Purpose: This research aimed to investigate the antibacterial activity and potential mechanism of luteolin against T. pyogenes. Materials and Methods: The broth microdilution method was used to determine the minimum inhibitory concentrations (MICs) of luteolin against various T. pyogenes strains. The potential mechanism of action of luteolin was elucidated through testing and analysing the luteolin-induced alterations of T. pyogenes in several aspects, including cell wall, cell membrane, protein expression, nucleic acid content, topoisomerase activity and energy metabolism. Results: The MIC values of luteolin against various T. pyogenes isolates and ATCC19411 were 78 μg/mL. The increased cell membrane permeability, destruction of cell wall integrity and TEM images after exposure to luteolin showed that the cell wall and membrane were damaged. The content of total protein and nucleic acid in T. pyogenes decreased significantly after treatment with luteolin (1/2 MIC) for 12, 24, and 36 h. Moreover, a hypochromic effect was observed in the absorption spectrum of luteolin when deoxyribonucleic acid (DNA) was added. In addition, after treatment with luteolin, a decrease in nicked or relaxed DNA content, which was catalysed by T. pyogenes-isolated DNA topoisomerase, was observed. In addition, the adenosine triphosphate (ATP) content in cells and the activity of succinate dehydrogenase (SDH) both decreased when T. pyogenes was exposed to different concentrations (1/4 MIC, 1/2 MIC, 1 MIC, 2 MIC) of luteolin for 1 h. Conclusion: Luteolin showed distinct antibacterial activity against T. pyogenes by multiple actions, which mainly include destroying the integrity of the cell wall and cell membrane, influencing the expression of proteins, inhibiting nucleic acid synthesis, and interfering with energy metabolism.

Inflammation widely exists in many diseases and poses a great threat to human and animal health. Rutin, quercetin-3-rhamnosyl glucoside, has a variety of pharmacological effects, including anti-oxidant, anti-inflammatory, antibacterial, anticancer and radioresistance effects. The current study focused on evaluation of its anti-inflammatory activity and described the mechanism of rutin in lipopolysaccharide-induced RAW 264.7 cells. The related gene and protein expression levels were investigated by quantification real-time PCR and western blotting, respectively. This study revealed that rutin can decrease inducible nitric oxide synthase (iNOS) gene and protein expression levels, effectively increase IκB gene expression, reduce toll-like receptor 4 (TLR4), myeloid differentiation factor 88 (MyD88), tumour necrosis factor receptor-associated factor 6 (TRAF6) and p65 gene expression and inhibit the phosphorylation of IκB and p65 and the proteins expression of TLR4, MyD88 and TRAF6. These results suggest that rutin might exert anti-inflammatory effect on LPS-stimulated RAW 264.7 cells and will be potentially useful as an adjuvant treatment for inflammatory diseases.

Research on the extraction technology, component analysis, and antioxidant, antibacterial, analgesic and anti-inflammatory activities of flavonoids fraction from Tribulus terrestris L. leaves was carried out. The extraction process was optimized by response surface method, and the maximum yield 0.27% for flavonoids fraction was achieved with concentration of ethanol solution 25.87%, ratio of solvent to material 30:1 ml/g, and ultrasonic extraction time 27.93 min. Moreover, 14 compositions were identified separately from flavonoids fraction by HPLC-DAD-ESI-MS2. In addition, flavonoids fraction exhibited a better antioxidant activity demonstrated by assays of ABTS, DPPH radical scavenging activity and ferric reducing antioxidant power activity. Furthermore, the antibacterial, analgesic and anti-inflammatory activities of flavonoids fraction were also proved to be stronger. Therefore, the present findings suggest that flavonoids fraction from Tribulus terrestris L. leaves can be a very interesting candidate for the research and development of natural and healthy herbal medicine for the pharmaceutical and food industries.

