Search

In Cameroon, malaria is still the cause of several deaths yearly and leading to the continued search for new potent leads to fight against Plasmodium falciparum . Medicinal plants like Hypericum lanceolatum Lam. are introduced in local preparations for the treatment of affected people. The bioassay-guided fractionation of the crude extract of the twigs and stem bark of H. lanceolatum Lam. led to the identification of the dichloromethane-soluble fraction as the most active (with 32.6% of the parasite P. falciparum 3D7 survival) which was further purified by successive column chromatography to obtain four compounds identified by their spectrometric data as two xanthones 1,6-dihydroxyxanthone ( 1 ) and norathyriol ( 2 ) and two triterpenes betulinic acid ( 3 ) and ursolic acid ( 4 ). In the antiplasmodial assay against P. falciparum 3D7, the triterpenoids 3 and 4 displayed the most significant potencies with IC 50 values of 2.8 ± 0.8  μ g/mL and 11.8 ± 3.2  μ g/mL, respectively. Furthermore, both compounds were also the most cytotoxic against P388 cell lines with IC 50 values of 6.8 ± 2.2  μ g/mL and 2.5 ± 0.6  μ g/mL, respectively. Further insights on the inhibition method of the bioactive compounds and their drug-likeness were obtained from their molecular docking and ADMET studies. The results obtained help in identifying additional antiplasmodial agents from H. lanceolatum and support its use in folk medicine for the treatment of malaria. The plant might be considered as a promising source of new antiplasmodial candidates in new drug discovery., Competing Interests: The authors declare that they have no conflicts of interest., (Copyright © 2023 Gervais Mouthé Happi et al.)

Phytochemical investigation of the methanolic extract of the trunk bark of Caloncoba welwitschii (Oliv.) Gilg (Achariaceae) led to the isolation of four new compounds, including three new 30-norfriedelane triterpenes, welwitschiilactones D-F ( 1 - 3 ), one new friedelane triterpene, welwitschioic acid ( 4 ) as well as ten known compounds: stigmastane-3,6-dione (7), a mixture of β -sitosterol and stigmasterol ( 6a and 6b ), a mixture of β -sitosterol and stigmasterol glucoside ( 11a and 11b ), (2 S ,3 S ,4 R ,5 R )- N -(1,3,4,5-tetrahydroxyndecan-2-yl)tetradecanamide ( 10 ), 1- O - β - D- glucopyranosyl-(2 S ,3 R ,8 E )-2-[(2' R )-2-hydroxylpalmitoylamino]-8-octadecene-1,3-diol (12), 3 β ,21 β -dihydroxy-27-oxo-30-nor-(D:A)-friedo-olean-20(29))en-27,19α-lactone ( 8 ), 21 β- hydroxy-3,27-dioxo-30-nor-(D:A)-friedo-olean-20(29)-en-27,19α-lactone ( 9 ) and 2 β ,21 β -dihydroxy-27-oxo-30-nor-(D:A)-friedo-olean-20(29)-en-27,19 α -lactone ( 5 ). The structures of all the isolated compounds were determined by extensive spectroscopic analyses (1D and 2D NMR as well as ESI-MS). The relative configuration of the 20-oxymethine in 1 as well as that of 19-oxymethine in 2 and 3 has been established using the NOESY spectrum. In an experiment, a sample of welwitschiilactone C ( 5 ) was chemically modified through reduction reaction to give a new hemi-synthetic derivative namely 2 β ,3 β ,21 β -trihydroxy-30-nor-(D:A)-friedo-olean-20(29)-en-27,19α-lactone ( 5a) .

The triterpenes represent one of the most reported subclasses of specialized metabolites from the plant kingdom. They play a key role in the protection of plants and their metabolism in addition to displaying a high structural diversity and large scale of biological activities. The scaffold can undergo several reactions like oxidation or substitution at different positions of the skeleton leading to the formation of several types of compounds. More specifically, triterpene dimer is a small group of compounds found in nature (from plants precisely). Until 2021, the chemical and pharmacological works reported in the literature indicated the identification of 90 natural dimeric triterpenes and 11 synthetic derivatives from 19 plants species and very few of them have been biologically evaluated for their antibacterial, antioxidant, antiproliferative or molluscicide activities. This review aims to compile the literature on the occurrence, chemistry and biological activities of the triterpenoid dimers. To attend this goal, a literature survey has been done in a number of online libraries including Scifinder, PubMed, Web of Science and Google Scholar using keywords terpene, triterpene, dimer, celastroloid without language restriction. This paper provides the easiest access to the information on triterpene dimers for readers and researchers in view to enhancing the continuity of research works on this topic., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The stem bark of Ancistrocarpus densispinosus Oliv. exhibited triterpenoids, including the rare fernane-type, fern-9(11)-ene-2α,3β-diol ( 1 ) a possible chemotaxonomically distinct biomolecule for the genus. Other triterpenoids that were isolated from this plant include the ursane-type ursolic acid ( 2 ) and corosolic acid ( 3 ), friedelane-type friedelin ( 4 ) and canophyllol ( 5 ), lupane-type lupeol ( 6 ), betulin ( 7 ), betulinic acid ( 8 ) and hennadiol ( 9 ), oleanoic acid ( 10 ), maslinic acid ( 11 ) and taraxerol ( 12 ) and three sterols. This is the first report of the chemistry of a plant of the Ancistrocarpus . The structures of the compounds were elucidated based on their NMR, IR and MS techniques and by comparisons of their experimental data with those reported. The twelve triterpenoids 1 - 12 were found to be inactive against five bacterial strains Escherichia coli, Bacillus subtilis, Pseudomonas agarici, Micrococcus luteus and Staphylococcus warneri; inactive against KB-3-1 cervix carcinoma cancer cell line and inactive as antioxidants in the DPPH assay.

