Inhibitory effects of Satureja hortensis L. essential oil on growth and aflatoxin production by Aspergillus parasiticus

In an effort to screen the essential oils of some Iranian medicinal plants for novel aflatoxin (AF) inhibitors, Satureja hortensis L. was found as a potent inhibitor of aflatoxins B1 (AFB1) and G1(AFG1) production by Aspergillus parasiticus NRRL 2999. Fungal growth was also inhibited in a dose-dependent manner. Separation of the plant inhibitory substance(s) was achieved using initial fractionation of its effective part (leaf essential oil; LEO) by silica gel column chromatography and further separation by reverse phase-high performance liquid chromatography (RP-HPLC). These substances were finally identified as carvacrol and thymol, based on the interpretation of 1H and 13C NMR spectra. Microbioassay (MBA) on cell culture microplates contained potato-dextrose broth (PDB) medium (4 days at 28 degrees C) and subsequent analysis of cultures with HPLC technique revealed that both carvacrol and thymol were able to effectively inhibit fungal growth, AFB1 and AFG1 production in a dose-dependent manner at all two-fold concentrations from 0.041 to 1.32 mM. The IC50 values for growth inhibition were calculated as 0.79 and 0.86 mM for carvacrol and thymol, while for AFB1 and AFG1, it was reported as 0.50 and 0.06 mM for carvacrol and 0.69 and 0.55 mM for thymol. The results obtained in this study clearly show a new biological activity for S. hortensis L. as strong inhibition of aflatoxin production by A. parasiticus. Carvacrol and thymol, the effective constituents of S. hortensis L., may be useful to control aflatoxin contamination of susceptible crops in the field.     

Chemical composition and antiaflatoxigenic activity of Carum carvi L., Thymus vulgaris and Citrus aurantifolia essential oils

In order to find out plants useful to controlling aflatoxins (AFs) production, the essential oils (EOs) from 12 medicinal plants prepared by hydrodistillation were studied with special reference to the inhibition of Aspergillus parasiticus growth and AFs production. The toxigenic fungus was cultured in presence of various oils in 6-well microplates using a microbioassay technique. The mycelial mass was estimated as an index of fungal growth, while the aflatoxins B₁ (AFB₁) and G₁ (AFG₁) were measured by high performance liquid chromatography (HPLC). Among plants tested, Thymus vulgari and Citrus aurantifolia were found to inhibit both A. parasiticus and AF production. The EOs from Mentha spicata L., Foeniculum miller, Azadirachta indica A. Juss, Conium maculatum and Artemisia dracunculus were only inhibited fungal growth, while Carum carvi L. effectively inhibited AF production without any obvious effect on fungal growth. The other plants including Ferula gummosa, Citrus sinensis, Mentha longifolia and Eucalyptus camaldulensis had no effect on A. parasiticus growth and AF production at all concentrations used. The IC₅₀ values of T. vulgaris, C. aurantifolia and C. carvi for AF inhibition were reported as 93.5, 285.6, and 621.9 μg/ml for AFB₁, while they were calculated as 11.7, 50.1, and 56.0 μg/ml for AFG₁. These results indicate that the EOs of some medicinal plants may be considered as potential candidates to protect foods and feeds from toxigenic fungus growth and subsequent AF contamination.     

Progesterone Release from PDMS-Modified Silica Xerogels Containing Ag Nanoparticles

Silicon - The objective of this study is to investigate the effects of adding PDMS and Ag nanoparticles on chemical and physical properties of silica xerogels as well as release behavior of...