1H-NMR-guided isolation of enantiomeric coumarin-monoterpenes with anti-inflammatory activity from Gerbera piloselloides

Systematic review of natural coumarins in plants (2019-2024): Chemical structures and pharmacological activities

Coumarins constitute one of the most substantial classes of secondary metabolites, characterised by a fundamental α-benzopyranone skeleton, which serves as an overarching nomenclature for o-hydroxycinnamyl lactone moieties. These chemical constituents are widely distributed in various plant species. Based on the nature and loci of their substituents, these compounds can be further classified into simple coumarins, furanocoumarins, pyranocoumarins, isocoumarins, biscoumarins and other coumarins. Contemporary pharmacological research has revealed that coumarins exhibit a spectrum of properties, including antibacterial, antioxidant, anticancer, anti-inflammatory and hypoglycaemic activities. Owing to their diverse of structures and pharmacological actions, coumarins are widely used in cuisine, cosmetics and pharmaceutical industries. An extensive body of scholarly literature has been produced in this domain, although a notable paucity in the compilation and updating of references has been identified since 2019. Herein, the chemical structures and pharmacological activities of coumarins reported for the first time between 2019 and 2024 were systematically summarised. In total, 220 scholarly articles involving 574 coumarins reported for the first time in plants were included in this review. In addition, the biosynthetic pathways of some common types of coumarins (simple coumarins, furanocoumarins, and pyranocoumarins) are also preliminarily summarised in this paper. Meticulously analyzing and synthesising the published literature will lay a solid foundation for further investigation and extensive utilisation of coumarin derivatives.

Phytochemical and biological studies on rare and endangered plants endemic to China. Part XLIV. Integrated NMR/EI-MS/LC-PDA-ESIMS approach for dereplication and targeted isolation of fortunefuroic acids from Keteleeria fortunei across diverse geographical origins

Secondary metabolites in plants of the same species, though originating from distinct geographical regions, frequently display both similarities and notable variations. A prior study on the vulnerable Chinese endemic conifer Keteleeria fortunei, collected from Yunnan province (KFYN), led to the isolation of fortunefuroic acids (FFAs) A-I. These compounds represent a unique class of triterpenoids characterized by a rare furoic acid moiety within the lateral chain. The distinct 23,27-epoxy-23,25(27)-dien-26-oic acid unit present in FFAs can be readily identified by characteristic proton NMR signals (δH-24: ca 6.36 ppm; δH-27: ca 7.97 ppm), a prominent ion fragment at m/z 125 in the EI-MS, and typical UV absorption peak around λmax 245 nm. In this study, an integrated approach was employed to dereplicate and isolate FFA-type compounds from K. fortunei collected from Fujian Province (KFFJ). This approach combined NMR, EI-MS, and LC-PDA-ESIMS data to detect and analyze compounds with molecular weights in the range of 464-468 Da, a distinguishing feature of FFA-type compounds. Consequently, six previously undescribed FFAs K-P (1-6) were obtained, alongside the re-isolation of FFAs A-D and H. Compound 1 exhibits a rare 17,14-friedo-cyclaorane type skeleton, while compound 2 is characterized as a 3,4-seco-cyclaorane-3,26-dioic acid. Compounds 3-6 are identified as derivatives of 9βH-lanost-26-oic FFAs. Additionally, a previously unreported lanost-26-oic acid derivative (7) was also identified, exhibiting an inhibitory effect on ATP-citrate lyase. Their chemical structures and absolute configurations were determined through spectroscopic analysis, GIAO NMR calculations combined with DP4+ probability analyses, and electronic circular dichroism calculations. The isolated FFAs have the potential to serve as chemotaxonomic markers for the genus Keteleeria within the Pinaceae family. This study marks the first application of integrated NMR/EI-MS/LC-PDA-ESIMS methods for both dereplication and the discovery of new natural products. Notably, the KFFJ samples were collected from a location approximately 1500 km away from that of KFYN. Understanding the impact of geographical origins on specialized metabolites may provide valuable insights into the sustainable utilization and conservation of endangered plant species.

