Journal
PHARMACEUTICAL BIOLOGY
Volume 53, Issue 5, Pages 758-766Publisher
INFORMA HEALTHCARE
DOI: 10.3109/13880209.2014.942791
Keywords
beta-Amyloid; dementia; glycosides; oxidative stress
Funding
- Research Excellence Fund, Research Management Institute, Universiti Teknologi MARA, Malaysia [600-RMI/ST/DANA 5/3/DST (465/2011)]
- Institute of Graduate Studies, Universiti Teknologi MARA, Malaysia
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Context: Soybean and its fermented products are the most common source of isoflavones in human food. Objective: The present study quantifies the major glycosides and aglycones in soybean and its fermented product tempeh isoflavone extracts. The comparision of antioxidant effects and BACE1 inhibitory activity between the isoflavones of soybean and tempeh were also established. Materials and methods: The major isoflavones such as daidzein and genistein (aglycones), and their sugar conjugates (glycosides) daidzin and genistin in soybean and tempeh isoflavones were quantified using HPLC analysis. Comparative studies on BACE 1 (beta-site amyloid precursor protein cleaving enzyme 1 or beta-secretase 1) inhibition and free-radical scavenging activities (diphenyl-1-picrylhydrazyl (DPPH) and ferrous ion chelating ability) were conducted. Results: The amount of actives (mg/100 g) in soybean isoflavone compared with tempeh isoflavone is as follows: daidzein 16.72 mg/100 g versus 38.91 mg/100 g, genistein 11.10 mg/100 g versus 24.03 mg/100 g, daidzin 6.16 mg/100 g versus 0.69 mg/100 g, and genistin 24.61 mg/100 g versus 6.57 mg/100 g. The IC50 values of soybean and tempeh isoflavones against BACE1 were 10.87 and 5.47 mg/ml, respectively. The tempeh isoflavone had a more potent DPPH free-radical scavenging activity (IC50 = 2.67 mg/ml) than the soybean isoflavone (IC50 = 10 mg/ml). The ferrous ion chelating ability of the isoflavones was practically similar (IC50 = 10.40 mg/ml, soybean and 11.13 mg/ml, tempeh). Discussion and conclusion: The present study indicates that tempeh is a healthy supplement to alleviate oxidative stress through the enrichment of aglycones.
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