Antimalarial compounds from the climbing stems of salacia debilis

Salacia debilis Walp., (Celastraceae) is used traditionally in West Africa for the treatment of malaria. However, no scientific reports validating these effects and its active constituents are on record. Therefore, this study is aimed at evaluating the antimalarial effects, of its ethanolic extract and isolated compounds against Plasmodium falciparum 3D7 and P. berghei ANKA strains. Using chromatographic, spectrometric and spectroscopic techniques three compounds were isolated and characterised. The extract of S. debilis was active against P. falciparum 3D7, in an in vitro assay with IC50 of 12.0 ± 0.32 µg/ml. The three isolated compounds, namely 1,10-dihydroxy-6H-benzo[c]chromen-6-one (1), 8- hydroxy-3,4-dimethoxydibenzo[b,d]furan-1-carboxylic acid (2) and benzyl-2-methoxybenzoate (3), also showed antimalarial activity against Plasmodium berghei ANKA strain in curative and suppressive in vivo assays. The ethanolic extract and isolated compounds of S. debilis possess antimalarial effects. The isolated compounds may be responsible, at least in part, for the observed activities of the extract.

Ursane-type triterpene oligoglycosides with anti-hepatosteatosis and anti-hyperlipidemic activity from the leaves of Ilex paraguariensis A. St.-Hil

The methanol extract from the leaves of Ilex paraguariensis A. St.-Hil. (Aquifoliaceae), popularly known as mate, maté, or yerba maté, inhibits the intracellular triglyceride accumulation in HepG2 cells and suppresses the plasma triglyceride elevation in olive oil-treated mice. Three new triterpene saponins, termed mateosides I (1), II (2), and III (3), were isolated from the extract along with 29 known compounds. The structures of 1-3 were elucidated based on chemical and spectroscopic evidence. Among the isolates, principal saponin constituents, 2 and matesaponins 1 (7) and 2 (9), potently inhibited the triglyceride accumulation in HepG2 cells simultaneously treated with oleic acid and high glucose. In vivo assay of the methanol extract of I. paraguariensis revealed that 7 and 9 showed anti-hyperlipidemic activities in olive oil-treated mice. These results suggested that the saponin constituents of I. paraguariensis could be valuable bioactive marker for the anti-obesogenic activity.

Nine pairs of megastigmane enantiomers from the leaves of Eucommia ulmoides Oliver

Nine pairs of megastigmane enantiomers (1a/1b-9a/9b), comprising two new compounds (6S,9R)-blumenol C (7b), (6S,9S)-blumenol C (8b), two pairs of enantiomers (+)-(6R)-eucomegastigmane A (1a), (-)-(6S)-eucomegastigmane A (1b), (+)-(3S,4S)-eucomegastigmane B (5a), (-)-(3R,4R)-eucomegastigmane B (5b) isolated by chiral resolution firstly, and twelve known compounds, were isolated from the leaves of Eucommia ulmoides Oliver. Their structures were elucidated based on extensive spectroscopic analysis. Absolute configurations of the megastigmane enantiomers were assigned by comparing experimental ECD and OR with calculated ECD and OR. Docking-based virtual screening of all compounds showed that megastigmane enantiomers have weak intermolecular interactions with the binding site residues of angiotensin-converting enzyme (ACE) and angiotensin II type 1 receptor (AT₁R).

Universal access to megastigmanes through controlled cyclisation towards highly substituted cyclohexenes

We report the selective formation of cyclohexenes with a tetrasubstituted double bond, the structural key element of megastigmanes. For this purpose the ZrCl₄-mediated epoxide ring opening of epoxy-geranylacetone was employed. This approach provides a universal entry to the preparation of the members of the megastigmane family, which was exemplified in the asymmetric synthesis of tectoionol B.

