Schincalide A, a Schinortriterpenoid with a Tricyclo[5.2.1.0(1,6)]decane-Bridged System from the Stems and Leaves of Schisandra incarnate

Recent progress on triterpenoid derivatives and their anticancer potential

Cancer poses a significant global public health challenge, with commonly used adjuvant or neoadjuvant chemotherapy often leading to adverse side effects and drug resistance. Therefore, advancing cancer treatment necessitates the ongoing development of novel anticancer agents with diverse structures and mechanisms of action. Natural products remain crucial in the process of drug discovery, serving as a primary source for pharmaceutical leads and therapeutic advancements. Triterpenoids are particularly compelling due to their complex structures and wide array of biological activities. Recent research has demonstrated that naturally occurring triterpenes and their derivatives have the potential to serve as promising candidates for new drug development. This review aims to comprehensively explore the anticancer properties of triterpenoids and their synthetic analogs, with a focus on recent advancements. Various aspects, such as synthesis, phytochemistry, and molecular simulation for structure-activity relationship analyses, are summarized. It is anticipated that triterpenoid derivatives will emerge as notable anticancer agents following further investigation into their mechanisms of action and in vivo studies.

Triterpenoids from the stems and leaves of Schisandra incarnata

Six undescribed triterpenoids, schincarins A‒F, categorized as the preschisanartane (schincarin A), 3,4-secocycloartane (schincarins B‒D), 3,4; 9,10-disecocycloartane (schincarin E), and 3,4-secolanostane (schincarin F) classes, along with twelve known analogues, were obtained from the stems and leaves of Schisandra incarnata Stapf. Their structures were elucidated on the basis of extensive spectroscopic analyses. The absolute configuration of schincarin A was corroborated by analysis of the experimental ECD spectrum, and single-crystal X-ray diffraction with Mo Kα irradiation. Schincarin A represented the first example of preschisanartane-type triterpenoid with two oxa-bridged hemiketals. Among the selected compounds which were evaluated for immunosuppressive activities, schincarin C and kadsudilactone A showed potential inhibition against ConA-induced T-cell proliferation with IC₅₀ values of 5.83 and 6.32 μM, and LPS-induced B cell proliferation with IC₅₀ values of 10.21 and 11.49 μM, respectively.

Dibenzocyclooctadiene lignans from the stems of Schisandra sphaerandra

Chemical investigation into the stems of the medicinal plant Schisandra sphaerandra led to the isolation and identification of a new dibenzocyclooctadiene lignan sphaerandrin A (1) and 11 known ones gomisin B (2), schirubrisin B (3), kadsuphilin B (4), schizandrin (5), benzoylgomisin Q (6), angeloylgomisin Q (7), gomisin G (8), schisanwilsonin O (9), isogomisin O (10), schisantherin D (11), and wuweizisu C (12). The structure of the new compound was elucidated by comprehensive spectroscopic methods including 1 D/2D NMR, HRESIMS, and CD spectrometry. To the best of our knowledge, compounds 2 - 11 were obtained from this species for the first time. All the compounds were evaluated for the cytotoxic activity against the triple-negative breast cancer cell lines MDA-MB-231 and HCC-1937.

Kadanguslactones A-E, further oxygenated terpenoids from Kadsura angustifolia fermented by a symbiotic endophytic fungus, Penicillium ochrochloron SWUKD4.1850

