Carthamus caeruleus L. is traditionally used in Algerian medicine, particularly for burn treatment, but its therapeutic potential remains insufficiently studied. This study aimed to evaluate the antioxidant and anti-inflammatory properties of the root aqueous extract, and to perform phytochemical characterization to identify its bioactive compounds. Phytochemical analysis was conducted using spectrophotometry and reverse-phase high-performance liquid chromatography (RP-HPLC). The antioxidant potential was assessed through various assays, including ferric reducing antioxidant power (FRAP), total antioxidant capacity (TAC), DPPH radical scavenging, hydroxyl radical scavenging, ferrous ion chelation, and hydrogen peroxide decomposition. Anti-inflammatory activity was evaluated using membrane stabilization, protein denaturation, and membrane peroxidation assays. The extract exhibited moderate levels of polyphenols, flavonoids, and condensed tannins, quantified as 21.19 ± 0.37 mg GAE/g, 0.72 ± 0.013 mg QE/g, and 27.28 ± 1.04 mg TAE/g of dry extract, respectively. RP-HPLC analysis identified 22 phytochemical compounds, primarily phenolic acids, flavonoids, and tannins, with orientin and vanillin as the major constituents. The extract demonstrated significant antioxidant activity, with moderate efficacy in TAC and FRAP assays (IC₅₀ values of 5405.1 ± 4.42 and 1132.35 ± 4.97 µg/mL, respectively). Notable activities included DPPH and hydroxyl radical scavenging (34.43 ± 4.83 and 512.81 ± 9.46 µg/mL, respectively), ferrous ion chelation (2462.76 ± 1.38 µg/mL), lipid peroxidation inhibition (22.32 ± 3.31%), and hydrogen peroxide decomposition (263.93 ± 7.87 µg/mL). Additionally, the extract stabilized erythrocyte membranes under osmotic, thermal, and oxidative stress conditions (98.13 ± 0.15%, 70 ± 1.27%, and 89 ± 0.87%, respectively), inhibited ovalbumin denaturation (81.05 ± 2.2%), and protected against lipid peroxidation in brain homogenates (69.25 ± 0.89%). These findings support the traditional therapeutic applications of C. caeruleus and highlight its potential as a source of antioxidant and anti-inflammatory agents.

Avian colibacillosis remains a major threat to poultry production and food security, whereas its antibiotic-based control accelerates antimicrobial resistance. This study investigated the antibacterial potential of the hydroethanolic extract of Thymus vulgaris, alone and in combination with antibiotics, against avian pathogenic Escherichia coli (APEC). The phytochemical composition of the extract was analyzed by HPLC, while its antibacterial activity was assessed using agar diffusion and minimum inhibitory concentration (MIC) assays. Antibiotic-extract interactions were evaluated by the checkerboard method, and mechanisms of action were explored through assays targeting membrane permeability, proton pump inhibition, catalase inhibition, oxidative stress, and biofilm formation. Its antioxidant, anti-inflammatory, and cytotoxic activities were also evaluated. HPLC analysis revealed 16 phenolic compounds, including rosmarinic, ferulic, and salicylic acids, as well as flavonoids such as quercetin and luteolin, with an extraction yield of 15% ± 0.55. The extract displayed significant antibacterial activity (MIC: 5.46-10.93 mg/ml, p < 0.05). In synergy tests, the extract enhanced ampicillin efficacy 4-8-fold and showed additive effects with ciprofloxacin and tetracycline (2-4-fold). Mechanistic assays demonstrated disruption of bacterial membranes (32.66% electrolyte leakage, p < 0.05), inhibition of H⁺-ATPase proton pumps (p < 0.05), catalase activity reduction by 79.2% (p < 0.05), >50% decrease in cell hydrophobicity, and inhibition of biofilm formation (49.07-72.47%), alongside eradication of mature biofilms (41.89-64.67%) (p < 0.05). Beyond antimicrobial effects, the extract exhibited notable antioxidant capacity. In DPPH radical scavenging, the extract showed an IC₅₀ of 9.76 ± 0.228 μg/ml (p < 0.05), while in the TAC assay, it reached 467.25 ± 1.889 μg/ml (p < 0.05), and it reduced ampicillin-induced lipid peroxidation by 42.85% (p < 0.05). Anti-inflammatory testing revealed inhibition of protein denaturation (4.95-52.48% at 15-2000 µg/ml, p < 0.05), although weaker than aspirin. Hemolysis assays confirmed the extract was non-hemolytic at concentrations up to 11 mg/ml (p < 0.05). In conclusion, Thymus vulgaris extract demonstrated safe, multi-target bioactivity, supporting its potential as a promising alternative to combat avian colibacillosis and antimicrobial resistance.