Many plant parts have been widely used in the treatment of immune diseases in Vietnam, yet just few of them are known about their mechanism of action. The goal of this study was to investigate the in vitro inhibitory effects of in vitro inhibitory effect of crude ethanol extracts and fractions of thirteen medicinal plants on proliferation of human peripheral blood mononuclear cells (PBMCs), interleukin-2 secretion and antioxidant activity. PBMCs were extracted from the whole blood of healthy volunteers. The effects of thirteen crude extracts in ethanol and twenty four fractionated extracts in chloroform, ethyl acetate and water on in vitro proliferation of PBMCs were evaluated using MTT test. Interleukin - 2 (IL - 2) concentrations secreted by PBMC were determined by ELISA method. The antioxidant capacity of ethanol extracts and fractionated extracts were assessed using the DPPH method. The results showed that out of thirteen crude ethanol extracts, six extracts inhibited PBMC proliferation and two extracts stimulated PBMC proliferation and five extracts had no effect on PBMC proliferation. The inhibitory extracts reduced the amount of IL-2, while the stimulant extracts while the stimulant extracts had no effect on IL-2 secretion compared to the control. The chloroform extract of Wedelia chinesis showed the strongest inhibitory activity with an IC₅₀ concentration 16.1 µg/ml. The chloroform extract of Piper betle showed the strongest DPPH capture capacity with DPPH₅₀ 1.94 µg/ml and 2.1 times stronger than vitamin C. In conclusion, the chloroform extract of Wedelia chinensis may be considered for the treatment of autoimmune diseases.

Reactive oxygen species (ROS) or oxidative stress has been reported with strongly involving to pathogenesis of many diseases in human. On the other hand, ROS play a critical regulation as secondary signal to maintain intracellular redox equilibrium. Basically, the antioxidant defense systems in the body counteract with overproduced ROS. However, when the redox balance is broken under severe oxidative stress conditions, it leads to tissue injuries and numerous disorders. In this review, we briefly introduce the systems of ROS and antioxidants systems in the body and discuss the opposite roles of ROS in normal physiological conditions and diseases. For ROS-related diseases, conventional and currently developed antioxidant therapies are also described in this review.