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Mycotoxins in food are increasingly a food safety hazard concern in particular in developing countries. This study was performed to determine the occurrence and determinants of aflatoxin and fumonisin contamination in rice and maize and to assess health risks through dietary intake exposure among ethnic minority groups in northern Vietnam. A total of 111 rice and 102 maize samples, were tested for occurrence of fungi and mycotoxins, i.e. aflatoxins (AF’s) and fuminisin B (FB). Results showed that 107 (96.4%) rice and 84 (82.4%) maize samples were contaminated by fungi. Aspergillus flavus was found in 68 (61.3%) rice and 30 (29.4%) maize samples, Aspergilus parasiticus in 40 (36.0%) rice and 27 (26.7%) maize samples. AF’s - were detected in 27 rice (24.3%) and 27 maize samples (26.4%) at minimum and maximum levels in rice of 2.06 and 77.8 ng/g and 20.5 and 110 ng/g in maize, respectively. Nine (8.1%) rice and 24 (23.5%) maize samples contained FB at ranges of 2.3–624 ng/g in rice and 5.6–89.8 ng/g in maize. Data collected through interviews and observations in households showed that type of crop, storage duration and presence of fungi, particularly mycotoxigenic fungi were important risk factors for AF’s and FB contamination. Based on daily food consumption data, the estimated average exposure dose of aflatoxin B1(AFB1) from rice was 21.7 ng/kg bw/day for adults and 33.7 ng/kg bw/day for children. For FB, the rice based average exposure amounted to 536 ng/kg bw/day for adults and 1019 ng/kg bw/day for children. The calculated excess risk of liver cancer incidence by ingestion of cereals containing AFB1 was 1.5 per 100,000 adults and 2.3 per 100,000 children per year. The average intake of FB was calculated to be lower than the tolerable diet intake (TDI). Our findings highlight that rice and maize are contaminated with mycotoxins at levels representing actual health hazards for the ethnic minority groups consuming these stable cereals. Proper drying and storage conditions in households are likely to reduce the mycotoxin contamination.

Fungal infection and aflatoxin contamination were evaluated on 114 samples of dried and milled spices such as ginger, garlic and black pepper from southern Benin and Togo collected in November 2008–January 2009. These products are dried to preserve them for lean periods available throughout the year. Fungal contamination was evaluated after plating on selective media with a total of 20 fungal genera identified, ranging from 7 in garlic to 14 in ginger. Ginger and pepper showed high incidence of fungal contamination compared to garlic that had lower levels of fungal contamination. Species of Aspergillus were dominant on all marketed dried and milled spices irrespective of country. Gene characterization and amplification analysis showed that most of the Aspergillus flavus isolates possess the cluster genes for aflatoxin production. Aflatoxin B1 assessment by Thin Layer Chromatography showed that only garlic (1 sample) and ginger (4 samples) were naturally contaminated with aflatoxin B1 ranging from 390 μg/kg to 1045 μg/kg respectively. Previous reports have mostly highlighted the risk of mycotoxin exposure from staple crops and vegetables in Africa, but such risks now need to be evaluated further for other products such as dried and milled spices.

Studies conducted in Benin, in which the main staple foods are maize, cassava, groundnuts and yams, showed high levels of aflatoxin residues in blood of the exposed population. The natural contamination with fungi and aflatoxins in cassava chips sold at markets in Benin, West Africa was investigated. A total of sixty samples were sampled from open markets in 11 districts of 3 agroecological zones and analyzed for the presence of mycoflora and aflatoxin B 1 , B 2 , G 1 and G 2 . Fourteen genera of fungi were associated with marketed dried cassava chips. Within these, twenty- two isolates were identified to species level, whereas four were identified only to genus. The dominating fungal species isolated were Rhizopus oryzae , Nigrospora oryzae , Chrysonilia sitophila , Cladosporium resinae , Cladosporium herbarum , Apergillus niger and Aspergillus flavus . Fifty-four out of sixty samples were contaminated with A . flavus . The rate of occurrence in CFU/g of A. flavus fungi was lower than for all other fungal species together. Aflatoxin was not detected in any of the samples analyzed using HPLC with post-column photochemical derivatization and fluorescence detection. The limit of detection (LOD) was 0.1 μg/kg. Results from this study suggest cassava chips are unlikely to be a source of aflatoxin in Benin, and that other staples such as maize and groundnuts are more important in aflatoxin exposure. Therefore it can be speculated that staples like maize and groundnut are more important in aflatoxin exposure.

