Susana Lorán

Chemical composition and antimicrobial activity of essential oils of Thymus algeriensis, Eucalyptus globulus and Rosmarinus officinalis from Morocco

BACKGROUND The present study reports on the antimicrobial activity and chemical composition of the essential oils (EOs) of Thymus algeriensis, Eucalyptus globulus and Rosmarinus officinalis from Morocco. RESULTS The composition of these species was analysed by GC-MS, and 65 components were identified. Eucalyptus globulus EO showed a great similarity with EOs from other regions, with 1,8-cineole (79.85%) the major component. Also rich in this constituent was Rosmarinus officinalis (43.99%). However, the chemical profile of Thymus algeriensis was rather different, and for the first time such a high content of borneol (23.48%) has been described in this EO. The antimicrobial activity of these species has also been studied against seven pathogenic and spoiling bacteria of significant importance. According to the results, Thymus algeriensis showed the best bacteriostatic and bactericidal effect, followed by Eucalyptus globulus and Rosmarinus officinalis. CONCLUSIONS As far as we know this is the first time that minimum inhibitory and bactericidal concentration values have been reported for Eucalyptus globulus EO. Our data support the possible use of this EO as well as Thymus algeriensis EO, as potential natural agents in preservatives for food and pharmaceutical products.

Occurrence and exposure assessment of Fusarium mycotoxins in maize germ, refined corn oil and margarine

Analytical methods were validated for the analysis of fumonisins (FB1 and FB2), deoxynivalenol (DON) and zearalenone (ZEA) in maize germ, corn oil and margarine. A survey of 74 samples consisting of 12 wet-milled maize germ, 12 dry-milled maize germ, 25 refined corn oil, and 25 corn oil margarine was conducted. Results revealed that 100% and 87.5% of maize germ samples presented FB1 and FB2, respectively, attaining concentrations for the sum of both toxins of 1302±541 μg kg(-1) in wet-milled and 820±831 μg kg(-1) in dry-milled maize germ. The lower incidence of FB1, FB2 and DON in edible oil and margarine (4-8%) may be related with the industrial processes for their obtaining besides the high water-solubility of these mycotoxins. In contrast, 25% of maize germ samples were positive for ZEA as well as 32% of corn oil and 24% of margarine, which may be related with its lipophilic nature. A number of samples exceeded the maximum limits indicating that strict control is needed, though estimated dietary exposure was less than 0.2% tolerable daily intakes in all cases.

Risk assessment of PCDD/PCDFs and indicator PCBs contamination in Spanish commercial baby food

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) as well as polychlorinated biphenyls (PCBs) are ubiquitous highly toxic environmental pollutants which exhibit a potential risk for human health. PCDD/Fs and PCBs contamination has been measured in samples of commercial baby food products: processed cereal and meat-and-fish-based baby food, which were made of individual samples collected from Spanish markets and pharmacies. They all presented a low dioxin content with a mean concentration ranging between 0.014 pg WHO-TEQ g(-1) product for fish-based baby food and 0.089 pg WHO PCDD/Fs-TEQ g(-1) product for processed cereal containing gluten. The mean concentration of the sum of the seven indicator PCBs was between 0.03 ng g(-1) product for fish-based baby food and 0.29 ng g(-1) product for gluten-free cereals. The estimated PCDD/Fs and indicator PCBs mean daily intake through the consumption of this kind of food has been calculated taking into account body weight and food consumption data for children aged 6-12 months. In order to assess the health risk derived from the exposure to these pollutants in children during the first year of life, data concerning infant formulae contamination has been also considered.

Effects of Phenolic Acids on the Growth and Production of T‐2 and HT‐2 Toxins by Fusarium langsethiae and F. sporotrichioides

