The crystal structure of sulfamethoxazole, interaction with DNA, DFT calculation, and molecular docking studies

• X-ray structure of Sulfamethoxazole (SMX).
• DFT calculation of SMX and the spectral properties.
• The DNA interaction with SMX, Kb = 4.37 × 104 M−1.
• Molecular docking study of SMX with DHPS from E. coli and S. pneumoniae.

Sulfamethoxazole (SMX) [4-amino-N-(5-methyl-1,2-oxazol-3-yl)benzenesulfonamide] is structurally established by single crystal X-ray diffraction measurement. The crystal packing shows H-bonded 2D polymer through N(7)H(7A)---O(2), N(7)H(7B)---O(3), N(1)H(1)---N(2), C(5)H(5)---O(3)S(1) and N(7)(H7A)---O(2)S(1). Density Functional Theory (DFT) and Time Dependent-DFT (TD-DFT) computations of optimized structure of SMX determine the electronic structure and has explained the electronic spectral transitions. The interaction of SMX with CT-DNA has been studied by absorption spectroscopy and the binding constant (Kb) is 4.37 × 104 M−1. The in silico test of SMX with DHPS from Escherichia coli and Streptococcus pneumoniae helps to understand drug metabolism and accounts the drug–molecule interactions. The molecular docking of SMX–DNA also helps to predict the interaction feature.

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