Aflatoxin B1 (AFB1) causes oxidative stress and hepatocyte apoptosis through its epoxidized metabolite AFBO, which is catalyzed by CYP450 enzymes. Ferulic acid (FA) is a phenolic acid commonly found in plants and is known for its antioxidant capacity. However, the role of FA in AFB1-induced liver injury is still elusive. In this study, rats were exposed to AFB1 and simultaneously treated with FA for 30 days. The results showed that I) FA alleviated the histopathological changes induced by AFB1, inhibited the elevation of serological indexes induced by AFB1, and reduced the production of AFBO in liver. II) AFB1-induced increase in CYP450 expression was significantly reduced by FA. The molecular docking results of FA and CYP2A6 showed high fitness score and interaction. III) FA obviously inhibited the production of MDA, and significantly activated the Nrf2/GST pathway and antioxidant enzymes (SOD and GST). IV) AFB1-induced hepatocyte apoptosis, the high expression of p53, bax, cyt-c, caspase-9, caspase-3, and the low expression of bcl-2 were all restored by FA. It has been suggested from these results that FA proved effective against AFB1-induced liver damage in rats via inhibiting CYP450 enzyme, promoting antioxidant pathway Nrf2/GST, activating antioxidant enzymes (SOD and GST), and regulating the mitochondrial pathway.

Previous studies reported that Aflatoxin B1 (AFB1) causes cell damage through its metabolite aflatoxin B1-8, 9-epoxide (AFBO), which is catalyzed by CYP450 enzymes. AFBO can be detoxified by glutathione S transferase (GST). Ferulic acid (FA) is known for its antioxidant capacity and intestinal protective function. However, the mechanism of AFB1 causing duodenal injury and the role of FA in AFB1-induced intestinal damage remains unclear. In this study, rats were exposed to AFB1 and treated with FA for 30 days. The results showed that I) FA alleviated the histopathological changes of duodenum and the ultrastructural changes of tight junctions between duodenal epithelial cells induced by AFB1. II) FA reduced the content of AFB1-ALB adduct in blood. III) The low expression of tight junction proteins (Claudin-1 and ZO-1) and the high expression of ROCK1 and ROCK2 induced by AFB1 were significantly reversed by FA. IV) The high expression of CYP2A6 and CYP3A4 were significantly down-regulated by FA, and the activity of GST was promoted by FA. V) The binding affinity of FA to CYP2A6 is very similar to the binding affinity of AFB1 to CYP2A6, which meaning that there is a competitive relationship between FA and AFB1 when conjugating to CYP2A6. These results suggested that FA proved effective in alleviating AFB1-induced duodenal barrier damage via up-regulating tight junction proteins, down-regulating ROCK, competing CYP450 enzyme, and activating GST in duodenal epithelial cells of rats.

Trueperella pyogenes (T. pyogenes) is an opportunistic pathogen associated with a variety of diseases in many domestic animals. Therapeutic treatment options for T. pyogenes infections are becoming limited due to antimicrobial resistance, in which efflux pumps play an important role. This study aims to evaluate the inhibitory activity of luteolin, a natural flavonoid, on the MsrA efflux pump and investigate its mechanism. The results of antimicrobial susceptibility testing indicated that the susceptibility of msrA-positive T. pyogenes isolates to six macrolides increased after luteolin treatment, while the susceptibility of msrA-negative isolates showed no change after luteolin treatment. It is suspected that luteolin may increase the susceptibility of T. pyogenes isolates by inhibiting MsrA activity. After 1/2 MIC luteolin treatment for 36 h, the transcription level of the msrA gene and the expression level of the MsrA protein decreased by 55.0–97.7% and 36.5–71.5%, respectively. The results of an affinity test showed that the equilibrium dissociation constant (KD) of luteolin and MsrA was 6.462 × 10^–5 M, and hydrogen bonding was predominant in the interaction of luteolin and MsrA. Luteolin may inhibit the ATPase activity of the MsrA protein, resulting in its lack of an energy source. The current study illustrates the effect of luteolin on MsrA in T. pyogenes isolates and provides insight into the development of luteolin as an innovative agent in combating infections caused by antimicrobial-resistant bacteria.