Antifungal activity of sterols and dipsacus saponins isolated from Dipsacus asper roots against phytopathogenic fungi

The in vivo antifungal activity of crude extracts of Dipsacus asper roots was evaluated against the phytopathogenic fungi Botrytis cinerea, Colletotrichum coccodes, Blumeria graminis f. sp. hordei, Magnaporthe grisea, Phytophthora infestans, Puccinia recondita and Rhizoctonia solani using a whole-plant assay method. Ethyl acetate and acetone extracts, at 1000μg/mL, suppressed the development of tomato gray mold (TGM) and tomato late blight (TLB) by 90%. Through bioassay-guided isolation, five antifungal substances were isolated from the D. asper roots and identified as β-sitosterol (1), campesterol (2), stigmasterol (3), cauloside A (4) and a novel dipsacus saponin, named colchiside (3-O-β-d-xylopyranosyl-23-O-β-d-glucopyranosyl-28-O-β-d-(6-O-acetyl)-glucopyranosyl hederagenin) (5). Of those, cauloside A (4) displayed the greatest antifungal efficacy against rice blast, TGM and TLB. Colchiside (5) moderately suppressed the development of TLB, but exhibited little effect against the other diseases. The synergistic effects of the isolated compounds against TLB were also assessed. Synergistic and additive interactions were observed between several of the sterol compounds. This study indicated that the crude extracts of, and bioactive substances from, the roots of D. asper suppress TGM and TLB. In addition, cauloside A (4) and colchiside (5) could be used as antifungal lead compounds.

Six new furostanol glycosides from Smilax glauco-china and their cytotoxic activity

Six new steroidal saponins, namely glauco-chinaosides A-F, and one known compound were isolated from the tubers of Smilax glauco-china. Their structures were elucidated by a combination of spectroscopic analysis and hydrolysis followed by spectral and chromatographic analysis. Compounds 1-7 were tested in vitro for their cytotoxic activities against four human tumor cell lines (SH-SY5Y, SGC-7901, HCT-116, and Lovo). Compounds 1, 2, and 5 exhibited cytotoxic activity against SGC-7901, with IC₅₀ values of 2.7, 11.5, and 6.8 μM, respectively.

Sterols from the Octocoral Nephthea columnaris

Two new sterols, columnaristerols B (1) and C (2), along with two known analogues, 5,6-epoxylitosterol (3) and litosterol (4), were obtained from the octocoral Nephthea columnaris. The structures of new sterols 1 and 2 were elucidated by using spectroscopic methods and comparing the spectroscopic data with those of known related metabolites. Sterol 3 was found to suppress superoxide anion production and elastase secretion by human neutrophils.

UV-C radiation increases sterol production in the microalga Pavlova lutheri

Plant sterols have become well-known to promote cardiovascular health through the reduction of low density lipoprotein cholesterol in the blood. Plant sterols also have anti-inflammatory, anti-cancer, anti-oxidative and anti-atherogenicity activities. Microalgae have the potential to become a useful alternative source of plant sterols with several species reported to have higher concentrations than current commercial ones. In order to increase phytosterol production and optimise culture conditions, the high sterol producer Pavlova lutheri was treated in different dosages (50-250 mJ m^-2) of UV-C radiation and several concentrations (1-500 μmol/L) of hydrogen peroxide (H₂O₂) and the sterol contents were quantified for two days after the treatments. The contents of malondialdehyde (MDA) superoxide dismutase (SOD) as indications of cell membrane damage by lipid peroxidation and repair of oxidative stress, respectively, were measured. Higher activities of SOD and MDA were observed in the treated biomass when compared to the controls. Total sterols increased in P. lutheri due to UV-C radiation (at 100 mJ m^-2) but not in response to H₂O₂ treatment. Among the nineteen sterol compounds identified in P. lutheri, poriferasterol, epicampesterol, methylergostenol, fungisterol, dihydrochondrillasterol, and chondrillasterol increased due to UV-C radiation. Therefore, UV-C radiation can be a useful tool to boost industrial phytosterol production from P. lutheri.

