Objective: To study the effect and anti-influenza A virus (H1N1) mechanism of volatile oil from Cinnamomi Ramulus (VOCR) and its major component cinnamaldehyde in vivo. Method: Totally 70 KM mice were divided into seven groups:the control group

the model group

the Ribavirin group (0.15 g· kg-1)

VOCR high and low dose groups (0.348

0.174 mg· kg-1) and cinnamaldehyde high and low dose groups (0.264

0.132 mg· kg-1)

with 10 mice in each group. The model group was intratracheally injected with 50 μL H1N1 liquid to reproduce the H1N1 model and then continuously given drugs for 5 d to observe the inhibitory effect in the hemagglutination titer in lung tissues. The ELISA test was conducted to observe the effect on the secretions of serum interleukin-2(IL-2)

IL-6 and tumor necrosis factor-α(TNF-α). Flow cytometry was used to detect the effect on T cell subsets after the five-day continuous treatment in the VOCR (0.348 mg· kg-1) group

the cinnamaldehyde (0.264 mg· kg-1) group

the control group

the model group and the Ribavirin (0.15 g· kg-1) group. Result: Compared with the normal group

the model group showed significant increases in the hemagglutination titer in lung tissues

mice serum IL-6 and TNF-α but notable decreases in CD4+/CD8+ and IL-2 content (P<0.05). Compared with the normal group

the VOCR (0.348 mg· kg-1) group and the cinnamaldehyde (0.264 mg· kg-1) group showed reduction in the serum levels of IL-6 and TNF-α separately (P<0.05);the Cinnamaldehyde (0.264 mg· kg-1) obviously increased the rate of CD4+ to CD8+ T cells (P<0.05). All groups show no remarkable effect on serum IL-2 content. Conclusion: VOCR and cinnamaldehyde could significantly decrease the hemagglutination titer in lung tissues of H1N1-infected mice and show a better anti-H1N1 effect. The mechanism of anti-influenza A virus effect s correlated with the regulation of the ratio between the secretions of serum cytokines IL-2

IL-6

TNF-α and the increase in T cell subsets of model mice.