New Dihydroisocoumarin Root Growth Inhibitors From the Sponge-Derived Fungus Aspergillus sp. NBUF87

Importance of quorum sensing crosstalk in the brown alga Saccharina latissima epimicrobiome

Brown macroalgae are colonized by diverse microorganisms influencing the physiology of their host. However, cell-cell interactions within the surface microbiome (epimicrobiome) are largely unexplored, despite the significance of specific chemical mediators in maintaining host-microbiome homeostasis. In this study, by combining liquid chromatography coupled to mass spectrometry (LC-MS) analysis and bioassays, we demonstrated that the widely diverse fungal epimicrobiota of the brown alga Saccharina latissima can affect quorum sensing (QS), a type of cell-cell interaction, as well as bacterial biofilm formation. We also showed the ability of the bacterial epimicrobiota to form and inhibit biofilm growth, as well as to activate or inhibit QS pathways. Overall, we demonstrate that QS and anti-QS compounds produced by the epimicrobiota are key metabolites in these brown algal epimicrobiota communities and highlight the importance of exploring this epimicrobiome for the discovery of new bioactive compounds, including potentially anti-QS molecules with antifouling properties.

Discovery of Natural Product Inspired 3-Phenyl-1H-isochromen-1-ones as Highly Potent Antioxidant and Antiplatelet Agents: Design, Synthesis, Biological Evaluation, SAR and in silico Studies

BACKGROUND

Several natural/synthetic molecules having structure similar to 1H-isochromen-1-ones have been reported to display promising antioxidants and platelet aggregation inhibitory activity. Isocoumarin (1H-2-benzopyran-1-one) skeleton, either whole or as a part of molecular framework, have been explored for their antioxidant or antiplatelet activities.

INTRODUCTION

Based on literature, a new prototype i.e., 3-phenyl-1H-isochromen-1-ones based compounds have been rationalized to possess both antioxidant as well as antiplatelet activities. Consequently, no reports are available regarding its inhibition either by cyclooxygenase-1 (COX-1) enzyme or by arachidonic acid (AA)-induced platelet aggregation. This prompted us to investigate 3-phenyl-1H-isochromen-1-ones towards antioxidant and antiplatelet agents.

METHODS

The goal of this work to identify new 3-phenyl-1H-isochromen-1-ones based compounds via synthesis of a series of analogues and performing in vitro antioxidant as well as AA-induced antiplatelet activities and then, identification of potent compounds by SAR and molecular docking studies.

RESULTS

Out of all synthesized 3-phenyl-1H-isochromen-1-ones analogues, five compounds showed 7-folds to 16-folds highly potent antioxidant activities than ascorbic acid. Altogether, ten 3-phenyl-1H-isochromen-1-one analogues displayed antioxidant activities in 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. Almost, all the 3-phenyl-1H-isochromen-1-one analogues exhibited potent AA-induced antiplatelet activity; few of them displayed 7-folds more activity as compared to aspirin. Further, in silico analysis validated the wet results.

CONCLUSION

We disclose the first detailed study for the identification of 3-phenyl-1H-isochromen-1-one analogues as highly potent antioxidant as well as antiplatelet agents. The article describes the scaffold designing, synthesis, bioevaluation, structure-activity relationship and in silico studies of pharmaceutically privileged bioactive 3-phenyl-1H-isochromen-1-one class of heterocycles.

Marine natural products

This review covers the literature published in 2019 for marine natural products (MNPs), with 719 citations (701 for the period January to December 2019) 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 (1490 in 440 papers for 2019), together with the relevant biological activities, source organisms and country of origin. Pertinent reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. Methods used to study marine fungi and their chemical diversity have also been discussed.

Natural isocoumarins: Structural styles and biological activities, the revelations carry on …

Isocoumarins and dihydroisocoumarins are lactonic phytochemicals plentiful in microbes and higher plants. These are an amazing small scaffolds consecrated with all types of pharmacological applications. Our previous review covered the period 2000-2016, documenting the then known natural products of this class; the current article is a critical account of discovery of known as well as undescribed structural types and pharmacological activities reported in the course of 2016-2020. The classification revealed in our previous review based on the biogenetic origin is further buttressed by discovery of new members of each class and some new structural types hitherto unknown have also been identified. Similarly, the biological activities and SAR conclusions identified were found to be valid as well, nonetheless with new accompaniments. The most recent available literature on the structural diversity and biological activity of these natural products has been included. The information documented in this article are collected from scientific journals, books, electronic search engines and scientific databases.

Lophiostomin A–D: new 3,4-dihydroisocoumarin derivatives from the endophytic fungus Lophiostoma sp. Sigrf10

Four new 3,4-dihydroisocoumarin congeners, named lophiostomin A–D (1–4), together with two known α-pyridones (5 and 6) were isolated from cultures of the endophytic fungus Lophiostoma sp. Sigrf10 obtained from Siraitia grosvenorii. The structures of the new compounds were determined via combined analysis involving 1D and 2D NMR, high-resolution electrospray ionization mass spectrometry (HRESIMS), and electronic circular dichroism (ECD) spectra, as well as quantum chemical ECD computations for assigning the absolute configurations. All the compounds were evaluated for their antibacterial and antifungal activities. Compounds 1 and 2 displayed moderate inhibitory activities against the spore germination of Magnaporthe oryzae, whereas 5 and 6 were active against the following tested pathogenic bacteria: Bacillus subtilis, Agrobacterium tumefaciens, Ralstonia solanacearum, and Xanthomonas vesicatoria.

Four new 3,4-dihydroisocoumarin congeners, named lophiostomin A–D (1–4), together with two known α-pyridones (5 and 6) were isolated from cultures of the endophytic fungus Lophiostoma sp. Sigrf10 obtained from Siraitia grosvenorii.