Chemical Composition of Laurencia obtusa Extract and Isolation of a New C15-Acetogenin

A new C₁₅-acetogenin, sagonenyne (20), exhibiting an unusual single tetrahydropyran ring was isolated from an ethyl acetate extract of Laurencia obtusa collected on the Corsican coastline. Its structure was established by detailed NMR spectroscopic analysis, mass spectrometry, and comparison with literature data. Twenty-three known compounds were identified in the same extract by means of column chromatography steps, using a ¹³C-NMR computer aided method developed in our laboratory. In addition to sesquiterpenes, which represent the main chemical class of this extract, diterpenes, sterols, and C₁₅-acetogenins were identified. The crude extract was submitted to a cytotoxicity assay and was particularly active against THP-1 cells, a human leukemia monocytic cell line.

New Cytotoxic Secondary Metabolites from Marine Bryozoan Cryptosula pallasiana

A new sterol, (23R)-methoxycholest-5,24-dien-3β-ol (1), two new ceramides, (2S,3R,4E,8E)-2-(tetradecanoylamino)-4,8-octadecadien-l,3-diol (6) and (2S,3R,2′R,4E,8E)-2-(tetradecanoylamino)-4,8-octadecadien-l,3,2′-triol (7), together with three known sterols (2–4), a lactone (5) and two ceramides (8,9), were isolated from the marine bryozoan Cryptosula pallasiana, collected at Huang Island of China. The structures of the new compounds were elucidated by extensive spectroscopic analyses, chemical methods and quantum electronic circular dichroism (ECD) calculations. Among the isolated compounds, sterol 1 possessed a rare side chain with a methoxy group at C-23, and a double bond between C-24 and C-25. Ceramides 6 and 7 possessed 14 carbons in their long-chain fatty acid base (FAB), which were different from the normal ceramides with 16 carbons in the FAB. Moreover, compounds 5 and 8 were isolated for the first time from marine bryozoans. Compounds 1–9 were evaluated for their cytotoxicity against human tumor cell lines HL-60, Hep-G2 and SGC-7901. The results showed that lactone 5 appears to have strong cytotoxicity against the test tumor cell lines, with IC₅₀ values from 4.12 μM to 7.32 μM, and sterol 1 displayed moderate cytotoxicity with IC₅₀ values between 12.34 μM and 18.37 μM, while ceramides 6–9 showed weak cytotoxicity with IC₅₀ ranging from 21.13 μM to 58.15 μM.

New Marine Sterols from a Gorgonian Pinnigorgia sp

Continuous chemical investigation of the gorgonian coral Pinnigorgia sp. resulted in the isolation of two new sterols, 5α,6α-epoxy-(22E,24R)-3β,11-dihydroxy-9,11-secoergosta-7-en-9-one (1) and (22R)-acetoxy-(24ξ)-ergosta-5-en-3β,25-diol (2). The structures of sterols 1 and 2 were elucidated using spectroscopic methods. Sterol 1 displayed inhibitory effects on the generation of superoxide anions and the release of elastase by human neutrophils with IC₅₀ values of 8.65 and 5.86 μM, respectively. The structure of a known metabolite, pubinernoid A (3), is revised as (+)-loliolide (4).

Sterols from Thai Marine Sponge Petrosia (Strongylophora) sp. and Their Cytotoxicity

Eight new sterols (1–5 and 11–13), together with eight known compounds (6–10 and 14–16) were isolated from marine sponge Petrosia sp. The structures of these compounds were elucidated on the basis of extensive spectroscopic analysis. The cytotoxicity of some compounds against a panel of human cancer cell lines is also reported.

Polyhydroxy Sterols Isolated from the Red Sea Soft Coral. Lobophytum crassum and their Cytotoxic Activity

One new (1) together with four known sterols (2 - 5) and a sesquiterpene (6) were isolated from a polar extract of the Red Sea soft coral Lobophytum crassum. The compounds were identified as 24-methylenecholest-5-ene-lα,3β,1lα-triol 1-acetate (1), 24-methylenecholest-5-ene-la,3β,llα-triol (2), 24- methylenecholest-5-ene-3β-ol (3), 24-methylenecholestane-la,3β,5α,6β,I la-pentol (4), 24-methylenecholestane-3β,5α,6β-triol (5) and alismoxide (6) based on extensive NMR analysis. The cytotoxicity of compounds 1 - 6 was evaluated in vitro using three human cancer cell lines viz., HepG2, Hep-2 and HCT-I 16. Compound 1 showed selective cytotoxic activity against HepG2, while 3 exhibited cytotoxicity against all tested cell lines.

