Synthesis of polyhydroxysterols (V): efficient and stereospecific synthesis of 24-methylene-cholest-5-ene-3beta,7alpha-diol and its C-7 epimer

Architecture of the native major royal jelly protein 1 oligomer

Honeybee caste development is nutritionally regulated by royal jelly (RJ). Major royal jelly protein 1 (MRJP1), the most abundant glycoprotein among soluble royal jelly proteins, plays pivotal roles in honeybee nutrition and larvae development, and exhibits broad pharmacological activities in humans. However, its structure has long remained unknown. Herein, we identify and report a 16-molecule architecture of native MRJP1 oligomer containing four MRJP1, four apisimin, and eight unanticipated 24-methylenecholesterol molecules at 2.65 Å resolution. MRJP1 has a unique six-bladed β-propeller fold with three disulfide bonds, and it interacts with apisimin mainly by hydrophobic interaction. Every four 24-methylenecholesterol molecules are packaged by two MRJP1 and two apisimin molecules. This assembly dimerizes to form an H-shaped MRJP1₄-apisimin₄-24-methylenecholesterol₈ complex via apisimin in a conserved and pH-dependent fashion. Our findings offer a structural basis for understanding the pharmacological effects of MRJPs and 24-methylenecholesterol, and provide insights into their unique physiological roles in bees.

Isolation and structure elucidation of natural products of three soft corals and a sponge from the coast of Madagascar

We investigated the three soft corals Sarcophyton stellatum, Capnella fungiformis and Lobophytum crassum and the sponge Pseudoceratina arabica, which have been collected at the coast of Madagascar. In addition to previously known marine natural products, S. stellatum provided the new (+)-enantiomer of the cembranoid (1E,3E,11E)-7,8-epoxycembra-1,3,11,15-tetraene (2). Capnella fungiformis afforded three new natural products, ethyl 5-[(1E,5Z)-2,6-dimethylocta-1,5,7-trienyl]furan-3-carboxylate (6), ethyl 5-[(1E,5E)-2,6-dimethylocta-1,5,7-trienyl]furan-3-carboxylate (7) and the diepoxyguaiane sesquiterpene oxyfungiformin (9a). The extracts of all three soft corals exhibited moderate activities against the malarial parasite Plasmodium falciparum. Extracts of the sponge Pseudoceratina arabica proved to be very active against a series of Gram-positive and Gram-negative bacteria.

Biotransformation of cholesterol and 16,17-alpha epoxypregnenolone by novel Cladosporium sp. strain IS547

Nowadays, there are a few steroid drugs or intermediates that have been obtained via the transformation of microorganisms, and many strains of transformed steroids have not been found yet. Therefore, it is very significant to screen for the strains that have the abilities to transform steroids to produce valuable products. This study has focused on the screen and identification of strains, the structural identification of converted products, and the optimization of transformation conditions, as well as the establishment of transformation systems. A soil microbiota was screened for strain involved in the biotransformation of steroids. A new isolate IS547 is capable of converting a variety of steroids (such as cholesterol, ergosterol, hydrocortisone, progesterone, pregnenolone, and 16,17-alpha-epoxypregnenolone). Based on the 18S rDNA gene sequence comparison, the isolate IS547 has been demonstrated to be very closely related to Cladosporium sp. genus. Present paper is the first report regarding the microbial transformation by Cladosporium sp. to produce active intermediates, which include 7-hydroxy cholesterol, 20-droxyl-16α,17α-epoxypregna-4-dien-3-one, 7-ketocholesterol, and 7-droxyl-16α,17α-epoxypregna-4-dien-3,20-dione. Under the optimum conditions, the yields of product 3 and product 4 were 20.58 and 17.42%, respectively, higher than that prior to the optimization. The transformation rate increased significantly under the optimum fermentation conditions. This study describes an efficient, rapid, and inexpensive biotransformation system for the production of active pharmaceutical intermediates.

Biotransformation of Cholesterol and 16α,17α-Epoxypregnenolone and Isolation of Hydroxylase in Burkholderia cepacia SE-1

The metabolism of cholesterol is critical in eukaryotes as a precursor for vitamins, steroid hormones, and bile acids. Some steroid compounds can be transformed into precursors of steroid medicine by some microorganisms. In this study, the biotransformation products of cholesterol and 16α,17α-epoxypregnenolone produced by Burkholderia cepacia SE-1 were investigated, and a correlative enzyme, hydroxylase, was also studied. The biotransformation products, 7β-hydroxycholesterol, 7-oxocholesterol, and 20-droxyl-16α,17α-epoxypregn-1,4-dien-3-one, were purified by silica gel and Sephadex LH-20 column chromatography and identified by nuclear magnetic resonance and mass spectroscopy. The hydroxylase was isolated from the bacterium and the partial sequences of the hydroxylase, which belong to the catalases/peroxidase family, were analyzed using MS/MS analyses. The enzyme showed activity toward cholesterol and had a specific activity of 37.2 U/mg of protein at 30°C and pH 7.0.

