Objective:To investigate the effects of Commelina communis L. on hypoxia/reoxygenation (H/R)-induced apoptosis of myocardial cells and expression of inflammatory factors through regulating NADPH oxidase 4 (Nox4). Methods:H9c2 cells were subjected to H/R to establish the injury model. These cells were then treated with different concentrations of Commelina communis L. extract. Cell activity and apoptosis were measured by MTT method and flow cytometry, respectively. Superoxide dismutase (SOD), malondialdehyde (MDA) and lactate dehydrofenase (LDH) levels were detected. ELISA was performed to detect TNF-α, IL-1β and IL-6 levels. Western blot was used to detect the expression of Bcl-2-associated X protein (Bax), cysteine-containing aspartic protease 3 (Caspase-3) and Nox4. Real-time quantitative PCR (qPCR) was used to measure the expression of Nox4 at mRNA level. H9c2 cells were transfected with si-Nox4 and subjected to H/R. Changes in the activity and apoptosis of H9c2 cells, and the expression of SOD, MDA, LDH and inflammatory factors were observed after inhibiting Nox4 expression. H9c2 cells transfected with pcDNA3.1-Nox4 were treated with Commelina communis L. extract and subjected to H/R to evaluate the effects on the cell activity and apoptosis, as well as the expression of SOD, MDA, LDH and inflammatory factors. Results:The survival rate and SOD activity of H9c2 cells exposed to H/R were significantly reduced, but the apoptosis rate, the levels of Caspase-3, Bax protein, MDA, LDH TNF-α, IL-1β and IL-6, and the expression of Nox4 at both mRNA and protein levels were dramatically increased ( P<0.05). As with inhibition of Nox4 expression, Commelina communis L. extract at the concentrations of 10 μg/ml and 20 μg/ml could obviously increase the survival rate and SOD activity of H9c2 cells after H/R exposure, and reduce the apoptosis rate and the expression of Caspase-3, Bax protein, MDA, LDH TNF-α, IL-1β and IL-6, as well as Nox4 expression at mRNA and protein levels ( P<0.05). Overexpression of Nox4 reversed the effects of Commelina communis L. extract on promoting cardiomyocyte cell activity and SOD activity, inhibiting cell apoptosis, and downregulating the expression of Caspase-3, Bax protein, MDA, LDH, TNF-α, IL-1β and IL-6 in the H/R injury model. Conclusions:Commelina communis L. could protect against H/R-induced myocardial cell injury, improve cell activity, and inhibit cell apoptosis and the expression of inflammatory factors through regulating Nox4 expression.