Results from this study suggest that the most effective conversion
of nicotine to cotinine was observed in EESC, implying that
nicotine metabolism could be promoted by combinational effect
of various bioactive components including RES, OXY, and other
components. Similar patterns in nicotine conversion to cotinine
by plant extracts rather than single bioactive component were
found in several studies. Hesperidin supplementation showed protective
effects by modulating biochemical marker enzyme activities
in the plasma and histopathological findings induced by nicotine
(Balakrishnan and Menon 2007). The dose of hesperidin used in
the study was 25 mg/kg body weight, which is not physiologically
relevant. Hence, many researchers approached their studies
with plant extracts rather than single bioactive component. Lee
(2003) observed that pretreatment of tea polyphenols in the cell
derived from hepatocyte increased nicotine metabolism to cotinine.
This finding suggested that cell membrane permeability of
tea polyphenols could be a key factor to exert more positive effects
in facilitating cotinine production. In addition, Lee (2003)
found that tea polyphenols treatment enhanced nicotine to cotinine
turnover, suggesting that it could retard the nicotine conversion
into the NNK, a carcinogenic metabolite. A previous study
reported that pretreatment of plant extracts promoted 2 to 3 times
higher cotinine production than nontreatment (Kim and others
2002). The result suggested that bioactive component(s) of plant
extracts can easily penetrate cell membrane and is stable, resulting
in activating nicotine metabolism (Kim and others 2002). Hong
et al. also reported that catechins and quercetin in green tea and
onion promoted the degradation of nicotine into cotinine, nontoxic
to the human body, by providing hydrogen with ROS produced
from nicotine exposure (Hong and others 2003). Likewise,this study has also demonstrated that EESC, plant extracts, has a significant
effect on cotinine formation compared to single bioactive
component such as RES orOXY, entailing nicotinemetabolism to
cotinine could be mediated by cytochrome P450 enzyme activity
in the human liver by synergic effect of bioactive components in
EESC. Thus, we further tested whether CYP2A6, mainly responsible
for nicotine conversion to cotinine, was induced by single
component or plant extract (EESC) containing diverse bioactive
components. Further study on identifying possibility that other
potent components in EESC could contribute nicotine detoxifying
effect is necessary to be carried out.