Development of novel HER2 inhibitors against gastric cancer derived from flavonoid source of Syzygium alternifolium through molecular dynamics and pharmacophore-based screening

Tirumalasetty Muni Chandra Babu,1 Aluru Rammohan,2 Vijaya Bhaskar Baki,1 Savita Devi,3 Duvvuru Gunasekar,2 Wudayagiri Rajendra1 1Bioinformatics Center, Division of Molecular Biology, Department of Zoology, 2Natural Products Division, Department of Chemistry, Sri Venkateswara University, Tirupati, Andhra Pradesh, 3Pathogen Biology Laboratory, Department of Biotechnology and Bioinformatics, School of Life Sciences, University of Hyderabad, Hyderabad, India Abstract: Continuous usage of synthetic chemotherapeutic drugs causes adverse effects, which prompted for the development of alternative therapeutics for gastric cancer from natural source. This study was carried out with a specific aim to screen gastroprotective compounds from the fruits of Syzygium alternifolium (Myrtaceae). Three flavonoids, namely, 1) 5-hydroxy-7,4'-dimethoxy-6,8-di-C-methylflavone, 2) kaempferol-3-O-β-D-glucopyranoside, and 3) kaempferol-3-O-α-L-rhamnopyranoside were isolated from the above medicinal plant by employing silica gel column chromatography and are characterized by NMR techniques. Antigastric cancer activity of these flavonoids was examined on AGS cell lines followed by cell cycle progression assay. In addition, pharmacophore-based screening and molecular dynamics of protein–ligand complex were carried out to identify potent scaffolds. The results showed that compounds 2 and 3 exhibited significant cytotoxic effect, whereas compound 1 showed moderate effect on AGS cells by inhibiting G2/M phase of cell cycle. Molecular docking analysis revealed that compound 2 has higher binding energies on human growth factor receptor-2 (HER2). The constructed pharmacophore models reveal that the compounds have more number of H-bond Acc/Don features which contribute to the inhibition of HER2 activity. By selecting these features, 34 hits were retrieved using the query compound 2. Molecular dynamic simulations (MDS) of protein–ligand complexes demonstrated conspicuous inhibition of HER2 as evidenced by dynamic trajectory analysis. Based on these results, the compound ZINC67903192 was identified as promising HER2 inhibitor against gastric cancer. The present work provides a basis for the discovery a new class of scaffolds from natural products for gastric carcinoma. Keywords: gastric cancer, cell cycle, pharmacophore, molecular docking, molecular dynamic

Biogenesis of silver nanoparticles using endophytic fungus Pestalotiopsis microspora and evaluation of their antioxidant and anticancer activities

Vasudeva Reddy Netala,1 Murali Satyanarayana Bethu,2,3 Bobbu Pushpalatha,1 Vijaya Bhaskar Baki,4 Sani Aishwarya,1 J Venkateswara Rao,2 Vijaya Tartte5 1Department of Biotechnology, Sri Venkateswara University, Tirupati, 2Biology Division, Indian Institute of Chemical Technology, Hyderabad, 3Academy of Scientific and Innovative Research, New Delhi, 4Department of Bioinformatics, 5Department of Botany, Sri Venkateswara University, Tirupati, India Abstract: An endophytic fungal strain isolated from the leaves of Gymnema sylvestre was identified as Pestalotiopsis microspora VJ1/VS1 based on nucleotide sequencing of internal transcribed spacer region (ITS 1-5.8S-ITS 2) of 18S rRNA gene (NCBI accession number KX213894). In this study, an efficient and ecofriendly approach has been reported for the synthesis of silver nanoparticles (AgNPs) using aqueous culture filtrate of P. microspora. Ultraviolet-visible analysis confirmed the synthesis of AgNPs by showing characteristic absorption peak at 435 nm. Fourier transform infrared spectroscopy analysis revealed the presence of phenolic compounds and proteins in the fungal filtrate, which are plausibly involved in the biosynthesis and capping of AgNPs. Transmission electron microscopy (TEM) showed that the AgNPs were spherical in shape of 2–10 nm in size. Selected area electron diffraction and X-ray diffraction studies determined the crystalline nature of AgNPs with face-centered cubic (FCC) lattice phase. Dynamic light scattering analysis showed that the biosynthesized AgNPs possess high negative zeta potential value of -35.7 mV. Biosynthesized AgNPs were proved to be potential antioxidants by showing effective radical scavenging activity against 2,2'-diphenyl-1-picrylhydrazyl and H2O2 radicals with IC50 values of 76.95±2.96 and 94.95±2.18 µg/mL, respectively. The biosynthesized AgNPs exhibited significant cytotoxic effects against B16F10 (mouse melanoma, IC50 =26.43±3.41 µg/mL), SKOV3 (human ovarian carcinoma, IC50 =16.24±2.48 µg/mL), A549 (human lung adenocarcinoma, IC50 =39.83±3.74 µg/mL), and PC3 (human prostate carcinoma, IC50 =27.71±2.89 µg/mL) cells. The biosynthesized AgNPs were found to be biocompatible toward normal cells (Chinese hamster ovary cell line, IC50 =438.53±4.2 µg/mL). Cytological observations on most susceptible SKOV3 cells revealed concentration-dependent apoptotic changes that include cell membrane blebbing, cell shrinkage, pyknotic nuclei, karyorrhexis followed by destructive fragmentation of nuclei. The results together in this study strongly provided a base for the development of potential and versatile biomedical applications of biosynthesized AgNPs in the near future. Keywords: AgNPs, Pestalotiopsis microspora, 18S rRNA, SKOV3, B16F10, AO-EB stainin