The ethyl acetate fraction of corn silk exhibits dual antioxidant and anti-glycation activities and protects insulin-secreting cells from glucotoxicity.
BACKGROUND
In this study, we aimed to develop a Stigmata Maydis (corn silk) fraction with dual bio-activities against oxidative stress and protein glycation to protect β-cells from diabetes-induced failure.


METHODS
Corn silk fractions were prepared by partition and chemically characterised by thin-layer chromatography. Free radical scavenging assay, glycation assay, and cell-based viability test (neutral red) were employed to decide the best fraction. Cell death analysis was executed by annexin V/ Propidium iodide staining. Cell proliferation was measured by WST-1. Finally, β-cell function was evaluated by β-cell marker gene expression (RT-PCR) and acute insulin secretion test.


RESULTS
Four corn silk fractions were prepared from an ethanolic crude extract of corn silk. In vitro assays indicate ethyl acetate fraction (YMS-EA) was the most potent fraction. YMS-EA also attenuated the hydrogen peroxide- or methylglyoxal-induced induction of reactive oxygen species, reduction of cell viability, and inhibition of cell proliferation. However, YMS-EA was unable to prevent hydrogen peroxide-induced apoptosis or advanced glycation end-products-induced toxicity. Under hyperglycemic conditions, YMS-EA effectively reduced ROS levels, improved mRNA expression of insulin, glucokinase, and PDX-1, and enhanced glucose-stimulated insulin secretion. The similarity of bioactivities among apigenin, luteolin, and YMS-EA indicated that dual activities of YMS-EA might be derived from those compounds.


CONCLUSIONS
We concluded that YMS-EA fraction could be developed as a preventive food agent against the glucotoxicity to β-cells in Type 2 diabetes.
School of Pharmacy, College of Medicine, National Taiwan University, Taipei, Taiwan, ROC.
Chia-Chuan
CC
Chang
Department of Psychiatry, Cheng Hsin General Hospital, Taipei, Taiwan, ROC.
Wei
W
Yuan
Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei, Taiwan, ROC.
Hsiao-Yuh
HY
Roan
Division of Basic Chinese Medicine, National Research Institute of Chinese Medicine, Ministry of Health and Welfare, Taipei, Taiwan, ROC.
Jia-Ling
JL
Chang
Department of Applied Science, National Hsinchu University of Education, Hsinchu, Taiwan, ROC.
Hsiu-Chen
HC
Huang
The Center of Translational Medicine, Taipei Medical University, Taipei, Taiwan, ROC.|The Ph.D. Program for Medical Biotechnology, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan, ROC.
Yu-Ching
YC
Lee
Institute of Neuroscience, Brain Research Centre, National Yang-Ming University, Taipei, Taiwan, ROC.
Huey Jen
HJ
Tsay
Division of Basic Chinese Medicine, National Research Institute of Chinese Medicine, Ministry of Health and Welfare, Taipei, Taiwan, ROC. hk.liu@nricm.edu.tw.|Ph.D Program for the Clinical Drug Discovery from Herbal Medicine, College of Pharmacy, Taipei Medical University, Taipei, Taiwan, ROC. hk.liu@nricm.edu.tw.
Hui-Kang
HK
Liu
D000085:Acetates / Q000737:chemistry; D000818:Animals; D000975:Antioxidants / Q000737:chemistry / Q000494:pharmacology*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D005260:Female; D017127:Glycation End Products, Advanced / Q000032:analysis / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000633:toxicity; D008297:Male; D051379:Mice; D018384:Oxidative Stress / Q000187:drug effects*; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology*; D051381:Rats; D017382:Reactive Oxygen Species / Q000032:analysis / Q000378:metabolism; D003313:Zea mays / Q000737:chemistry*
D000085:Acetates; D000975:Antioxidants; D017127:Glycation End Products, Advanced; D010936:Plant Extracts; D017382:Reactive Oxygen Species; C007650:ethyl acetate; D006861:Hydrogen Peroxide
Advanced glycation end products; Glucotoxicity; Methylglyoxal; Reactive oxygen species; Stigmata Maydis (corn silk); β-cell failure