Dual action antifungal small molecule modulates multidrug efflux and TOR signaling.

There is an urgent need for new strategies to treat invasive fungal infections, which are a leading cause of human mortality. Here, we establish two activities of the natural product beauvericin, which potentiates the activity of the most widely deployed class of antifungal against the leading human fungal pathogens, blocks the emergence of drug resistance, and renders antifungal-resistant pathogens responsive to treatment in mammalian infection models. Harnessing genome sequencing of beauvericin-resistant mutants, affinity purification of a biotinylated beauvericin analog, and biochemical and genetic assays reveals that beauvericin blocks multidrug efflux and inhibits the global regulator TORC1 kinase, thereby activating the protein kinase CK2 and inhibiting the molecular chaperone Hsp90. Substitutions in the multidrug transporter Pdr5 that enable beauvericin efflux impair antifungal efflux, thereby impeding resistance to the drug combination. Thus, dual targeting of multidrug efflux and TOR signaling provides a powerful, broadly effective therapeutic strategy for treating fungal infectious disease that evades resistance.

Oxaspirol B with p97 Inhibitory Activity and Other Oxaspirols from Lecythophora sp. FL1375 and FL1031, Endolichenic Fungi Inhabiting Parmotrema tinctorum and Cladonia evansii.

A new metabolite, oxaspirol D (4), together with oxaspirols B (2) and C (3) were isolated from Lecythophora sp. FL1375, an endolichenic fungus isolated from Parmotrema tinctorum, whereas Lecythophora sp. FL1031 inhabiting the lichen Cladonia evansii afforded oxaspirols A (1), B (2), and C (3). Of these, oxaspirol B (2) showed moderate p97 ATPase inhibitory activity. A detailed characterization of all oxaspirols was undertaken because structures proposed for known oxaspirols have involved incomplete assignments of NMR spectroscopic data leading only to their planar structures. Thus, the naturally occurring isomeric mixture (2a and 2b) of oxaspirol B was separated as their diacetates (5a and 5b) and the structures and absolute configurations of 1, 2a, 2b, 3, and 4 were determined by the application of spectroscopic techniques including two-dimensional NMR and the modified Mosher's ester method. Oxaspirol B (2) and its diacetates 5a and 5b were evaluated for their ATPase inhibitory activities of p97, p97 mutants, and other ATP-utilizing enzymes, and only 2 was found to be active, indicating the requirement of some structural features in oxaspirols for their activity. Additional biochemical and cellular assays suggested that 2 was a reversible, non-ATP competitive, and specific inhibitor of p97.

Functional chromatographic technique for natural product isolation.

Natural product discovery arises through a unique interplay between chromatographic purification and biological assays. Currently, most techniques used for natural product purification deliver leads without a defined biological action. We now describe a technique, referred to herein as functional chromatography, that deploys biological affinity as the matrix for compound isolation.

Structure-activity relationship (SAR) of withanolides to inhibit Hsp90 for its activity in pancreatic cancer cells.

Withaferin A (WA), a naturally occurring steroidal lactone, directly binds to Hsp90 and leads to the degradation of Hsp90 client protein. The purpose of this study is to investigate the structure activity relationship (SAR) of withanolides for their inhibition of Hsp90 and anti-proliferative activities in pancreatic cancer cells. In pancreatic cancer Panc-1 cells, withaferin A (WA) and its four analogues withanolide E (WE), 4-hydroxywithanolide E (HWE), 3-aziridinylwithaferin A (AzWA) inhibited cell proliferation with IC50 ranged from 1.0 to 2.8 µM. WA, WE, HWE, and AzWA also induced caspase-3 activity by 21-, 6-, 11- and 15-fold, respectively, in Panc-1 cells, while withaperuvin (WP) did not show any activity. Our data showed that WA, WE, HWE, and AzWA, but not WP, all directly bound to Hsp90 and induced Hsp90 aggregation,hence inhibited Hsp90 chaperone activity to induce degradation of Hsp90 client proteins Akt and Cdk4 through proteasome-dependent pathway in pancreatic cancer cells. However, only WA, HWE and AzWA disrupted Hsp90-Cdc37 complexes but not WE and WP. SAR study suggested that the C-5(6)-epoxy functional group contributes considerably for withanolide to bind to Hsp90, inhibit Hsp90 chaperone activity, and result in Hsp90 client protein depletion. Meanwhile, the hydroxyl group at C-4 of ring A may enhance withanolide to inhibit Hsp90 activity and disrupt Hsp90-Cdc37 interaction. These SAR data provide possible mechanisms of anti-proliferative action of withanolides.

