We also found that ethanolic extract of dried roselle calyces (HS-EE) at 1.0 g/kg, which decreased the fasting
blood glucose of chronic diabetic rats by 32±2 %
(Wisetmuen et al., 2008), increased the basal insulin
release of normal rats and had a tendency to
increase as well in chronic diabetic rats although
not statistically significant. However, we found the
regeneration of islets (increase in the number of
islets) in chronic diabetic rats treated with HS-EE
(Table 2). It is possible that the islets of diabetic
rats, which were formerly partially destroyed by
STZ, still did not function properly hence the
insulin release was not high enough to make a
difference. Additionally, in the situation that the
increase in insulin level was not significantly
increased, HS-EE caused an increase in tissue
insulin sensitivity might be accounted for its
hypoglycemic activity as well which is an
interesting topic for further investigation.