Chlospicenes A and B, cyclopropane cracked lindenane sesquiterpenoid dimers with anti-nonalcoholic steatohepatitis activity from Chloranthus henryi

Mass spectral database-based methodologies for the annotation and discovery of natural products

Natural products (NPs) have long held a significant position in various fields such as medicine, food, agriculture, and materials. The chemical space covered by NPs is extensive but often underexplored. Therefore, high-throughput and efficient methodologies for the annotation and discovery of NPs are desired to address the complexity and diversity of NP-based systems. Mass spectrometry (MS) has emerged as a powerful platform for the annotation and discovery of NPs. MS databases provide vital support for the structural characterization of NPs by integrating extensive mass spectral data and sample information. Additionally, the released annotation methodologies, based on a variety of informatics tools, continuously improve the ability to annotate the structure and properties of compounds. This review examines the current mainstream databases and annotation methodologies, focusing on their advantages and limitations. Prospects for future technological advancements are then discussed in terms of novel applications and research objectives. Through a systematic overview, this review aims to provide valuable insights and a reference for MS-based NPs annotation, thereby promoting the discovery of novel natural entities.

Structurally diversified sesquiterpenoids from Chloranthus henryi and their neuroprotective activities on H2O2 damaged PC12 cells

Fifteen undescribed sesquiterpenoid monomers, including six pairs of sesquiterpenoid enantiomers (1a/1b-3a/3b and 5a/5b-7a/7b) and three analogues (4, 8, and 9), together with two known sesquiterpenoid dimers (10 and 11) were isolated from the whole plant of Chloranthus henryi Hemsl. Their structures were characterized by spectroscopic data analysis, ECD calculations, and single crystal X-Ray diffractions. Compounds 1a and 1b were highly aromatic cadinane-type sesquiterpenoids. At a concentration of 10 μM, compounds 8, 10, and 11 exhibited potent neuroprotective activity against H2O2-induced PC12 cell damage. Compounds 10 and 11 significantly decreased the level of ROS. In addition, compound 11 increased the levels of p-AMPK, p-SIRT1, and SIRT3 in the H2O2-induced PC12 cell damage via activated the AMPK/SIRT signaling pathway.

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.

Anti-inflammatory lindenane sesquiterpenoid dimers from the roots of Chloranthus holostegius var. trichoneurus

Two new lindenane-type sesquiterpenoid dimers, chlotrichenes C and D (1 and 2) together with five known lindenane-type sesquiterpenoid dimers (3-7) were isolated from the roots of Chloranthus holostegius var. trichoneurus, a famous natural medicine named as "Sikuaiwa" for subduing swellings and relieving pain. The structures including absolute configuration were elucidated by their 1D and 2D NMR, HRESIMS, and ECD data. Compounds 1 and 2 were classical [4 + 2] lindenane-type sesquiterpenoid dimers that differed from known analogs in oxidation profile, side chain profile, and double bond position. The new isolates and compound 3 exhibited significant inhibitory activity on IL-1β production (IC50: 1-15 μM) in LPS-induced THP-1 cells and other compounds exhibited inhibitory activity on NO production in LPS-induced RAW 264.7 cells (IC50: 24-33 μM).

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.

Isolation and biomimetic synthesis of phenylpropionyl phenylethylamines from Chloranthus henryi

In this study, ten phenylpropionyl phenylethylamines, including five previously undescribed ones (1a/b, 2a/b, and 3), five known analogues (4-8), and two established phenylpropanoids precursors (9, 10) were isolated from the aerial parts of Chloranthus henryi Hemsl. Their structures, including absolute configurations, were determined by high-resolution mass spectrometry, enantio-separation, electronic circular dichroism calculation, and single crystal diffraction. Compounds 1a and 1b were the first examples of natural hetero-[2 + 2] cycloaddition products between phenylpropionyl phenylethylamine and phenylpropene. The plausible hetero-[2 + 2] biosynthesis pathway was confirmed by a photocatalytic biomimetic synthesis in eight steps, which also led to the production of three other potential natural homo-[2 + 2] adducts (1'a/b, 2', and 3'). Bioactivity screening indicated that these adducts bear medium inhibitory activity on nitric oxide generation, with IC50 values of 6-35 μM in RAW 264.7 macrophages.

Anti-Inflammatory Peroxidized Chlorahololide-Type Dimers Are Artifacts of Shizukaol-Type Dimers: From Phenomena Discovery and Confirmation to Potential Underlying Mechanism

In our research on naturally occurring sesquiterpenes, eight shizukaol-type dimers, one chlorahololide-type dimer, and one sarcanolide-type dimer were isolated from the roots of Chloranthus fortunei. As the project was implemented, we accidentally discovered that shizukaol-type dimers can be converted into peroxidized chlorahololide-type dimers. This potential change was discovered after simulations of the changes in corresponding shizukaols showed that three peroxide products were generated (1-3), indicating that peroxidation reactions occurred. HPLC-HR-MS analysis results obtained for the shizukaol derivatives further demonstrate that the reaction occurred, and the type of substituent of small organic ester moieties at positions C-15' and C-13' of unit B were not decisively related to the reaction. Quantum chemical calculations of the mode dimer further demonstrated this phenomenon. The highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy of the precursor and production revealed the advantageous yield of 4β-hydroperoxyl production. Additionally, the potential reaction mechanism was speculated and validated using the free energy in the reaction which successfully explained the feasibility of the reaction. Finally, the anti-inflammatory activity of the precursors and products was evaluated, and the products of peroxidation showed better anti-inflammatory activity.

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.

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.

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.

Visible-light enabled synthesis of cyclopropane-fused indolines via dearomatization of indoles

An efficient synthesis of methylene-unsubstituted cyclopropane-fused indolines via photoredox catalyzed dearomative cyclopropanation of indole derivatives was developed. A broad range of indoles bearing a variety of functional groups were compatible...