Commiphoratones A and B, Two Sesquiterpene Dimers from Resina Commiphora

Medicinal plant resin natural products: structural diversity and biological activities

Covering: up to the mid of 2023Plants secrete defense resins rich in small-molecule natural products under abiotic and biotic stresses. This comprehensive review encompasses the literature published up to mid-2023 on medicinal plant resin natural products from six main contributor genera, featuring 275 citations that refer to 1115 structurally diverse compounds. The scope of this review extends to include essential information such as the racemic nature of metabolites found in different species of plant resins, source of resins, and revised structures. Additionally, we carefully analyze the reported biological activities of resins, organizing them based on the their structures. The findings offer important insights into the relationship between their structure and activity. Furthermore, this detailed examination can be valuable for researchers and scientists in the field of medicinal plant resin natural products and will promote continued exploration and progress in this area.

Terpenoids from Myrrh and Their Cytotoxic Activity against HeLa Cells

The oleo-gum resin of Commiphora myrrha (Nees) Engl. has a long history of medicinal use, although many of its constituents are still unknown. In the present investigation, 34 secondary metabolites were isolated from myrrh resin using different chromatographic techniques (silica flash chromatography, CPC, and preparative HPLC) and their structures were elucidated with NMR spectroscopy, HRESIMS, CD spectroscopy, and ECD calculations. Among the isolated substances are seven sesquiterpenes (1-7), one disesquiterpene (8), and two triterpenes (23, 24), which were hitherto unknown, and numerous substances are described here for the first time for C. myrrha or the genus Commiphora. Furthermore, the effects of selected terpenes on cervix cancer cells (HeLa) were studied in an MTT-based in vitro assay. Three triterpenes were observed to be the most toxic with moderate IC₅₀ values of 60.3 (29), 74.5 (33), and 78.9 µM (26). Due to the different activity of the structurally similar triterpenoids, the impact of different structural elements on the cytotoxic effect could be discussed and linked to the presence of a 1,2,3-trihydroxy substructure in the A ring. The influence on TNF-α dependent expression of the intercellular adhesion molecule 1 (ICAM-1) in human microvascular endothelial cells (HMEC-1) was also tested for 4-6, 9-11, 17, 18, 20, and 27 in vitro, but revealed less than 20% ICAM-1 reduction and, therefore, no significant anti-inflammatory activity.

Commiphoratones C-E: Three Spiro-Sesquiterpene Dimers from Resina Commiphora

Three new sesquiterpene dimers commiphoratones C−E (1−3), unprecedented carbon skeletons possessing a spiro center, were isolated from Resina Commiphora. Their structures were assigned by spectroscopic methods, ECD calculations and X-ray...

Three new carabrane sesquiterpenoid derivatives from the whole plant of Carpesium abrotanoides L

Dicarabrols B and C (1 and 2), two new carabrane sesquiterpenoid dimers, along with one new carabrane sesquiterpenoid (3) were isolated from the whole plant of Carpesium abrotanoides L. Their full structures were established by extensive analysis of HR-ESI-MS and NMR spectroscopic data, and time-dependent density functional theory (TDDFT) electronic circular dichroism (ECD) calculations. Dicarabrol B possesses a novel C₃₀ skeleton featuring a methylene-tethered bridge between two sesquiterpene moieties, while dicarabrol C presents the unique linkage of a cyclopentane ring in the molecule. Dicarabrol C exhibited potent inhibitory effects on HL-60 cells with an IC₅₀ value of 3.7 μmol·L^-1.

Populusene A, an Anti-inflammatory Diterpenoid with a Bicyclo[8,4,1]pentadecane Scaffold from Populus euphratica Resins

Populusene A (1), an unprecedented carbon skeleton featuring a bicyclo[8.4.1]pentadecane nucleus and a bridgehead double bond (anti-Bredt system), and populusin A (2), a cembrane-type diterpenoid possessing an uncommon dioxatricyclo[6.6.1.12,5]hexadecane scaffold, were isolated from the exudates of Populus euphratica. Their structures were elucidated by spectroscopic, computational, and crystallographic methods. A plausible biosynthetic route for 1 and 2 was proposed. Compounds 1 and 2 were found to significantly inhibit the production of TNF-α and IL-6 and the expression of iNOS, COX-2, and p-NF-κB at 125 nM in RAW264.7 cells.

Commiphoranes K-O, New Terpenoids from Resina Commiphora and Their Anti-Inflammatory Activities

Commiphorane K (1), a new dinorditerpenoid, commiphoranes L-N (2-4), three new germacrane-type sesquiterpenoids, and commiphorane O (5), one new guaiane-type sesquiterpenoid, were isolated from Resina Commiphora. Their structures were characterized by spectroscopic and computational methods. In particular, the structure of 4 was confirmed by X-ray crystallography. Compounds 2-5 were evaluated for their anti-inflammatory activities. The result shows that compound 2 suppresses lipopolysaccharide (LPS)-stimulated production of TNF-α in RAW264.7 cells in a dose-dependent manner.

Horienoids A and B, Two Heterocoupled Sesquiterpenoid Dimers from Hedyosmum orientale

Two eudesmane-guaiane/lindenane heterocoupled sesquiterpenoid dimers, horienoids A (1) and B (2) with new carbon skeletons, from Hedyosmum orientale were characterized by a combined method. Compound 1 featured a unique 2,10-dioxabicyclo[6.2.1]undecane core moiety with an anti-Bredt bridgehead double bond. Their biogenetic pathways were proposed to involve Diels-Alder and cascade rearrangement reactions as the key steps. Compound 2 exhibited a potent anti-inflammatory effect on LPS-induced BV-2 microglial cells.

