Manping X. Liu

Geopyxins A-E, ent-kaurane diterpenoids from endolichenic fungal strains Geopyxis aff. majalis and Geopyxis sp. AZ0066: structure-activity relationships of geopyxins and their analogues.

Four new ent-kaurane diterpenoids, geopyxins A-D (1-4), were isolated from Geopyxis aff. majalis, a fungus occurring in the lichen Pseudevernia intensa, whereas Geopyxis sp. AZ0066 inhabiting the same host afforded two new ent-kaurane diterpenoids, geopyxins E and F (5 and 6), together with 1 and 3. The structures of 1-6 were established on the basis of their spectroscopic data, while the absolute configurations were assigned using modified Moshers ester method. Methylation of 1-3, 5, and 6 gave their corresponding methyl esters 7-11. On acetylation, 1 and 7 yielded their corresponding monoacetates 12 and 14 and diacetates 13 and 15. All compounds were evaluated for their cytotoxic and heat-shock induction activities. Compounds 2, 7-10, 12, 14, and 15 showed cytotoxic activity in the low micromolar range against all five cancer cell lines tested, but only compounds 7-9, 14, and 15 were found to activate the heat-shock response at similar concentrations. From a preliminary structure-activity perspective, the electrophilic α,β-unsaturated ketone carbonyl motif present in all compounds except 6 and 11 was found to be necessary but not sufficient for both cytotoxicity and heat-shock activation.

Smardaesidins A - G, Isopimarane and 20-Nor-isopimarane Diterpenoids from Smardaea sp., a Fungal Endophyte of the Moss Ceratodon purpureus

Five new isopimarane diterpenes, smardaesidins A-E (1- 5) and two new 20-nor-isopimarane diterpenes, smardaesidins F (6) and G (7), together with sphaeropsidins A (8) and C-F (10-13) were isolated from an endophytic fungal strain, Smardaea sp. AZ0432, occurring in living photosynthetic tissue of the moss Ceratodon purpureus . Of these, smardaesidins B (2) and C (3) were obtained as an inseparable mixture of isomers. Chemical reduction of sphaeropsidin A (8) afforded sphaeropsidin B (9), whereas catalytic hydrogenation of 8 yielded 7-O-15,16-tetrahydrosphaeropsidin A (14) and its new derivative, 7-hydroxy-6-oxoisopimara-7-en-20-oic acid (15). The acetylation and diazomethane reaction of sphaeropsidin A (8) afforded two of its known derivatives, 6-O-acetylsphaeropsidin A (16) and 8,14-methylenesphaeropsidin A methyl ester (17), respectively. Methylation of 10 yielded sphaeropsidin C methyl ester (18). The planar structures and relative configurations of the new compounds 1-7 and 15 were elucidated using MS and 1D and 2D NMR experiments, while the absolute configurations of the stereocenters of 4 and 6-8 were assigned using a modified Moshers ester method, CD spectra, and comparison of specific rotation data with literature values. Compounds 1-18 were evaluated for their potential anticancer activity using several cancer cell lines and cells derived from normal human primary fibroblasts. Of these, compounds 8, 11, and 16 showed significant cytotoxic activity. More importantly, sphaeropsidin A (8) showed cell-type selectivity in the cytotoxicity assay and inhibited migration of metastatic breast adenocarcinoma (MDA-MB-231) cells at subcytotoxic concentrations.

Structure–Activity Relationships for Withanolides as Inducers of the Cellular Heat-Shock Response

To understand the relationship between the structure and the remarkably diverse bioactivities reported for withanolides, we obtained withaferin A (WA; 1) and 36 analogues (2-37) and compared their cytotoxicity to cytoprotective heat-shock-inducing activity (HSA). By analyzing structure-activity relationships for the series, we found that the ring A enone is essential for both bioactivities. Acetylation of 27-OH of 4-epi-WA (28) to 33 enhanced both activities, whereas introduction of β-OH to WA at C-12 (29) and C-15 (30) decreased both activities. Introduction of β-OAc to 4,27-diacetyl-WA (16) at C-15 (37) decreased HSA without affecting cytotoxicity, but at C-12 (36), it had minimal effect. Importantly, acetylation of 27-OH, yielding 15 from 1, 16 from 14, and 35 from 34, enhanced HSA without increasing cytotoxicity. Our findings demonstrate that the withanolide scaffold can be modified to enhance HSA selectively, thereby assisting development of natural product-inspired drugs to combat protein aggregation-associated diseases by stimulating cellular defense mechanisms.

Sesquiterpenes and other constituents of Xylaria sp. NC1214, a fungal endophyte of the moss Hypnum sp.

Oxygenated guaiane-type sesquiterpenes, xylaguaianols A-D (1-4), an iso-cadinane-type sesquiterpene isocadinanol A (5), and an α-pyrone 9-hydroxyxylarone (6), together with five known sesquiterpenes (7-11), and four known cytochalasins (12-15) were isolated from a culture broth of Xylaria sp. NC1214, a fungal endophyte of the moss Hypnum sp. The structures of all compounds were elucidated by the analysis of their spectroscopic data and relative configurations of 1-5 were determined with the help of NMR NOESY experiments. Cytochalasins C (12), D (13), and Q (14) were investigated for their cytotoxic activity against five tumor cell lines. Cytochalasin D showed significant cytotoxicity against all five cell lines, with IC50s ranging from 0.22 to 1.44 μM, whereas cytochalasins C and Q exhibited moderate, but selective cytotoxicity.

17β-Hydroxy-18-acetoxywithanolides from Aeroponically Grown Physalis crassifolia and Their Potent and Selective Cytotoxicity for Prostate Cancer Cells

When cultivated under aeroponic growth conditions, Physalis crassifolia produced 11 new withanolides (1-11) and seven known withanolides (12-18) including those obtained from the wild-crafted plant. The structures of the new withanolides were elucidated by the application of spectroscopic techniques, and the known withanolides were identified by comparison of their spectroscopic data with those reported. Withanolides 1-11 and 16 were evaluated for their potential anticancer activity using five tumor cell lines. Of these, the 17β-hydroxy-18-acetoxywithanolides 1, 2, 6, 7, and 16 showed potent antiproliferative activity, with some having selectivity for prostate adenocarcinoma (LNCaP and PC-3M) compared to the breast adenocarcinoma (MCF-7), non-small-cell lung cancer (NCI-H460), and CNS glioma (SF-268) cell lines used. The cytotoxicity data obtained for 12-15, 17, and 19 have provided additional structure-activity relationship information for the 17β-hydroxy-18-acetoxywithanolides.

Discovery of Potent 17β-Hydroxywithanolides for Castration-Resistant Prostate Cancer by High-Throughput Screening of a Natural Products Library for Androgen-Induced Gene Expression Inhibitors

Prostate cancer (PC) is the second most prevalent cancer among men in Western societies, and those who develop metastatic castration-resistant PC (CRPC) invariably succumb to the disease. The need for effective treatments for CRPC is a pressing concern, especially due to limited durable responses with currently employed therapies. Here, we demonstrate the successful application of a high-throughput gene-expression profiling assay directly targeting genes of the androgen receptor pathway to screen a natural products library leading to the identification of 17β-hydroxywithanolides 1-5, of which physachenolide D (5) exhibited potent and selective in vitro activity against two PC cell lines, LNCaP and PC-3. Epoxidation of 5 afforded physachenolide C (6) with higher potency and stability. Structure-activity relationships for withanolides as potential anti-PC agents are presented together with in vivo efficacy studies on compound 6, suggesting that 17β-hydroxywithanolides are promising candidates for further development as CRPC therapeutics.