Abstract
Ligustrum lucidum Ait (LL), Lysimachia christinae Hance (LC), Mentha piperita Linn (MP), and Cinnamomum cassia Presl (CC) are common spices used in Asia. The present study investigated the anti-Salmonella effects of the four spices using aqueous extracts. The amount of phenolic acids and flavonoids in each spice aqueous extract was determined as indicators of purity. Mice were pretreated with LL, LC, MP or CC aqueous extract for 7 days. Following infection with Salmonella enterica serovar Typhimurium strain ST21 (ST21), the aqueous extract of each spice was subsequently administered for 4 days. ST21 infected mice had lower body weight compared with the control group. The administration of spice aqueous extracts significantly increased body weight following infection. ST21 infection increased the fecal ST21 counts compared with the control group; however, following spice aqueous extract treatments, ST21 counts significantly decreased. The spice treatments also significantly reduced ST21 count in blood and the organs. Notably, ST21 infection increased interferon (IFN)-γ and interleukin (IL)-6 levels in serum whilst spice treatments reduced these cytokines. In the spleen, spice treatment significantly lowered IFN-γ, IL-6, IL-1β, and tumor necrosis factor (TNF)-α levels, but increased IL-12 levels. ST21 infection stimulated the production of immunoglobulin (Ig)A and IgM in serum whilst spice aqueous extract treatment significantly decreased these levels. In summary, LL and MP aqueous extract treatments had the most significant effect in protecting against ST21 infection. Results of the RAW 264.7 cell infection model suggested that the mechanisms involved in the anti-ST21 effect of each spice were individually different. All four aqueous extracts demonstrated different mechanisms in attenuating ST21 invasion with the protective effect of LC aqueous extract potentially involving TNF-α expression. The present findings suggested that the four spices may be considered as potent functional foods due to their anti-Salmonella effects.