In this work, antibacterial activity of finger citron essential oil (FCEO, Citrus medica L. var. sarcodactylis) and its mechanism against food-borne bacteria were evaluated. A total of 28 components in the oil were identified by gas chromatography-mass spectrometry, in which limonene (45.36%), γ-terpinene (21.23%), and dodecanoic acid (7.52%) were three main components. For in vitro antibacterial tests, FCEO exhibited moderately antibacterial activity against common food-borne bacteria: Escherichia coli, Staphylococcus aureus, Bacillus subtilis and Micrococcus luteus. It showed a better bactericidal effect on Gram-positive bacteria than Gram-negative. Mechanisms of the antibacterial action were investigated by observing changes of bacteria morphology according to scanning electron microscopy, time-kill analysis, and permeability of cell and membrane integrity. Morphology of tested bacteria was changed and damaged more seriously with increased concentration and exposure time of FCEO. FCEO showed a significant reduction effect on the growth rate of surviving bacteria and lead to lysis of the cell wall, intracellular ingredient leakage, and consequently, cell death.

Dendrobium officinale oligosaccharides (DOO), as a novel prebiotic, offer promising therapeutic potential for the treatment of inflammatory diseases. In this study, the alleviating effect of DOO on dextran sulfate sodium (DSS)-induced chronic colitis in mice was investigated. DOO treatment relieved the main symptoms of weight loss, colon shortening, and bloody stool caused by colitis. DOO ameliorated histopathological colon tissue damage and reduced levels of pro-inflammatory factors (TNF-α, IL-6, IL-1β). Western blot results suggested that DOO downregulated the phosphorylation levels of key proteins in the NF-κB signaling pathway, including IKKα/β, IκBα and p65. 16S rRNA sequencing suggested that DOO altered the diversity and composition of gut microbiota in DSS-induced mice. It promoted the intestinal colonization of beneficial bacteria such as Dubosiella, Lactobacillus and Alistipes, and inhibited the abnormal overgrowth of Akkermansia. Furthermore, DOO increased the secretion of short-chain fatty acids (SCFAs) such as acetic acid, propionic acid, and butyric acid to maintain intestinal homeostasis. These findings suggest the potential of DOO as a therapeutic agent for ulcerative colitis (UC).