Structure Elucidation of the Main Tetrahydroxyxanthones of Hypericum Seeds and Investigations into the Testa Structure

Polyprenylated Benzophenones and Tocotrienol Derivatives from the Edible Fruits of Garcinia oblongifolia Champ. ex Benth. and Their Cytotoxicity Activity

The fruits of Garcinia oblongifolia Champ. ex Benth. were famous as an edible fruit in tropical regions of China. Because of its unique taste and great nutritional value, the ripe fresh fruits of G. oblongifolia could be eaten directly or used as raw materials for natural beverages and food supplements. In this work, six new polyprenylated benzophenones (1-6) and one new dimeric tocotrienol derivative (7), together with 18 known ones (8-25), were isolated from the fruits of G. oblongifolia. Compounds 1-4 were peculiar polycyclic polyprenylated acylphloroglucinols (PPAPs) featuring the rare carbon skeleton of a bicyclo[3.4.1]decane-1,3-diketone. Moreover, all isolates (1-25) were evaluated for their cytotoxicity activities against nasopharyngeal carcinoma (NPC) cell lines (CNE1 and CNE2). Among these isolates, compound 6 exhibited the strongest cytotoxicity activity on CNE1 and CNE2 cells with the IC₅₀ values of 7.8 ± 0.2 and 9.1 ± 0.3 μM, respectively. Further mechanistic investigation demonstrated that 6 could induce mitophagy to promote Caspase-9/GSDME-mediated pyroptosis through triggering ROS in NPC cells.

Three New Xanthones from Hypericum scabrum and Their Quorum Sensing Inhibitory Activities against Chromobacterium violaceum

Quorum sensing (QS) plays an important role in the production of virulence factors and pathogenicity in pathogenic bacteria and is, therefore, a hopeful target to fight against bacterial infections. During our search for natural QS inhibitors, two new xanthonolignoids (1 and 2), each existing as a racemic mixture, one new simple oxygenated xanthone (7), and eight known analogs (3–6, 8–11) were isolated from Hypericum scabrum Linn. Chiral separation of 1 yielded a pair of enantiomers 1a and 1b. The structures of these compounds were elucidated by spectroscopic analysis and ECD (electrostatic circular dichroism) calculations. All isolates were evaluated for their QS inhibitory activity against Chromobacterium violaceum. Both 9 and 10 exhibited the most potent QS inhibitory effects with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of 31.25 and 62.5 μM, respectively. Crystal violet staining was used to further evaluate the biofilm inhibition potential of compounds 7, 9 and 10, and the formation of biofilms increased with decreasing drug concentration in a classic dose-dependent manner. The results of a cytotoxicity assay revealed that compounds 7, 9 and 10 exhibited no cytotoxic activity on PC-12 cells at the tested concentration.

Recent advances in the synthesis of xanthones and azaxanthones

A useful chemical toolbox for (aza)xanthones from 2012 to 2020 that covers the optimization of known procedures and novel methodologies.