valencene and decanaldehyde

Bovine mastitis is a costly disease in the dairy industry and does not always respond to antibiotic treatment. The major components of terpeneless, cold-pressed Valencia orange oil - citral, linalool, decanal and valencene - were examined as potential alternative treatments for Staphylococcus aureus-associated mastitis. The minimum inhibitory concentration (MIC) of all four components against S. aureus was determined after incubation for 24 h. Growth inhibition assays were performed for all effective components on S. aureus for either a 3 h or 72 h treatment. These components were tested for the ability to disrupt pre-formed S. aureus biofilms after 24 h of treatment by measuring absorbance at 540 nm. Cytotoxicity against immortalized bovine mammary epithelial (MAC-T) cells was measured using an MTT assay following a 1 h exposure. Only concentrations below the 50 % cytostatic concentration (CC50) were used in an adherence and invasion assay of S. aureus on MAC-T cells, and for measurements of virulence and biofilm gene expression via qPCR. The MICs of citral and linalool were 0.02 % and 0.12 %, respectively, but decanal and valencene were ineffective. Citral and linalool were capable of inhibiting growth of S. aureus after 24 h at their MIC values and inhibited pre-formed biofilms of S. aureus . The concentrations below the CC50 were 0.02 % for citral and 0.12 % for linalool. These concentrations inhibited the adhesion and invasion ability of S. aureus and downregulated virulence genes. Only 0.12 % linalool downregulated the expression of S. aureus biofilm-forming genes. These components should be considered for further in vivo study.

Topics: Acyclic Monoterpenes; Aldehydes; Animals; Anti-Bacterial Agents; Bacterial Adhesion; Biofilms; Cattle; Cell Line; Cell Survival; Endocytosis; Epithelial Cells; Gene Expression Profiling; Microbial Sensitivity Tests; Monoterpenes; Plant Oils; Real-Time Polymerase Chain Reaction; Sesquiterpenes; Staphylococcus aureus; Virulence; Virulence Factors

Product 1 (82.25% valencene), product 2 (73.36% decanal), product 3 (78.12% octanal), and product 4 (90.61% linalool) were isolated from sweet orange oil by combined usage of molecular distillation and column chromatography. The antioxidant activity of sweet orange oil and these products was investigated using 2,2-diphenyl-1-picrylhydrazyl and reducing power assays. In this test, product 1 (82.25% valencene), product 2 (73.36% decanal), and product 4 (90.61% linalool) had antioxidant activity, but lower than sweet orange oil. The antimicrobial activity was investigated in order to evaluate their efficacy against 5 microorganisms. The results showed that sweet orange oil, product 2 (73.36% decanal), product 3 (78.12% octanal), and product 4 (90.61% linalool) had inhibitory and bactericidal effect on the test microorganisms (except Penicillium citrinum). Valencene did not show any inhibitory effect. Saccharomyces cerivisiae was more susceptible, especially to the crude sweet orange oil (minimal inhibitory concentration 6.25 μL/mL). The cytotoxicity was evaluated on Hela cells using the 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. All test samples showed significant cytotoxicity on the cell lines with IC(50) values much less than 20 μg/mL.

Topics: Acyclic Monoterpenes; Aldehydes; Anti-Infective Agents; Antioxidants; Aspergillus niger; Chromatography, Thin Layer; Citrus sinensis; Escherichia coli; HeLa Cells; Humans; Microbial Sensitivity Tests; Monoterpenes; Odorants; Penicillium; Plant Oils; Saccharomyces cerevisiae; Sesquiterpenes; Staphylococcus aureus; Taste