Eleusine indica (goosegrass) populations resistant to fluazifop, an acetyl-CoA carboxylase (ACCase: EC6.4.1.2)-inhibiting herbicide, were found in several states in Malaysia. Dose-response assay indicated a resistance factor of 87.5, 62.5 and 150 for biotypes P2, P3 and P4, respectively. DNA sequencing and allele-specific PCR revealed that both biotypes P2 and P3 exhibit a single non-synonymous point mutation from TGG to TGC that leads to a well known Trp-2027-Cys mutation. Interestingly, the highly resistant biotype, P4, did not contain any of the known mutation except the newly discovered target point Asn-2097-Asp, which resulted from a nucleotide change in the codon AAT to GAT. ACCase gene expression was found differentially regulated in the susceptible biotype (P1) and highly resistant biotype P4 from 24 to 72h after treatment (HAT) when being treated with the recommended field rate (198gha(-1)) of fluazifop. However, the small and erratic differences of ACCase gene expression between biotype P1 and P4 does not support the 150-fold resistance in biotype P4. Therefore, the involvement of the target point Asn-2097-Asp and other non-target-site-based resistance mechanisms in the biotype P4 could not be ruled out.
In this study, a new series of sulfonamides derivatives was synthesized and their inhibitory effects on DPPH and jack bean urease were evaluated. The in silico studies were also applied to ascertain the interactions of these molecules with active site of the enzyme. Synthesis was initiated by the nucleophilic substitution reaction of 2-(4-methoxyphenyl)-1-ethanamine (1: ) with 4-(acetylamino)benzenesulfonyl chloride (2): in aqueous sodium carbonate at pH 9. Precipitates collected were washed and dried to obtain the parent molecule, N-(4-{[(4-methoxyphenethyl)amino]sulfonyl}phenyl)acetamide (3): . Then, this parent was reacted with different alkyl/aralkyl halides, (4A-M: ), using dimethylformamide (DMF) as solvent and LiH as an activator to produce a series of new N-(4-{[(4-methoxyphenethyl)-(substituted)amino]sulfonyl}phenyl)acetamides (5A-M: ). All the synthesized compounds were characterized by IR, EI-MS, 1H-NMR, 13C-NMR and CHN analysis data. All of the synthesized compounds showed higher urease inhibitory activity than the standard thiourea. The compound 5 F: exhibited very excellent enzyme inhibitory activity with IC50 value of 0.0171±0.0070 µM relative to standard thiourea having IC50 value of 4.7455±0.0546 µM. Molecular docking studies suggested that ligands have good binding energy values and bind within the active region of taget protein. Chemo-informatics properties were evaluated by computational approaches and it was found that synthesized compounds mostly obeyed the Lipinski' rule.