Three new depsidones, parmosidones F – G (1 – 2), and 8′-O-methylsalazinic acid (3), and 3 new diphenylethers, parmetherines A – C (4 – 6), together with 2 known congeners were isolated from the whole thalli of Parmotrema dilatatum, a foliose chlorolichen. Their structures were unambiguously determined by extensive spectroscopic analyses and comparison with literature data. The isolated polyphenolics were assayed for their α-glucosidase inhibitory activities. Newly reported benzylated depsidones 1 and 2 in particular inhibited α-glucosidase with IC50 values of 2.2 and 4.3 µM, respectively, and are thus more potent than the positive control, acarbose.

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This study investigated a set of new potential antidiabetes agents. Derivatives of usnic acid were designed and synthesized. These analogs and nineteen benzylidene analogs from a previous study were evaluated for enzyme inhibition of α‐glucosidase. Analogs synthesized using the Dakin oxidative method displayed stronger activity than the pristine usnic acid (IC50>200 μM). Methyl (2E,3R)‐7‐acetyl‐4,6‐dihydroxy‐2‐(2‐methoxy‐2‐oxoethylidene)‐3,5‐dimethyl‐2,3‐dihydro‐1‐benzofuran‐3‐carboxylate (6b) and 1,1′‐(2,4,6‐trihydroxy‐5‐methyl‐1,3‐phenylene)di(ethan‐1‐one) (6e) were more potent than an acarbose positive control (IC50 93.6±0.49 μM), with IC50 values of 42.6±1.30 and 90.8±0.32 μM, respectively. Most of the compounds synthesized from the benzylidene series displayed promising activity. (9bR)‐2,6‐Bis[(2E)‐3‐(2‐chlorophenyl)prop‐2‐enoyl]‐3,7,9‐trihydroxy‐8,9b‐dimethyldibenzo[b,d]furan‐1(9bH)‐one (1c), (9bR)‐3,7,9‐trihydroxy‐8,9b‐dimethyl‐2,6‐bis[(2E)‐3‐phenylprop‐2‐enoyl]dibenzo[b,d]furan‐1(9bH)‐one (1g), (9bR)‐2‐acetyl‐6‐[(2E)‐3‐(2‐chlorophenyl)prop‐2‐enoyl]‐3,7,9‐trihydroxy‐8,9b‐dimethyldibenzo[b,d]furan‐1(9bH)‐one (2d), (9bR)‐2‐acetyl‐6‐[(2E)‐3‐(3‐chlorophenyl)prop‐2‐enoyl]‐3,7,9‐trihydroxy‐8,9b‐dimethyldibenzo[b,d]furan‐1(9bH)‐one (2e), (6bR)‐8‐acetyl‐3‐(4‐chlorophenyl)‐6,9‐dihydroxy‐5,6b‐dimethyl‐2,3‐dihydro‐1H‐[1]benzofuro[2,3‐f][1]benzopyran‐1,7(6bH)‐dione (3e), (6bR)‐8‐acetyl‐6,9‐dihydroxy‐5,6b‐dimethyl‐3‐phenyl‐2,3‐dihydro‐1H‐[1]benzofuro[2,3‐f][1]benzopyran‐1,7(6bH)‐dione (3h), (6bR)‐3‐(2‐chlorophenyl)‐8‐[(2E)‐3‐(2‐chlorophenyl)prop‐2‐enoyl]‐6,9‐dihydroxy‐5,6b‐dimethyl‐2,3‐dihydro‐1H‐[1]benzofuro[2,3‐f][1]benzopyran‐1,7(6bH)‐dione (4b), and (9bR)‐6‐acetyl‐3,7,9‐trihydroxy‐8,9b‐dimethyl‐2‐[(2E)‐3‐phenylprop‐2‐enoyl]dibenzo[b,d]furan‐1(9bH)‐one (5c) were the most potent α‐glucosidase enzyme inhibitors, with IC50 values of 7.0±0.24, 15.5±0.49, 7.5±0.92, 10.9±0.56, 1.5±0.62, 15.3±0.54, 19.0±1.00, and 12.3±0.53 μM, respectively.

A novel oxime polyketide, maydisone (1), along with two known compounds, 7-hydroxy-2,5dimethylchromone (2) and 2,5-dimethylbenzoic acid (3) were isolated from the cultures of Bipolaris maydis. Their structures were identified by the application of NMR and MS data analyses and comparison with previous reports. Compound 1 showed the most powerful inhibition of α-glucosidase, with an IC 50 value of 68.30 ± 0.83 µM.

The lichen Usnea baileyi is a fruticose lichen belonging to the Usnea genus. It is well known as a rich source of natural xanthone dimers and possesses various bioactivities. Nevertheless, the chemical investigation on this type of lichen is still rare as most of researches reported its components without structural elucidation. Herein, in the continuous study on this type of lichen, we further isolate xanthone dimers from the dichloromethane extract and explore three new xanthone dimers, eumitrins F−H (1−3). Their structures were elucidated unambiguously by spectroscopic analyses, including high resolution electrospray ionisation mass spectrometry (HRESIMS), 1D and 2D nuclear magnetic resonance spectroscopy (1D and 2D NMR), and DP4 probability. All compounds were evaluated for their enzyme inhibition against αglucosidase, tyrosinase, and antibacterial activity. They revealed moderate antimicrobial and weak tyrosinase inhibition. For α-glucosidase inhibition, compound 3 displayed the most significant inhibitory against α-glucosidase possessing an IC50 value of 64.2 µM.

Chemical investigation of the lichen Parmotrema dilatatum led to the isolation of a new chlorinated compound, named dilatatone (1), along with a known compound, sernanderin (2).Their chemical structures were determined by analysis of their 1D and 2D NMR spectra, HRESIMS, and ECD data. Both compounds showed weak α-glucosidase activity.

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Synthesis of Pendant Polyaminopolycarboxylic Acid Crown Ethers:Potential Ligands for MRI Contrasting Agents.--(LAKSHMI, B.; DEVI, A. P.; NAGARAJAN, M.; J.