Cytinus hypocistis (L.) L. is an edible parasitic plant that grows within the roots of its host. In addition to its use as
famine food in the past, it is also tradidionally used for treating several illnesses such as intestinal problems,
inflammations, tumors, and bleeding. This species is rich in hydrolysable tannins, compounds often associated
with inhibiting starch digestion. Therefore, the present work investigated how effectively C. hypocistis tannin-rich
extracts inhibited enzymes involved in starch digestion and if such effect also occurs in vivo. The latter premise
was approached using the starch tolerance test in mice. Two optimized hydroethanolic extracts were used, a
heat-assisted and an ultrasound-assisted extract, with known hydrolysable tannin content. Both extracts
demonstrated potent inhibition of α-amylase. Inhibitions were of the mixed type with inhibitor constants in the
15 μg/mL range. The inhibition of the intestinal α-glucosidase was at least ten times less effective. The inhibition
of the α-amylase was negatively affected by in vitro gastrointestinal digestion and bovine serum albumin. In vivo,
both extracts inhibited starch digestion at doses between 100 and 400 mg/mL in healthy mice. The highest doses
of the ultrasound and heat extracts diminished the peak glucose levels in the starch tolerance test by 46 and
59.3%, respectively. In streptozotocin diabetic mice, this inhibition occurred only at the dose of 400 mg/mL.
Under this condition, diminution of the peak glucose concentration in the starch tolerance test was equal to
36.7% and 48.8% for the ultrasound and heat extracts, respectively. Maltose digestion was not inhibited by the
C. hypocistis extracts. Qualitatively and quantitatively, thus, the actions of both extracts were similar. The results
allow adding a new biological property to C. hypocistis, namely, the ability to decrease the hyper-glycemic
excursion after a starch-rich meal, propitiating at the same time a diminished caloric intake.
This research was financed by Conselho Nacional de Pesquisa e
Desenvolvimento (CNPq) and Fundaç˜ao Arauc´aria. The authors are
grateful to the Foundation for Science and Technology (FCT, Portugal)
for financial support through national funds FCT/MCTES (PIDDAC) to
CIMO (UIDB/00690/2020 and UIDP/00690/2020) and SusTEC (LA/P/
0007/2020). A. R. Silva is grateful to FCT and FSE for her Doctoral Grant
(SFRH/BD/145834/2019), and L. Barros for her institutional scientific
employment program-contract. R. C. G. Corrêa is a research grant
recipient of Cesumar Institute of Science, Technology, and Innovation
(ICETI).
