Sesquiterpenoids Isolated from Two Species of the Asteriscus Alliance

Cynasibirolide A, One New Humulanolide Sesquiterpene from Cynanchum acutum subsp. sibiricum

Cynasibirolide A (1), one new humulanolide sesquiterpene, together with four known analogs, asteriscanolide (2), (1S,8S)-8-hydroxyhumula-2Z,6E,9E-trien-1,12-olide (3), (1S,7R)-8-oxohumula-2Z,9E-dien-1,12-olide (4), and (+)-6,7,9,10-tetrahydroasteriscunolide (5) were isolated from the roots and rhizomes of Cynanchum acutum subsp. sibiricum. Their structures and configurations were elucidated by spectroscopic methods, including 2D-NMR techniques, and the structure of 1 was confirmed by single-crystal X-ray diffraction. All compounds were evaluated for their anti-complementary activity in vitro, and compound 3 exhibited anti-complement effect with CH₅₀ value of 0.45 mM.

Integrated Chemical Characterization, Network Pharmacology and Transcriptomics to Explore the Mechanism of Sesquiterpenoids Isolated from Gynura divaricata (L.) DC. against Chronic Myelogenous Leukemia

Chronic myelogenous leukemia (CML) is a serious threat to human health, while drugs for CML are limited. Herbal medicines with structural diversity, low toxicity and low drug resistance are always the most important source for drug discoveries. Gynura divaricata (L.) DC. is a well-known herbal medicine whose non-alkaline ingredients (GD-NAIs) were isolated. The GD-NAIs demonstrated potential anti-CML activity in our preliminary screening tests. However, the chemical components and underlying mechanism are still unknown. In this study, GD-NAIs were tentatively characterized using UHPLC-HRMS combined with molecular networking, which were composed of 75 sesquiterpenoids. Then, the anti-CML activities of GD-NAIs were evaluated and demonstrated significant suppression of proliferation and promotion of apoptosis in K562 cells. Furthermore, the mechanism of GD-NAIs against CML were elucidated using network pharmacology combined with RNA sequencing. Four sesquiterpenoids would be the main active ingredients of GD-NAIs against CML, which could regulate PD-L1 expression and the PD-1 checkpoint pathway in cancer, PI3K/AKT, JAK/STAT, TGF-β, estrogen, Notch and Wnt signaling pathways. In conclusion, our study reveals the composition of GD-NAIs, confirms its anti-CML activity and elucidates their underlying mechanism, which is a potential countermeasure for the treatment of CML.

Chemo-Geographic Variations in Wild Population of Asteriscus graveolens in Israel Based on Volatile Composition Analyses

Asteriscus graveolens is an aromatic desert shrub which holds medicinal potential. This species belongs to the Asteraceae family and is endemic to the Mediterranean region. In the present study, wild plants were sampled from eleven locations throughout southern Israel and the volatile profiles from leaves and flowers were analyzed using GC/MS. Three methods for volatile sampling were tested for a representative population: solvent extraction (methyl tert-butyl ether), hydrodistillation of the essential oil and headspace solid-phase microextraction. In all methods, the majority of volatiles were characterized as oxygenated mono- and sesquiterpenes. Only solvent extraction was able to detect asteriscunolides that were previously reported as anticancer molecules. Hence, that method was chosen for further analyses. The leaves were dominated by three asteriscunolide isomers, cis-chrysanthenyl acetate and intermedeol. The flowers were dominated by bisabolone, 6-hydroxybisabol-2-en-1-one, cis-chrysanthenyl acetate, epi-α-cadinol, and germacrene-D. k-Means clustering analysis of these data divided the population into four clusters that significantly differ in their volatile composition as was further demonstrated by MANOVA analysis. Geographically, A. graveolens populations growing in Israel were found to be chemically diverse with unique varieties in the Dead Sea basin and the Arava region. This work demonstrates that chemo-geographic variation of volatile composition exists within A. graveolens population growing in Israel, so future research evaluating the medicinal potential of that plant should take this into consideration.

