Naturally Occurring Organohalogen Compounds-A Comprehensive Review

The present volume is the third in a trilogy that documents naturally occurring organohalogen compounds, bringing the total number-from fewer than 25 in 1968-to approximately 8000 compounds to date. Nearly all of these natural products contain chlorine or bromine, with a few containing iodine and, fewer still, fluorine. Produced by ubiquitous marine (algae, sponges, corals, bryozoa, nudibranchs, fungi, bacteria) and terrestrial organisms (plants, fungi, bacteria, insects, higher animals) and universal abiotic processes (volcanos, forest fires, geothermal events), organohalogens pervade the global ecosystem. Newly identified extraterrestrial sources are also documented. In addition to chemical structures, biological activity, biohalogenation, biodegradation, natural function, and future outlook are presented.

Trifluoromethylated Quinolone-Hydantoin Hybrids: Synthesis and Antibacterial Evaluation

A series of new trifluoromethyl-substituted quinolones and hydantoin hybrids has been synthesized and evaluated against Gram-positive bacterium (Staphylococcus aureus MTCC 96) and Gram-negative bacteria (Pseudomonas aeruginosa MTCC 441, Klebsiella pneumonia MTCC 109, and Escherichia coli MTCC 442). Compound  19c, having the 6-propene group on the quinolone ring, showed similar activity to a standard drug (chloramphenicol) by exhibiting MIC values of 50 µg/mL against S. aureus and P. aeruginosa. Physicochemical properties of compound 19c were also determined, which were in line with Lipinski’s rule of five, suggesting the suitability of compound 19c in biological systems. Various types of binding interactions of 19c within the active site of DNA gyrase of S. aureus were also streamlined by molecular docking studies, suggesting its capability to block the catalytic process of the DNA gyrase, which could be the possible reason for its antibacterial potential.

Marine Indole Alkaloids-Isolation, Structure and Bioactivities

Indole alkaloids are heterocyclic natural products with extensive pharmacological activities. As an important source of lead compounds, many clinical drugs have been derived from natural indole compounds. Marine indole alkaloids, from unique marine environments with high pressure, high salt and low temperature, exhibit structural diversity with various bioactivities, which attracts the attention of drug researchers. This article is a continuation of the previous two comprehensive reviews and covers the literature on marine indole alkaloids published from 2015 to 2021, with 472 new or structure-revised compounds categorized by sources into marine microorganisms, invertebrates, and plant-derived. The structures and bioactivities demonstrated in this article will benefit the synthesis and pharmacological activity study for marine indole alkaloids on their way to clinical drugs.

Marine natural products

This review covers the literature published between January and December in 2018 for marine natural products (MNPs), with 717 citations (706 for the period January to December 2018) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1554 in 469 papers for 2018), together with the relevant biological activities, source organisms and country of origin. Reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. The proportion of MNPs assigned absolute configuration over the last decade is also surveyed.

Natural indole-containing alkaloids and their antibacterial activities

As the growth in resistance to bacterial infection treatments poses a grave threat to global health in the 21st century, there is a constant need to explore novel antibacterial agents that have the ability to overcome drug resistance. Indole-containing alkaloids are widely distributed in nature, and a variety of indole-containing alkaloids have already been applied in clinical practice, proving that indole-containing alkaloids are fascinating and privileged scaffolds for the development of novel drugs. Moreover, indole-containing alkaloids could exert their antibacterial activity through the inhibition of efflux pumps, the biofilm, filamentous temperature-sensitive protein Z, and methicillin-resistant Staphylococcus aureus pyruvate kinase; so, indole-containing alkaloids constitute an important source of novel antibacterial agents. This review is an endeavor to highlight the advances in the development of indole-containing alkaloids with antibacterial potential, covering articles published in the recent 10 years.

LAMA-1: A Cerebroside Isolated from the Deep-Sea-Derived Fungus Penicillium chrysogenum

Chemical investigation of the ethyl acetate extract of Penicillium chrysogenum strain S003, a fungus isolated from Red Sea deep sediment, led to the isolation of a cerebroside molecular species LAMA (1) along with three other known compounds, ergosterol (2), epidioxyergosterol (3), and kojic acid (4). The structures of the isolated compounds were elucidated by interpretation of spectral data, including detailed 1D and 2D NMR (One and two dimensional Nuclear Magnetic Resonance) and mass spectrometry. The cytotoxic activities of isolated compounds 1–4 against five human carcinoma cells were evaluated using sulforhodamine B (SRB) assay. Compounds 2 and 3 displayed promising cytotoxic profiles against lung cancer (A-549), prostate (DU-145), breast adenocarcinoma (MCF-7), and hepatocellular (HepG2) cell lines, with IC₅₀ values of 21.26, 19.3; 1.50, 6.10; 16.95, 13.6; and 2.89, 3.07 µM, respectively, while they were inactive against HeLa cells. Compounds 1 and 4 showed weak cytotoxic profiles against all cell lines under investigation.

Large-Scale Production of Bioactive Terrein by Aspergillus terreus Strain S020 Isolated from the Saudi Coast of the Red Sea

The diversity of symbiotic fungi derived from two marine sponges and sediment collected off Obhur, Jeddah (Saudi Arabia), was investigated in the current study. A total of 23 isolates were purified using a culture-dependent approach. Using the morphological properties combined with internal transcribed spacer-rDNA (ITS-rDNA) sequences, 23 fungal strains (in the majority Penicillium and Aspergillus) were identified from these samples. The biological screening (cytotoxic and antimicrobial activities) of small-scale cultures of these fungi yielded several target fungal strains which produced bioactive secondary metabolites. Amongst these isolates, the crude extract of Aspergillus terreus strain S020, which was cultured in fermentation static broth, 21 L, for 40 days at room temperature on potato dextrose broth, displayed strong antimicrobial activities against Pseudomonas aeruginosa and Staphylococcus aureus and significant antiproliferative effects on human carcinoma cells. Chromatographic separation of the crude extract by silica gel column chromatography indicated that the S020 isolate could produce a series of chemical compounds. Among these, pure crystalline terrein was separated with a high yield of 537.26 ± 23.42 g/kg extract, which represents the highest fermentation production of terrein to date. Its chemical structure was elucidated on the basis of high-resolution electrospray ionization mass spectrometry (HRESIMS) or high-resolution mass spectrometry (HRMS), 1D, and 2D NMR spectroscopic analyses and by comparison with reported data. The compound showed strong cytotoxic activity against colorectal carcinoma cells (HCT-116) and hepatocellular carcinoma cells (HepG2), with IC₅₀ values of 12.13 and 22.53 µM, respectively. Our study highlights the potential of A. terreus strain S020 for the industrial production of bioactive terrein on a large scale and the importance of future investigations of these strains to identify the bioactive leads in these fungal extracts.