Abstract:
Centella asiatica (C. asiatica ) or Asiatic pennywort, locally known as Bua-bok, is a
local Thai herb consumed in both fresh squeezed juice and fresh form. C. asiatica is used as
traditional medicine to cure various diseases. The most interesting phytochemical compounds
in C. asiatica are triterpenoids, namely asiaticoside, madecassoside, asiatic acid, and
madecassic acid. Although triterpenoids from C. asiatica have been claimed to provide
various health benefits, there are no scientific evidences of bioaccessibility and bioavailability
of the phytochemical especially asiatic acid, and madecassic acid in this plant. The aims of
the present study were to analyze and determine the digestive stability and bioaccessibilty of
triterpenoids using the coupled in vitro digestion and Caco-2 human intestinal cells.
Moreover, angiotensin I converting enzyme (ACE) inhibitory activity the main characteristic
of current hypertensive drugs was investigated. Preliminary results showed that asiaticoside
and madecassoside were converted to asiatic acid and madecassic acid by enzymes in the
plant cells during storage. As a result, levels of asiaticoside and madecassoside decreased so
much that they could not be determined. Therefore, this study focused only the triterpenic
form, asiatic acid and madecassic acid from C. asiatica. The results revealed that major
triterpenoids were stable during simulated gastric and small intestinal digestion. The
aqueous fraction, representing bioaccessibility, accounts for 60-70% triterpenoids in the herb.
Caco-2 cells accumulated triterpenoids (30-40%) from aqueous fraction generated during
digestion of C. asiatica in a time dependent manner and also these compounds were stable
after accumulating in the monolayer. As to the antihypertension property, it was found that
freeze-dried C.asiatica at 0.1, 0.5 and 1.0 g had the ACE inhibitory activity about 20-70%
relative to the captopril, potent ACE inhibitor (97% ACE inhibitory activity). C. asiatica juice
also had the ACE inhibitory activity about 54%. After the simulated digestion, C.asiatica
maintained 50-60% ACE inhibitory activity. In conclusion these results showed that asiatic
acid and madecassic acid from C. asiatica were stable after a simulated digestion. Caco-2
human intestinal cell efficient accumulated these bioactive compounds without degradation.
Due to its relatively high bioaccessibility and cellular uptake and also exhibition of ACE
inhibitory activity, consumption of C.asiatica may promote potential health benefits by
reducing high blood pressure.