Two new friedelane-type triterpenes named 12alpha-hydroxyfriedelane-3,15-dione and 3beta-hydroxyfriedelan-25-al, together with six known compounds were isolated from the stems of Drypetes paxii Hutch. (Euphorbiaceae). Their structures were established on the basis of conventional 1 dimensional (1D) NMR methods, 2D shift-correlated NMR experiments and mass spectra. The five friedelane-type triterpene derivatives and one olean-12-ene triterpene saponin were tested for antimicrobial activity against some gram-positive and gram-negative bacteria, and they appeared to be modestly active.

The MeOH extract of the stem barks of Drypetes tessmanniana (Euphorbiaceae) afforded two new triterpene derivatives characterized as 3beta-O-(E)-3,5-dihydroxycinnamoyl-11-oxo-olean-12-ene and 3beta,6alpha-dihydroxylup-20(29)-ene together with seven known compounds. Their structures were established on the basis of spectral analysis.

In addition to fatty acids, a mixture of sterols (beta-sitosterol, stigmasterol, campesterol and stigmastanol), lupeol, arctigenin methylether, sesamin, vanillic acid (1), 2,6-dimethoxy-1,4-benzoquinone (2), betulinic acid and two pentacyclic triterpene acetates were isolated from Fagara tessmannii Engl. They were identified as 3beta-acetoxy-16beta-hydroxybetulinic acid (3a) and 3beta,16beta-diacetoxybetulinic acid (3b), and their structures were established using 1 and 2D NMR spectra and by comparison with published data. Two derivatives of the compounds were prepared. Some isolated compounds were evaluated for their antifungal and antibacterial activities. Compounds 1 and 3a showed significant inhibition of alpha-glucosidase.

Chemical studies of the CH2 Cl2 -MeOH extract of the seeds of Gambeya africana (Baker) Pierre led to the isolation of 15 compounds. Their structures were established on the basis of spectroscopic methods and chemical reactions. They comprised five new fatty acid esters of erythrodiol, [3 beta-octacosanoyloxy-12-oleanen-28-ol, 3 beta-triacontanoyloxy-12-oleanen-28-ol, 3 beta-dotriacontanoyloxy-12-oleanen-28-ol, 3 beta-tetratriacontanoyloxy-12-oleanen-28-ol and 3 beta-hexatriacontanoyloxy-12-oleanen-28-ol], one new steroidal glycoside, [3 beta-O-beta-xylopyranosylchondrillasterol] and nine known compounds, (3 beta-octadecanoyloxy-12-oleanene, 3 beta-eicosanoyloxy-12-oleanene, 3 beta-docosanoyloxy-12-oleanene, 3 beta-acetoxy-12-oleanene, erythrodiol, 28-hydroxy-beta-amyrone, chondrillasterol, chondrillasterone and 3 beta-O-beta-glucopyranosylchondrillasterol).

Two new 30-norfriedelane triterpenoids namely glaucalactone C (1) and glaucanoic acid (2) along with sixteen known compounds (3 – 18) have been isolated from the methanolic extracts of the stem bark and fruits of Caloncoba glauca (P.Beauv.) Gilg (Achariaceae). The structures of all the isolated compounds have been established with the aid of their extensive spectroscopic analyses (1D and 2D-NMR) as well as mass spectrometry. Six compounds (1 – 5 , 9) were screened for antiplasmodial activity against two strains P. falciparum Dd2 and P. falciparum 3D7. The results showed that glaucanoic acid (2) was the most active one with IC 50 values of (3.5 ± 0.1 μg/mL) and (4.6 ± 0.7 μg/mL) against Pf Dd2 and Pf 3D7, respectively, while glaucalactone C (1) moderately inhibited Pf Dd2 (9.4 ± 0.1 μg/mL) and weakly Pf 3D7 (15.9 ± 2.3 μg/mL). The molecular docking analyses of the isolated compounds showed that compounds 1 – 4 and 9 – 11 are potential drug targets and were further supported by their ADMET studies that revealed welwitschiilactones B and C (4 and 5) as well as β -sitosterol (10) as the most qualified compounds to be safe as drugs. The results indicate that C. glauca is an important source of good candidates in new antiplasmodial drug development. 30-norfriedelane triterpenoids isolated from the stem bark and fruits of Caloncoba glauca (P.Beauv.) Gilg (Achariaceae), their antiplasmodial potencies and molecular docking studies. [Display omitted] • Two undescribed 30-norfriedelane triterpenes glaucalactone C and glaucanoic acid were obtained from Caloncoba glauca. • The isolated triterpenes display good and moderate antiplasmodial activities against Plasmodium falciparum 3D7. • We discussed on the structure-activity relationship of the isolated 30-norfriedelane triterpenes. • We reported the molecular docking studies of the isolated compounds to three selected Plasmodium protein complexes. [ABSTRACT FROM AUTHOR]