Article citationsMore>>

K. D. Setchell, C. Clerici, E. D. Lephart, S. J. Cole, C. Heenan, D. Castellani, B. E. Wolfe, L. Nechemias- Zimmer, N. M. Brown, T. D. Lund, R. J. Handa and J. E. Heubi, “S-Equol, a Potent Ligand for Estrogen Receptor Beta, Is the Exclusive Enantiomeric form of the Soy Isoflavone Metabolite Produced by Human Intestinal Bacterial Flora,” The American Journal of Clinical Nutrition, Vol. 81, No. 5, 2005, pp. 1072-1079.

has been cited by the following article:

• TITLE: The Development of S-Equol Diastereoisomer Specific ELISA

  AUTHORS: Takayuki Minekawa, Akira Kambegawa, Kumiko Shindome, Shizuka Takehara, Hidetoshi Arakawa

  KEYWORDS: S-Equol; Diastereoisomer; Immunoassay; ELISA; Isoflavone; Deconjugation

  JOURNAL NAME: American Journal of Analytical Chemistry, Vol.3 No.6, June 21, 2012

  ABSTRACT: Equol is a metabolite of soybean isoflavone, daidzein, and many health benefits are expected. Endogenous equol in urine is S-equol and mostly exists as glucuronate or sulfate conjugate. In this study we preliminary established the simple enzyme-linked immunosorbent assay (ELISA) without deconjugation, then developed the S-equol specific ELISA involves deconjugation showing high stereospecificity to S-equol without using stereospecific antibody. For the simple ELISA, we used a polyclonal antibody that targets the regions not influenced by inhibition by conjugation of glucuronate and sulfate and achieved the correlation coefficient; r = 0.975, but the value was 30 % lower than high performance liquid chromatography (HPLC). Developing upon this we invented the specific ELISA established from S-equol homogeneous combination for the standard and enzyme-labeled antigen to enhance stereospecificity. The correlation with HPLC was favorable: r = 0.986, y = 0.996x – 6. Compared to the previous method using (R,S)-equol combination, cross-reactivity with R-equol was reduced from 65 to 13 %, and that with daidzein from 0.31% to 0.08%, markedly increased in the specificity. This study is expected to be applied for both simple clinical researches, and stereospecific immunoassays in which specific antibody preparation is difficult.