New Anti-Inflammatory 9,11-Secosterols with a Rare Tricyclo[5,2,1,1]decane Ring from a Formosan Gorgonian Pinnigorgia sp

Pinnigorgiols D (1) and E (2), two new 9,11-secosterols with a rearranged carbon skeleton, were isolated from a Taiwan gorgonian Pinnigorgia sp. The structures of these two compounds were elucidated on the basis of spectroscopic methods and were proven to possess a tricyclo[5,2,1,1]decane ring. The new secosterols 1 and 2 displayed significant inhibitory effects on the generation of superoxide anions and the release of elastase by human neutrophils.

Saponins of Agave: Chemistry and bioactivity

The genus Agave comprises more than 400 species with geographical presence in the tropical and sub-tropical regions of the world. These plants have a rich history of folkloric use and are known for a wide spectrum of applications. Secondary metabolites of diverse chemical classes have been reported from Agave species. Owing to their pharmacological significance, the steroidal saponins of Agave have caught the attention of phytochemists, biologists and drug discovery scientists. The present review describes 141 steroidal saponins and sapogenins and covers the literature published from 1970 to 2015. It is a comprehensive and coherent presentation of the structures, methods of chemical profiling, structure elucidation and biological activities of the saponins and sapogenins reported from Agave. The article provides a perspective of the research on steroidal compounds of Agave.

Topsensterols A-C, Cytotoxic Polyhydroxylated Sterol Derivatives from a Marine Sponge Topsentia sp

Three new polyhydroxylated sterol derivatives topsensterols A–C (1–3) have been isolated from a marine sponge Topsentia sp. collected from the South China Sea. Their structures were elucidated by detailed analysis of the spectroscopic data, especially the NOESY spectra. Topsensterols A–C (l–3) possess novel 2β,3α,4β,6α-tetrahydroxy-14α-methyl Δ⁹⁽¹¹⁾ steroidal nuclei with unusual side chains. Compound 2 exhibited cytotoxicity against human gastric carcinoma cell line SGC-7901 with an IC₅₀ value of 8.0 μM. Compound 3 displayed cytotoxicity against human erythroleukemia cell line K562 with an IC₅₀ value of 6.0 μM.

The Role of Spongia sp. in the Discovery of Marine Lead Compounds

A comprehensive review on the chemistry of Spongia sp. is here presented, together with the biological activity of the isolated compounds. The compounds are grouped in sesquiterpene quinones, diterpenes, C21 and other linear furanoterpenes, sesterterpenes, sterols (including secosterols), macrolides and miscellaneous compounds. Among other reports we include studies on the intraspecific diversity of a Mediterranean species, compounds isolated from associated sponge and nudibranch and compounds isolated from S. zimocca and the red seaweed Laurentia microcladia. Under biological activity a table of the reported biological activities of the various compounds and the biological screening of extracts are described. The present review covers the literature from 1971 to 2015.

Marine Natural Products as Models to Circumvent Multidrug Resistance

Multidrug resistance (MDR) to anticancer drugs is a serious health problem that in many cases leads to cancer treatment failure. The ATP binding cassette (ABC) transporter P-glycoprotein (P-gp), which leads to premature efflux of drugs from cancer cells, is often responsible for MDR. On the other hand, a strategy to search for modulators from natural products to overcome MDR had been in place during the last decades. However, Nature limits the amount of some natural products, which has led to the development of synthetic strategies to increase their availability. This review summarizes the research findings on marine natural products and derivatives, mainly alkaloids, polyoxygenated sterols, polyketides, terpenoids, diketopiperazines, and peptides, with P-gp inhibitory activity highlighting the established structure-activity relationships. The synthetic pathways for the total synthesis of the most promising members and analogs are also presented. It is expected that the data gathered during the last decades concerning their synthesis and MDR-inhibiting activities will help medicinal chemists develop potential drug candidates using marine natural products as models which can deliver new ABC transporter inhibitor scaffolds.

