A New Diterpene and Anti-inflammatory Sesquiterpene Lactones from Sigesbeckia orientalis

Siegesbeckia orientalis ethanol extract impedes RAGE-CD11b interaction driven by HMGB1 to alleviate neutrophil-involved neuronal injury poststroke

BACKGROUND

Ischemic stroke is a life-threatening cerebrovascular disease with limited therapeutic options. During the progression of acute ischemic stroke (AIS), neutrophil-involved inflammation mediated by high mobility group box 1 (HMGB1) considerably contributes to intensification of neuronal injury. Siegesbeckia orientalis L. (SO), one of the primary sources of Sigesbeckiae Herba, is promising in anti-neuroinflammation and neutrophil function modulation. Consequently, it is supposed that SO could fight against neuronal inflammatory injury following AIS.

PURPOSE

The current study struggles to explore the ameliorative effects of ethanol extract of SO (EESO) on neuronal inflammatory injury following AIS, and dissect the related mechanisms focusing on HMGB1-driven neutrophil recruitment and neutrophil extracellular traps (NETs) generation.

METHODS

Murine photothrombotic stroke model was established to evaluate the ameliorative effects of EESO administration against AIS. Histopathological examination and immunofluorescence staining were conducted for the observation of cerebral neuronal injury, neutrophil infiltration and NETs generation. Additionally, inflammatory indexes and serum HMGB1 levels were also detected through qPCR and ELISA, respectively. In vitro, the effects of EESO-containing serum administration on neutrophil migration and NETs generation were also assessed. HMGB1-overexpressed mimic transfection, cellular thermal shift assay and coimmunoprecipitation were employed to investigate whether the compounds from EESO-containing serum targeted HMGB1 to block the receptor for advanced glycation end products (RAGE)-CD11b interaction. Furthermore, potential active compounds of EESO targeting HMGB1 were screened and verified.

RESULTS

EESO administration alleviated photochemically induced murine AIS as revealed by remarkably reducing infract volume as well as improving cerebral blood flow and neurological functions. Moreover, EESO administration prominently mitigated secondary neuronal injury, restrained neutrophil infiltration and NETs generation, as well as lowered the levels of serum pro-inflammatory mediators and HMGB1. In vitro, the compounds in EESO-containing serum directly interacted with neuron-derived HMGB1. HMGB1-driven neutrophil migration and NETs generation through the RAGE-CD11b interaction were also reversed by EESO-containing serum administration. Additionally, isoimperatorin, 4,7-dimethyltetral-1-one, perillartine and darutigenol, as the active components, contributed to the suppressive effects of EESO on neutrophil migration and NETs generation driven by HMGB1.

CONCLUSION

In the present study, it was demonstrated that HMGB1 promoted interaction between CD11b and RAGE to drive NETs generation for the first time. Furthermore, EESO was proved to target neuron-derived HMGB1 to inhibit neutrophil infiltration and NETs generation against neuronal inflammatory injury poststroke, which was attributed to the components absorbed in the blood including isoimperatorin, 4,7-dimethyltetral-1-one, perillartine and darutigenol.

A review on medical plants Siegesbeckia based on diterpenoids and sesquiterpenoids: phytochemistry, pharmacology and clinical applications

Natural products, owing to their chemical diversity, biological activity, and historical success, continue to be a precious source of lead compounds and potential candidates for drug discovery. Siegesbeckia, in particular, presents a promising avenue for drug discovery due to its long history of usage in traditional Chinese medicine and its well-established clinical applications. Diterpenoids and sesquiterpenoids, the characteristic metabolites of Siegesbeckia, have consistently attracted considerable attention in related scientific research because of their diverse structures and extensive range of bioactivities, including anti-inflammatory and anti-cancer properties. Herein, we provide an overview of the phytochemistry, biosynthesis, pharmacological action, as well as clinical applications of Siegesbeckia. This paper will provide a valuable reference for advancing further research and development of Siegesbeckia.

Two new chlorinated sesquiterpenes from Sigesbeckia orientalis

Two new chlorinated guaianane-type sesquiterpenes (named chlosigesolides A and B) together with eight known compounds were isolated from the leaves and twigs of Sigesbeckia orientalis. Their structures were determined by analysis of HR-ESI-MS, 1D- and 2D-NMR spectral data as well as comparison with the literature. Absolute configurations of new compounds were elucidated by NOESY and ECD methods. Chlosigesolide A inhibited NO production in LPS-stimulated RAW264.7 macrophages with IC50 value of 10.9 ± 0.8 μM. Other compounds exhibited inhibitory activity at IC50 in range of 26.5 to 49.7 μM.

Highly Modified Sesquiterpene Lactones with Cytotoxic Activities from Strobocalyx chunii

Three new germacranolide sesquiterpene lactones (SLs), strochunolides A-C (1-3, respectively), and a new guaianolide SL, strochunolide D (4), were isolated from Strobocalyx chunii and structurally characterized. Compound 1 is the first example of a dihomo-germacranolide SL, characterized by an unprecedented 6/10/5 tricyclic scaffold incorporating an additional fused δ-lactone C-ring. The structure of a known germacranolide SL, spicatolide C (5), was revised as its 8-epimer. Compound 3 exhibited potent in vitro cytotoxic activity against the HL-60 cell line, with an IC50 value of 0.18 ± 0.01 μM.

