In vitro and in vivo antibacterial effects of extracts of Scutellaria baicalensis and Rheum palmatum in sheep

This studyinvestigated the anti-inflammatory, antioxidation, and in vivo antibacterial effects of the ethyl acetate extract of Scutellaria baicalensis and the water extract of Rheum palmatum on Tibetan fine sheep. Twelve 10-month-old Tibetan sheep (33.5 ± 7.3 kg) were divided into three groups (n = 4): control, S. baicalensis, and R. palmatum. The sheep in the control group were inoculated with S. baicalensis and R. palmatum extracts, while the sheep in the S. baicalensis and R. palmatum groups were fed S. baicalensis and R. palmatum extracts, respectively. Sheep inoculated with Salmonella, E. coli, and S. aureus were fed for 6 consecutive days. Each sheep was fed 10 mg of S. baicalensis dried ethyl acetate extract and 5 g of dried R. palmatum water extract daily. In vitro plate inhibition test and 16S rDNA sequencing of rumen microorganisms were used to analyze the rumen microbiota and the antibacterial effects of experimental treatments on Salmonella, E. coli, and S. aureus. The anti-inflammatory and antioxidant effects of the S. baicalensis ethyl acetate extract and R. palmatum water extract on Tibetan sheep were analyzed by testing serum biochemical and antioxidant indexes and histopathological sections. Baicalin and baicalein were identified as the main active components of the ethyl acetate fraction of Baicalein (141.19 and 31.35 mg·g⁻¹ , respectively). The main active component of R. palmatum water extract was rhein (0.33 mg·g⁻¹). Among the extracts of S. baicalensis, the ethyl acetate fraction of S. baicalensis showed the strongest antibacterial effect in vitro, exerting an inhibitory effect on Salmonella, E. coli, and S. aureus, with inhibition zone diameters of 2.12, 5.94, and 6.07 mm, respectively. In vivo, the serum lactate dehydrogenase and urea levels were significantly decreased in the S. baicalensis and R. palmatum groups. The serum alanine aminotransferase and aspartate aminotransferase levels were significantly increased in S. baicalensis group, while the serum glutathione peroxidase level was significantly decreased. Feeding with the two Chinese herbs did not significantly improve the liver and kidney lesions in the sheep, but rather aggravated steatosis and inflammatory infiltration of the liver and kidney, increased the thickness of rumen epithelium, and decreased the thickness of the cuticle. Although no inhibition effect was observed in the three bacteria fed in the rumen, the levels of Bacteroidota, Proteobacteria, Acidobacteriota, Rikenellaceae_RC9_gut_group, Christensenellaceae_R-7_group, Pseudobutyrivibrio, Ruminococcaceae_unclassified, Butyrivibrio were decreased at the phylum and genus level. While the relative abundance of Actinobacteriota and Papillibacter were increased and the synergistic and antagonistic functions among rumen bacteria were enriched. These findings provide a basis for exploring the rumen epithelial absorption of volatile fatty acids and other metabolisms. Although the results indicate that the ethyl acetate and water extracts had antibacterial effects in vitro, these were not effective in the treatment of infected animals. Taken together, these results suggest that prevention should be the first choice, and treatment should be the second choice.