Flos populi (Male Inflorescence of Populus tomentosa Carrière) Aqueous Extract Suppresses Salmonella Pullorum Infection by Affecting T3SS-1

Pullorum disease, caused by Salmonella Pullorum (S. Pullorum), is one of the most serious infectious diseases in the poultry industry. Flos populi is traditionally used in Eastern Asian countries to treat various intestinal diseases. However, the anti-infection mechanism of Flos populi is not very clear. In this study, we evaluated the anti-infective effects on S. Pullorum of Flos populi aqueous extract (FPAE) in chickens. FPAE significantly reduced S. Pullorum growth in vitro. At the cellular level, FPAE reduced S. Pullorum adhesion and invasion on DF-1 cells but did not affect its intracellular survival or replication in macrophages. Further investigation revealed that FPAE inhibited the transcription of T3SS-1 genes, which is the main virulence factor that mediates S. Pullorum adhesion and invasion in host cells. The results suggest that the anti-infective effect of FPAE likely occurs through the inhibition of S. Pullorum T3SS-1, thereby impairing its ability to adhere to and invade cells. Further, we evaluated its therapeutic effect on animal models (Jianghan domestic chickens) and found that FPAE reduced the bacterial loads in organs and decreased the mortality and weight loss of infected chickens. Our findings provide novel insights into the potential development of FPAE against S. Pullorum as an effective anti-virulence therapeutic substitute for antibiotics.

Antioxidant and anti-inflammatory constituents from Flos populi

Investigation of the n-butanol extract of Flos populi led to the isolation of one new phenolic glycoside, 4'-hydroxybenzyl-2-hydroxybenzoate-1'-O-β-D-glucopyranoside (1), together with twelve known compounds, which have been determined on the basis of spectroscopic analysis including UV, IR, HR-ESI-MS and 1D/2D NMR. The antioxidant capacity of all compounds were evaluated by ABTS radical-scavenging test and ferric reducing antioxidant power (FRAP) assay. And during a screening procedure for the anti-inflammatory activities among most compounds on lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophage cells, compound 13 exhibited remarkable inhibitory effects on nitric oxide (NO), tumor necrosis factor-α (TNF-α), interleukin (IL)-6 and IL-1β, suggesting that it might be a promising candidate as an anti-inflammatory agent.

Anti-inflammatory and analgesic activity of aqueous extract of Flos populi

ETHNOPHARMACOLOGICAL RELEVANCE

Flos populi is an important traditional Chinese medicine prepared from the male inflorescence of Populus tomentosa Carr. or Populus canadensis Moench (Salicaceae family). Flos populi is mainly used for the treatment of various inflammatory diseases and anti diarrhea in East Asian countries. The objective of this study was to investigate the anti-inflammatory and analgesic properties of the aqueous extract of Flos populi (FPAE).

MATERIALS AND METHODS

Cotton pellets-induced granuloma, carrageenan-induced paw oedema, arachidonic acid-induced right ear oedema and xylene-induced ear oedema were used to assess anti-inflammatory activity of FPAE and analgesic activity was evaluated by hot plate test, acetic acid-induced abdominal writhing test and formalin test.

RESULTS

FPAE produced significant dose-response anti-inflammatory activity against cotton pellets-induced granuloma. FPAE at dosages of 50, 100 and 200 mg/kg bw. significantly reduced carrageenan-induced paw edema by 48.84% (P<0.05), 54.95% (P<0.05), and 62.05% (P<0.05) at 5h after carrageenan injection, respectively. FPAE significantly (P<0.05) reduced the ear oedema induced by arachidonic acid and peaked at the dose of 200 mg/kg bw. (40.78%). A significant (P<0.05) dose dependent inhibition of xylene-induced oedema was produced by FPAE and peaked at the highest dose of 200 mg/kg bw. (23.95%). FPAE (50, 100 and 200 mg/kg bw.) produced significant dose-response analgesic activity in the hot-plate test. However, the low percentage inhibition (<50%) suggests that it is not a centrally acting analgesic. Extract at dosages of 50, 100 and 200 mg/kg bw., p.o. significantly reduced acetic acid-induced writhing by 39.6% (P<0.05), 45.4% (P<0.05), and 51.8% (P<0.05), respectively. The extract also caused marked dose-dependent inhibition of formalin-induced pain in the second phase (P<0.05).

CONCLUSION

The findings in this study suggest that the aqueous extract of Flos populi possesses anti-inflammatory and analgesic activities. These results may support the fact that this plant is used traditionally to cure inflammatory diseases.