In the present research, the effect of cinnamaldehyde has been investigated on mucositis and total salivary antioxidant capacity (TAC) in gamma-irradiated rats. Several studies have addressed to evaluate the anti-inflammatory, antibacterial and antioxidant effects of cinnamaldehyde. Reduction in the production of prostaglandin E2 and inhibition of cyclooxygenase-2 (COX-2) expression and subsequent significant decrease in Interleukin-1ß , increase in glutathione peroxidase activity , and bactericidal activity against Streptococcus and Staphylococcus species, lactobacilli, and other gram positive and negative bacteria  are the results brought about as the effect of cinnamaldehyde. Clinical findings of the present study showed a significantly delayed onset of mucositis in CR than the SR group, and in terms of the mucositis severity, the difference of scale of mucositis was statistically significant on the second day of the experiment in the CR group. The clinical anti-mucositis effects were evident in CR compared to the SR group. Mucositis begins with inflammatory phase and continues with ulcerative and bacteriological phase ; On the other hand, radiotherapy leads to the induction of oxidative stress, thereby resulting in tissue damage ; thus, it is likely that through the anti-inflammatory and antioxidant mechanisms, cinnamaldehyde may delay the onset of mucositis. Moreover, alteration in oral microflora including the appearance of Streptococcus mutans, lactobacilli and gram-negative bacilli in the bacteriological phase can aggravate the severity of mucositis , and it seems that cinnamaldehyde can cause clinical influence on mucositis via its antibacterial properties; this conclusion, however, requires further and more accurate investigation. In addition, study on a greater number of samples in each group can perhaps describe the difference in the severity of mucositis between the two groups more precisely on more days during the ten-day period.
In a study by Gowder et al., it has been shown oral administration of cinnamaldehyde has a delayed effect on serum antioxidant of the rat's kidney tissue following passing through the liver metabolism, so as it contributes to an increase in antioxidants such as superoxide desmotase, glutathione proxidase, and glutathion-s-transferase . The results achieved from the analysis of salivary antioxidant capacity indicated a significantly higher level of TAC in C compared to the other groups only on the tenth day of the experiment. It appears that ip injection of cinnamaldehyde may have a delayed effect on salivary TAC, the exact mechanism of which is not yet clear. Therefore, it is recommended that to shed light on the relative mechanism, studies be conducted in a longer period of time; the prophylactic use of cinnamaldehyde is also suggested to be initiated several days before the radiation and the antioxidant effects be evaluated during irradiation to benefit from antioxidant effects of cinnamaldehyde on mucositis improvement, since there are bodies of evidence indicating the delayed and time-dependent properties of cinnamaldehyde .
TAC demonstrated a decreasing trend in the CR group during the ten-day study period; nonetheless, it showed an increase compared to the SR group in mutual comparison between the study groups, as salivary antioxidant concentration was higher in CR than the SR group although the difference was not statistically significant. Regarding the radiotherapy-induced oxidative stress which may lead to DNA damage and loss of acinar precursors of the salivary glands , reduced TAC in the CR group might be due to damage to the salivary glands , as well as delayed and time-dependent effect of cinnamaldehyde . Although, it is not clear that the oxidative stress induced by ionizing radiation on malignant cells may be faded by the anti-oxidative effects of cinnamaldehyde or any other remedies which have been suggested to be protective for normal tissues .
In the examination of weight change, a significant increase was observed in S compared to the C group; such a weight loss in the latter can be ascribed to the allergic and toxic nature of cinnamaldehyde  in comparison with the safe injection of normal saline. The weight change has not been statistically significant in the other groups.
In the end, it is suggested that further researches be implemented to assess the clinical and histopathological effect of cinnamaldehyde on radiotherapy-induced mucositis and the relative mechanisms.