Chemical constituents of the soft corals Sinularia vanderlandi and Sinularia gravis from the coast of Madagascar

The crude extracts of the Madagascan soft corals Sinularia vanderlandi and Sinularia gravis (Alcyoniidae) showed activity against Plasmodium falciparum which led us to study their chemical constituents. The new cadinane-type sesquiterpenoid vanderlandin (1) has been obtained from S. vanderlandi along with 24-methylenecholesterol (2). Four new compounds, the spatane-type diterpenoid gravilin (3), the monoalkylmonoacylglycerol 4, the dihomoditerpenoid ketone 5, and isodecaryiol (9), along with the three known compounds (+)-(S)-geranyllinalool (6), (-)-(R)-nephthenol (7), and 11,12-epoxysarcophytol A (8) have been isolated from the methanol extract of S. gravis. The structures were elucidated based on extensive spectroscopic methods, in particular various 2D NMR techniques. The structure of isodecaryiol (9) including its absolute configuration could be confirmed by X-ray diffraction.

Sterols from Mytilidae show anti-aging and neuroprotective effects via anti-oxidative activity

For screening anti-aging samples from marine natural products, K6001 yeast strain was employed as a bioassay system. The active mussel extract was separated to give an active sterol fraction (SF). SF was further purified, and four sterol compounds were obtained. Their structures were determined to be cholesterol (CHOL), brassicasterol, crinosterol, and 24-methylenecholesterol. All compounds showed similar anti-aging activity. To understand the action mechanism involved, anti-oxidative experiments, reactive oxygen species (ROS) assays, and malondialdehyde (MDA) tests were performed on the most abundant compound, CHOL. Results indicated that treatment with CHOL increases the survival rate of yeast under oxidative stress and decreases ROS and MDA levels. In addition, mutations of uth1, skn7, sod1, and sod2, which feature a K6001 background, were employed and the lifespans of the mutations were not affected by CHOL. These results demonstrate that CHOL exerts anti-aging effects via anti-oxidative stress. Based on the connection between neuroprotection and anti-aging, neuroprotective experiments were performed in PC12 cells. Paraquat was used to induce oxidative stress and the results showed that the CHOL and SF protect the PC12 cells from the injury induced by paraquat. In addition, these substance exhibited nerve growth factor (NGF) mimic activities again confirmed their neuroprotective function.

Polyoxygenated 24,28-epoxyergosterols inhibiting the proliferation of glioma cells from sea anemone Anthopleura midori

Eleven sterols (1-11) and one carotenoid (12) were isolated and identified from sea anemone Anthopleura midori. Compounds 1-6 are rare polyoxygenated ergosterols with a 24,28-epoxy moiety. The structures of these epoxyergosterols were determined by NMR and HRESIMS analyses as well as their chemical-physical properties. Epoxyergosterols 1 and 2 were found to be new natural products and 3-6 are new compounds. Bioactive assay showed that compounds 1, 2, 3, 5, 7, 8, 11, and 12 inhibited the proliferation of rat glioma C6 and human glioma U251 cells with IC50 in a range of 2.41-80.45 μM. Further investigation suggested that 1 and 3 induced apoptosis in glioma cells and 1 blocked U251 cells at the G0/G1 phase.

Polyhydroxylated sterols from the Indonesian soft coral Sinularia sp. and their effect on farnesoid X-activated receptor

Chemical investigation of the Indonesian soft coral Sinularia sp. resulted in the isolation of three known (1, 2 and 7) and five new (3-6 and 8) sterols, characterized by either 24-methylcholestane or gorgostane skeletons. The stereostructures of the new compounds have been elucidated by application of HR-MS and 2D NMR techniques. The isolated steroids have been evaluated for their interaction with the farnesoid X-activated receptor (FXR) and some of them, including the new compound 3 and gorgosterol (7), showed a consistent antagonistic activity, potentially useful for the treatment of cholestasis. The FXR antagonistic activity of gorgosterol (7) was also supported by gene expression experiments. Our results represent the first evaluation of soft coral steroids for interaction with nuclear receptors and qualify gorgosterol (7) as a new chemotype of FXR antagonist.

Acylated pregnane glycosides from Caralluma tuberculata and their antiparasitic activity

Five pregnane glycosides were isolated from Caralluma tuberculata (1-5), in addition to a known one (russelioside E, 6). The structures of the isolated compounds were elucidated by the analysis of NMR data and FAB-MS experiments. All the isolated compounds were tested for their antimalarial and antitrypanosomal activities as well as their cytotoxicity against human diploid embryonic cell line (MRC5).

Steroids: partial synthesis in medicinal chemistry

This article reviews the progress in the chemistry of the steroids that was published between January and December 2004. The reactions and partial synthesis of estrogens, androgens, pregnanes, cholic acid derivatives, cholestanes and vitamin D analogues are covered. There are 127 references.