Kynapcin-12

Kynapcin-12 is a prolyl oligopeptidase (POP) inhibitor isolated from Polyozellus multiplex, and its structure was assigned as 1 having a p-hydroquinone moiety by spectroscopic analyses and chemical means. This Letter describes the total syntheses of the proposed structure 1 for kynapcin-12 and 2',3'-diacetoxy-1,5',6',4″-tetrahydroxy-p-terphenyl 2 isolated from Boletopsis grisea, revising the structure of kynapcin-12 to the latter. These syntheses involved double Suzuki-Miyaura coupling, CAN oxidation, and LTA oxidation as key steps. The inhibitory activities of synthetic compounds against POP and cancer cells were also evaluated.

Alzheimer's disease (AD), a major neurodegenerative disorder, is associated with the enzymatic reaction of β-secretase (BACE1) on the amyloid precursor protein (APP) for the generation of neurotoxic amyloid-β (Aβ). Therefore, Aβ accumulation and oxidative stress-induced neuronal cell death are the pathogenic hallmarks of AD. In this study, we tried to identify BACE1 inhibitors and neuroprotectants from natural products, in particular, from the Korean mushroom Polyozellus multiplex. Four p-terphenyls were identified from the ethanolic extract of P. multiplex; polyozellin (1), thelephoric acid (2), polyozellic acid (3), and kynapcin-12 (4). Compounds 1-4 effectively inhibited BACE1 activity with a half-maximal inhibitory concentration (IC50) of 3.08, 3.50, 4.78, and 15.79 μM, respectively. Compounds 1-3 reduced the production of neurotoxic Aβ1-42 production in APPswe-N2a cells in a concentration-dependent manner. When HT22 cells were stressed with 5 mM glutamate, compounds 2 and 3 significantly recovered cell viability. It was correlated with their inhibitory properties against glutamate-mediated Ca(2+) influx, intracellular reactive oxygen species (ROS) generation, lipid peroxidation, reduction in Bcl-2 and Bid levels, and enhanced phosphorylation of mitogen-activated protein kinase (MAPK). Thus, P. multiplex and the isolated p-terphenyls might be useful in the development of lead compounds for the prevention of neurodegenerative diseases, especially AD.

Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) is highly pathogenic to humans and has created health care threats worldwide. This urgent situation has focused the researchers worldwide towards the development of novel vaccine or small molecule therapeutics for SARS-CoV-2. Although several vaccines have already been discovered and are in use for the masses, no therapeutic medication has yet been approved by FDA for the treatment of COVID-19. Keeping this in view, in the present study, we have identified promising hits against the main protease (Mpro) of SARS-CoV-2 from edible mushrooms. Structure-based virtual screening (VS) of 2433 compounds derived from mushrooms was performed with Mpro protein (6LU7). Four promising hits, namely, Kynapcin-12 (M_78), Kynapcin-28 (M_82), Kynapcin-24 (M_83), and Neonambiterphenyls-A (M_366) were identified based on the result of docking, Lipinski's rule, 100 ns molecular dynamics (MD) simulation and MM/PBSA binding free energy calculations. Finally, the inhibitory properties of these hits were compared with three known inhibitors, baicalein (1), baicalin (2), and biflavonoid (3). Data indicated that M_78, M_82 and M_83 compounds present in edible mushroom Polyozellus multiplex were potent inhibitors of Mproprotein (6LU7). It could be concluded that edible mushroom Polyozellus multiplex has potential activity against SARS-CoV-2 infection and identified molecules could be further explored as therapeutic inhibitors against SARS-CoV-2.