The effect of natural phenolic acids was tested on the growth and production of T-2 and HT-2 toxins by Fusarium langsethiae and F. sporotrichioides, on Mycotoxin Synthetic medium. Plates treated with 0.5 mM of each phenolic acid (caffeic, chlorogenic, ferulic and p-coumaric) and controls without phenolic acid were incubated for 14 days at 25 °C. Fungal biomass of F. langsethiae and F. sporotrichioides was not reduced by the phenolic acids. However, biosynthesis of T-2 toxin by F. langsethiae was significantly reduced by chlorogenic (23.1%) and ferulic (26.5%) acids. Production of T-2 by F. sporotrichioides also decreased with ferulic acid by 23% (p < 0.05). In contrast, p-coumaric acid significantly stimulated the production of T-2 and HT-2 toxins for both strains. A kinetic study of F. langsethiae with 1 mM ferulic acid showed a significant decrease in fungal biomass, whereas T-2 production increased after 10 days of incubation. The study of gene expression in ferulic supplemented cultures of F. langsethiae revealed a significant inhibition for Tri5, Tri6 and Tri12 genes, while for Tri16 the decrease in gene expression was not statistically significant. Overall, results indicated that phenolic acids had a variable effect on fungal growth and mycotoxin production, depending on the strain and the concentration and type of phenolic acid assayed.

Inhibition of Fusarium Growth and Mycotoxin Production in Culture Medium and in Maize Kernels by Natural Phenolic Acids

The possible role of natural phenolic compounds in inhibiting fungal growth and toxin production has been of recent interest as an alternative strategy to the use of chemical fungicides for the maintenance of food safety. Fusarium is a worldwide fungal genus mainly associated with cereal crops. The most important Fusarium mycotoxins are trichothecenes, zearalenone, and fumonisins. This study was conducted to evaluate the potential of four natural phenolic acids (caffeic, ferulic, p-coumaric, and chlorogenic) for the control of mycelial growth and mycotoxin production by six toxigenic species of Fusarium . The addition of phenolic acids to corn meal agar had a marked inhibitory effect on the radial growth of all Fusarium species at levels of 2.5 to 10 mM in a dose-response pattern, causing total inhibition (100%) in all species except F. sporotrichioides and F. langsethiae . However, the effects of phenolic acids on mycotoxin production in maize kernels were less evident than the effects on growth. The fungal species differed in their responses to the phenolic acid treatments, and significant reductions in toxin concentrations were observed only for T-2 and HT-2 (90% reduction) and zearalenone (48 to 77% reduction). These results provide data that could be used for developing pre- and postharvest strategies for controlling Fusarium infection and subsequent toxin production in cereal grains.

Evaluation of daily intake of PCDD/Fs and indicator PCBs in formula-fed Spanish children

Human exposure to polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) occurs predominantly via food intake. In this study, the exposure assessment of these contaminants has been estimated for infant formula-fed children up to 1 year of age. PCDD/F concentrations in the infant formulae was low, ranging between 0.09 and 0.17 pg WHO-TEQ g−1 fat and between 0.30 and 0.46 pg WHO-TEQ g−1 fat when results were calculated with the lower and medium bound values, respectively. Indicator PCB contamination levels were below 1 ng g−1 fat in all cases. Thus, the estimated daily intake of PCDD/Fs and indicator PCBs for infants has been assessed taking into account the above-mentioned contamination levels as well as different scenarios of body weight and food consumption data for babies aged 0–12 months. The results vary in the different scenarios considered but, on the whole, the daily estimated dioxin and indicator PCBs intake of the average infant population due to the consumption of infant formulae does not exceed the tolerable daily intake (TDI) of 2 pg WHO-TEQ kg−1 bw day−1 recommended by the Scientific Committee on Food (available at http://ec.europa.eu/food/fs/sc/scf/out90_en.pdf) nor the threshold value of 10 ng kg−1 bw day−1 proposed by the Dutch National Institute of Health and Environment (RIVM) (Baars et al. 2001. Report no. 711701025, National Institute of Public Health and the Environment (RIVM), Bilthoven, The Netherlands).

In vitro antifungal activity of several essential oils from aromatic plants of Aragón (NE, Spain)

In this study we have evaluated the antifungal activity of thirteen essential oils (EOs), collected in four different geographical areas of Aragon, north eastern Spain, against a selection of three strains of the genus Fusarium (Fusarium verticilloides CECT 2987, Fusarium verticilloides CECT 2982 and Fusarium graminearum CECT 2150). In vitro antifungal activity was evaluated by the disc diffusion method. Three of the EOs assayed (Thymus vulgaris Local, Thymus vulgaris French and Satureja montana) showed an important activity against the three strains studied by producing a zone diameter of inhibition ≥ 19 mm. In addition, Fusarium graminearum was the most sensitive strain against the essential oils studied. However, in those cases in which no inhibition was observed, it could be seen a lower growth density of the moulds inoculated than in the corresponding negative control. Therefore, more precise data about the antifungal activity of these EOs are needed.