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Chemical investigations of a methanolic extract of the twigs of Vernonia amygdalina Delile (Asteraceae) resulted in the isolation and identification of three previously undescribed highly oxygenated Δ 7,9(11) stigmastane-type steroids namely vernonins U-W (1-3) along with six known compounds (4-9). The structural characterization of all the isolated compounds has been conducted via comprehensive 1D and 2D-NMR spectroscopy as well as HRMS. The seven steroidal derivatives 1-7 were evaluated for their antiplasmodial activity against the chloroquine-resistant strain P. falciparum Dd2 (PfDd2) and their hemolytic effect on human red blood cells (RBCs). Vernonins U (1), A (4) and stigmasterol-3-O-β-d-glucopyranoside (7) showed the highest activity with IC 50 values of (5.47 ± 0.01) μg/mL, (6.02 ± 0.13) μg/mL and (6.34 ± 0.80) μg/mL, respectively, against PfDd2, while vernonin W (3) showed moderate activity of (21.20 ± 0.40) μg/mL. None of the tested compounds displayed hemolytic effects on human RBCs up to 100 μg/mL indicating their safety. These results enrich the known chemistry of V. amygdalina and support its use in folk medicine for the treatment of malaria. This encourages further research towards new antiplasmodial drug candidates from this plant., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

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 PfDd2 and Pf3D7, respectively, while glaucalactone C (1) moderately inhibited PfDd2 (9.4 ± 0.1 μg/mL) and weakly Pf3D7 (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., Competing Interests: Declaration of Competing Interest None., (Copyright © 2023 Elsevier B.V. All rights reserved.)

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 phytochemical exploration of the Entandrophragma candollei stem bark extract led to the isolation and identification of twenty compounds including three undescribed phragmalin-class limonoids named encandollens C-E (1-3), the undescribed protolimonoid 5 together with sixteen known compounds. The structures of all the isolated compounds were determined by interpretation of their spectroscopic and spectrometric data including HRMS, 1D and 2D NMR analyses. The assignment of the absolute and relative stereochemistry of the undescribed compounds was achieved using SC-XRD analyses as well as NOESY experiments. The previously reported structure of odoratone (5a) was corrected as 23 R,24 S-dihydroxy-22 S,25-epoxytirucall-7-en-3-one (5) based on its NMR and SC-XRD data. Prieurianin (4) exhibited high cytotoxic activity on KB3-1 cell lines with an IC 50 of 1.47 μM compared to the reference griseofulvin (IC 50  = 17-21 μM). The results of the in silico docking of compound 4 supported and delivered further insights on its cytotoxicity., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Two new ergostane-type steroids named tiamenones A and B (1-2) were isolated from the bark of Entandrophragma angolense (Meliaceae) along with ten known compounds identified as 20S-hydroxy-4,6,24(28)-ergostatrien-3-one (3), 3β,7α,20β-trihydroxyergosta-5,24(28)-diene (4), 3β,5α-dihydroxyergosta-7,22-diene (5), stigmasterol, β-sitosterol, β-amyrin, oleanolic acid, asperphenamate, sucrose and daucosterol. The structures of the isolated compounds have been established using NMR spectroscopic and mass spectrometric analyses. The assignment of relative and absolute configurations of compound 1 was achieved by a NOESY experiment and comparison of its NMR data with those of known compound reported in literature. Compounds 1-3, β-amyrin and asperphenamate were evaluated for their antibacterial potencies against five bacterial model strains viz. Escherichia coli DSMZ 1058, Pseudomonas agarici DSMZ 11810, Bacillus subtilis DSMZ 704, Micrococcus luteus DMSZ 1605 and Staphylococcus warneri DSMZ 20036 and their cytotoxicity on two cell lines KB3-1 and HT-29. No potencies were exhibited by the tested compounds even at the highest concentration of 0.5 mg/mL. Compounds 1-3 were found to be potential HIV-1 inhibitors based on their molecular docking analyses., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Chemical investigation of the roots of Entandrophragma congoënse (Meliaceae) led to the isolation of two new 3,4-seco-tirucallane triterpenes, namely seco-tiaminic acids B and C (1 and 2) together with nine known compounds: 3,4-secotirucalla-21-formyl-23-oxo-4(28),7,24-trien-3-oic acid (3), methyl angolensate (4), molucensin N (5), molucensin O (6), piscidinol A (7), 7α,20(S)-dihydroxy-4,24(28)-ergostadien-3-one (8), 24-methylene-cholest-5-en-3β,7α-diol (9), entilin A (10), and entilin B (11). Their structures were determined using extensive spectroscopic methods including 1D and 2D NMR, HRMS, and CD analyses; new results were compared to existing data in the literature. The two newly identified seco-tiaminic acids showed moderate antiplasmodial and cytotoxic activities against a chloroquine-sensitive strain of the malaria parasite (Plasmodium falciparum NF54) and were cytotoxic toward an L6 rat skeletal myoblast cell line, respectively., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Two new tirucallane-type triterpenoids were isolated from the bark of Entandrophragma congoënse (Meliaceae) along with five known compounds gladoral A, bipendensin, 4-hydroxymethyl-3,5-dimethyldihydrofuran-2(3H)-one, scopoletin and 5,7-dimethoxy-6-hydroxycoumarin. Their structures were elucidated by means of spectroscopic analyses including 1D and 2D-NMR spectroscopy, high resolution mass spectrometric data as well as the comparison of data with those reported in the literature. The tested compounds (1-4) displayed moderated antiplasmodial activity against erythrocytic stages of chloroquine-resistant Plasmodium falciparum strain NF54 and low cytotoxicity on L6 cell lines. All the isolated compounds are reported for the first time from the genus Entandrophragma., (Copyright © 2015 Elsevier B.V. All rights reserved.)