Four pairs of meroterpenoid enantiomers with coumarin- and chromone-monoterpene skeletons from Gerbera piloselloides and their bioactive activities

Phytochemical investigations of the extracts from the whole plant of Gerbera piloselloides resulted in the isolation and identification of four pairs of previously unreported meroterpenoid enantiomers with coumarin- and chromone-monoterpene skeletons (1a/1b-4a/4b), including two pairs of 5-methylcoumarin monoterpenes and two pairs of 5-methylchromone monoterpenes. The structures and absolute configurations of these compounds were definitively determined through NMR and MS data, NMR calculation with DP4+ analysis, electronic circular dichroism (ECD) data, and X-ray diffraction analysis. Structurally, compounds 1-4 feature 5-methylphenylpropanoid-substituted monoterpene frameworks. All compounds were evaluated for neuroprotective activity and cytotoxicity against the human cancer cell line SGC-7901 in vitro. Compounds 1, 1a, and 1b exhibited inhibitory effects with IC50 values ranging from 12.07 to 12.44 μM against SGC-7901 compared with the positive control vorinostat (IC50 value 0.37 μM). Furthermore, the hypothetical biogenetic pathways for these compounds were discussed.

LC-MS coupled with diagnostic ion strategy facilitated the discovery of 5-methylcoumarin meroterpenoids from Gerbera piloselloides

Plant-derived natural products remain crucial in drug development. However, the identification of undescribed natural products is becoming increasingly challenging. A comprehensive strategy combining LC-MS with diagnostic ions was proposed for the discovery of undescribed 5-methylcoumarin meroterpenoids. Thirteen undescribed 5-methylcoumarin meroterpenoids, including five pairs of enantiomers (1a/1b and 5a/5b-8a/8b), were isolated from the whole plant of Gerbera piloselloides. Their structures and absolute configurations were unambiguously determined based on their spectroscopic data, calculated and experimental ECD data and X-ray diffraction analysis. Bioassays conducted on scopolamine-induced injury PC12 cells revealed that compounds 5a/5b, 7a/7b and 8a/8b possessed mild protective effects. Additionally, compounds 2 and 8 showed notable IL-6 inhibition in lipopolysaccharide-induced BEAS-2B cells.

Cyclobrachycoumarin from Gerbera piloselloides Inhibits Colorectal Cancer In Vitro and In Vivo

Gerbera piloselloides, a plant in the Asteraceae family, is a traditional Chinese medicinal herb known for its unique therapeutic properties, including reported anti-tumor and antioxidant effects. Recent studies suggest that the main constitute of G. piloselloides, coumarins, may have potential anti-tumor activity. Recent research suggests that coumarins, the active compounds in G. piloselloides, may hold potential anti-tumor activity. However, the pharmacodynamic constituents remain unidentified. This study aims to isolate and characterize the bioactive compounds of G. piloselloides and to assess its anti-tumor effects. Initially, seven compounds, including coumarins, a ketone, and a furanolide, were isolated and identified from G. piloselloides by semi-preparative high-performance liquid chromatography (HPLC) and nuclear magnetic resonance (NMR) analysis. The anti-tumor effects of these compounds were evaluated across four different cancer cell lines. Among them, the compound cyclobrachycoumarin showed a significant inhibitory effect on colorectal cancer (CRC) cell proliferation and was selected for further investigation. Cyclobrachycoumarin was found to induce CRC cell apoptosis and cell cycle arrest in a dose-dependent manner. This treatment also led to increased levels of ROS and cleaved PARP, along with decreased expressions of survivin, cyclin D1, and CDK1. In vivo studies further demonstrated that cyclobrachycoumarin effectively reduced tumor growth in HT-29 xenograft models by promoting apoptosis and cell cycle arrest, with a favorable tolerability profile. In summary, this study suggests that cyclobrachycoumarin may be a promising candidate for safe and effective CRC therapy.

Larvicidal potential of Trachyspermum ammi essential oil and Delphinium speciosum extract against malaria, dengue, and filariasis mosquito vectors

