Diverse Chemosensitizing 8,9-Secolindenane-Type Sesquiterpenoid Oligomers and Monomers from Sarcandra glabra

Structurally diverse sesquiterpenoids from Sarcandra glabra and their anti-inflammatory activities

Fifteen sesquiterpenoids, including five previously undescribed monomers with oxidative rearranged skeletons (sarglabenoids A-E, 1-5) and three previously unreported lindenane [2 + 2] dimers (sarglabenoids F-H, 6-8), alongside seven related precursors (9-15), were isolated from the root of Sarcandra glabra. The structures of these compounds were elucidated using a combination of high-resolution electrospray ionization mass spectrometry, one-dimensional and two-dimensional nuclear magnetic resonance spectroscopy, the circular dichroism exciton chirality method, electronic circular dichroism, and nuclear magnetic resonance calculations integrated with DP4+ analysis. Compounds 1 and 2 feature an unique 5/5 spiro ring system, which is likely derived from a pinacol rearrangement of precursor 14. Compounds 3 and 4 are seco-C8/9 derivatives formed via Baeyer-Villiger oxidation of precursors 14 and 15, while compounds 6-8 represent the [2 + 2] dimers of various lindenane monomers (9-13). Notably, compounds 4 and 5 exhibited moderate inhibition of Interleukin-1β production in non-cytotoxic concentration in lipopolysaccharide-induced Tohoku Hospital Pediatrics-1 cells, with IC50 values of 16.28 ± 0.76 μM and 11.32 ± 0.77 μM respectively.

A review of botany, ethnomedicine, phytochemistry, pharmacology and toxicology of Sarcandra species

BACKGROUND

Sarcandra is one of the five genera of Chloranthaceae, which has a long history of medicinal use and high medicinal value, with excellent therapeutic effects on liver cancer, pneumonia, colitis, bone fractures, and dysentery. Among its species, Sarcandra glabra (Thunb.) Nakai has been extensively utilized in diverse compound formulations, toothpaste, tea, daily commodities, as well as health supplements. Therefore, in terms of its medicinal properties and effectiveness, the genus has considerable potential for development and utilization.

PURPOSE

This paper presents a systematic review of the botany, ethnomedicine, phytochemistry, pharmacology, and toxicology of Sarcandra plants, aiming to deepen our understanding of Sarcandra properties further, to provide a reference for the rational utilization of Sarcandra plant resources, and at the same time laying a foundation for the development of new medicines and the study of natural products.

METHODS

In this paper, we collected information about Sarcandra species through PubMed, Science Direct, Web of Science, Baidu Scholar, Google Scholar, CNKI, and other databases using the keywords Sarcandra, botany, traditional uses, chemical compounds, pharmacology and toxicology. Its botanical-related information was obtained through the Flora of China (www.iplant.cn).

RESULTS

Three species of Sarcandra plants worldwide are distributed from eastern Asia to India. This genus has a long history of medicinal uses, high medicinal value, and a wide range of applications. At present, 462 compounds have been isolated and identified from Sarcandra plants, and their diversity contributes to the diversity of the pharmacological effects of Sarcandra plants. Numerous studies have shown that Sarcandra plants exhibit significant antitumor, antibacterial, anti-inflammatory, antimalarial, antiviral, antithrombocytopenia, immunomodulatory, antioxidant, hepatoprotective, hypoglycemic and hypolipidemic effects, with low toxicity and side effects. However, most studies have focused on Sarcandra glabra (Thunb.) Nakai and studies on other plants of the genus have yet to be explored.

CONCLUSIONS

Sarcandra plants have a wide range of clinical uses and diverse chemical compounds. However, the main research has been concentrated on Sarcandra glabra (Thunb.) Nakai, and future research should explore the medicinal properties of other Sarcandra plants to expand their potential clinical applications. Meanwhile, the pharmacological activities of compounds from Sarcandra species need to be studied in greater depth and detail to provide an appropriate scientific basis for developing new drugs and natural product research.

Terpenoids of plants from Chloranthaceae family: chemistry, bioactivity, and synthesis

Covering: 1976 to December 2023Chloranthaceae is comprised of four extant genera (Chloranthus, Sarcandra, Hedyosmum, and Ascarina), totaling about 80 species, many of which have been widely used as herbal medicines for diverse medical purposes. Chloranthaceae plants represent a rich source of structurally interesting and diverse secondary metabolites, with sesquiterpenoids and diterpenoids being the predominant structural types. Lindenane sesquiterpenoids and their oligomers, chemotaxonomical markers of the family Chloranthaceae, have shown a wide spectrum of bioactivities, attracting significant attention from organic chemists and pharmacologists. Recent achievements also demonstrated the research value of two unique structural types in this plant family, sesquiterpenoid-monoterpenoid heterodimers and meroterpenoids. This review systematically summarizes 682 structurally characterized terpenoids from 22 Chloranthaceae plants and their key biological activities as well as the chemical synthesis of selected terpenoids.

