Colletofragarone A2 and Colletoins A-C from a Fungus Colletotrichum sp. Decrease Mutant p53 Levels in Cells

Natural ten-membered lactones: sources, structural diversity, biological activity, and intriguing future

Covering: 2012 to 2022Ten-membered lactones (TMLs) are an interesting and diverse group of natural polyketides that are abundant in fungi and, to a lesser extent, in bacteria, marine organisms, and insects. TMLs are known for their ability to exhibit a wide spectrum of biological activity, including phytotoxic, cytotoxic, antifungal, antibacterial, and others. However, the random discovery of these compounds by scientific groups with various interests worldwide has resulted in patchy information about their distribution among different organisms and their biological activity. Therefore, despite more than 60 years of research history, there is still no common understanding of the natural sources of TMLs, their structural type classification, and most characteristic biological activities. The controversial nomenclature, incorrect or erroneous structure elucidation, poor identification of producing organisms, and scattered information on the biological activity of compounds - all these factors have led to the problems with dereplication and the directed search for TMLs. This review consists of two parts: the first part (Section 2) covers 104 natural TMLs, published between 2012 and 2022 (after the publishing of the previous review), and the second part (Section 3) summarizes information about 214 TMLs described during 1964-2022 and as a result highlights the main problems and trends in the study of these intriguing natural products.

A monoacylglyceryltrimethylhomoserine, 21F121-A, containing a branched acyl group from Penicillium glaucoroseum

A new monoacylglyceryltrimethylhomoserine, 21F121-A (1), was isolated from the culture of Penicillium glaucoroseum (21F00121) by LCMS-guided purification. The structure was elucidated by NMR and mass spectrometries. The absolute configuration of the homoserine moiety was analyzed by the ECD spectrum after acid hydrolysis, and the S-configuration of the glycerol moiety was determined based on the spectrum of the 1,2-dibenzoyl derivative after acid hydrolysis. Although a variety of diacylglyceryltrimethylhomoserine is distributed in lower plants and fungi, a limited number of studies on monoacyl derivatives have been reported. This is the fourth sample of monoacylglyceryltrimethylhomoserine discovered from a natural source, and the second sample isolated from a fungus. Compound 1 contains an unusual branched pentaene chain attached at the sn-1 position of glycerol and weakly inhibited the growth of HCT116 cells.

Arteperoxides A-C, tris-normonoterpene-sesquiterpene conjugates with peroxide-bridges from Artemisia judaica exhibiting antiosteoclastogenic activity

Antiosteoclastogenic-guided screening was conducted with 120 extracts of the medicinal plants collected in Egypt that led to the selection of Artemisia judaica L. (Asteraceae). Three undescribed davanone-related terpenoids, arteperoxides A-C, were isolated from the extract with two known derivatives, hydroxydavanone and davana acid. Structural analysis revealed that arteperoxides A-C were tris-normonoterpene-sesquiterpene conjugates with peroxide bridges. Although davanone derivatives with peroxides, such as a hydroperoxyl and peroxyhemiketal groups, have been isolated from Artemisia species, arteperoxides A-C are the first variations observed to contain peroxide bridges between two terpene-derived units. The absolute configurations of arteperoxides A and B were studied based on their spectroscopic data compared with those of the semisynthetic analogs that have ether linkages. The natural and synthetic compounds were tested for the antiosteoclastogenic activity, and arteperoxide C and hydroxydavanone were more potent than other compounds at 20 μM.

Colletofragarone A2 Inhibits Cancer Cell Growth In Vivo and Leads to the Degradation and Aggregation of Mutant p53

Mutant p53 not only loses its original tumor suppressor function but also acquires new abilities regarding oncogenic progression. Therefore, the strategy of targeting mutant p53 has attracted attention for cancer therapy. We isolated colletofragarone A2 (CF) from the fungus Colletotrichum sp. (13S020), which decreases mutant p53 levels in cells, and herein examine its effect on mutant p53. CF showed more potent cytotoxic activities on cells with p53R175H structural mutants than those with different p53 statuses such as a DNA-contact mutant, wild-type, and null cells. CF markedly decreased tumor cell growth in vivo using a mouse xenograft model with HuCCT1 (p53R175H) cells. Cotreatment of SK-BR-3 (p53R175H) cells with CF and cycloheximide decreased mutant p53 levels by promoting p53 degradation. In the presence of MG-132, CF induced the accumulation of the aggregated mutant p53. These results suggest that CF inhibits the function of molecular chaperones such as HSP90.

Shikinefragalides A-D, new tricyclic macrolides produced by Stachybotryaceae sp. FKI-9632

Four new tricyclic macrolides, named shikinefragalides A (1), B (2), C (3) and D (4), were isolated by physicochemical (PC) screening from a static culture material of Stachybotryaceae sp. FKI-9632. Their structures were elucidated as new analogs of colletofragarones by MS and NMR analyses. Compounds 1 and 2 showed weak antimalarial activity and cytotoxicity.