting LDL oxidation was defined as the time interval between the initiation and intercept of the two tangents drawn to the lag and propagation phase of the absorbance curve at 234 nm (A). Values are means ± SD (n = 4). #p<0.001 compared with untreated LDL, by Fisher’s PLSD test after ANOVA. There was a significant positive correlation between a lag time for starting LDL oxidation and total polyphenol content (B).
Fig. 3
Fig. 3
Effect of “Suioh” intake on LDL oxidation in healthy subjects. After overnight fasting, 13 healthy volunteers consumed 18 g of raw “Suioh” leaves. Blood was sampled before and 0.5, 1, 2, and 4 h after intake. We measured LDL oxidizability in the presence of AMVN-CH3O (final concentration 200 µM) by lag time assay (A), TBARS assay (B) and agarose gel electrophoresis (C). Data are mean ± SEM (n = 13). p<0.1, *p<0.05, **p<0.01 compared with before consumption of “Suioh” by Fisher’s PLSD test after ANOVA.

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