Salaterpene E, a eudesmane-type sesquiterpene from Salacia longipes var. camerunensis

A mixture of two compounds with potent antiplasmodial activity in vitro against the W2 strain of Plasmodium falciparum (half maximal inhibitory concentration, 1.12 μg/mL) was obtained in a previous investigation of the CH2Cl2-MeOH extract of the seeds of Salacia longipes var. camerunensis. Separation by column chromatography led now to the isolation of salaterpene E (1) and (1R,2R,4S,5S,6R,7R,9S,10R)-2-acetoxy-1,6,9-tribenzoyloxy-4-hydroxy-dihydro-β-agarofuran (2). The structure of 1 was elucidated by spectroscopic analysis, and its absolute configuration was established unambiguously by means of single-crystal X-ray diffraction. Also the absolute configurations of the recently described salaterpenes A (2a) and D (2b) were determined by this method using the anomalous scattering of the oxygen atoms only.

Megastigmane Glycosides from the Leaves of Tripterygium wilfordii

Two new megastigmane glycosides, named wilfordonisides A and B (1 and 2), and four known compounds (3–6) were isolated from the leaves of Tripterygium wilfordii, and one new aglycon, named wilfordoninol A (2a), was acquired by enzymatic hydrolysis of 2. The absolute stereostructures of the compounds were determined by Mosher's method and by CD. At a concentration of 10 μM, compounds 1, 3, and 5 inhibited STAT1 translocation by 38.1 ± 0.9%, 55.8 ± 0.8%, and 53.9 ± 1.0%, respectively.

Soluble epoxide hydrolase inhibitory and anti-inflammatory components from the leaves of Eucommia ulmoides Oliver (duzhong)

Eucommia ulmoides leaves have been used as a functional food and drink in China. The purpose of this study was to identify the bioactive constituents with soluble epoxide hydrolase (sEH) inhibitory activity and anti-inflammatory properties. Twenty-seven known compounds (1-27) were isolated from the leaves of E. ulmoides Oliver, and their structures were identified by NMR and ESIMS analysis; three of these, 2,5-dimethoxy-3-glucopyranosyl cinnamic alcohol (11), foliasalacioside E2 (26), and icariside F2 (27), were obtained from this plant for the first time. Compounds 1-7 exhibited soluble epoxide hydrolase (sEH) inhibitory activity at 100 μM; among them, quercetin (1) and kaempferol (5) displayed potential activities with IC50 values of 22.5 ± 0.9 and 31.3 ± 2.6 μM, respectively, with noncompetitive inhibition mode. Nuclear factor kappa B (NF-κB) inhibitory activity of the isolated compounds was evaluated by the NF-κB liciferase assay in HepG2 cells. Compounds 1, 9, 20, and 27 displayed potent NF-κB inhibitory effects, with IC50 values of 15.14 ± 2.29, 15.23 ± 2.34, 16.88 ± 2.17, and 16.25 ± 2.19 μM, respectively, whereas other compounds showed weak inhibition of NF-κB transcriptional activity ranging from 17.54 to 92.6 μM. A structure-activity relationship of flavonoids 1-9 was also discussed. The results obtained in this work might contribute to the understanding of pharmacological activities of E. ulmoides leaves and further investigation on its potential application values for food and drug.

Chemical Constituents and Antioxidant Activity of Ficus callosa

One new megastigmane glycoside, ficalloside (1), and eleven known compounds, were isolated from methanol extract of Ficus callosa leaves by repeated column chromatography. Their structures were established on the basis of spectral and chemical evidence. The antioxidant activities of these compounds were measured using the oxygen radical absorbance capacity (ORAC) assay. Compound 8 exhibited potent antioxidant activity of 10.6 μM trolox equivalents at the concentration of 2 μM. At this concentration, compounds 4-7 and 9-12 showed significant antioxidant activity with ranging of 2.1~6.1 μM trolox equivalents.

Structural revisions of blumenol C glucoside and byzantionoside B

The absolute stereochemistry of blumenol C glucoside and byzantionoside B was revised here as (6R,9S)- and (6R,9R)-9-hydroxymegastigman-4-en-3-one 9-O-beta-D-glucopyranosides, respectively, by modified Mosher's method. The empirical rules of (13)C-NMR chemical shift to determine the absolute stereochemistry of C-9 of 9-hydroxymegastigmane 9-O-beta-D-glucopyranoside were also discussed.