Chemically Characterized Essential Oils of Citrus reticulata and Thymus vulgaris L. and Their Nanoemulsions Inhibited the Pathogenic Microbes Causing Mastitis in Cattle

Abstract

Essential oils (EOs) of Citrus reticulata (C. reticulata, mandarin) peels and Thymus vulgaris (T. vulgaris) are well known active microbial inhibitors. Nanoemulsion preparation is a modern technique for enhancing antimicrobial potentialities. EOs of both plants were prepared and chemically characterized using gas chromatography/mass spectrometry. Methyl-N-methyl anthranilate (non terpenoidal compound) and monoterpene hydrocarbons are the main components of mandarin peels EO with relative concentrations of 61.07% and 35.15%, respectively. Whereas, T. vulgaris was characterized by abundance of oxygenated monoterpenes and monoterpene hydrocarbons with relative concentrations of 66.89%, and 25.74%, respectively. The antimicrobial potentialities of EOs and their nanoemulsions were assayed. Mandarin EO exhibited strong activities against Citrobacter diversus (ATCC 13315), Proteus vulgaris (ATCC 13315), and Escherichia coli (resis.) with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of 12.5 and 25 μg mL⁻¹, respectively. On the other hand, mandarin nanoemulsion showed potentialities against all strains with MIC and MBC of 3.13 and 6.25 μg mL⁻¹, respectively. T. vulgaris EO showed antibacterial potentialities against C. diversus, P. vulgaris, Staphylococcus aureus, and E. coli (resis.) with MIC of 0.19 μg mL⁻¹ and a moderate activity against the other strains. Also, its nanoemulsion exhibited better growth inhibition against C. diversus, P. vulgaris, and E. coli (resis.) at 0.19 μg mL⁻¹. Mandarin EO possessed significant antifungal activities against Candida albicans, Candida tropicalis, and Candida glabrata with MIC of 0.19, 0.78, and 1.56 μg mL⁻¹, respectively. The mandarin nanoemulsion had a significant activity against C. glabrata and C. tropicalis with MIC of 0.39 and 1.56 μg mL⁻¹, respectively. T. vulgaris EO and its nanoemulsion are significant antifungals for all strains with MIC of 0.19 and 0.39 μg mL⁻¹, respectively. The findings deduced the significant role of EOs of both plants and their nanoformulations as antimicrobial agents in food and pharmaceutical industries.

Keywords:

• Mandarin
• Thymus vulgaris
• antimicrobial
• pathogenic microbes
• mastitis
• nanoemulsion