The fermentation of Kadsura angustifolia with an endophytic fungus, Penicillium ochrochloron SWUKD4.1850 yielded five additional undescribed oxygenated terpenoids, kadanguslactones A-E, together with ten known compounds. Their structures were established by the extensive 1D, 2D-NMR, HR-ESI-MS, CD and X-ray crystallography data analysis. Kadanguslactone A is the first example of 1,30-cyclo-3,4; 9,10-disecocycloartanes that combine a five-membered lactone ring A with a cyclopentane ring B consisting of C-1, C-4, C-5, C-10, C-30. Kadanguslactone B was a rare highly oxygenated 18-norschiartane-type bisnortriterpenoid with spirocyclis rings F and G, whereas kadanguslactone C was an uncommon henrischinin-type schitriterpenoid containing a unique 3-one-2-oxabicyclo [3,2,1]-octane motif. The cytotoxicity against HepG2 cell line of all compounds were evaluated. Except nigranoic acid, all other metabolites have been first found in unfermented K. angustifolia, suggesting that main functional ingredients from K. angustifolia may be converted by P. ochrochloron SWUKD4.1850 into highly oxygenated terpenoids. This study provided a fascinating prospective for setting up alternative processing techniques to enhance the functionality and utility of Chinese herbal medicine.

Synthesis of bridged tricyclo[5.2.1.01,5]decanes via nickel-catalyzed asymmetric domino cyclization of enynones

The restricted availability, expense and toxicity of precious metal catalysts such as rhodium and palladium challenge the sustainability of synthetic chemistry. As such, nickel catalysts have garnered increasing attention as replacements for enyne cyclization reactions. On the other hand, bridged tricyclo[5.2.1.01,5]decanes are found as core structures in many biologically active natural products; however, the synthesis of such frameworks with high functionalities from readily available precursors remains a significant challenge. Herein, we report a nickel-catalyzed asymmetric domino cyclization reaction of enynones, providing rapid and modular synthesis of bridged tricyclo[5.2.1.01,5]decane skeletons with three quaternary stereocenters in good yields and remarkable high levels of regio- and enantioselectivities (92-99% ee).

Enhanced production of unusual triterpenoids from Kadsura angustifolia fermented by a symbiont endophytic fungus, Penicillium sp. SWUKD4.1850

Highly oxygenated schitriterpenoids are interesting for study of their structures, bioactivities and synthesis. From Kadsura angustifolia fermented by an associated symbiotic endophytic fungus, Penicillium sp. SWUKD4.1850, nine undescribed triterpenoids, kadhenrischinins A-H, and 7β-schinalactone C together with four known triterpenoids, henrischinins A and B, schinalactone C and nigranoic acid were isolated and established by the extensive 1D-, 2D-NMR, HR-ESI-MS and ECD data analysis. Except nigranoic acid, all these metabolites have been first detected in non-fermented K. angustifolia. Structurally, kadhenrischinins A-D belong to the relatively rare class of highly oxygenated schitriterpenoids that contain a unique 3-one-2-oxabicyclo [3,2,1]-octane motif, while kadhenrischinins E-H feature a cyclopentane ring in a side chain rarely found in the family Schisandraceae. These results indicated that fermentation of K. angustifolia with SWUKD4.1850 induced the production of highly oxygenated schitriterpenoids from nigranoic acid, which provided a guidance to obtain desired compounds from those plants initially thought not to produce. This is the first report on the fermentation of K. angustifolia medical plant and the first discovery of highly oxygenated schitriterpenoids by microbial technology.

Effects of an Endophytic Fungus Umbelopsis dimorpha on the Secondary Metabolites of Host-Plant Kadsura angustifolia

Fungal endophytes live widely inside plant tissues and some have been revealed to provide benefits to their host and ecological environment. Considering the fact that endophytes are engaged in remarkably stable long-term interactions with the host for their whole life cycle, it's conceivable that both partners have substantial influence on each other's metabolic processes. Here, we investigated the fermented products of an endophytic fungus Umbelopsis dimorpha SWUKD3.1410 grown on host-plant Kadsura angustifolia and wheat bran, respectively, to assess the impact of SWUKD3.1410 on the secondary metabolites of K. angustifolia. Twenty compounds (1-20) were isolated and identified as 11 schitriterpenoids (1-9, 17-18), two lignans (10, 20), two sesquiterpenoids (11-12), one trinorsesquiterpenoid (13), one monoterpene (14), one sterol (19), and two simple aromatic compounds (15-16) by the extensive 1D-, 2D-NMR and HR-ESI-MS data analysis. Except for nigranoic acid (1), compounds 2-19 have been firstly found from K. angustifolia. Of them, metabolites 2, 11, and 14 were identified to be new. Obtained results indicated that U. dimorpha SWUKD3.1410 could not only produce the same/similar components as its host does, and modify the host-plant components, but also enhance the production of these highly oxygenated schitriterpenoids/schinortriterpenoids in plants. This study suggested an interesting prospective for setting up alternative processing techniques to improve the quality of crude drugs derived from K. angustifolia and increase their values.

