Novel ceramides from the fungus Lactarium volemus

Chemical constituents of two Cameroonian medicinal plants: Sida rhombifolia L. and Sida acuta Burm. f. (Malvaceae) and their antiplasmodial activity

An extensive phytochemical investigation of the EtOH/H₂O (7:3) extracts of Sida rhombifolia L. and Sida acuta Burm. f., yielded a previously undescribed ceramide named rhombifoliamide (1) and a xylitol dimer (2), naturally isolated here for the first time, as well as the thirteen known compounds viz, oleanolic acid (3), β-amyrin glucoside (4), ursolic acid (5), β-sitosterol glucoside (6), tiliroside (7), 1,6-dihydroxyxanthone (8), a mixture of stigmasterol (9) and β-sitosterol (10), cryptolepine (11), 20-Hydroxyecdysone (12), (E)-suberenol (13), thamnosmonin (14) and xanthyletin (15). Their structures were elucidated by the analyses of their spectroscopic and spectrometric data (1 D and 2 D NMR, and HRESI-MS) and by comparison with the previously reported data. The crude extracts, fractions, and some isolated compounds were tested against chloroquine-sensitive (3D7) and chloroquine-resistant (Dd2) Plasmodium falciparum strains. All the tested samples demonstrated moderate and/or significant activities against 3D7 (IC₅₀ values: 0.18-20.11 µg/mL) and Dd2 (IC₅₀ values: 0.74-63.09 µg/mL).

A new isoquinoline and ceramide from the stem barks of Discoglypremna caloneura (Pax) Prain (Euphorbiaceae) with antiproteinase and cytotoxic activities

Two new compounds, an isoquinoline (1) and caloneuramide (2), a ceramide were isolated from the stem bark of Discoglypremna caloneura together with seven known compounds namely aurantiamide acetate (3), acetylaleuritolic acid (4), 3α-hydroxylaleuritolic acid 2α-p-hydroxybenzoate (5), mixture of stigmasterol (6) and β-sitosterol (7), mixture of 7-oxo-stigmasterol (8) and 7-oxo-β-sitosterol (9). Their structures were determined based on data from literature and spectroscopic methods. Derivatization reactions on the isoquinoline led to two new compounds, the methylated (10) and acetylated (11) derivatives. Some compounds and extracts were evaluated for their cytotoxic and antiproteinase activity. Antiproteinase effect of compounds 1, 10 and 11 exhibited IC₅₀ values of 10.77, 1.19 and 3.61 μg/mL respectively; significantly low compared to the standard drug, acetyl salicylic acid (IC₅₀ = 20.28 μg/mL). Ethyl acetate and methanol extract exhibited moderate cytotoxicity activity on Chang liver cells with CC₅₀ values of 167.90 ± 2.20 and 106.30 ± 2.03 μg/mL compared to the reference drug cucurmin (CC₅₀ = 11.05 ± 1.04 μg/mL).

Ceramide channel: Structural basis for selective membrane targeting

A ceramide commonly found in mammalian cells, C16-ceramide (N-palmitoyl-d-erythro-sphingosine), is capable of forming large, protein-permeable channels in the mitochondrial outer membrane (MOM). However, C16-ceramide is unable to permeabilize the plasma membrane of erythrocytes. This specificity is unexpected considering that ceramide forms channels in simple phosphoglycerolipid membranes. Synthetic analogs of C16-ceramide with targeted changes at each of the functional regions of the molecule including methylation, altered hydrocarbon chain length, and changes in the stereochemistry, were tested to probe the role of ceramide's molecular features on its ability to form channels in these two different membrane types. The ability to permeabilize the MOM was relatively insensitive to modifications of the various functional groups of ceramide whereas the same modifications resulted in plasma membrane permeabilization (a gain of function rather than a loss of function). Some analogs (ceramine, NBD-labeled ceramide, C18,1 ceramide) gained another function, the ability to inhibit cytochrome oxidase. The gain of deleterious functions indicates that constraints on the structure of ceramide that is formed by the cell's synthetic machinery includes the avoidance of deleterious interactions. We propose that the specific structure of ceramide limits the size of its interactome (both proteins and lipids) thus reducing the likelihood of unwanted side effects.

Strepsiamide A-C, New Ceramides from the Marine Sponge Strepsichordaia Lendenfeldi

Investigation of the lipophilic extract of the Indonesian sponge Strepsichordaia lendenfeldi afforded three new ceramides, given the names strepsiamides A–C (1–3). The compounds showed cytotoxic activities against L5187Y and Hela cell lines. All structures were unambiguously established by 1D and 2D NMR spectroscopic and mass (EI-, APCI- and GC-MS) spectrometric data.

A sphingolipid and tyrosinase inhibitors from the fruiting body ofphellinus linteus

This paper for the first time reports the isolation of 5 compounds from Phellinus linteus. A sphingolipid (1) and two tyrosinase inhibitory compounds (2, 3) along with two carboxylic acids (4, 5), were isolated from the fruiting body of Phellinus linteus (Berk & Curt) Aoshima. The structure of compound 1 was identified as 1-omicron-beta-D-glucopyranosyl-(2S, 3R, 4E, 8E)-2-[(2R)-2-hydroxyhexadecanoylamino]-9-methyl-4,8-octadecadiene-1,3-diol, known as cerebroside B, based on spectroscopic methods such as 1 D and 2D NMR as well as by acid hydrolysis. Compounds 2 -5 were identified as protocatechualdehyde (2), 5-hydroxymethyl-2-furaldehyde (HMF) (3), succinic acid (4), and fumaric acid (5) based on the spectroscopic evidence. Compounds 2 and 3 inhibited the oxidation of L-tyrosine catalyzed by mushroom tyrosinase with an IC50 of 0.40 and 90.8 microg/mL, respectively. The inhibitory kinetics, which were analyzed by the Lineweaver-Burk plots, were found to be competitive and noncompetitive inhibitors with a Ki of 1.1 microM and 1.4 mM, respectively.

Ceramide constituents from five mushrooms

Five mushrooms, Panellus serotinus, Lyophyllum connatum, Amanita pantherina, Sarcodon aspratus and Lepista nuda, have been investigated chemically. Two new ceramides, (2S,3R,4E,8E)-N-hexadecanoyl-2-amino-9-methyl-4,8-octadecadiene-1,3-diol (1) and (2S,3R,4E,8E,9'Z,12'Z)-N-9',12'-octadecadienoyl-2-amino-9-methyl-4,8-octadecadiene-1,3-diol (2), have been isolated from Panellus serotinus. Compound 2 was also isolated from Lyophyllum connatum. Two new ceramides, (2S,2'R,3R,4E,8E)-N-2'-hydroxypentadecanoyl-2-amino-9-methyl-4,8-octadecadiene-1,3-diol (4) and (2S,2'R,3R,4E,8E)-N-2'-hydroxytetradecanoyl-2-amino-9-methyl-4,8-octadeca-diene-1,3-diol (5), have been isolated from Amanita pantherina with (2S,2'R,3R,4E,8E)-N-2'-hydroxyhexadecanoyl-2-amino-9-methyl-4,8-octadecadiene-1,3-diol (3), a known synthetic compound. Compounds 3 and 4 were also isolated from Sarcodon aspratus and compound 3 was isolated from Lepista nuda. The structures of the new compounds were elucidated on the basis of their spectral data.