Suppressive Effects of Siegesbeckia orientalis Ethanolic Extract on Proliferation and Migration of Hepatocellular Carcinoma Cells through Promoting Oxidative Stress, Apoptosis and Inflammatory Responses

Previous studies have demonstrated that Siegesbeckia orientalis (SO) has a suppressive effect on the growth and migration of endometrial and cervical cancer cells. The present study examined the effect of SO ethanolic extract (SOE) on the proliferation and migration of hepatocellular carcinoma (HCC) and examined the effects of SOE on non-cancerous cells using HaCaT keratinocytes as a model. The SOE effectively inhibited the proliferation of Hepa1-6 (IC₅₀ = 282.4 μg/mL) and HepG2 (IC₅₀ = 344.3 μg/mL) hepatoma cells, whereas it has less cytotoxic effect on HaCaT cells (IC₅₀ = 892.4 μg/mL). The SOE treatment increased the generation of ROS in HCC, but decreased the expression of antioxidant enzymes such as superoxide dismutase, glutathione peroxidase and catalase. In contrast, it reduced intracellular ROS formation and upregulated the expression of the related antioxidant enzymes in the H₂O₂-stimulated HaCaT cells. The SOE intervention also down-regulated the anti-apoptotic Bcl-2 and the migration-related proteins including matrix metalloproteinases (MMPs) and β-catenin in the HCC, suggesting that SOE could promote HCC apoptosis and inhibit HCC migration. On the contrary, it reduced apoptosis and promoted the migration of the keratinocytes. Additionally, the SOE treatment significantly up-regulated the pro-inflammatory cytokines, including TNF-α, IL-6 and IL-1β, in Hepa1-6 and HepG2 cells. Conversely, it significantly decreased the expression of these cytokines in the H₂O₂-induced HaCaT cells. These findings indicated that SOE treatment can delay the progression of HCC by increasing oxidative stress, promoting inflammatory response, inducing cancer cell apoptosis and inhibiting their migration. It also has protective effects from pro-oxidant H₂O₂ in non-cancerous cells. Therefore, SOE may provide a potential treatment for liver cancer.

Ethnobotanical Survey on Bitter Tea in Taiwan

Ethnopharmacological evidence: In Taiwan, herbal tea is considered a traditional medicine and has been consumed for hundreds of years. In contrast to regular tea, herbal teas are prepared using plants other than the regular tea plant, Camellia sinensis (L.) Kuntze. Bitter tea (kǔ-chá), a series of herbal teas prepared in response to common diseases in Taiwan, is often made from local Taiwanese plants. However, the raw materials and formulations have been kept secret and verbally passed down by store owners across generations without a fixed recipe, and the constituent plant materials have not been disclosed.

Aim of the study: The aim was to determine the herbal composition of bitter tea sold in Taiwan, which can facilitate further studies on pharmacological applications and conserve cultural resources.

Materials and methods: Interviews were conducted through a semi-structured questionnaire. The surveyed respondents were traditional sellers of traditional herbal tea. The relevant literature was collated for a systematic analysis of the composition, characteristics, and traditional and modern applications of the plant materials used in bitter tea. We also conducted an association analysis of the composition of Taiwanese bitter tea with green herb tea (qing-cao-cha tea), another commonly consumed herbal tea in Taiwan, as well as herbal teas in neighboring areas outside Taiwan.

Results: After visiting a total of 59 stores, we identified 32 bitter tea formulations and 73 plant materials. Asteraceae was the most commonly used family, and most stores used whole plants. According to a network analysis of nine plant materials used in high frequency as drug pairs, Tithonia diversifolia and Ajuga nipponensis were found to be the core plant materials used in Taiwanese bitter tea.

Conclusion: Plant materials used in Taiwanese bitter tea were distinct, with multiple therapeutic functions. Further research is required to clarify their efficacy and mechanisms.

Four New Acyclic Diterpenes From Siegesbeckia orientalis

Four new acyclic diterpenes, siegetalises A-D (1-4), were isolated from the aerial parts of Siegesbeckia orientalis. Their chemical structures were elucidated by extensive analysis of high-resolution electrospray ionization mass spectrometry and nuclear magnetic resonance spectral data. The effects of the isolated compounds on the activity of xanthine oxidase were evaluated by the oxidative reaction with xanthine as a substrate. At a concentration of 50 µM, compounds 1-4 exhibited xanthine oxidase inhibitory activity at levels of 13.59% ± 0.51%, 19.64% ± 1.54%, 17.45% ± 1.26%, and 21.36% ± 1.40%, respectively.

Guaianolide sesquiterpenes and benzoate esters from the aerial parts of Siegesbeckia orientalis L. and their xanthine oxidase inhibitory activity

Five undescribed (four guaianolide sesquiterpenes and a benzoate ester derivative) and seven known compounds were isolated from the aerial parts of S. orientalis L. Their chemical structures were determined by extensive analysis of HR-ESI-MS and NMR spectroscopic methods. Absolute configurations were elucidated by experimental and TD-DFT calculated ECD spectra. Twelve isolated compounds exhibited potential xanthine oxidase inhibitory activity with IC₅₀ values ranging from 0.76 ± 0.17 μM to 31.80 ± 0.97 μM. Molecular docking studies predicted that the binding energies of all isolated compounds with xanthine oxidase were lower than that of the positive control allopurinol. Benzyl 2-hydroxy-6-O-β-D-glucopyranosylbenzoate and benzyl 2-methoxy-6-O-β-D-glucopyranosylbenzoate displayed not only the best docking score but also the highest in vitro xanthine oxidase inhibitory activity with IC₅₀ values of 0.76 ± 0.17 μM and 0.98 ± 0.26 μM, respectively.