Bitter melon, Momordica charantia, is a widely-used treatment for diabetes in traditional medicine systems throughout
the world. The compounds responsible for this biological activity are still under
investigation, but curcurbitane triterpenoids are thought to be paramount. We investigated
the gastrointestinal transport of a saponin-enriched n-BuOH fraction of M. charantia using a two-compartment transwell human intestinal epithelial cell Caco-2 monolayer
system, simulating the intestinal barrier. Eleven triterpenoids in this extract were
transported from the apical to basolateral direction across Caco-2 cell monolayers
and were identified or tentatively identified by HPLC-TOF-MS. Cucurbitane-type triterpenoids
permeated to the basolateral side with apparent permeability coefficient (Papp) values for 3-β-7-β,25-trihydroxycucurbita-5,23(E)-dien-19-al, momordicines I and II at 15.8 ×10-
6, 7.03 ×10-
6 and 4.34 ×10-
6 cm/s, respectively. Also, small amounts of these triterpenoids were absorbed inside
the epithelial cells themselves, suggesting additional bioactivity for these compounds.
To our knowledge, this is the first report of the transport of the reputed anti-diabetes
cucurbitane-type triterpenoids in human intestinal epithelial cell monolayers; these
results therefore point to a novel mechanism for the possible bioavailability of these
bitter melon compounds in vivo.
