Xenobiotic C-sulfonate derivatives; metabolites or metabonates?

1. The production of sulfate conjugates is a well-known and established pathway within the field of xenobiotic metabolism. In addition to the usual attachment of a sulfonate grouping via an oxygen atom (O-sulfonates) to yield a sulfate conjugate, so-called "N-sulfates" (N-sulfonates) have been reported and "S-sulfates" (S-sulfonates) mooted to exist. 2. The few examples cited in the literature where the sulfur atom of the sulfonate group was attached directly to a carbon atom of the xenobiotic (C-sulfonates) and subsequently excreted as a metabolite have been collated, examined and reviewed. 3. The potential mechanisms of formation of these C-sulfonates are discussed, both biological and chemical; the potential role of the gut microbiome raised and hopefully by highlighting this curiosity further fruitful investigation will be stimulated.