Investigation of the False Positive Results of Dithiocarbamate Pesticides due to Endogenous Nonpathogenic Carbon Disulfide in Organically Grown Plants (Moringa oleifera)

摘要

Moringa plant belongs to the family Moringaceae within the order Brassicales. It is a magical plant which contains 7 timesthe vitamin C content of oranges,4 times the vitamin A content of carrots, 4 times the calcium content of milk ,3 times the potassiumcontent of bananas and 2 times the protein content of yogurt (gram to gram) . The most widely distributed species is Moringa oleiferaLam., referred as drumstick tree for the shape of its seed pods. Leaves of M. oleifera are rich in a unique glucosinolate namedglucomoringin. Moringa were found to release CS2 when submitted to experimental conditions of dithiocarbamate residue analysis.Gas chromatography was used to quantitate CS2 and control samples were obtained from Moringa plantations cultivated inexperimental areas, in which no treatment with fungicides of the dithiocarbamate group was applied. Endogenous CS2 levels werecompared with dithiocarbamate residues measured in Moringa samples from the field trials following applications of the macozeebfungicide. Use small leaves resulted in an observed decrease in CS2 concentration comparable to the large leaves. Temperature levelused has an effect on the concentration of CS2 measured as an indicator for dithiocarbamate pesticide residue. And use of hightemperature (100 °C) in drying of Moringa leaves after harvesting may lead to some biochemical changes that caused an observedincrease in CS2 concentration comparable to drying at (50 °C). Evidence for formation of dithiocarbamate compound from moringinin moringa leaves are metabolized/detoxified principally by the mercapturic acid pathway. Conjugation with glutathione (GSH)promoted by glutathione transferases gives rise to the corresponding Glucosinolate -. Isothiocyanate conjugates. These undergofurther enzymatic modifications to give rise sequentially to the cysteinylglycine cysteine - Isothiocyanate andN-acetylcysteine-Isothiocyanate conjugates, all of which are dithiocarbamates. The detection of an ion with a m/z value 430.40, withthe following fragments m/z 165.10 and m/z 121.05 respectively, among the ions analyzed by GC-MS gives a clear evidence forformation of dithiocarbamate by addition of glutathione to the isothiocyanate formed from glucosinolate in moringa plant.