Anti-inflammatory and anti-arthritic effects of taraxasterol on adjuvant-induced arthritis in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Taraxasterol was isolated from the traditional Chinese medicinal herb Taraxacum which has been frequently used as a remedy for inflammatory diseases. In the present study, we determined the in vivo anti-arthritic effect of taraxasterol on arthritis induced by Freund's complete adjuvant (FCA) in rats.

MATERIALS AND METHODS

Rats were immunized with FCA by intradermal injection into the right hind metatarsal footpad, and were orally treated daily with taraxasterol at 2, 4 and 8mg/kg from day 2-28 after immunization. Paw swelling, arthritis index, body weight, spleen index and thymus index were evaluated. The levels of TNF-α, IL-1β, PGE2, OPG and RANKL in sera were measured using ELISA. Histopathological changes in joint tissues were examined using hematoxylin and eosin (H&E).

RESULTS

Taraxasterol significantly suppressed paw swelling and arthritis index, attenuated body weight loss, decreased the spleen index and thymus index induced by FCA. Furthermore, taraxasterol significantly inhibited the overproduction of serum TNF-α, IL-1β, PGE2 and RANKL, and increased serum OPG production in FCA-induced rats. Histopathological examination indicated that taraxasterol attenuated synovial hyperplasia, bone and cartilage damage, and inflammatory cell infiltration.

CONCLUSIONS

These results suggest that taraxasterol has the potential protective effect against FCA-induced arthritis in rats.

Structural Features and Potent Antidepressant Effects of Total Sterols and β-sitosterol Extracted from Sargassum horneri

The purified total sterols and β-sitosterol extracted from Sargassum horneri were evaluated for their antidepressant-like activity using the forced swim test (FST) and tail suspension test (TST) in mice. Total sterols and β-sitosterol significantly reduced the immobility time in the FST and TST. Total sterols were administered orally for 7 days at doses of 50, 100, and 200 mg/kg, and β-sitosterol was administered intraperitoneally at doses of 10, 20, and 30 mg/kg. β-sitosterol had no effect on locomotor activity in the open field test. In addition, total sterols and β-sitosterol significantly increased NE, 5-HT, and the metabolite 5-HIAA in the mouse brain, suggesting that the antidepressant-like activity may be mediated through these neurotransmitters.

Fluorinated Sterols Are Suicide Inhibitors of Ergosterol Biosynthesis and Growth in Trypanosoma brucei

Trypanosoma brucei, the causal agent for sleeping sickness, depends on ergosterol for growth. Here, we describe the effects of a mechanism-based inhibitor, 26-fluorolanosterol (26FL), which converts in vivo to a fluorinated substrate of the sterol C24-methyltransferase essential for sterol methylation and function of ergosterol, and missing from the human host. 26FL showed potent inhibition of ergosterol biosynthesis and growth of procyclic and bloodstream forms while having no effect on cholesterol biosynthesis or growth of human epithelial kidney cells. During exposure of cloned TbSMT to 26-fluorocholesta-5,7,24-trienol, the enzyme is gradually killed as a consequence of the covalent binding of the intermediate C25 cation to the active site (kcat/kinact = 0.26 min(-1)/0.24 min(-1); partition ratio of 1.08), whereas 26FL is non-productively bound. These results demonstrate that poisoning of ergosterol biosynthesis by a 26-fluorinated Δ(24)-sterol is a promising strategy for developing a new treatment for trypanosomiasis.

Protective Role of Flavonoids and Lipophilic Compounds from Jatropha platyphylla on the Suppression of Lipopolysaccharide (LPS)-Induced Inflammation in Macrophage Cells

Seventeen polyphenols (e.g, apigenin, genistein, and luteolin glycosides) and 11 lipophilic compounds (e.g., fatty acids, sterols, and terpenes) were detected by LC-MS/MS-ESI and GC-MS, respectively, in Jatropha platyphylla. Extracts from pulp, kernel, and leaves and fractions were studied to know their effect on some pro-inflammatory mediators. Phenolic and lipophilic extracts showed significant inhibitory effects on ROS and NO production while not affecting mitochondrial activity or superoxide generation rate in lipopolysaccharide (LPS)-induced inflammation in RAW 264.7 macrophage cells. In addition, NO production was also diminished by lipophilic leaf fractions F1 and F2 with the latter fraction showing a greater effect and composed mainly of sterols and terpene. Furthermore, total extracts showed nonselective inhibitions against cyclooxygenase COX-1 and COX-2 activities. All together, these results suggest that J. platyphylla extracts have potential in treating inflammatory diseases and their activity is mediated by flavonoids and lipophilic compounds.

