Mining Steroidal Withanolides and Nonribosomal Peptides for Anticancer and Antibacterial Activity

Cancer presents a significant global health challenge, accounting for over 9 million deaths annually. A class of steroidal lactones derived from the Solanaceae family were examined for anti-cancer activity. Among these, withanolide J and physaperuvin G from Withania obtusifolia, showed inhibitory activity against leukemia cells and central nervous system glioma cells. In silico molecular docking simulations examined molecular docking with phosphorylated and unphosphorylated forms of the signal transducer and activator of transcription 3 (STAT3), elucidating a potential role of withanolides in cancer apoptosis. Withanolides were also examined in silico for docking with hemagglutinin (HA), a key surface glycoprotein for viral transmission in H5N1 influenza virus. A comprehensive withanolide library was compiled for HA inhibition, facilitating rapid screening of potential inhibitors. Molecular docking, pharmacokinetic analyses, and molecular dynamics simulations identified three promising compounds: 2-[(1S)-1-hydroxy-1-[(2S,4S,5S,10R,14S)-5-hydroxy-10,14-dimethyl-9-oxo-15-pentacyclo[9.7.0.02,4.05,10.014,18] octadic 7-enyl]ethyl]-4,5-dimethyl-2,3-dihydropyran-6-one, (1S,2R,6S,7R,9R,11S,12S,15R,16S)-15-[(1S)-1-[(2R)-4,5-dimethyl-6-oxo-2,3-dihydropyran-2-yl]ethyl]-6-hydroxy-2,16-dimethyl-8-oxapentacyclo[9.7.0.02,7.07,9.012,16]octadecan-3-one, and Exodeconolide F which exhibited superior binding affinities (-6.086, -6.087, and -6.373 kcal/mol, respectively) compared to the positive control, umifenovir (-3.139 kcal/mol). Non-ribosomal peptides are synthesized by peptide synthetases and exhibit structurally complex architectures and potent antimicrobial activity. To assess the biosynthetic potential of bacteria for producing cationic non-ribosomal peptides, an in silico analysis was conducted on over 11,000 bacterial genomes to determine the most genetically competent microbe for producing polymyxins. When purified from Paenibacillus polymyxa and identified through MALDI-TOF/TOF and nano-spray analyses, polymyxin B exhibited a 20-fold increase in specific activity. The compound effectively inhibited the growth of multidrug-resistant pathogens, including Pseudomonas aeruginosa (≤4 mg/ml), Klebsiella pneumoniae (≤2 mg/ml), and Acinetobacter baumannii (≤2 mg/ml). Collectively, these findings identify the potential of withanolides and non-ribosomal peptides as agents for cancer, bacterial, and viral treatment.