Natural Occurring Terpene Cyclic Anhydrides: Biosynthetic Origin and Biological Activities

Cyclic acid anhydride is a not very widespread structure in nature, but with a determining role in natural products possessing this functionality in their skeleton. To the best of our knowledge, no revision of terpenes containing cyclic anhydrides has been previously reported. The result was that more than 100 terpenic cyclic anhydrides and related compounds were found to be in need of being reported. This review has been systematically organized by terpene skeletons, from the smallest to largest, describing their sources and bioactivities. In addition, different biosynthetic pathways for their final oxidations, namely, routes A, B and C, leading to the formation of these heterocyclic natural products, have been proposed. We have also included the most plausible precursors of these natural products, which mostly happened to be present in the same natural source. Some molecules derived from terpene cyclic anhydrides, such as their natural imide derivatives, have also been described due to their significant biological activity. In this sense, special attention has been paid to cantharidin because of its historical relevance and its broad bioactivity. A plausible biosynthesis of cantharidin has been proposed for the first time. Finally, cyclic anhydride structures that were firstly assigned as anhydrides and later corrected have been also described.

Sarcanoids A and B, two new lindenane-type sesquiterpenoid dimers from the aerial parts of Sarcandra glabra

Sarcanoids A and B (1 and 2), two new lindenane-type sesquiterpenoid dimers with a γ-hydroxysenecioate moiety at C-15', were isolated from the ethyl acetate extract of Sarcandra glabra. The structures were elucidated by extensive analysis of spectroscopic data, and their absolute configurations were determined by single-crystal X-ray crystallography. Compounds 1 and 2 showed moderate inhibitory activities on the nitric oxide (NO) production induced by lipopolysaccharide (LPS) in RAW264.7 macrophages.

Trisarcglaboids A and B, two cytotoxic lindenane sesquiterpenoid trimers with a unique polymerization mode isolated from Sarcandra glabra

Trisarcglaboids A and B (1 and 2), representing the first example of lindenane sesquiterpenoid trimers repolymerized based on the classical [4 + 2] type dimer, together with known biogenic precursors chlorahololide D (3) and sarcandrolide A (4), were identified as chemical components of the root of Sarcandra glabra. The novel trimeric lindenane sesquiterpenoid skeletons, including their absolute configurations, were characterized using MS, NMR, ECD, and X-ray single crystal diffraction. The proposed Diels-Alder cycloaddition between Δ2(3) of the tiglic acyl group of the classical [4 + 2] type dimer and Δ15(4),5(6) of the third lindenane may serve as the key biogenic step. In addition, compound 1 exerted significant cytotoxicity against five human cancer cell lines with IC50 values ranging from 1 to 7 μM, potentially through blocking Akt phosphorylation and activating the endogenous apoptosis pathway.

Chemistry and bioactivity of lindenane sesquiterpenoids and their oligomers

Covering: 1925 to July 2023Among the sesquiterpenoids with rich structural diversity and potential bioactivities, lindenane sesquiterpenoids (LSs) possess a characteristic cis, trans-3,5,6-carbocyclic skeleton and mainly exist as monomers and diverse oligomers in plants from the Lindera genus and Chloranthaceae family. Since the first identification of lindeneol from Lindera strychnifolia in 1925, 354 natural LSs and their oligomers with anti-inflammatory, antitumor, and anti-infective activities have been discovered. Structurally, two-thirds of LSs exist as oligomers with interesting skeletons through diverse polymeric patterns, especially Diels-Alder [4 + 2] cycloaddition. Fascinated by their diverse bioactivities and intriguing polycyclic architectures, synthetic chemists have engaged in the total synthesis of natural LSs in recent decades. In this review, the research achievements related to LSs from 1925 to July of 2023 are systematically and comprehensively summarized, focusing on the classification of their structures, chemical synthesis, and bioactivities, which will be helpful for further research on LSs and their oligomers.

Structurally diverse triterpenoid alkaloids from Buxus rugulosa

Four new nortriterpenoid alkaloids, namely buxrugulines E-H (1-4), along with five known ones (5-9), were isolated from the twigs and leaves of Buxus rugulosa. Their structures were identified based on extensive NMR data and MS spectroscopic analyses. Our bioassays revealed that compounds 5, 6 and 8 exhibited potent cytotoxicity in vitro against MCF-7 cell lines, with IC50 values ranging from 6.70 to 11.00 μM, respectively.

