Reduction of digoxin to 20R-dihydrodigoxin by cultures of Eubacterium lentum

Abstract

The anaerobic bacterium Eubacterium lentum, a common constituent of the intestinal microflora, inactivates digoxin by reducing the unsaturated lactone ring. Reduction of the cardiac glycoside by growing cultures of E. lentum ATCC 25559 proceeded in a stereospecific manner, with the 20R-dihydrodigoxin constituting more than 99% of the product formed. This is in contrast to the 3:1 ratio of 20R and 20S epimers formed in the chemical catalytic hydrogenation. Formation of the reduced glycosides proceeded quantitatively when an overall concentration of 10 micrograms/ml was added to the cultures. E. lentum did not hydrolyze the digitoxose sugars from C-3 of the parent glycoside. However, the synthetically prepared sugar-hydrolyzed metabolites (digoxigenin, digoxigenin monodigitoxoside, and digoxigenin bisdigitoxoside) were reduced to the corresponding dihydro metabolites. Repetition of the experiments with a feces sample from a volunteer who was known to be a converter of digoxin to dihydrodigoxin gave results identical to those obtained with pure E. lentum cultures.

Metabolism of cyadox by the intestinal mucosa microsomes and gut flora of swine, and identification of metabolites by high‐performance liquid chromatography combined with ion trap/time‐of‐flight mass spectrometry

“…Activity and toxicity of hydrogenation compounds are often decreased. For instance, 20R‐dihydrodigoxin, formed by the hydrogenation of digoxin after incubation with Eubacterium lentum , is essentially inactive. Hydrogenation of rubratoxin B (Rb) to saturate the lactone ring reduced the acute toxicity significantly.…”

Eggerthella lenta bacteraemia in a patient with Caroli disease

“…5 days (Lamy & Seifert, 2012); and secondly, that the digoxin degradation rate was very different from prior studies, i.e. a 21 % reduction versus about 100 % after 7 days (Robertson et al, 1986), possibly due to metabolic variability among E. lenta isolates, or to substrate competition caused by amino acids from the culture medium (Lu et al, 2014). Both circumstances pose questions about false-negative blood cultures, especially regarding fastidious, anaerobic bacteria, and about how much E. lenta digoxin reduction variability could affect patients under digoxin regimes.…”

“…Eggerthella lenta (formerly Eubacterium lentum) is an obligate anaerobic, non-spore-forming, Gram-positive rod found as a normal commensal of the human intestinal flora. Of note, these bacteria are capable of reducing digoxin into several metabolites (Robertson et al, 1986), which could affect patients taking this drug. Disease due to this microorganism is unusual, but central nervous system (Arias et al, 2006), articular (Pardo Sánchez et al, 2008;Bok & Ng, 2009), blood (Thota et al, 2011;Venugopal et al, 2012) and disseminated infections (Salameh et al, 2012) have been reported.…”

Reductive inactivation of digitoxin by Eubacterium lentum cultures

“…Reduction of the 20,22-unsaturated lactone ring of the cardenolides introduces a center of asymmetry at C-20, and Reuning et al (17) have determined the stereochemistry of dihydrodigoxin (DHDG3) excreted in urine after DG3 administration in humans as 20R. In a previous study it was found that E. lentum is not only capable of reducing DG3 to give 20R-DHDG3, but it can perform the reduction on the sugar-hydrolyzed metabolites of DG3 as well to form the corresponding 20R-dihydro metabolites (18). Since DHDT3 is known to be an important metabolite of DT3 in humans (2), it was worthwhile to determine whether this metabolite is also formed by E. lentum.…”

“…Instrumentation. The high-performance liquid chromatography (HPLC) system was equipped with a Beckman model 11OA pump (Beckman Instruments, Inc., Fullerton, Calif.), a Rheodyne injection loop (200 ,ul), a normal-phase (Lichrosorb Si 60; Jones Chromatography) column, and a Kratos model FS 970 fluorescence detector (18,19). Deuterated solvents were used for determining nuclear magnetic resonsance (NMR) spectra with a Bruker HX-90 or HX-270 spectrometer.…”