Glycoside carbamates from benzoxazolin-2(3H)-one detoxification in extracts and exudates of corn roots.
Zea mays was incubated with the natural phytotoxin benzoxazolin-2(3H)-one (BOA) to investigate the detoxification process. A hitherto unknown detoxification product, 1-(2-hydroxyphenylamino)-1-deoxy-beta-gentiobioside 1,2-carbamate (3), was isolated and identified. A reinvestigation of known BOA detoxification products by NMR methods led to the finding that the structure of benzoxazolin-2(3H)-one-N-beta-glucoside (1) first reported from Avena sativa has to be revised. In fact, the correct structure is that of the isomeric 1-(2-hydroxyphenylamino)-1-deoxy-beta-glucoside 1,2-carbamate 2, which is structurally related to 3. It was now shown with a synthetic mixture of 1 and 2 that 1 underwent spontaneous isomerization to form 2 in solution. Thus, N-glucosylation of BOA in the plant led finally to the carbamate 2. In contrast to BOA-6-O-glucosylation, BOA-induced N-glucosylation appears first after 6-8 h of incubation. As soon as N-glucosylation is possible, BOA-6-O-glucoside is not further accumulated, whereas the amount of glucoside carbamate increases continuously during the next 40 h. Synthesis of gentiobioside carbamate seems to be a late event in BOA detoxification. All detoxification products are released into the environment via root exudation.
Sicker
D
D
Institut für Organische Chemie, Universität Leipzig, Johannisallee 29, D-04103, Leipzig, Germany.
Schneider
B
B
Hennig
L
L
Knop
M
M
Schulz
M
M
D001583:Benzoxazoles / Q000493:pharmacokinetics*; D002219:Carbamates / Q000032:analysis* / Q000302:isolation & purification*; D006027:Glycosides / Q000032:analysis / Q000302:isolation & purification* / Q000378:metabolism; D008658:Inactivation, Metabolic / Q000502:physiology; D018517:Plant Roots / Q000378:metabolism; D003313:Zea mays / Q000378:metabolism*
C448124:1-(2-hydroxyphenylamino)-1-deoxy-gentiobioside 1,2-carbamate; D001583:Benzoxazoles; D002219:Carbamates; D006027:Glycosides; C017057:benzoxazolone