In addition to the cytokines, P. acnes can induce the release of reactive oxygen species which are highly toxic to the cells [7]. The
excessive production of these inflammatory mediators results in a destructive phenomenon leading to scarring. In the
present study, anti-inflammatory activity of Thai medicinal plants was investigated in terms of free radical scavenging
and cytokine reducing activity. The results revealed that G. mangostana possesses the most significant antioxidant
activity at IC50 of 6.13 μg/ml. H. cordata, E. odoratum, and S. alata had moderate antioxidant effect. The DPPH
radical scavenging test is widely accepted for in vitro determination of antioxidant activity of natural products but it
cannot actually generate free radicals from the living cells. To overcome this aspect, polymorphonuclear leukocytes
were used to produce free radicals after stimulation. In this experiment, G. mangostana significantly reduced the ROS
production with the highest inhibitory ratio at 77.80±1.28%. H. cordata, S. siamea, E. odoratum, and S. alata showed
moderate inhibitory activity. Moreover, G. mangostana extract could significantly reduce the TNF-α production
generated from PBMC by stimulating with P. acnes. Taken together, the results suggested that G. mangostana was
effective in scavenging free radicals in all studies and was able to reduce the production of pro-inflammatory cytokines.
Therefore, this plant may have a remarkable anti-inflammatory effect and possibly reduces cell damage.