Abstract:

Objective: To understand the inhibitory activity of bioactive components in buckwheat bran on pancreatic lipase,
which can provide evidence to explain its mechanism for lowing serum lipids. Methods: Ethanol extract of buckwheat bran
(mainly containing rutin) and high-pressure hydrolysate of the residue left after ethanol extraction (a mixture of quercetin,
isoquercetin and rutin) were obtained from tartary buckwheat bran, while water extract (mainly consisting of fagopyritols)
was prepared from common buckwheat bran for evaluation of their inhibitory activity on pancreatic lipase in comparison
with the lipase inhibitor orlistat. The mechanism of the hydrolysate for inhibiting pancreatic lipase was investigated by
examining the effect of the order of addition of substrate, inhibitor and enzyme on the inhibitory activity. Results: The
sequence of inhibitory activity toward pancreatic lipase was orlistat > hydrolysate > ethanol extract > water extract, with IC50
values of 0.47, 1.94, 2.53 and 17.6 mg/mL, respectively. The inhibitory mechanism of the hydrolysate on pancreatic lipase
belonged to the competitive type, which was mainly associated with the presence of flavonoids interacting with the substrate
to block its interaction with the lipase. Conclusion: Buckwheat flavonoids present in the ethanol extract and the hydrolysate
exert inhibitory effects on pancreatic lipase, especially those of the latter. Buckwheat fagopyritols in the water extract from
common buckwheat bran show no inhibitory effect on pancreatic lipase at a low concentration, but can inhibit this enzyme at
a high concentration.

Key words: buckwheat flavonoids, buckwheat fagopyritols, rutin, quercetin, isoquercetin, pancreatic lipase, inhibitor