Abstract:
Exposure to arsenic in drinking water is associated with cancer, and
noncarcinogenic effects including cardiovascular diseases. The present study investigated the
effect of subchronic exposure to sodium arsenite via drinking water on vascular and platelet
responses and treatment with Andrographis paniculata (AP). Concentration-dependent
accumulation of arsenic in blood, an adrenal gland, and the pancreas, with no significant
morphological change of aortic vasculature was demonstrated. Descending aortic rings
isolated from rats exposed to 50 ppm arsenite for 4 weeks showed a slight
hyperresponsiveness to norepinephrine and hyporesponsiveness to acetylcholine, while their
responses in opposite direction were demonstrated following 13-week exposure. Arsenicinduced
platelet hyperaggregation to thrombin was significantly demonstrated after exposure
to 1 ppm arsenite for 4 weeks.
Among three major diterpenoids isolated from AP, 14-deoxy-11,12-didehydroandrographolide
(AP3) showed more potent antiplatelet activity than andrographolide (AP1)
while neoandrographolide (AP4) has no effect in vitro. The antiaggregation exhibited timeand
concentration-dependent manner and accompanied by the platelet serotonin release. The
inhibition of extracellular signal regulated kinase1/2 (ERK1/2) phosphorylation may
contribute to antiplatelet activity of these compounds. The standardized aqueous extract of old
storage plant with high AP3 content (CRI) showed less antiplatelet activity than that of freshly
harvested plant with lower AP3 content (KS). HPLC fingerprint indicated that KS contained
more amounts of compounds other than AP1 and AP3, which may contribute to high
antiplatelet activity. AP1, AP3 and KS showed less potent inhibition on arsenite-treated
platelets in vitro; however, they effectively inhibited aggregation of platelets isolated from
arsenic-treated animals. Oral administration of the extract at higher doses or for longer
duration than that prescribed for the common cold could inhibit platelet aggregation and
serotonin release in response to low dose thrombin in normal rats and partially attenuate those
in arsenic-treated rats.
These findings suggest the potential use of this plant extract or its pure
compounds as therapeutic or preventive substances for cardiovascular disorders associated
with arsenic exposure. However, this plant should be used with caution in individuals with
bleeding disorders or simultaneously with antiplatelet drugs