Asulam

Description

Asulam is a sulfonamide and can be formulated as a sodium salt. It is very water soluble and is a very systemic herbicide following foliar and root uptake, owing to its physicochemical properties (Table 1). The Log P (Kow) of 1.01 and pKa of 4.82 are optimal for phloem mobility in the plant (4). These properties contribute to the herbicidal effectiveness against perennial weeds where translocation to underground meristematic organs is essential for effective control.

Chemical properties

Light Brown Solid

The Uses of Asulam

Carbamate herbicide; folic acid biosynthesis inhibitor.

The Uses of Asulam

Herbicide.

The Uses of Asulam

Systemic, pre- and postemergence herbicide used to control several perennial grasses and certain broad-leaved weeds such as brackenfern, crabgrass, itchgrass, paragrass, tansy ragwort, and wild mustard, in alfalfa, uncropped land, certain ornamentals and turf.

Definition

ChEBI: A carbamate ester that is methyl carbamate substituted by a (4-aminophenyl)sulfonyl group at the nitrogen atom.

Health Hazard

Low order of toxicity; no adverse effect onskin reported; ingestion of large dose couldproduce cholinergic effects.
LD50 oral (rat): 2000 mg/kg.

Pharmacology

Asulam-induced growth inhibition of carrot cell cultures was reversed by 4-aminobenzoic acid (8), and depletion of folate derivatives in treated plants (7) provides further evidence that the synthesis of folic acid is the primary target of asulam. Furthermore, asulam is structurally related to sulfonilamide and to sulfonamide antimicrobial drugs, which are competitive inhibitors of 7,8-dihydropteroate synthase (DHPS) (5,9).

Environmental Fate

Soil. It is not persistent in soils since its half-life is approximately 6–14 days (Hartley and Kidd, 1987). The short persistence time is affected by soil temperature and moisture content. The half-life of asulam in a heavy clay soil having a moisture content of 34% and maintained at 20°C was 7 days (Smith and Walker, 1977). In soil, sulfanilamide was reported as a product of hydrolysis. In non-sterile soils, this compound further degraded to unidentifiable products (Smith, 1988) which may include substituted anilines (Bartha, 1971).
Photolytic. The reported photolytic half-lives for asulam in water at pH 3 and 9 were 2.5 and 9 days, respectively (Humburg et al., 1989)
Chemical/Physical. Forms water-soluble salts (Hartley and Kidd, 1987). When heated to 75°C, asulam decomposed to sulfanilic acid, carbamic acid and sulfanilamide. At 90°C, 4-nitro- and 4-nitrosobenzene sulfonic acids were released (Rajagopal et a