It has been shown that the growth inhibitory effects of
these rhinacanthin drugs on tumor cells correlated with variation
in chemical structure.3,14) Previously reported that the
presences of a C-3 hydroxy group on the naphthoquinone
ring (R5OH), two methyl substituents on the C-2 of propyl
chain (R1 and R2) and naphthoate ester containing a hydroxyl
group at C-1 and a methoxy group at C-4 on the naphthalene
ring related with increase growth inhibitory effects in tumor
cell line models.14) In the present study, we found that rhinacanthin-N
was the most potent antiproliferative agent
among three rhinacanthins tested. Therefore, our data are in
agreement with previous study indicating that the presence of
naphthoate ester and the substitutions of a C-1 hydroxy and a
C-4 methoxy groups on the naphthalene ring are important
structures for inhibition of cancer cell survival. Moreover, it
is suggested that the presence of naphthoate ester moiety in
1, 4 naphthoquinone structure has greater antitumor activity
than aliphatic ester.
In conclusion, our findings for the first time demonstrate
that three main naphthoquinone esters: rhinacanthins-C, -N
and -Q isolated from the roots of Rhinacanthus nasutus
KURZ. are capable to inhibit proliferation and induce apoptosis
in human cervical carcinoma (HeLaS3) cells in a dose- and
time-dependent manners. It can be considered that the antitumor
efficacy of rhinacanthin drugs results from multiple of
actions, such as interfering with cell cycle progression, inducing
apoptosis mediated by the activation of caspase-3 activity
as well as targeting DNA topoisomerase II of tumor
cells. These observations also support that R. nasutus KURZ.,
a Thai medicinal plant, may possibility served to use as a
naturally therapeutic potential drug for treating in cancer patients