Heterophylly (juvenile-adult leaf dimorphism) is widespread among native woody species of the Mascarene Islands, but the causes to this phenomenon have so far not been fully explained. The absence of mammals and dominance of now extinct giant tortoises and flightless birds are characteristics of the original Mascarene fauna. The present study investigates the hypothesis that the distinct morphology and colouration of juvenile leaves signalled unpalatability to browsing giant tortoises or birds. Juvenile and adult leaves of 28 heterophyllous woody species endemic to the islands of Mauritius and Rodrigues were screened for possible chemical defences against herbivory. The screening comprised the following classes of secondary compounds: alkaloids, cyanogenic constituents, saponins, simple phenolics, tannins and anthocyanins. The screening showed that there are no consistent significant differences between juvenile and adult leaves regarding any of the studied secondary compound classes, with the exception of the level of anthocyanins, which was significantly higher in juvenile leaves. This difference was also clearly reflected in a generally high degree of red patterning of juvenile leaves. Based on comparisons with floras of other oceanic islands once inhabited by tortoises and birds, and an evaluation of feeding habits of these herbivores, we suggest that the reduced lamina and partly red colouration of juvenile leaves may be an evolutionary response to selective herbivory by birds.

Passibiflorin, (1S,4R)-1-(β- d -glucopyranosyloxy)-4-(6-deoxy-β- d -gulopyranosyloxy)-2-cyclopentene-1-carbonitrile, was isolated from Passiflora colinvauxii endemic to the Galapagos Islands; the plant is only the second known source of passibiflorin. The glycoside was identified by spectroscopic methods. Some preparations of the plant material contained the corresponding amide, the structure of which was inferred from spectroscopic data and confirmed by chemical correlation with passibiflorin. Chemotaxonomic implications of the occurrence of bisglycosidic cyclopentanoids in Passiflora are briefly discussed.

A new cyanogenic glycoside isolated from pods of Acacia sieberiana var. woodii has been shown by chemical and spectroscopic methods to be (2S)-2-[(6-O-α- l -arabinopyranosyl-β- d -glucopyranosyl)oxy]-3-methylbut-3-enenitrileo. Acid-catalysed hydrolysis of the glycoside afforded arabinose and proacacipetalin, and base-catalysed double-bond migration gave 2- [(6-O-α- l -arabinopyranosyl-β- d -glucopyranosyl)oxy ]-3-methylbut-2-enenitrile.

In this new design of the picrate test (Guignard Method) for small scale cyanide determination under field conditions, hydrolysis of the cyanogenic compounds is catalysed by ‘β-glucuronidase’, a commercial enzyme preparation from Helix pomatia. The method described facilitates the quantification of small amounts of cyanogenic compounds in plant material, with a detection limit about 60 ng of released HCN (equivalent to 1μg of amygdalin). False positive tests produced by hydrolysis products of glucosinolates could be excluded by inhibition of the myrosinae enzyme system present in plants that contain glucosinolates. The total weight of equipment needed for a total of 1000 determinations (in groups of eight) does not exceed 500 g, thus making the method convenient for field work.

The structure of plantamajoside, a phenylpropanoid glycoside isolated from Plantago major subs major , is deduced from chemical, spectral and other physical evidence, to be 3,4-dihydroxy-β-phenethyl- O -β- d -glucopyranosyl-(1 →3)-4- O -caffeoyl-β- d -glucopyranoside. The Minimum Inhibitory Concentration value has been evaluated for seven plant pathogenic bacteria and for E. coli (ML 30) and S. aureus (502 A) after preliminary investigations by the agar diffusion method.

