Human Fecal Metabolism of Soyasaponin I

Abstract

The metabolism of soyasaponin I (3-O-[alpha-L-rhamnopyranosyl-beta-D-galactopyranosyl-beta-Dglucuronopyranosyl]olean-12-ene-3beta,22beta,24-triol) by human fecal microorganisms was investigated. Fresh feces were collected from 15 healthy women and incubated anaerobically with 10 mmol soyasaponin I/ g feces at 37 degrees C for 48 h. The disappearance of soyasaponin I in this in vitro fermentation system displayed apparent first-order rate loss kinetics. Two distinct soyasaponin I degradation phenotypes were observed among the subjects: rapid soyasaponin degraders with a rate constant k = 0.24 +/-0.04 h(-)(1) and slow degraders with a k = 0.07 +/-0.02 h(-)(1). There were no significant differences in the body mass index, fecal moisture, gut transit time, and soy consumption frequency between the two soyasaponin degradation phenotypes. Two primary gut microbial metabolites of soyasaponin I were identified as soyasaponin III (3-O-[beta-D-galactopyranosyl-beta-D-glucuronopyranosyl]olean-12-ene-3beta,22beta,24-triol) and soyasapogenol B (olean-12-ene-3beta,22beta,24-triol) by NMR and electrospray ionized mass spectroscopy. Soyasaponin III appeared within the first 24 h and disappeared by 48 h. Soyasapogenol B seemed to be the final metabolic product during the 48 h anaerobic incubation. These results indicate that dietary soyasaponins can be metabolized by human gut microorganisms. The sugar moieties of soyasaponins seem to be hydrolyzed sequentially to yield smaller and more hydrophobic metabolites. KeywordsCollege of Veterinary Medicine, Soyasaponin; metabolism; human gut microorganisms The metabolism of soyasaponinolean-12-ene-3 ,22 ,24-triol) by human fecal microorganisms was investigated. Fresh feces were collected from 15 healthy women and incubated anaerobically with 10 mmol soyasaponin I/g feces at 37°C for 48 h. The disappearance of soyasaponin I in this in vitro fermentation system displayed apparent first-order rate loss kinetics. Two distinct soyasaponin I degradation phenotypes were observed among the subjects: rapid soyasaponin degraders with a rate constant k ) 0.24 ( 0.04 h -1 and slow degraders with a k ) 0.07 ( 0.02 h -1 . There were no significant differences in the body mass index, fecal moisture, gut transit time, and soy consumption frequency between the two soyasaponin degradation phenotypes. Two primary gut microbial metabolites of soyasaponin I were identified as soyasaponin III (3-O-[ -D-galactopyranosyl--D-glucuronopyranosyl]olean-12-ene-3 ,-22 ,24-triol) and soyasapogenol B (olean-12-ene-3 ,22 ,24-triol) by NMR and electrospray ionized mass spectroscopy. Soyasaponin III appeared within the first 24 h and disappeared by 48 h. Soyasapogenol B seemed to be the final metabolic product during the 48 h anaerobic incubation. These results indicate that dietary soyasaponins can be metabolized by human gut microorganisms. The sugar moieties of soyasaponins seem to be hydrolyzed sequentially to yield smaller and more hydrophobic metabolites.

Metabolism of Soyasaponin I by Human Intestinal Microflora and Its Estrogenic and Cytotoxic Effects

“…The parental constituent soyasaponin I showed a peak at m/z 941 [M-H] − ion. Of these metabolites, M1 and M3 were soyasaponin III and soyasapogenol B, respectively, as previously reported (Hu et al, 2004 , which matched that of soyasapogenol B 3-β-D-glucuronide.…”

“…The pharmacological effects of these soyasaponin, or triterpenoid glycoside, constituents of natural products may depend on their metabolism by intestinal bacteria (Kobashi and Akao, 1997;Kim, 2002). Hu et al (2004) reported that human fecal microflora potently hydrolyzed soyasaponin I via soyasaponin III to soyasapogenol B. However, they did not find other metabolite(s).…”

Soyasaponin I, III, and Soyasapogenol B Inhibit Proliferation and Modulate PKC Expression in Caco-2 Human Colon Cancer Cells

“…Soyasaponins vary in the composition of their sapogenol as well as the number, type, and point(s) of attachment of their sugar moieties to the sapogenol. Berhow, & Singletary, 2005Gurfinkel & Rao, 2003;Hu, Reddy, Hendrich, & Murphy, 2004a;Hu, Zheng, Hyde, Hendrich, & Murphy, 2004b) and one in vivo study (Koratkar & Rao, 1997) conducted to investigate the anti-mutagenic or anti-carcinogenic properties of soyasaponins. These studies have shown soyasaponins suppress the growth of cancer cells and the effect of soy saponins depend on the type of saponin, dose and cancer cell lines tested.…”

“…tract, and that they are metabolized by gut microflora into their aglycone soyasapogenol. To better understand this process, Hu et al (2004b) conducted a human fecal metabolism study which tracked the metabolism of the primary soyasaponin in heat treated soy foods, soyasaponin I (Murphy, Hu, Barua, & Hauck, 2008). The results show that soyasaponin I is rapidly metabolized within the first 24 hours by microflora into soyasaponin III.…”

“…Results from Hu et al (2004a and2004b) and animal metabolism studies (Gestetner et al, 1968;Yoshikoshi et al, 1995) indicates that it may not be practical to test crude mixtures of soyasaponins on human colon cancer cells in vitro, simply because soyasaponins are quickly metabolized by gut microflora and may not be present long enough or in significant quantities to have an effect within the colon. Therefore, it would be more pertinent to test the metabolites of soyasaponins rather than the native soyasaponins themselves.…”