Discovery of four modified classes of triterpenoids delineated a metabolic cascade: compound characterization and biomimetic synthesis

Stereochemical insights into enantioselective antiplasmodial lignanamides from the twigs and leaves of Solanum erianthum

Stereochemical investigations on the twigs and leaves of Solanum erianthum afforded five pairs of lignanamide enantiomers and a previously undescribed phenolic amide (3). Particularly, two pairs of previously undescribed lignanamide racemates (1a/1b-2a/2b) represent the first case of natural products that feature an unreported 5/5-fused N/O-biheterocyclic core. Their structures, including the absolute configurations, were determined unambiguously by using spectroscopic analyses and electronic circular dichroism calculations. A speculative biogenetic pathway for 1-3 was proposed. Interestingly, these lignanamides exhibited enantioselective antiplasmodial activities against drug-sensitive Plasmodium falciparum 3D7 strain and chloroquine-resistant Plasmodium falciparum Dd2 strain, pointing out that chirality plays an important role in drug development.

Intriguing steroid glycosides for cancer therapy by suppressing the DNA damage response and mTOR/S6K signaling pathways

Two rare 8-hydroxysteroid glycosides (6-7), and their downstream metabolites (1-5) with an unprecedented 6/6/5/5/5-pentacyclic scaffold, together with seven known analogues (8-14) were isolated from the twigs and leaves of Strophanthus divaricatus. Their structures were fully assigned by analysis of the spectroscopic and ECD data, NMR calculations, X-ray crystallographic study, and chemical methods. In addition, the inhibitory effects of 1-14 on liver and lung cancer cell lines were evaluated, and preliminary structure-activity relationship was discussed. Data-independent acquisition (DIA)-based quantitative proteomic analysis and biological verification of H1299 cells suggested that this family of compounds may play an anticancer role by suppressing both DNA damage response (DDR) and mTOR/S6K signaling pathways.

The dichapetalins and dichapetalin-type compounds: structural diversity, bioactivity, and future research perspectives

Covering mainly from 2013 up to 2023 with relevant references to work done before 2013First reported in 1995, the dichapetalins and analogous compounds constitute a novel class of natural dammarane-type merotriterpenoids characterized by their unique 2-phenylpyrano moiety annellated to ring A of the dammarane skeleton. They have been reported from only two genera: Dichapetalum (Dichapetalaceae) and Phyllanthus (Phyllanthaceae). About 100 novel dichapetalins and dichapetalin-type compounds, including the acutissimatriterpenes and their antitumour and other bioactivities have been reported. In the present review, we cover the distribution, ethnobotanical and medicinal importance and the diversity of secondary metabolites reported from the two genera Dichapetalum and Phyllanthus from 2013 to date, with appropriate reference to relevant information prior to 2013. We also propose and discuss possible biosynthetic pathways, antitumour activity against a broad range of human and murine cancer cell lines, structure activity relationships, and other biological activities and mechanisms of action. Finally, the review deals with future perspectives which include expansion of the structural diversity and bioactivity scope, possible simplification of the structural complexity of the compounds to enhance their drug-likeness, in silico studies, and continuation of the search for new dichapetalins and dichapetalin-type compounds from the over 200 Dichapetalum and over 1200 Phyllanthus species yet to be investigated. It is envisaged that the present review will stimulate further multidisciplinary and interdisciplinary studies.

Dichapetalin-type triterpenoids from Dichapetalum longipetalum and their anti-inflammatory activity

A phytochemical research on the twigs of Dichapetalum longipetalum (Turcz.) Engl. Resulted in five undescribed dichapetalin-type triterpenoids 1-5. Their chemical structures were determined by spectroscopic analysis of HR-ESIMS and NMR spectra and the absolute configuration of compound 1 was completely elucidated by single crystal X-ray crystallography. Through preliminary anti-inflammatory activity assessment, compound 1 exhibited inhibitory effect on LPS-induced NO production in RAW264.7 murine macrophages with an IC50 value of 2.09 μM.

