The chemokine receptor, CCR2, is predominantly expressed on monocytes/macrophages, and on a subset of memory T cells. It binds to several CC type chemokines of the monocyte chemoattractant protein ...(MCP) family of which MCP-1 exhibits the highest affinity. CCR2/MCP-1 expression/association in monocyte/macrophage/T cells has been associated with inflammatory processes such as rheumatoid arthritis, multiple sclerosis and atherosclerosis. Neutralization of CCR2 with either a peptide or receptor antagonist results in the prevention of joint swelling in rodent models of arthritis. In this paper, bioassay-guided discovery of CCR2 receptor antagonists derived from natural product extracts are reported. These antagonists belong to two main classes exemplified by bisthiodiketopiperazines and cytochalasins. Six compounds, including emestrin, two new emestrin analogs, and chaetomin represent the first group of compounds. These compounds inhibited the binding of MCP-1 to CCR2 (CHO membrane) with IC50 values of 0.8 to 9 microM and exhibited good activity in a whole cell assay using MCP-1 and human monocytes with IC50's ranging from 4-9 microM. Cytochalasins A and B represented the second group and inhibited the binding activity with IC50 values of 5 and 188 microM, respectively. This is the first report of natural product antagonists of the CCR2 receptor.
The potent insecticidal agent nodulisporic acid A (1a), representative of a new class of indole terpenes, was isolated from fermentations of a Nodulisporium sp. Nodulisporic acid A was active against ...the larvae of the blowfly and mosquito at sub-part-per-million levels. The structure followed mainly from a consideration of spectroscopic evidence, including Dunkel's computerized 2D INADEQUATE analysis. The relative stereochemistry of the eastern and western hemispheres of 1a and its methyl ester, 1b, were independently determined on the basis of ROESY, NOESY, NOEDS, and J vic evidence. By employing the same methods, the complete relative stereochemistry was determined by analysis of suitable transformation products, using the reduced β-ketodihydropyrrole ring as a stereochemical bridge between the two zones. These results were confirmed by X-ray analysis of the 7-p-bromobenzoate methyl ester derivative, 1c. The absolute stereochemistry was established by application of the advanced Mosher method to methyl ester 1b. Of biogenetic interest is the presence of a unique isoprenylated indole moiety not previously found in other indole mycotoxins.
Xanthonol, a novel dimeric xanthone, was isolated from a fermentation broth of a non-sporulating fungal species using Sephadex LH20 followed by HPLC and the structure elucidated by spectral analysis. ...Xanthonol exhibited insecticidal and anthelmintic activities against larvae of Lucilia sericata, Aedes aegypti, and Haemonchus contortus with LD90 of 33, 8, and 50 microg/ml, respectively.
Cholesterol homeostasis is tightly controlled process that involves a variety of regulators including liver X receptors (LXR). Agonists of LXR are expected to increase cholesterol efflux, lower LDL, ...and raise HDL levels. Screening of a natural product library of microbial extracts using a LXR-scintillation proximity assay (SPA) binding assay and bioassay-guided fractionation of a number of fungal extracts led to the isolation of five ergostane and a cycloartane derivative. These compounds exhibited IC50 value ranging 0.5 approximately 9 microM in the binding assay for a-receptor and a number of these showed in vitro agonist activity in the coactivator association assays but lacked the cell based LXR activation. The isolation and LXR activity of these compounds are described.
HIV-1 integrase is one of the three enzymes that are critical for replication and spread of HIV and its inhibition is one of the most promising new drug targets for anti-retroviral therapy with ...potential advantage over existing therapies. This paper describes the isolation and structure elucidation of exophillic acid, a novel dimeric 2, 4-dihydroxy alkyl benzoic acid, derived from Exophiala pisciphila, a fungus isolated from a soil sample collected in Georgia, USA. Exophillic acid (1) and aquastatin A (2), a related compound, inhibited the strand transfer reaction of HIV-1 integrase with IC50 values of 68 and 50μM, respectively.
Integracides, 4,4-dimethylergostane triterpenoids, are inhibitors of HIV-1 integrase, a critical enzyme in replication of HIV-1. The chemistry and structure−activity relationship of integracide B and ...related natural products are described. A charged group, e.g., a sulfate, carboxyl, or amino, is required for the HIV-1 integrase activity. These compounds showed HIV-1 integrase activity with IC50 values in the range 4.8−15 μM and exhibited antiviral activity in a viral spread assay, but with only a small or no therapeutic window.
Discovery and development of podocarpic acid dimers (e.g., 3–5) are described.
Liver X receptors are nuclear receptors that regulate metabolism of cholesterol. They are activated by oxysterols ...resulting in increased transcription of the ABCA1 gene, promoting cholesterol efflux and HDL formation. We have identified podocarpic acid anhydride as a 1
nM agonist of LXRα and β receptors. Functionally this agonist was over 8–10-fold better activator of LXR receptors compared to one of the natural ligands, 22-(
R)-hydroxy cholesterol, in HEK-293 cells. An imide analog increased the level of HDL by 26%, decreased LDL by 10.6%, and increased triglyceride by 51% in hamsters. Discovery, synthesis, SAR and details of the activities of dimers have been described.
HIV-1 integrase is a critical enzyme in the replication of HIV-1. It is absent in the host cells and therefore is a good target for treatment of HIV-1 infections. Integracides are members of the ...tetracyclic triterpenoids family that were isolated from the fermentation broth of a Fusarium sp. Integracide A, a sulfated ester, exhibited significant inhibitory activity against strand transfer reaction of HIV-1 integrase. The discovery, structure elucidation including single crystal X-ray structure and HIV-1 inhibitory activity of these compounds are described.
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