Catechol-Bearing Polyketide Derivatives from Sparticola junci

Polyoxygenated Cyclohexenes from Uvaria grandiflora with Multi-Enzyme Targeting Properties Relevant in Type 2 Diabetes and Obesity

Shikimic acid-derived polyoxygenated cyclohexene natural products commonly occurring in several species of the Uvaria represent natural products with promising biological activities. While a number of derivatives have been reported from Uvaria grandiflora (U. grandiflora), further studies are needed to discover additional bioactive congeners, particularly derivatives with multi-protein target inhibitory properties implicated in diseases such as diabetes and obesity. In this paper, isolation and identification of a new highly oxygenated cyclohexene, uvagrandol (1), along with the known compound (-)-zeylenone (2) from the DCM sub-extract of U. grandiflora following in vitro and in silico assessment of their enzyme inhibitory properties against α-glucosidase, dipeptidyl peptidase IV, porcine lipase, and human recombinant monoacylglycerol lipase are reported. The structure of 1 was elucidated using 1D and 2D NMR data analysis. The absolute configuration of 1 was established by quantum chemical calculations via the Gauge-Independent Atomic Orbital (GIAO) NMR method followed by TDDFT-Electronic Circular Dichroism (ECD) calculations. The structures of the eight possible stereoisomers were optimized by means of DFT calculations (B3LYP/6-31+G[d,p] in vacuum), and then their isotropic shielding tensors were obtained using the GIAO method at mPW1PW91/6-31G(d,p) in chloroform. Through DP4+, the isomer of configuration (1S,2S,3R,6R) for 1 was predicted with 96.3% probability. Compounds 1 and 2 significantly inhibited the four target enzymes in vitro. Binding studies through molecular docking simulations showed strong binding affinities for (-)-zeylenone (2), thus validating the in vitro results. Our findings suggest the potential of polyoxygenated cyclohexenes, in particular (-)-zeylenone (2), in anti-diabetic and anti-obesity drug discovery.

COX Inhibitory and Cytotoxic Naphthoketal-Bearing Polyketides from Sparticola junci

Axenic fermentation on solid rice of the saprobic fungus Sparticola junci afforded two new highly oxidized naphthalenoid polyketide derivatives, sparticatechol A (1) and sparticolin H (2) along with sparticolin A (3). The structures of 1 and 2 were elucidated on the basis of their NMR and HR-ESIMS spectroscopic data. Assignment of absolute configurations was performed using electronic circular dichroism (ECD) experiments and Time-Dependent Density Functional Theory (TDDFT) calculations. Compounds 1-3 were evaluated for COX inhibitory, antiproliferative, cytotoxic and antimicrobial activities. Compounds 1 and 2 exhibited strong inhibitory activities against COX-1 and COX-2. Molecular docking analysis of 1 conferred favorable binding against COX-2. Sparticolin H (2) and A (3) showed a moderate antiproliferative effect against myelogenous leukemia K-562 cells and weak cytotoxicity against HeLa and mouse fibroblast cells.

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A personal selection of 32 recent papers is presented covering various aspects of current developments in bioorganic chemistry and novel natural products such as chlorahupetone A from Chloranthus henryi var. hupehensis.