Parasubindoles A-G, Seven Eremophilanyl Indoles from the Whole Plant of Parasenecio albus

Parasubindoles A-G (1-7), seven eremophilanyl indoles with an unprecedented 12 H-cyclopentane[ b]naphthalenespiro-1,3'-indole skeleton, were isolated from the whole plant of Parasenecio albus. Their structures with absolute configurations were elucidated by spectroscopic methods, single-crystal X-ray diffraction, and ECD analyses. Plausible biosynthetic pathways of 1-7 were postulated.

Alkaloids with Immunosuppressive Activity from the Bark of Pausinystalia yohimbe

Ten new alkaloids (1-10), including two pairs of enantiomeric mixtures (5a,b and 6a,b), and 15 known analogues (11-25) were obtained from the bark of Pausinystalia yohimbe. The structures of 1-25 were established by spectroscopic methods, and the absolute configurations of compounds 1-10 were resolved by X-ray diffraction and ECD data analyses. The in vitro immunosuppressive activities of selected isolates were tested. Compounds 11 and 16 exhibited moderate inhibition with IC₅₀ values of 16.8 and 27.6 μM against ConA-induced T lymphocyte proliferation and 13.5 and 40.5 μM against LPS-induced B lymphocyte proliferation, respectively.

Schincalactones A and B, Two 5/5/6/11/3 Fused Schinortriterpenoids with a 13-Membered Carbon Ring System from Schisandra incarnata

Two novel schinortriterpenoids (SNTs), schincalactones A (1) and B (2), featuring a unique 5/5/6/11/3 ring system, together with schincalide B (3), were isolated from Schisandra incarnata. Their structures were elucidated by detailed spectroscopic analysis, and the absolute configurations of 1 and 3 were confirmed by single-crystal X-ray diffraction. Compounds 1 and 2 possess a 13-membered carbon ring and are the first examples in the SNT family. Plausible biosynthetic pathways of 1-3 were postulated.

Natural Products Research in China From 2015 to 2016

This review covers the literature published by chemists from China during the 2015-2016 on natural products (NPs), with 1,985 citations referring to 6,944 new compounds isolated from marine or terrestrial microorganisms, plants, and animals. The emphasis is on 730 new compounds with a novel skeleton or/and significant bioactivity, together with their source organism and country of origin.

Survey of natural products reported by Asian research groups in 2016

The new natural products reported in peer-reviewed articles in 2016 in journals with good reputations were reviewed and analyzed. The advances that Asian research groups made in the field of natural products chemistry in 2016 were summarized. Compounds with unique structural features and/or promising bioactivities originating from Asian natural sources were discussed based on structural classification.

Spiroschincarins A-E: Five Spirocyclic Nortriterpenoids from the Fruit of Schisandra incarnata

Spiroschincarins A-E (1-5), five novel spirocyclic schinortriterpenoids featuring a unique 1-oxaspiro[6.6]tridecane motif, were isolated from the fruit of Schisandra incarnata. Their structures with absolute configurations were determined by extensive spectroscopic analyses, single-crystal X-ray diffractions, and experimental ECD (electronic circular dichroism). A hypothetical biogenetic pathway of 1-5 was postulated.