Metabolism of the Strobilurin Fungicide Mandestrobin in Wheat

Degradation of the strobilurin fungicide mandestrobin in illuminated water-sediment systems

The degradation behavior of mandestrobin (1) was investigated in aerobic aquatic water-sediment systems exposed to continuous artificial sunlight (λ>290 nm). [14C]mandestrobin uniformly labeled at the phenoxy or benzyl ring was individually applied to the overlying water of the system at a rate equivalent to 262.5 g a.i./ha. The transformation of 1 was mainly proceeded via photoinduced bond cleavage at the benzyl phenyl ether and the subsequent rearrangement reaction. Interestingly, some of the photodegradates and microbial metabolites of 1 observed in the aquatic photodegradation and water-sediment (dark) studies, respectively, were never detected. Furthermore, the observed photoproducts were less formed and were steadily degraded or metabolized to carbon dioxide or strongly adsorbed to bottom sediment. The fate of 1 and its degradates in illuminated water-sediment systems was considered to reflect realistic conditions more precisely, as it accounts for various effects attributed to sunlight.

Efficient synthesis of carbon-14 labeled metabolites of the strobilurin fungicide mandestrobin using biomimetic iron-porphyrin catalyzed oxidation

Biomimetic oxidation using synthetic iron-porphyrin (F20 TPPFeCl) as a catalyst eliminated a xylene moiety of the fungicide mandestrobin, uniformly labeled with carbon-14 at the benzyl ring, to produce the corresponding radiolabeled metabolite 1. This reaction mechanism was investigated by identifying chemical structures of intermediate 5 and p-xyloquinone derivatives 6 and 7, as by-products. Optimization of reaction factors based on the mechanism improved the yield of 1 from mandestrobin up to 87%. Finally, various carbon-14 labeled metabolites of mandestrobin were prepared from 1.

Cytogenotoxic activity of herbicidal and fungicidal pesticides on Triticum aestivum root meristem

Phytotoxicity, cytotoxicity and genotoxicity of pesticides with various mechanisms of targeted activity were studied in a hydroponic culture of 2-day-old seedlings of Triticum aestivum. All studied pesticides (with the exception of metribuzin) exhibited dose-dependent phytotoxicity (inhibited the growth of the main root and reduced the yield of root biomass). All studied pesticides did not affect mitotic index in the root apex meristem but did affect the duration of some phases of mitosis. Herbicides increased, while fungicides, on the contrary, decreased the duration of the cytokinesis phase. All pesticides (1 μg/mL) exhibited genotoxic activity: in the root apex meristem the number of cells with mitotic abnormalities was significantly higher than in the control variant (7-14 times). The genotoxic activity of metribuzin and tebuconazole was 2 times lower than for tribenuron-methyl, fenoxaprop-P-ethyl, epoxiconazole and azoxystrobin. The genotoxicity of the studied pesticides was combined: depending on the class of the pesticide, clastogenic or aneugenous effects dominated.

Residue analysis of fungicides fenpicoxamid, isofetamid, and mandestrobin in cereals using zirconium oxide disposable pipette extraction clean-up and ultrahigh-performance liquid chromatography-tandem mass spectrometry

In the present study, a fast multiresidue method determining three novel fungicides fenpicoxamid, isofetamid, and mandestrobin in cereals was developed and validated for the first time using ultrahigh-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). Samples were extracted by QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) methodology, and cleaned up using the disposable pipette extraction (DPX) tips containing primary secondary amine (PSA) and silica gel modified with zirconium oxide (Z-Sep) in less than 1 min. Linearity (r > 0.99) of three fungicides in the calibration range of 0.001-0.1 µg mL^-1 was satisfactory. Mean recoveries (n = 15) from all matrices were between 84.8% and 100.3% as the corresponding intra-day and inter-day relative standard deviations (RSDs) were less than 10.6%. Limits of quantitation (LOQs) of all analytes in different matrices were defined at 0.01 mg kg^-1. The results indicate this method can serve as a sensitive and rapid approach to monitoring contents of fenpicoxamid, isofetamid, and mandestrobin in cereals.