Water decoction made from the seed of
Hunteria umbellata
is widely used in the traditional management of diabetes mellitus by Nigerian herbalists, particularly, in the southwest region of the country. Recently, a new bisindole alkaloid, erinidine,
was isolated but its antihyperglycemic profile remains largely un-investigated scientifically. This forms the basis for the current
study which is primarily designed at investigating the antihyperglycemic profile of erinidine and other fractions in both
in vitro
and
in vivo models of diabetes mellitus. In the present study, erinidine was isolated and purified using the earlier described
methods and its antihyperglycemic potentials tested in
in vitro models such as dipeptidylpeptidase (IV), glycogen phosphorylase,
HIT-T15 cell insulin secretion, glucose uptake activity, aldose reductase assays and α-glucosidase inhibition assay testings. In
addition, 50 mg/kg of erinidine and that of other fractions were evaluated in
in vivo models of normal and chemically-induced
hyperglycemic rats. Results showed that erinidine was a light yellow, amorphous solid with UV (CHCl
3) λ
max 256 nm, HRESIMS
m/z 382.1881 [(M+H)
+] (calculated for C
22H
26N
4O
2, 382.1876) and melting point of 230 ºC. The
in vitro study showed the
antihyperglycemic action of erinidine to be weakly mediated via α-glucosidase inhibition mechanism as the results for other
in
vitro tests such as dipeptidylpeptidase (IV), glycogen phosphorylase, HIT-T15 cell insulin secretion, glucose uptake activity and
aldose reductase assays were all negative. However, the
in vivo results showed 50 mg/kg erinidine given
per os to normal and
alloxan-induced hyperglycemic rats to significantly (
p<0.05,
p<0.001) attenuate an increase in their post-absorptive blood glucose
concentrations after 3 g/kg glucose loading in the rats, suggesting its antihyperglycemic mechanism to be via α-glucosidase
inhibition. This result, although, further corroborated the
in vitro findings but also suggests that erinidine needs to be biotransformed
in vivo for its inhibitory activity on intestinal glucose absorption to become evident. Thus, the present study suggests
erinidine to be the possible antihyperglycemic agent in
Hunteria umbellata seed extract mediating its antihyperglycemic action
via intestinal glucose uptake inhibition.