A comprehensive review on the chemical constituents, sesquiterpenoid biosynthesis and biological activities of Sarcandra glabra

Sarcandra glabra (Thunb.) Nakai is a perennial evergreen herb categorised within the Sarcandra Gardner genus under the Chloranthaceae family. Indigenous to tropical and subtropical regions of East Asia and India, this species is extensively distributed across China, particularly in the southern regions (Sichuan, Yunnan, and Jiangxi). In addition to its high ornamental value, S. glabra has a rich history of use in traditional Chinese medicine, evident through its empirical prescriptions for various ailments like pneumonia, dysentery, fractures, bruises, numbness, amenorrhea, rheumatism, and other diseases. Besides, modern pharmacological studies have revealed various biological activities, such as antitumour, anti-bacterial, anti-viral anti-inflammatory and immunomodulatory effects. The diverse chemical constituents of S. glabra have fascinated natural product researchers since the 1900s. To date, over 400 compounds including terpenoids, coumarins, lignans, flavonoids, sterols, anthraquinones, organic acids, and organic esters have been isolated and characterised, some featuring unprecedented structures. This review comprehensively examines the current understanding of S. glabra's phytochemistry and pharmacology, with emphasis on the chemistry and biosynthesis of its unique chemotaxonomic marker, the lindenane-type sesquiterpenoids.

Lindenane sesquiterpenoid monomers and oligomers: Chemistry and pharmacological activities

Lindenane sesquiterpenoid monomers and oligomers, characterized by a sterically congested cyclopentane and an unusual trans-5/6 ring junction, are mainly found in Chloranthaceae species and the genus Lindera Thunb (Lauraceae). Numerous studies have shown that lindenane sesquiterpenoid monomers and oligomers exhibit a broad range of biological activities, such as cytotoxicity, anti-inflammation, neuroprotection, antifungal, and anti-malarial activities. This review covers publications from the first identification of lindeneol in 1925-2023 and classifies the lindenane sesquiterpenoid derivatives into sesquiterpenoid monomers, sesquiterpenoid-monoterpene conjugates, sesquiterpenoid homodimers, sesquiterpenoid heterodimers, and trimeric sesquiterpenoids. In addition, their biological activities are summarized. This review will establish a scientific basis and provide guidance for utilizing this unique class of natural products as potential lead compounds to develop their application in treating diseases corresponding to inflammation, cancer, and plasmodium.

Two new sesquiterpenoids from the roots of Sarcandra glabra

Two new sesquiterpenoids, sarglanoids G and H (1 and 2), together with two known analogues (3-4) were isolated from the roots of Sarcandra glabra. Compound 2 was a rare elemene-type sesquiterpenoid with a furan ring fragment, which is mostly lactone ring in its analogues. The structures of new compounds were determined on the basis of extensive spectroscopic methods including HR-ESI-MS, 1D and 2D NMR, and the absolute configuration of 1 was established by ECD calculations. Their anti-inflammatory activities were also evaluated.

Rearranged Lindenane Sesquiterpenoid Trimers from Chloranthus fortunei: Target Discovery and Biomimetic Conversion

Seven lindenane-type sesquiterpenoid trimers, including four new ones (1-4) and three known analogues (5-7), were isolated from Chloranthus fortunei guided by high-performance liquid chromatography with photodiode array detection with characteristic absorption at 210 and 350 nm. Their structures, including absolute configurations, were achieved by high-resolution mass spectrometry, nuclear magnetic resonance, electronic circular dichroism, and quantum chemical calculations. Compound 1 was the first example of two lindenane units connected by a C-15-C-15' bond. The 5/7/5-fused ring system in 2 was presumably formed biogenetically by key keto-enol tautomerism and Cope rearrangement from 5. The 5/3/6 carbon skeleton in 3-5 and epi-cyclopropane in 3 and 6 might have originated from trishizukaol A (7) with a normal 3/5/6-fused ring system through vinylcyclopropane rearrangement. The biomimetic conversion from 7 to 3-6 was successfully achieved by adding a 365 nm ultraviolet lamp and a free radical initiator, and 2 was also spontaneously converted to 5 in methanol and CDCl₃, which proved the correctness of the structural identification and the speculation described above. Compounds 1-7 exhibited anti-inflammatory activity with IC₅₀ values in the range of 2.90-22.80 μmol/L.