In-vitro cell migration enhancing constituents from Decalepis hamiltonii, a plant used in the preparation of 'Pinda oil', a medicinal oil used in Ayurveda for wound management.

Decalepis hamiltonii, Wight & Arn. (Apocyanaceae) is a one of the raw materials used in the preparation of 'Pinda oil', a medicinal oil which is used for treatment of wounds in Ayurveda. Of the hexanes, dichloromethane, and ethyl acetate extracts derived from the plant raw materials used to prepare 'Pinda oil', the hexanes extract of D. hamiltonii exhibited the highest mean percentage wound closure (75.1 ± 2.9) compared to the negative controls (1% DMSO in DMEM, 4.2 ± 1.2 and 100% DMEM, 4.1 ± 0.9) in the scratch wound assay (SWA). Fractionation of the hexanes extract of stem of D. hamiltonii led to the isolation of 2-hydroxy-4-methoxybenzaldehyde (1) and a mixture of long chain esters of lupeol (2), which showed enhanced cell migration in SWA. It was observed that the esters of lupeol bind to the cell membrane and/or enter the cells during the SWA. It was found that these constituents are also present in 'Pinda oil' which may contribute to the enhancement of wound healing activity of 'Pinda oil'.

Synthesis and biological evaluation of novobiocin analogues as potential heat shock protein 90 inhibitors.

Recent studies have shown that novobiocin (NB), a member of the coumermycin (CA) family of antibiotics with demonstrated DNA gyrase inhibitory activity, inhibits Heat shock protein 90 (HSP90) by binding weakly to a putative ATP-binding site within its C-terminus. To develop more potent HSP90 inhibitors that target this site and to define structure-activity relationships (SARs) for this class of compounds, we have synthesized twenty seven 3-amido-7-noviosylcoumarin analogues starting from NB and CA. These were evaluated for evidence of HSP90 inhibition using several biological assays including inhibition of cell proliferation and cell cycle arrest, induction of the heat shock response, inhibition of luciferase-refolding in vitro, and depletion of the HSP90 client protein c-erbB-2/HER-2/neu (HER2). This SAR study revealed that a substantial increase in biological activity can be achieved by introduction of an indole-2-carboxamide group in place of 4-hydroxy-isopentylbenzamido group at C-3 of NB in addition to removal/derivatization of the 4-hydroxyl group from the coumarin ring. Methylation of the 4-hydroxyl group in the coumarin moiety moderately increased biological activity as shown by compounds 11 and 13. Our most potent new analogue 19 demonstrated biological activities consistent with known HSP90-binding agents, but with greater potency than NB.

A rare phytosterol, stigmast-5-en-3ß,7α,22α-triol and other secondary metabolites from Leea indica showing enhanced in vitro cell migration and proangiogenic activity.

Leea indica (Burm. f.) Merr. (Vitaceae) is used for the treatment of wounds in traditional medicine practiced in Sri Lanka. The current study is carried out to investigate its wound healing potential in terms of in vitro cell migration and proangiogenic activity. The scratch wound assay (SWA) guided fractionation of dichloromethane extract of L. indica led to the isolation of a rare phytosterol, stigmast-5-en-3ß,7α,22α-triol (1), betulin (2), lupeol (3), and ß-sitosterol (4) all of which showed enhanced cell migration in SWA and significant proangiogenic response in chorioallantoic membrane (CAM) assay. The identities of compounds 1-4 were established by the analysis of NMR spectroscopic data and comparison with those reported. This is the first report of the occurrence of compounds 1 and 2 in L. indica.

In-vitro cell migration enhancing and pro-angiogenic active secondary metabolites from Jeffreycia zeylanica (L.) H. Rob., S.C. Keeley & Skvarla (Asteraceae).

