Nicotine has been identified as a major factor to induce ROS
production that can cause oxidative stress and promote development
of cancer, brain dysfunction, and cardiovascular disease
(Muthukumaran and others 2008). Flavonoids that are believed
to have abundant prooxidant/antioxidants have been observed to
make a balance of antioxidant status. It is noteworthy that despite
lack of studies on theRES,OXY, or its combinational effect on cell
cytotoxicity and ROS production caused by nicotine, several studies
observed similar results inHepG2 cells. It has been reported that
resveratrol pretreatment significantly protected HepG2 cells from
toxic effects (Shin and others 2009; Lin and others 2012; Su and
others 2013). For instance, resveratrol showed its inhibitory effect
on cell cytotoxicity and oxidative stress promoted by arachidonic
acid (Shin and others 2009). In terms of antioxidative protection
from nicotine, previous studies have revealed that curcumin exerts
its protective effects against nicotine induced lung toxicity
by modulating lipid peroxidation and augmenting the antioxidant
defense system (Lin and others 2012). Nicotine is associated with
an increase in oxidative stress, leading to cell cytotoxicity and
ROS production (Lin and others 2012). The study also found that
cell cytotoxicity followed by oxidative stress promoted by nicotine
was attenuated by cotreatment with resveratrol (Lin and others
2012). Cell cytotoxicity and ROS production induced by H2O2
decreased by resveratrol treatment, and its inhibition capacity was
significantly strong in resveratrol compared to piceid (Su and others
2013). Polyphenols, such as resveratrol and curcumin, act as
antioxidants by directly scavenging free oxygen radicals, decreasing
superoxide radical production, and increasing mitochondrial oxidative
phosphorylation (Lin and others 2012). A previous study
suggested that antioxidant activity of medicinal herbs could remove
ROS accumulated in human body by smoking (Lee 2003).
To our knowledge, there is limited information on the inhibitory
effects of RES and OXY, which are bioactive components in
EESC on human hepatocyte cell cytotoxicity followed by mitochondrial
ROS production induced by nicotine. Results from this
study suggest that EESC could be a natural source for preventing
cell cytotoxicity and oxidation induced by nicotine.