Automatic MS/MS Data Mining Strategy for Discovering Target Natural Products: A Case of Lindenane Sesquiterpenoids

Untargeted liquid chromatography-tandem mass spectrometry (LC-MS/MS) is a widely used method for discovering natural products (NPs); however, automatic MS/MS data mining for the discovery of NPs remains a challenge. In this work, LindenaneExtractor, a program based on characteristic MS/MS ions of lindenane sesquiterpenoids (LSs) was developed to automatically extract the LSs features for target LS discovery in plant extracts. To build this program, fragmentation mechanisms of characteristic ions of LSs were elucidated and confirmed by quantum chemical calculation and deuterium-labeled compounds. Subsequently, the information of characteristic ions was integrated and coded to develop LindenaneExtractor, which was further examined by standards and several public databases. Finally, the target LS features in Sarcandra hainanensis extract were automatically extracted by LindenaneExtractor and visualized by feature-based molecular networking and two-dimensional (2D) retention time-m/z plot, leading to the discovery of 96 target LSs in total, 37 of these compounds were potentially new NPs and one was confirmed by further isolation. This work proposed a new strategy for target NP analysis and discovery based on automatic MS/MS data mining, which could significantly improve the efficiency and accuracy of NP discovery.

Sarglaromatics A-E: A Class of Naphthalene-Like Architecture Fused Norlindenane Sesquiterpene Dimers from Sarcandra glabra

Sarglaromatics A-E (1-5, respectively), five unprecedented naphthalene-like architecture-fused norlindenane sesquiterpene dimers, were discovered from the roots of Sarcandra glabra. The unique naphthalene core skeleton was obtained from classical lindenane [4 + 2] dimers via a free-radical-mediated C11-C11' bond formation reaction and 12'-decarboxylation. The highly fused octonary ring skeleton was elucidated by HRMS, NMR, ECD, quantum chemical calculations, and biogenetic inspiration. Compounds 1 and 2 showed significant anti-nonalcoholic steatohepatitis (NASH) activity by inhibiting lipid deposition in L02 cells.

Sarcanolides C-E: three new lindenane sesquiterpenoid dimers with anti-inflammatory activities from Sarcandra glabra

Three new lindenane-type sesquiterpenoid dimers, sarcanolides C-E (1-3), were isolated from the roots of Sarcandra glabra. Sarcanolide C (1) possesses a unique decacyclic scaffold with an unusual orthoformate unit. The structures of 1-3 were determined through extensive spectroscopic analysis, while their absolute configurations were determined by comparison of calculated and experimental electronic circular dichroism (ECD) spectra. Compounds 1-3 were evaluated for their inhibitory activity against LPS-induced nitric oxide (NO) production in RAW264.7 macrophages. All the isolates displayed a moderate inhibitory effect against NO production with IC50 values in the range of 13.4-17.2 μM, comparable to that of the positive control L-NMMA.

Shizukaol A exerts anti-inflammatory effect by regulating HMGB1/Nrf2/HO-1 pathway

BACKGROUND

Sarcandra glabra (Thunb.) Makino (Chloranthaceae) has a long history of being used in Traditional Chinese medicines (TCMs) to treat painful joints, fractures, arthritis, and other diseases caused by inflammation. It has been reported that lindenane-type sesquiterpenoid dimers are main anti-inflammatory ingredient of S. glabra. Meanwhile, shizukaol A, the precursor of these sesquiterpene dimers, possesses a good inhibitory effect on nitric oxide (NO) in our previous study. But its anti-inflammatory mechanism is still unclear.

PURPOSE

This study aimed to explore the possible anti-inflammatory mechanism and potential targets of shizukaol A in lipopolysaccharide (LPS)-induced RAW 264.7 cells.

METHODS

The release of NO and inflammatory cytokines in LPS-stimulated RAW 264.7 cells were measured by Griess reagent and ELISA, respectively. The relevant proteins including inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), nuclear factor kappa B (NF-κB) p65, High mobility group box 1 (HMGB1) were detected by western blot. Nuclear translocation of p65, HMGB1 and nuclear factor E2-related factor 2 (Nrf2) were examined by immunofluorescence. The level of reactive oxygen species (ROS) was tested by flow cytometry. The target of shizukaol A was investigated by molecular docking and Drug Affinity Responsive Target Stability (DARTS).

RESULTS

Shizukaol A had a good inhibitory effect on NO with half maximal inhibitory concentration (IC₅₀) of 13.79 ± 1.11 μM. Shizukaol A could down-regulate the expression of iNOS and COX-2. Further studies demonstrated that shizukaol A can significantly inhibit phosphorylation and nuclear translocation of NF-κB. Meanwhile, shizukaol A decreased the level of ROS and enhanced the expression of heme oxygenase-1 (HO-1) and NAD(P)H: quinone oxidoreductase 1 (NQO1). Furthermore, shizukaol A up-regulated the expression of Nrf2 and its nuclear translocation. More importantly, shizukaol A could inhibit activation of HMGB1 by targeting HMGB1.

CONCLUSION

Shizukaol A inhibited inflammation by targeting HMGB1 to regulate the Nrf2/HO-1 signaling pathway. Thus, shizukaol A may be an attractive therapeutic candidate for inflammatory diseases.

Natural disesquiterpenoids: an update

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