title: NMR evaluation of total statin content and HMG-CoA reductase inhibition in red yeast rice (Monascus spp.) food supplements.
abstract: BACKGROUND
  Red yeast rice (i.e., rice fermented with Monascus spp.), as a food supplement, is claimed to be blood cholesterol-lowering. The red yeast rice constituent monacolin K, also known as lovastatin, is an inhibitor of the hydroxymethylglutaryl-CoA (HMG-CoA) reductase. This article aims to develop a sensitive nuclear magnetic resonance (NMR) method to determine the total statin content of red yeast rice products.
  
  
  METHODS
  The total statin content was determined by a 400 MHz 1H NMR spectroscopic method, based on the integration of the multiplet at δ 5.37-5.32 ppm of a hydrogen at the hexahydronaphthalene moiety in comparison to an external calibration with lovastatin. The activity of HMG-CoA reductase was measured by a commercial spectrophotometric assay kit.
  
  
  RESULTS
  The NMR detection limit for total statins was 6 mg/L (equivalent to 0.3 mg/capsule, if two capsules are dissolved in 50 mL ethanol). The relative standard deviations were consistently lower than 11%. The total statin concentrations of five red yeast rice supplements were between 1.5 and 25.2 mg per specified daily dose. A dose-dependent inhibition of the HMG-CoA reductase enzyme activity by the red yeast rice products was demonstrated.
  
  
  CONCLUSIONS
  A simple and direct NMR assay was developed to determine the total statin content in red yeast rice. The assay can be applied for the determination of statin content for the regulatory control of red yeast rice products.
authors.affiliation: Chemisches und Veterinäruntersuchungsamt (CVUA) Karlsruhe, Weissenburger Strasse 3, 76187 Karlsruhe, Germany. lachenmeier@web.de.
authors.forename: Dirk W
authors.initials: DW
authors.lastname: Lachenmeier
authors.forename: Yulia B
authors.initials: YB
authors.lastname: Monakhova
authors.forename: Thomas
authors.initials: T
authors.lastname: Kuballa
authors.forename: Sigrid
authors.initials: S
authors.lastname: Löbell-Behrends
authors.forename: Sibylle
authors.initials: S
authors.lastname: Maixner
authors.forename: Matthias
authors.initials: M
authors.lastname: Kohl-Himmelseher
authors.forename: Asja
authors.initials: A
authors.lastname: Waldner
authors.forename: Christian
authors.initials: C
authors.lastname: Steffen