Mosquito-borne diseases, such as malaria, dengue, and Zika, pose major public health challenges globally, affecting millions of people. The growing resistance of mosquito populations to synthetic insecticides underscores the critical need for effective and environmentally friendly larvicides. Although chemical pesticides can initially be effective, they often lead to negative environmental consequences and health hazards for non-target species, including humans. This study aimed to evaluate the larvicidal effects of Trachyspermum ammi essential oil and Delphinium speciosum extract on the larvae of three major mosquito species: Aedes aegypti, Anopheles stephensi, and Culex quinquefasciatus. Mosquito larvae of Ae. aegypti, An. stephensi, and Cx. quinquefasciatus were reared under controlled laboratory conditions. The larvicidal activity of T. ammi essential oil and D. speciosum extract was evaluated through standard bioassays, using various concentrations of essential oils (10, 20, 40, 80, and 160 ppm) and extracts (160, 320, 640, 1280, and 2560 ppm) to determine the lethal concentration (LC50) values after 24 h of exposure. Fresh plant materials were collected, with the essential oil extracted via hydro-distillation, and the extract prepared using methanol solvent extraction. The chemical composition of T. ammi essential oil was examined using gas chromatography-mass spectrometry (GC-MS). Additionally, the preliminary analysis of the chemical compounds in D. speciosum extract was carried out using thin layer chromatography (TLC) and nuclear magnetic resonance spectroscopy (NMR) techniques. The results indicated that the essential oil of T. ammi exhibited more effective larvicidal activity compared to the D. speciosum extract. Specifically, the essential oil demonstrated LC50 values of 18 ppm for Cx. quinquefasciatus and 19 ppm for Ae. aegypti. In contrast, the D. speciosum extract showed the strongest larvicidal effect against An. stephensi, with an LC50 of 517 ppm. Concentrations of 40 ppm of the essential oil and 1280 ppm of the extract resulted in 100% mortality across all three species. Both the essential oil of T. ammi and the D. speciosum extract exhibited concentration-dependent larvicidal activity, and these results were statistically significant (p < 0.001) compared to the no-treatment group. GC-MS analysis revealed thymol (88.95%), o-cymen-5-ol (4.11%), and γ-terpinene (2.10%) as the major constituents of the T. ammi essential oil. Additionally, TLC verified the presence of alkaloids in both chloroform and methanolic extracts. Proton NMR identified a diterpene structure for these alkaloids. These findings suggest that T. ammi essential oil is a promising candidate for natural mosquito control strategies. Given its efficacy, further research is warranted to explore its potential in integrated vector management programs.

(+)/(-)-Gerbeloid A, a pair of unprecedented coumarin-based polycyclic meroterpenoid enantiomers from Gerbera piloselloides: Structural elucidation, semi-synthesis, and lipid-lowering activity

A pair of coumarin-based polycyclic meroterpenoid enantiomers (+)/(-)-gerbeloid A [(+)-1a and (-)-1b] were isolated from the medicinal plant Gerbera piloselloides, which have a unique caged oxatricyclo [4.2.2.03,8] decene scaffold. Their planar and three-dimensional structures were exhaustively characterized by comprehensive spectroscopic data and X-ray diffraction analysis. Guided by the hypothetical biosynthetic pathway, the biomimetic synthesis of racemic 1 was achieved using 4-hydroxy-5-methylcoumarin and citral as the starting material via oxa-6π electrocyclization and intramolecular [2 + 2] photocycloaddition. Subsequently, the results of the biological activity assay demonstrated that both (+)-1a and (-)-1b exhibited potent lipid-lowering effects in 3T3-L1 adipocytes and the high-fat diet zebrafish model. Notably, the lipid-lowering activity of (+)-1a is better than that of (-)-1b at the same concentration, and molecular mechanism study has shown that (+)-1a and (-)-1b impairs adipocyte differentiation and stimulate lipolysis by regulating C/EBPα/PPARγ signaling and Perilipin signaling in vitro and in vivo. Our findings provide a promising drug model molecule for the treatment of obesity.

Four new glycosides isolated from Gerbera delavayi Franch

Phytochemical investigation of the whole plant of Gerbera delavayi afforded four new glycosides including three coumarin glycosides, Gerbelavinside A (1), Gerbelavinside B (2) and Gerbelavinside C (3) and one acetophenone glycoside, Gerbelavinside F (4). The structures of isolated compounds were elucidated by analysis of 1D and 2D NMR, HR-ESI-MS, acid hydrolysis, as well as comparing with the literature. The isolated compounds were examined the effects of nitric oxide (NO) production inhibition in lipopolysaccharide (LPS)-induced RAW264.7 macrophage cells, and Gerbelavinside C presented a certain inhibitory activity.

1H NMR-guided isolation of hasubanan alkaloids from the alkaloidal extract of Stephania longa

1H NMR-guided fractionation led to the isolation of 16 alkaloids from the alkaloidal extract of Stephania longa, including 11 new hasubanan alkaloids (1-11) and five known alkaloids (12-16). Interestingly, compounds 2 and 11 are typically considered protonated tertiary amine compounds, whereas compounds 1 and 10 are regarded as oxidized versions of the corresponding compounds. Their gross structures were determined through an extensive analysis of spectroscopic data (NMR (nuclear magnetic resonance) and HRESIMS (high resolution electrospray ionization mass spectroscopy)), and their absolute configurations were established by comparing their experimental and calculated electronic circular dichroism (ECD) spectra. The new (3) and a known (12) compounds in all isolates displayed stronger antineuroinflammatory effects (IC50 values of 1.8 and 11.1 μM, respectively) than minocycline (IC50 value of 15.5 μM) against NO production on LPS-activated BV2 cells.