The genus Cinnamomum

262 K.K. Vijayan and R.V. Ajithan Thampuran
Ayurveda publications that cinnamon reduces the blood glucose level in non-insulin
dependent diabetes. Polansky and Anderson (1992) in their study of insulin activity in
isolated adipocytes observed that in the absence of added insulin, an extract of the herb
potentiated the activity of insulin-stimulated utilisation of glucose. In vivo study in rats
also gave encouraging results. Sharma et al. (1996a, b) investigated the hypoglycemic
potential of C. tamala bark extract as a single dose of 0, 100, 200 and 500 mg/kg body
weight in fasted rats. They obtained a good hypoglycemic effect, which was more pronounced
at lower doses (100–200 mg/kg). The same group extended the study with a
50% alcoholic extract of the leaves and obtained a significant reduction in plasma glucose
levels in normoglycemic rats at a dose of 250 mg/kg body weight (Sharma et al., 1996b).
In another in vitro study using pancreatic cell culture, Patole and Agte (1998) observed that
a 10% alcoholic extract of cinnamon enhanced insulin secretion (P0.01). Broadhurst
et al. (2000) investigated several medicinal herbs for their activity in reducing blood
glucose levels, and found that aqueous extract of cinnamon gave good results. Using rat
epidydimal adipocytes they studied the insulin dependent utilisation of glucose and
found that aqueous extract of cinnamon was very effective and concluded that dietary
cinnamon played a major role in improving glucose and insulin metabolism. Cinnamon
containing multi-herbal formulations used in traditional therapeutic practices has
also given well-defined hypoglycemic activity in in vitro studies. Using a Chinese drug
formulation Sangbackpitang (SBPT), Lee et al. (1999) obtained a significant reduction
of blood and serum glucose levels. The mechanism proposed was that of inhibition of
glycosidase catalysed reaction and upregulation of mascular GLU-T4 m-RNA expression.
Inhibition of aldose reductase enzyme activity was obtained for cinnamon in a study conducted
by Aida et al. (1987). In this investigation carried out on traditional oriental herb
prescriptions used for the treatment of diabetes and its implications, the investigators
found that an extract of cinnamon at a concentration of 0.1 mg/ml completely inhibited
the activity of aldose reductase enzyme. Aldose reductase enzyme has been implicated for
the pathogenesis of some chronic complications of diabetes like retinopathy, neuropathy
and nephropathy. Aldose reductase inhibitors in animal experiments, and recently in
clinical trials, improved cataract and peripheral neuropathy conditions. Even though very
promising results were reported on the high potential of using cinnamon as a therapeutic
agent for diabetes, no clinical study has been reported. The potential of this herb in reducing
blood glucose level and inhibiting complications due to diabetes definitely is a very
promising activity which requires further research to establish its utility.
Hypocholesterolemic action
Studies on the anti-cholesterolemic potential of cinnamon have given encouraging
results. Sambaiah and Sreenivasan (1991) observed that dietary cinnamon increased
bilary secretion of cholesterol and phospholipids without affecting the bile content.
Sharma et al. (1996b) studied the effect of a 50% alcoholic extract of cinnamon on rats
and reported a significant anti-hypercholesterolemic action and reduced serum triglyceride
at a single dose of 250 mg/kg body weight. In another investigation using triton
WR-1339-induced hyperlipidaemic rats, Kim et al. (1999, 2000) obtained suppression
of total serum cholesterol, triglycerides, phospholipids and low density lipoprotein
levels. The same group extended the study with 80% methanolic extract and its
chloroform fraction of different species of Cinnamomum and found that the extracts suppressed
the elevated serum total cholesterol and triglyceride levels in corn oil-induced