Abstract:
Opuntia ficus-indica biological effects are attributed to several bioactive metabolites. How-
ever, these actions could be altered in vivo by biotransformation reactions mainly via gut microbiota.
This study assessed gut microbiota effect on the biotransformation of O. ficus-indica metabolites both
in vitro and ex vivo. Two-time aliquots (0.5 and 24 h) from the in vitro assay were harvested post
incubation of O. ficus-indica methanol extract with microbial consortium, while untreated and treated
samples with fecal bacterial culture from the ex vivo assay were prepared. Metabolites were analyzed
using UHPLC-QTOF-MS, with flavonoid glycosides completely hydrolyzed in vitro at 24 h being con-
verted to two major metabolites, 3-(4-hydroxyphenyl)propanoic acid and phloroglucinol, concurrent
with an increase in the gallic acid level. In case of the ex vivo assay, detected flavonoid glycosides in
untreated sample were completely absent from treated counterpart with few flavonoid aglycones
and 3-(4-hydroxyphenyl)propanoic acid in parallel to an increase in piscidic acid. In both assays,
fatty and organic acids were completely hydrolyzed being used as energy units for bacterial growth.
Chemometric tools were employed revealing malic and (iso)citric acids as the main discriminating
metabolites in vitro showing an increased abundance at 0.5 h, whereas in ex vivo assay, (iso)citric,
aconitic and mesaconic acids showed an increase at untreated sample. Piscidic acid was a significant
marker for the ex vivo treated sample. DPPH, ORAC and FRAP assays were further employed to
determine whether these changes could be associated with changes in antioxidant activity, and all
assays showed a decline in antioxidant potential post biotransformation.