Jeffreycia zeylanica (L.) H. Rob., S. C. Keeley & Skvarla is used for the treatment of wounds in indigenous medicine practiced in Sri Lanka. The scratch wound assay (SWA) guided fractionation of hexanes extract of J. zeylanica led to the isolation of ethuliacoumarin (1), stigmasterol (2), ß-amyrin (3) and lupeol (4) and a non-resolved triterpene alcohol mixture HF5D1, all of which showed enhanced cell migration. The mixture HF5D1 contained glut-5-en-3ß-ol (5) and friedelin-3ß-ol (6). The identities of compounds 1-6 were established by the analysis of spectroscopic data and comparison of them with those reported. The compounds 1-4 and the non-resolved triterpene alcohol mixture, HF5D1 also exhibited significant proangiogenic response in chorioallantoic membrane (CAM) assay in addition to the enhanced cell migration. This is the first report of the occurrence of the compounds 1, 2, 4 and 5 in this plant.

Reassignment of NMR spectroscopic data of oleana-9(11),12-diene-3ß-ol isolated from Jeffreycia zeylanica and its wound healing potential in terms of cell migration and proangiogenic activity1.

Jeffreycia zeylanica (Asteraceae), a plant endemic to Sri Lanka, is used for the treatment of wounds. The scratch wound assay (SWA) guided fractionation of hexanes extract of J. zeylanica led to the isolation of oleana-9(11),12-diene-3ß-ol (1) which showed enhanced cell migration in SWA and significant proangiogenic response in chorioallantoic membrane (CAM) assay. Since the reported 1H NMR assignments of 1 were incomplete, and some 13C NMR assignments were inconsistent with our observations, reassignment of NMR spectroscopic data of 1 was carried out. Herein we report unambiguous assignment of NMR data of 1 based on 1D and 2D NMR spectra. This is the first report of 1 in J. zeylanica.

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 Mosher's 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,ß-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.

Asperpyrone D and other metabolites of the plant-associated fungal strain Aspergillus tubingensis.

Bioactivity-guided fractionation of a cytotoxic extract of Aspergillus tubingensis, a fungal strain occurring in the rhizosphere of the Sonoran desert plant, Fallugia paradoxa, afforded a dimeric naphtho-gamma-pyrone asperpyrone D, nine known naphtho-gamma-pyrones, funalenone, and the cytotoxic cyclic penta-peptide, malformin A1.

Citriquinones A and B, new benzoquinones from Penicillium citrinum.

Two new benzoquinones, citriquinone A (1) and B (2), were isolated from the methanol extract of a soil fungus, Penicillium citrinum. The structures of the new compounds were determined on the basis of detailed spectroscopic analysis. Citriquinone A (1) exhibited antibacterial activity against Bacillus sp. and cell migration inhibitory activity (CMIA) against human cancer cell line HEp 2.

Microbial biotransformation of 16α,17-epoxy-ent-kaurane-19-oic acid by Beauveria sulfurescens ATCC 7159-F.

Biotransformation of 16alpha,17-epoxy-ent-kaurane-19-oic acid (1) by Beauveria sulfurescens ATCC 7159-F led to the production of a new ent-kaurane diterpenoid, 7beta,17-dihydroxy-ent-kaur-15-en-19-oic acid (7), and four other ent-kauranes (8 - 11), all of which were identified as their methyl esters. Compounds 9 and 10 were found to be new stereoisomers. Structures of these were established by the extensive usage of their spectroscopic characteristics.

Actin microfilament aggregation induced by withaferin A is mediated by annexin II.

The actin cytoskeleton supports diverse cellular processes such as endocytosis, oriented growth, adhesion and migration. The dynamic nature of the cytoskeleton, however, has made it difficult to define the roles of the many accessory molecules that modulate actin organization, especially the multifunctional adapter protein annexin II. We now report that the compound withaferin A (1) can alter cytoskeletal architecture in a previously unknown manner by covalently binding annexin II and stimulating its basal F-actin cross-linking activity. Drug-mediated disruption of F-actin organization is dependent on annexin II expression by cells and markedly limits their migratory and invasive capabilities at subcytotoxic concentrations. Given the extensive ethnobotanical history of withaferin-containing plant preparations in the treatment of cancer and inflammatory and neurological disorders, we suggest that annexin II represents a feasible, previously unexploited target for therapeutic intervention by small-molecule drugs.