Crude extract of Helix pomatia , commercially available as β-glucuronidase, was immobilized on porous glass and packed in a column (50 × 3 mm I.D.). Similarly, β-glucuronidase from bovine liver, immobilized on agarose beads, was used as a post-column reactor in the high-performance liquid chromatography of phenolic glycosides. Electrochemical oxidation by glassy carbon electrodes was used for the detection of the phenolic products formed by the enzymatic reaction and proved to be useful for the identification and sensitive detection of phenolic glycosides. Enzymatic activities were in the range 0.1–1 I.U. The detection limits of various phenolic glycosides were 3–23 pmol. Peak broadening and the linearity of the system were evaluated. The reactor containing immobilized Helix pomatia crude extract was also shown to posses enzymatic activity towards cyanogenic glycosides.

A rapid, simple and reproducible high-performance liquid chromatography procedure is described for the qualitative and quantitative analysis of mixtures of cyanogenic glycosides. The separation is achieved by means of a reversed-phase (C8) column eluted with a phosphate buffer, pH 5.0, containing either 15 or 7.5% (v/v) methanol, 7.5% being necessary for resolution of epimeric pairs of the more hydrophilic glycosides. When this separation is combined with enzymatic post-column cleavage and electrochemical detection of the cyanide formed, a highly specific and very sensitive system is obtained. The method was applied to cyanogenic glycosides in crude plant tissue extracts, and compared with both a thin-layer chromatographic method and to a traditional determination of total cyanide released after hydrolysis. Sensitivity, selectivity and accuracy were found sufficient to enable its routine use for analysis of food and fodder samples, for example. Cyanohydrins could be detected qualitatively.

The NADPH-dependent Δ6 desaturation of linoleic acid is decreased by low ionic strength extraction of the microsomal fraction from rat liver. On the other hand, the NADH-dependent desaturase activity is slightly increased. Addition of the extract restores the NADPH-dependent Δ6 desaturase activity of the extracted microsomal fraction. Our results from gel filtration experiments on the extracted proteins show a correlation between the catalase activity of the eluate and the ability of the eluate to stimulate Δ6 desaturase activity. Both the NADH- and NADPH-dependent Δ6 desaturase activity of the extracted microsomal fraction are totally inhibited by exogenous hydrogen peroxide. The inhibitory effect of hydrogen peroxide is partly eliminated by addition of bovine catalase. Neither Superoxide dismutase, tert-butanol nor β-carotene stimulate the Δ6 desaturase activity of the extracted microsomal fraction. The Δ6 desaturase activity of the extracted microsomal fraction is decreased using NADH and NADPH simultaneously as electron donors. On the basis of these results we suggest that the decreased NADPH-dependent desaturase activity of the extracted microsomal fraction is due to a microsomal formation of hydrogen peroxide which possibly inactivates one or more components of the microsomal electron transport system. Furthermore, in the present microsomal fraction the formation of hydrogen peroxide seems to be NADPH-dependent.

A new diol glucoside, 2-β- d -glucopyranosyloxy-2-methylpropanol, the first reported naturally occurring monoglucoside of an aliphatic dihydric alcohol, was isolated from pods of Acacia sieberana var. woodii . Structure elucidation was based on 1 H and 13 C NMR spectroscopy, and enzymatic analyses. The compound was hydrolysed very slowly by almond β-glucosidase, but cleaved by a β-glucuronidase enzyme complex from Helix pomatia .

A new cyanogenic glucoside, isolated from pods of Acacia sieberiana var. woodii, was shown to be (2R)-2- (β- d -glucopyranosyloxy)-3-hydroxy-3-methylbutanenitrile by spectroscopic and chemical methods. The absolute configuration of this glucoside was correlated with that of proacacipetalin by oxymercuration of the latter, followed by borohydride reduction of the product.