Background: The genus Hypericum (family Clusiaceae) comprises various species that are
used in traditional medicine, such as wound healing, antidepressant, and anticancer agents.
Objective: The aim of this study was to evaluate the inhibitory capacity of extracts and fractions from
two Hypericum species used in the Brazilian folk medicine (H. brasiliense and H. connatum) against
the enzymes prolyl oligopeptidase (POP), dipeptidyl peptidase-IV (DPP-IV), and acetylcholinesterase
(AChE), as well as to identify their main active constituents.
Methods: Dried aerial parts of H. connatum and H. brasiliense were subjected to extraction with 8:2 methanol-H2O. Each
hydroalcoholic extract was fractioned resulting in ethyl acetate and aqueous fractions. The activity of POP, DPP-IV and
AChE was determined in vitro in 96-well microplates.
Results: The main components identified in the plant extracts were chlorogenic acid (1), quercitrin (2), rutin (3), quercetin
(4), and isoquercitrin (5). Hydroalcoholic extracts, ethyl acetate and aqueous fractions showed high POP inhibitory activity
with IC50 values of 2.6 to 3.7 µg/mL. AChE and DPP-IV inhibitory effects were very low for all extracts and substances.
Conclusion: Chlorogenic acid (1) and quercetin (4) were the main constituent responsible for the activity observed
against POP. Parallel artificial membrane permeability assay of ethyl acetate fractions of both species showed that the metabolite
that can effectively pass through the lipid membrane is 4, the aglycone form of 2, 3 and 5.