Remarkable Potential of Zerumbone to Generate a Library with Six Natural Product-like Skeletons by Natural Material-Related Diversity-Oriented Synthesis

Diversity-oriented synthesis (DOS) is an effective strategy for the quick creation of diverse and high three-dimensional compounds from simple starting materials. The selection of a starting material is the key to constructing useful, chemically diverse compound libraries for the development of new drugs. Here, we report a novel, general, and facile strategy for the creation of diverse compounds with high structural diversity from readily available natural products, such as zerumbone, as the synthetic starting material. Zerumbone is the major component of the essential oil from wild ginger, Zingiber zerumbet Smith. It is noteworthy that zerumbone has a powerful latent reactivity, partly because of its three double bonds, two conjugated and one isolated, and a double conjugated carbonyl group in an 11-membered ring structure. In fact, zerumbone has been shown to be a successful example of natural material-related DOS (NMRDOS). We will report that zerumbone can be converted in one chemical step from four zerumbone derivatives into rare and markedly different scaffolds by transannulation.

Bicyclo [6.3.0] Undecane Sesquiterpenoids: Structures, Biological Activities, and Syntheses

Sesquiterpenoids constitute a marvelously varied group of natural products that feature a vast array of molecular architectures. Among them, the unusual bicyclo [6.3.0] undecane sesquiterpenoids are one of the most representative. To date, only approximately 42 naturally occurring compounds with this unique scaffold, which can be classified into seven different groups, have been reported. As the first-found member of each type, dactylol, asteriscanolide, dumortenol, toxicodenane C, and capillosanane S are characteristic of the four methyl groups on the five-eight-membered ring system. Only 11-hydroxyjasionone and sinuketal decorate the core with an isopropyl group. These natural products exhibit a wide range of bioactivities, including antifouling, anti-inflammatory, immune suppression, cytotoxic, antimutagenic, antiplasmodial, and antiviral activities. It was noted that some total syntheses of precapnellane-sesquiterpenoids (dactylol, poitediol, precapnelladiene), asteriscanolide, and 11-hydroxyjasionone have been achieved, because their cyclooctanoid core represents an important target for the development of synthetic strategies to prepare eight-membered ring-containing compounds. This review focuses on these natural sesquiterpenoids and their biological activities and synthesis, and aims to provide a foundation for further research of these interesting compounds.

Exploring the Bioactive Terpenoid Content of an Algerian Plant of the Genus Pulicaria: The ent-Series of Asteriscunolides

Chemical analysis of the chloroform extract of the aerial parts of the Algerian plant Pulicaria undulata exhibiting anti-inflammatory activity resulted in the isolation of 10 new humulene sesquiterpenoids, 1-10, belonging to the asteriscunolide family of compounds. The structure and relative configuration have been defined by NMR data, whereas the absolute configuration has been established by ECD analysis. Compounds 1-10 include enantiomers of the known asteriscunolides A-D and tetrahydroasteriscunolide previously reported from the genera Asteriscus and Nauplius. Compounds 1 and 10 showed in vitro anti-inflammatory activity by inhibiting heat-induced albumin denaturation with IC₅₀ values of 23.76 and 220.42 μM.

Ruthenium-Catalyzed Metathesis Cascade Reactions in Natural Products Synthesis

In this account, we provide a brief summary of recent developments in ruthenium-catalyzed metathesis cascade reactions towards the total synthesis of natural products. We also highlight recent progress from our own laboratory regarding the synthesis of securinega alkaloids and humulanolides, which has resulted in the development of novel ruthenium-catalyzed metathesis cascade reactions. Inspired and guided by the pioneering and elegant research conducted in this area, we developed a regio-controlled relay dienyne metathesis cascade reaction and a cyclobutene-promoted RCM/ROM/RCM cascade reaction for the synthesis of securinega alkaloids and humulanolides, respectively.