title: Enhancement of β-secretase inhibition and antioxidant activities of tempeh, a fermented soybean cake through enrichment of bioactive aglycones.
abstract: BACKGROUND
  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.
  
  
  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 (β-site amyloid precursor protein cleaving enzyme 1 or β-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).
  
  
  CONCLUSIONS
  The present study indicates that tempeh is a healthy supplement to alleviate oxidative stress through the enrichment of aglycones.
authors.affiliation: Faculty of Pharmacy, Puncak Alam Campus, Universiti Teknologi MARA (UiTM) , Selangor Darul Ehsan , Malaysia and.
authors.forename: Aliya
authors.initials: A
authors.lastname: Ahmad
authors.forename: Kalavathy
authors.initials: K
authors.lastname: Ramasamy
authors.forename: Abu Bakar Abdul
authors.initials: AB
authors.lastname: Majeed
authors.forename: Vasudevan
authors.initials: V
authors.lastname: Mani
mesh_terms: D053829:Amyloid Precursor Protein Secretases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000975:Antioxidants / Q000302:isolation & purification / Q000494:pharmacology*; D016282:Aspartic Acid Endopeptidases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005285:Fermentation; D019833:Genistein / Q000378:metabolism*; D006801:Humans; D007529:Isoflavones / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology; D045730:Soy Foods; D013025:Glycine max / Q000378:metabolism
chemical_list: D000975:Antioxidants; D007529:Isoflavones; C004742:daidzein; D019833:Genistein; D053829:Amyloid Precursor Protein Secretases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human
keywords: dementia; glycosides; oxidative stress; β-Amyloid