Phytochemical analysis and evaluation of inhibitory potential of Ricinus communis leaf extract against novel Bacillus pathogens

Abstract Mastitis is a common and complex disease, mainly caused by aureus and non-aureus species, and Enterobacteriaceae . Recently, a new and serious group of Gram-positive bacteria, the sporulating bacilli, has emerged as a mastitis pathogen. The study aimed to identify and characterize novel Bacillus strains (HSM85, SLS01, and DA03) associated with bovine mastitis and to evaluate the antimicrobial efficacy of Ricinus communis (castor) leaf extract against these pathogens. In methodology, Bacillus strains were isolated from milk samples of mastitis-infected cows, and the antimicrobial activity of different solvent-based leaf extract fractions was assessed using MIC, MBC, killing and biofilm inhibition assays, and GC–MS analysis to identify bioactive compounds. In result we found, the chloroform (non-polar) fraction showed the highest antimicrobial activity, followed by the ethanol (polar) fraction. MIC and MBC values ranged from 25 to 200 and 25–400 µg/ml, respectively. Bacterial growth was significantly inhibited at ½ MIC, while control cells entered log phase within 4 h. Assays (MIC, MBC, MBC/MIC ≤ 4, killing, biofilm inhibition, and nucleic acid leakage) confirmed the bactericidal potential of Ricinus communis leaf extract against novel Bacillus strains. GC–MS analysis revealed 48–53 peaks across solvent extracts, identifying dominant compounds like phytol, phytyl palmitate, and tetracontane, with some solvent-specific presence. Ricinus communis leaf extract showed strong bactericidal activity against emerging Bacillus strains causing bovine mastitis, with the chloroform fraction showing the highest efficacy. Its bioactive compounds and multi-target properties suggest its potential as a natural alternative for managing mastitis in dairy cattle.