BROMUCONAZOLE

Bromuconazole is used on winter wheat and barley for the control of foliar mildews, rusts and other diseases.

Agricultural fungicide.

ChEBI: A member of the class of oxolanes carrying 1,2,4-triazol-ylmethyl and 2,4-dichlorophenyl substituents at position 2 as well as a bromo substituent at position 4. A foliar applied conazole fungicide for a range of crops including cereals, fruit, vegetables and vines.

Bromuconazole is a relatively stable compound which is not readily hydrolysed, is quite persistent in soil and is subject to relatively slow photodegradation. It is metabolised in plants but the parent compound tends to be the major residue. However, bromuconazole is almost completely metabolised in animals and birds (chickens) and its metabolites are rapidly eliminated.
As with many other triazole fungicides, metabolism is very complex. Bromuconazole exists in four forms (two diastereoisomeric pairs). There are numerous sites available for biotransformation (lack of regioselectivity) and there is also a lack of stereoselectivity at most sites. For example, there are also four forms of metabolite 5 (4-hydroxybromuconazole) (two diastereoisomeric pairs as with bromuconazole itself). Oxidation of secondary alcohols to ketones and the thiolation of certain sites further complicate the picture. Thiolation presumably occurs via the involvement of glutathione but mercapturic acid conjugates (N-acetylcysteines) do not appear to have been isolated.
Bromuconazole has been the subject of an evaluation by the Pesticide Safety Directorate of UK MAFF. All of the information presented below is derived from this source (PSD, 1996). All reported radiolabelled studies were conducted using [¹⁴C-phenyl]bromuconazole.

Bromuconazole was found to be stable in buffer at pH 5,7 and 9 at 25 °C over 30 days.
Aqueous photolysis using filtered light to simulate mid-summer sun at 50" N conducted at 25 °C and pH 4 caused slow photodegradation. The DT₅₀ of bromuconazole was 18.2 days. Over 28 days a 10% yield of CO₂ was obtained and six or more photoproducts were detected with none accounting for more than 8% of the total. No degradation occurred in dark controls.