Steroidal Saponins from the Rhizomes of Aspidistra typica

Eleven new furostanol saponins, typaspidosides B-L (1–11), one new spirostanol saponin, typaspidoside M (12), and five known spirostanol saponins, 25S-atropuroside (13), neoaspidistrin (14), (25S)-pratioside D₁ (15), 25S-aspidistrin (16) and 25S-neosibiricoside (17) were isolated from the rhizomes of Aspidistra typica Baill. The structures of the new compounds were established using 1D and 2D NMR (¹H-¹H COSY, HMQC, HMBC and ROESY) spectroscopy, high resolution mass spectrometry, and chemical methods. The aglycones of 1–3 (unusual furostanol saponins with opened E ring type), 9 and 10 (the methoxyl substituent at C-23 position) were found, identified from natural products for the first time. Moreover, the anti-HIV activities of the isolated steroidal glycosides were assessed, and compounds 13, 14, 16 and 17 exhibited high active against HIV-1.

Oxysterols: Synthesis and anti-leishmanial activities

Oxygenated sterols (2-16) were synthesized by skeletal rearrangement of steroidal allylic alcohols. All the derivatives were screened for their anti-leishmanial activities. Compounds 3, 11 and 12 showed potent activities. Compound 12 was found least toxic and induced highest nitric oxide (NO) at 48 h. Least toxicity of compound 12 on splenocytes validated its best anti-amastigote effect and induction of NO.

[STEROIDAL GENINS AND GLYCOSIDES OF SPIROSTAN AND FUROSTAN SERIES AS ANTHELMINTHIC AGENTS]

It was established that steroidal genins and their glycosides of the spirostan series and (especially) furostan series show anticestodal activity against Hymeiolepis nana species. Search for anthelminthic agents in the indicated series of compounds is a promising direction of research.

Aβ-42 lowering agents from the marine-derived fungus Dichotomomyces cejpii

The ascomycete Dichotomomyces cejpii was isolated from the marine sponge Callyspongia cf. C. flammea. Three new steroids (1-3), two of which are present as glycosides, with an untypical pattern of carbon-carbon double bounds, were obtained from fungal extracts, as well as the known xanthocillin X dimethyl ether (4). Compounds 2 and 4 were evaluated in an Alzheimer's disease cellular assay and found capable of preventing the enhanced production of amyloid β-42 in Aftin-5 treated cells. Aβ-42 lowering agents are considered as candidates for the treatment of neurodegenerative Alzheimer's disease.

7-Ketocholesterol and 5,6-secosterol induce human endothelial cell dysfunction by differential mechanisms

7-Ketocholesterol and 5,6-secosterol are cholesterol autoxidation products generated under oxidative stress by two distinct mechanisms. They are present in atherosclerotic plaques and are candidate players in the disease initiation and progression. While 7-ketocholesterol affects at cellular level, in particular apoptosis, are well known and reported on diverse cell lines, 5,6-secosterol is a recently discovered oxysterol with relatively few reports on the potential to affect endothelial cell functions. Endothelial cells have a central role in cardiovascular disease as they provide the barrier between blood and the vessel wall where atherosclerosis starts and progresses. Insults to endothelial cells provoke their dysfunction favoring pro-atherogenic and pro-thrombotic effects. In the present work, we tested 7-ketocholesterol and 5,6-secosterol on endothelial cells - focusing on apoptosis and the associated mitochondrial/lysosome alterations - and on endothelial function using the in vitro model of arterial relaxation of aortic rings. Our data provide evidence that 7-ketocholesterol and 5,6-secosterol are efficient instigators of apoptosis, which for 5,6-secosterol is associated to PKC and p53 up-regulation. In addition 5,6-secosterol is a potent inhibitor of endothelial-dependent arterial relaxation through PKC-dependent mechanisms. This may contribute to pro-atherogenic and pro-thrombotic mechanisms of 5,6-secosterol and highlights the role of cholesterol autoxidation in cardiovascular disease.