Antinociceptive grayanane-derived diterpenoids from flowers of Rhododendron molle

Twelve new grayanoids (1-12) along with five known compounds were isolated from flowers of Rhododendron molle. Their structures were fully characterized using a combination of spectroscopic analyses, computational calculations, and single crystal X-ray diffraction. Rhomollone A (1) possesses an unprecedented 5/6/6/5 tetra-cyclic ring system (B-nor grayanane) incorporating a cyclopentene-1,3-dione scaffold. Rhodomollein XLIII (2) is a dimeric grayanoid, containing a novel 14-membered heterocyclic ring with a C ₂ symmetry axis. The antinociceptive activities of compounds 3, 4, 6, 7, and 12-17 were evaluated by an acetic acid-induced writhing test. Among them, compounds 3, 7, 12, 15 and 16 displayed significant antinociceptive activities at a dose of 20 mg/kg with inhibition rates ranging from 41.9% to 91.6%. Compounds 6 and 13 inhibited 46.0% and 39.4% of the acetic acid-induced writhes at a dose of 2 mg/kg, while compound 17 inhibited 34.3% of the writhes at a dose of 0.4 mg/kg.

Spiromyrrhenes A–D: unprecedented diterpene–sesquiterpene heterodimers as intermolecular [4 + 2] cycloaddition products from Resina Commiphora that inhibit tumor stemness in esophageal cancer

The structures and stereochemistry of spiromyrrhenes A–D (1–4), isolated from Commiphora exudates, were elucidated using NMR and ECD methods.

Tricarabrols A–C, three anti-inflammatory sesquiterpene lactone trimers featuring a methylene-tethered linkage from Carpesium faberi

Three anti-inflammatory trimeric compounds constructed from carabrol-type sesquiterpenoids through a methylene-tethered linkage were characterized from Carpesium faberi.

Natural disesquiterpenoids: an update

This review highlights the progress on the isolation, bioactivity, biogenesis and total synthesis of dimeric sesquiterpenoids since 2010.

Survey of natural products reported by Asian research groups in 2018

The new natural products reported in 2018 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 2018 were summarized. Compounds with unique structural features and/or promising bioactivities originating from Asian natural sources were discussed based on their structural classification.

Neuroprotective Norsesquiterpenoids and Triterpenoids from Populus euphratica Resins

Two new octanorlanostane-type triterpenes, euphraticanoids A and B (1 and 2), two new trinorsesquiterpenoids, euphraticanoids C and D (3 and 4), and eight known triterpenoids (5, 6, 8–13) along with one steroid (7) were isolated from Populus euphratica resins. The structures of these new compounds, including their absolute configurations, were characterized by spectrocsopic, chemical, and computational methods. Biological evaluation revealed that compounds 4, 7–9, 12, and 13 display neuroprotective activities in H₂O₂-induced HT-22 cells with 4, 8, and 9 occurring in a concentration-dependent manner and 7, 12, and 13 reaching the maximum effects at 20 μM. Meanwhile, the neuroprotective properties of all isolates were accessed using glutamate-induced SH-SY5Y cells and disclosed that compounds 3, 4, 8, and 9 could dose-dependently protect neural cell injury in a concentration range of 10–40 μM. Finally, a brief structure–activity relationship was briefly discussed.

Anti-Mycobacterium tuberculosis Terpenoids from Resina Commiphora

Four new compounds including two new sesquiterpenoid dimers, commiphoroids E (1) and F (2), a new triterpenoid (3), and a new sesquiterpenoid (4), along with three known terpenoids (5−7) were isolated from Resina Commiphora, whose structures were identified by NMR spectra, HRESIMS, and X-ray diffraction analysis. Compounds 1 and 2 both bear an O-bridge ring and feature a plausible [4 + 2] Diels–Alder cycloaddition reaction. Antimycobacterial activities show that all the tested compounds (200 μM) could inhibit the growth of both sensitive and clinically multi-drug resistant (MDR) isolated strains. In addition, cellular toxicity of the isolates against human cancer cells and THP-1 monocyte cells was examined.

Fischernolides A–D, four novel diterpene-based meroterpenoid scaffolds with antitumor activities from Euphorbia fischeriana

Fischernolides A–D (1–4), representing the rare 28-carbon meroterpenoid skeleton of abietane and an acylphloroglucinol conjugate, bearing an α-furanone or α-pyrone ring, were isolated and identified from the roots of Euphorbia fischeriana.

Novel Terpenoids with Potent Cytotoxic Activities from Resina Commiphora

A novel sesquiterpene dimer, spirocommiphorfuran A (1); two new cadinane sesquiterpenoids, commiphorenes A (2) and B (3); along with three known terpenoids (4–6), were isolated from ResinaCommiphora. The structures of these new compounds were characterized by NMR, HRESIMS, quantum chemical computation, and X-ray diffraction analysis. Compound 1 features a 7-oxabicyclo[2.2.1]heptane-2-ene core, representing the first example of germacrane-type sesquiterpene dimer fused via a spiro ring system. Compound 2 is a novel sesquiterpene with a completely new carbon skeleton, which is characteristic of an additional carbon attaching to the cadinane backbone via a carbon–carbon bond. Additionally, compounds 2 and 4 exert acceptable cytotoxicity toward normal cells and high selectivity in cancer cells, especially in HepG2 cells.

Hot off the Press

A personal selection of 32 recent papers is presented covering various aspects of current developments in bioorganic chemistry and novel natural products such as mollebenzylanol A from Rhododendron molle.