Antimicrobial and in silico studies of the triterpenoids of Dichapetalum albidum

Here we report a new polyhydroxylated triterpene, 2β,6β,21α-trihydroxyfriedelan-3-one (4) isolated from the root and stem bark of Dichapetalum albidum A. Chev (Dichapetalaceae), along with six known triterpenoids (1-3, 5, 6, 8), sitosterol-3β-O-D-glucopyranoside (9), a dipeptide (7), and a tyramine derivative of coumaric acid (10). Friedelan-3-one (2) showed an antimicrobial activity (IC50) of 11.40 μg/mL against Bacillus cereus, while friedelan-3α-ol (1) gave an IC50 of 13.07 μg/mL against Staphylococcus aureus with ampicillin reference standard of 19.52 μg/mL and 0.30 μg/mL respectively. 3β-Acetyl tormentic acid (5) showed an IC50 of 12.50 μg/mL against Trypanosoma brucei brucei and sitosterol-3β-O-d-glucopyranoside (9) showed an IC50 of 5.06 μg/mL against Leishmania donovani with respective reference standards of IC50 5.02 μg/mL for suramin and IC50 0.27 μg/mL for amphotericin B. Molecular docking of the isolated compounds on the enzyme glucose-6-phosphate dehydrogenase (G6PDH) suggested 3β-acetyl tormentic acid (5) and sitosterol-3β-O-D-glucopyranoside (9) as plausible inhibitors of the enzyme in accordance with the experimental biological results observed.

Asymmetric Total Synthesis of (+)-Phainanoid A and Biological Evaluation of the Natural Product and Its Synthetic Analogues

Here, we report our detailed efforts toward the synthesis of phainanoids, a novel class of dammarane-type triterpenoids with potent immunosuppressive activities and unique structural features. Systematic model studies have been carried out, and efficient approaches have been established to construct the benzofuranone-based 4,5-spirocycle, the D/E/F tricyclic core, the [4.3.1] propellane, and the 5,5-oxaspirolactone moieties. The asymmetric synthesis of (+)-phainanoid A has been achieved through kinetic resolution of the tricyclic core followed by diastereoselective installation of the A/B/C and G/H rings and fragment coupling with the enantioenriched I/J rings. In addition, novel estrone-derived phainanoid analogues have been prepared. The immunosuppressive and cell survival assays revealed that (+)-phainanoid A and some of its synthetic analogues can specifically inhibit stimulation-induced lymphocyte proliferation but not cell survival at their effective concentrations. Preliminary structure-activity relationship information has been obtained, which could inspire future design of immunosuppressive phainanoid analogues.

Dichapetalins from the Twigs of Dichapetalum longipetalum with Cytotoxic Activities

Continued efforts to expand the structural diversity of dichapetalins and explore further the cytotoxic structure-activity relationships have led to the isolation of 17 undescribed analogues, dichapelonins A-Q (1-17), and three known compounds (18-20) from the twigs of Dichapetalum longipetalum. Compounds 1-17 comprise five compound classes as classified by varied C6-C2 conjugates at the A ring of the 13,30-cyclodammarane skeleton, and their structures were determined by spectroscopic data analysis, experimental electronic circular dichroism measurements, and X-ray crystallography. Biological tests revealed compounds 1-7 with a phenyl-butadiene appendage to be the most potent cytotoxic compound type of those evaluated.

Survey of natural products reported by Asian research groups in 2021

The new natural products reported in 2021 in peer-reviewed articles in journals with good reputations were reviewed and analyzed. The advances made by Asian research groups in the field of natural products chemistry in 2021 were summarized. Compounds with unique structural features and/or promising bioactivities originating from Asian natural sources were discussed based on their structural classification.

Ursane and 24-Noroleanane-Type Triterpenoids with Anti-HIV Activity from the Twigs and Leaves of Antirhea chinensis

Investigations on the twigs and leaves of Antirhea chinensis have led to the discovery of two undescribed pentacyclic triterpenoids ( 1 and 2 ) and nine known analogues. Compounds 1 and 2 , each assigned as the ursane and 24-noroleanane-type triterpenoids, featuring similar oxidation pattern of 3 β ,6 β ,19 α -trihydroxy-28-carboxyl. Their structures were elucidated via comprehensive analyses of spectroscopic data. Compound 1 displayed potent anti-HIV activity (EC 50 = 1.24 μ M) and high selectivity index (SI > 32.3).