The cytotoxicology of momordicins I and II on Spodoptera litura cultured cell line SL-1

Momordicin I and II are secondary metabolites from bitter melon (Momordica charantia L.) that are toxic to the Spodoptera litura ovary cell line (SL-1 cell). Both momordicin I and II significantly inhibited SL-1 cells proliferation. IC50 values after 24 h were 8.35 and 82.31 µg/mL, 6.11 and 77.49 µg/mL for 36 h, 4.93 and 49.42 µg/mL for 48 h for cells treated by momordicin I and II, respectively. IC50 values of the azadirachtin A control were 149.63, 54.54 and 23.66 µg/mL at 24, 36 and 48 h respectively, indicating that the cytotoxicity of momordicin I was significantly higher than that of momordicin II and azadirachtin A. Using inverted phase contrast microscopy we found that after 24 h exposure to momordicin I and II, cell shapes changed to circular, swelling increased, adherence ability declined and the cellular membrane bubbled. After 48 h exposure to momordicin I, most cells were suspended and dead; vacuole deformation and cytoplasm leakage indicated that momordicin I was more toxic to the cytoskeleton than momordicin II. Cells treated with momordicin I and II inhibited glucose absorption by 23.04 and 13.38% after 48 h and 47.60 and 20.92% after 60 h. Flow cytometry analysis suggested that SL-1 cells treated with momordicin I and II dramatically accumulated during the G2/M phase of the cell cycle, and total cell protein content increased by 56.93 and 35.81% respectively after 48 h treatment. Following treatment with momordicin I and II the karyotheca dissolved, the chromatin condensed abnormally and the nucleoli were damaged, migrated, or disappeared. The PI fluorescent value by FCM showed that the relative fluorescent intensity of SL-1 cells induced by momordicin I and II increased to 521.45 and 370.17, higher than 135.04 induced by control group treatment for 48 h. This indicated significant damage to the cytomembrane. Overall, the results demonstrate that suppression of cytoskeletal function, interference of mitotic figures and destruction of nuclear structure are effects of momordicin I and II exposure. These effects play major roles in momordicin I and II inhibition of SL-1 cells growth. The mode of action by which momordicins inhibit insect cell growth and development may be useful in the development of novel pest control formulations containing cucurbitane-type triterpene glycosides.

Oxy133, a novel osteogenic agent, promotes bone regeneration in an intramembranous bone-healing model

Current reconstructive techniques for complex craniofacial osseous defects are challenging and are associated with significant morbidity. Oxysterols are naturally occurring cholesterol oxidation products with osteogenic potential. In this study, we investigated the effects of a novel semi-synthetic oxysterol, Oxy133, on in vitro osteogenesis and an in vivo intramembranous bone-healing model. Rabbit bone marrow stromal cells (BMSCs) were treated with either Oxy133 or BMP-2. Alkaline phosphatase (ALP) activity, expression of osteogenic gene markers and in vitro mineralization were all examined. Next, collagen sponges carrying either Oxy133 or BMP-2 were used to reconstruct critical-sized cranial defects in mature rabbits and bone regeneration was assessed. To determine the mechanism of action of Oxy133 both in vitro and in vivo, rabbit BMSCs cultures and collagen sponge/Oxy133 implants were treated with the Hedgehog signalling pathway inhibitor, cyclopamine, and similar outcomes were measured. ALP activity in rabbit BMSCs treated with 1 μm Oxy133 was induced and was significantly higher than in control cells. These results were mitigated in cultures treated with cyclopamine. Expression of osteogenic gene markers and mineralization in BMSCs treated with 1 μm Oxy133 was significantly higher than in control groups. Complete bone regeneration was noted in vivo when cranial defects were treated with Oxy133; healing was incomplete, however, when cyclopamine was added. Collectively, these results demonstrate that Oxy133 has the ability to induce osteogenic differentiation in vitro in rabbit BMSCs and to promote robust bone regeneration in vivo in an animal model of intramembranous bone healing. Copyright © 2015 John Wiley & Sons, Ltd.