Alkaloids of Glycosmis arborea—II

Glycosmis pentaphylla (Rutaceae): A Natural Candidate for the Isolation of Potential Bioactive Arborine and Skimmianine Compounds for Controlling Multidrug-Resistant Staphylococcus aureus

Several multidrug-resistant organisms have emerged, which increases the threat to public health around the world and a limited number of therapeutics were available to counteract these issues. Thus, researchers are trying to find out novel antimicrobials to overcome multidrug-resistant issues. The present study aimed to isolate antibacterial principles against the clinical isolates of multidrug-resistant (MDR) Staphylococcus aureus from the ethyl acetate extract of Gycosmis pentaphylla. The isolation and structural characterization of bioactive compounds were carried out using various chromatographic techniques (TLC, column, HPLC, and LC-MS) and spectral studies such as FT-IR, CHNS analysis, ¹H-NMR, and ¹³C-NMR. The antimicrobial potential of isolated compounds was assessed according to the standard methods. The isolated compounds were identified as arborine and skimmianine, which exhibited a significant antibacterial effect with the lowest MIC and MBC values against MDR S. aureus and in vitro kinetic and protein leakage assays supported the antimicrobial activity. Significant morphological changes such as uneven cell surfaces and morphology, cell shrinkage, and cell membrane damages were observed in the MDR S. aureus upon the treatment of arborine and skimmianine. The present investigation concludes that the isolated arborine and skimmianine compounds from G. pentaphylla harbor a strong antibacterial activity against MDR S. aureus and may be used as alternative natural drugs in the treatment of MDR S. aureus.

Synthesis, antimicrobial evaluation, and docking studies of novel 4-substituted quinazoline derivatives as DNA-gyrase inhibitors

Quinazoline derivatives are reported to have anti-inflammatory, analgesic, antibacterial, and anticancer activities. The incorporation of "OCH₂CONH₂" (oxymethylcarbamide) at 4th position of the quinazoline ring was found to influence the biological activities of the molecules. With this rationale, some new oxadiazolyl methyloxy quinazolines, pyrazolyl acetoxy methyl quinazolines, triazolylmethyloxy quinazolines were synthesized from anthranilic acid through quinazolyl oxyacetylhydrazide intermediates. All the compounds were characterized by IR, ¹H-NMR, EI-MS, and C, H, N analyses and evaluated for their antimicrobial activity. Docking studies on the DNA-gyrase enzyme (1KZN) show their role in the antimicrobial activity of the molecules and explain the higher potency of compounds 6a, 6b, 8a, 8b based on ReRanking scores and binding poses of the molecules.

Pyrimidine as constituent of natural biologically active compounds

This review describes the various manifestations of the pyrimidine system (alkylated, glycosylated, benzo-annelated.). These comprise pyrimidine nucleosides as well as alkaloids and antibiotics--some of them have been discovered and isolated from natural sources already long time ago, others have been reported very recently. A short overview on pyrimidine syntheses (prebiotic synthesis, biosynthesis, and metabolism) is given. The biological activities of most of the pyrimidine analogs are briefly described, and, in some cases, syntheses are formulated.