New prospective insecticidal agents based on thiazolo[4,5-b]quinoxaline derivatives against cotton leafworm Spodoptera litura (Fabricius): Design, synthesis, toxicological, morphology, histological, and biomedical studies.

In this study, a new series of thiazolo[4,5-b]quinoxaline derivatives 3-8 were synthesized by treating 2,3-dichloroquinoxaline with thiosemicarbazone and thiourea derivatives under reflux conditions. The chemical structure of the newly designed derivatives was conducted using spectroscopic techniques. The insecticidal bioassay of the designed derivatives was evaluated against the 2nd and 4th larvae of S. litura after five days as toxicity agents via median lethal concentration (LC50) and the lethal time values (LT50). The results indicated that all the tested compounds had insecticidal effects against both instar larvae of S. litura with variable values. Among them, thiazolo[4,5-b]quinoxaline derivative 3 was the most toxic, with LC50 = 261.88 and 433.68 ppm against 2nd and 4th instar larvae, respectively. Moreover, the thiazolo[4,5-b]quinoxaline derivative 3 required the least time to kill the 50% population (LT50) of 2nd larvae were 20.88, 13.2, and 15.84 hs with 625, 1250, and 2500 ppm, respectively, while for the 4th larval instar were 2.75, 2.08, and 1.76 days with concentrations of 625, 1250, and 2500 ppm, respectively. Larvae's morphological and histological studies for the most active derivative 3 were investigated. According to SEM analysis, the exterior morphology of the cuticle and head capsule was affected. In addition, there were some histological alterations in the cuticle layers and the midgut tissues. Columnar cells began breaking down, and vacuolization occurred in the peritrophic membrane. Moreover, treating 4th S litura larvae hemolymph with compound 3 showed significant changes in biochemical analysis, such as total proteins, GPT, GOT, acetylcholinesterase (AChE), and alkaline phosphatase (AlP). Finally, the toxicity prediction of the most active derivative revealed non-corrosive, non-irritant to the eye, non-respiratory toxicity, non-sensitivity to the skin, non-hepatotoxic, and don't have toxicity on minnow toxicity and T. pyriformis indicating a good toxicity profile for human.

Design, synthesis, antimicrobial activity and molecular docking studies of some novel di-substituted sulfonylquinoxaline derivatives.

2,3-Dioxo-1,2,3,4-tetrahydroquinoxaline-6-sulfonyl chloride 1 was prepared via reaction of o-phenylene diamine with oxalic acid followed by chlorosulfonation with excess chlorosulfonic acid. A series of new sulfonylquinoxaline derivatives 2-6 were obtained upon reacting compound 1 with different types of amines. 2,3-Dichloro-6-morpholinosulfonylquinoxaline derivative 6 was subjected to further chemical reactions to afford many derivatives of 6-morpholino 2,3-disubstitutedquinoxalines, thus reaction of compound 6 with different secondary amines yielded mono and di secondary aminoquinoxaline derivatives 7-10 depending on the reactivity difference of the two chlorine atoms. Hydrazinolysis of compound 7 furnished hydrazino quinoxaline derivatives 11a-c. Additionally triazolo and pyrazolyl quinoxaline derivatives 12-14 were obtained through the reaction of compound 11a with phenyl isothiocyanate, formylpyrazole and ethyl acetoacetate. All the synthesized compounds were screened for their antibacterial and antifungal activities. Compounds 7a, 9b, 10a, 10c, 10f and 11c showed good to moderate antimicrobial activity against the tested Gram-positive, Gram-negative bacteria and fungi with MIC values ranging from 2.44 to 180.14 µM. Their MBC values were also evaluated using the same tested microorganisms. Moreover, screening against multi-drug resistant strains revealed the promiscuity of these new derivatives, especially compound 7a that showed comparable antibacterial activity (MIC 4.91-9.82 µM) with Norfloxacin (MIC 2.44-9.80 µM). Furthermore, these compounds were evaluated as DNA Gyrase inhibitors and the obtained results were in the range of 15.69-23.72 µM. Immunomodulatory effect was also investigated and compounds 7a, 11c, 10f, 10c, 10a and 9b showed high immunostimulatory action with ratio (142.6 ± 0.4, 135.7 ± 0.5, 117.8 ± 0. 39, 112.5 ± 0. 83, 86.4 ± 0. 47, 72.8 ± 0. 77) respectively. Molecular docking studies of the promising derivatives into DNA Gyrase binding site proved the usefulness of hybridizing quinoxaline scaffold with SO2 and morpholine moieties as a hopeful strategy in designing new DNA Gyrase binding molecules.

Antimicrobial evaluation of thiadiazino and thiazolo quinoxaline hybrids as potential DNA gyrase inhibitors; design, synthesis, characterization and morphological studies.

A series of thiadiazino[5,6-b]quinoxaline and thiazolo[4,5-b]quinoxaline derivatives was designed and synthetized from the reaction of 2,3-dichloro-6-(morpholinosulfonyl)quinoxaline (2) with thiosemicarbazide or thiocarbohydrazide and thiourea derivatives to give nineteen quinoxaline derivatives 3-16. All the synthesized compounds were evaluated for in vitro antimicrobial potential against various bacteria and fungi strains that showed considerable antimicrobial activity against tested microorganisms. The most potent compounds 2, 7, 9, 10, 12 and 13c were exhibited bactericidal activity, in addition to fungistatic activity by dead live assay. Moreover, these compounds showed a significant result against all multi-drug resistance (MDRB) used especially compound 13c that displayed the best results with MICs of MDRB (1.95, 3.9, 2.6, 3.9 µg/mL) for stains used in this study, compared with Norfloxacin (1.25, 0.78, 1.57, 3.13 µg/mL). Also, cytotoxicity on normal cell (Vero cells ATCC CCL-81) by MTT assay was performed with lower toxicity results. Additionally, morphological studies, immunostimulatory potency and DNA gyrase inhibition assay of most active compounds was done. A molecular docking study has also been carried out to support the effective binding of the most promising compounds at the active site of the target enzyme S. aureus DNA gyrase (2XCT).