Cytotoxic oligophenols from the rhizome of Wikstroemia indica

Wikstroemia: A Review on its Phytochemistry and Pharmacology

BACKGROUND

Wikstroemia (the family Thymelaeaceae) consists of medicinal plants which established great value in traditional medicines for many years. For instance, W. indica is always recommended for treatments of syphilis, arthritis, whooping cough, and cancer. No systematic review of bioactive compounds from this genus has been recorded to date.

OBJECTIVES

The objective of the current study is to review phytochemical investigations and pharmacological effects of Wikstroemia plant extracts and isolates.

METHODS

By searching on the internet, the relevant data about Wikstroemia medicinal plants were retrieved from internationally renowned scientific databases, such as Web of Science, Google Scholar, Sci-Finder, Pubmed, and so on.

RESULTS

More than 290 structurally diverse metabolites were separated and identified from this genus. They include terpenoids, lignans, flavonoids, coumarins, mono-phenols, diarylpentanoids, fatty acids, phytosterols, anthraquinones, and others. Pharmacological records indicated that Wikstroemia plant crude extracts and their isolated compounds bring out various beneficial effects, such as anticancer, antiinflammatory, anti-aging, anti-viral, antimicrobacterial, antimalarial, neuroprotective, and hepatoprotective activities.

CONCLUSION

Wikstroemia has been regarded as a worthy genus with numerous phytochemicals and various pharmacological potentials. Modern pharmacological studies have successfully provided evidence for traditional uses. Nonetheless, their action mechanisms need to be further investigated. Although various secondary metabolites were identified from Wikstroemia plants, the current pharmacological research mainly concentrated on terpenoids, lignans, flavonoids, and coumarins.

Glycosylated coumarins, flavonoids, lignans and phenylpropanoids from Wikstroemia nutans and their biological activities

Wikstroemia nutans Champ. ex Benth., a traditional herbal medicine collected at the Lingnan region of China, was chemically investigated. A new biscoumarin glucoside, wikstronutin (1), along with three known bis- and tricoumarin glucosides (2–4), two flavonoid glycosides (5–6), and eleven lignan glucosides (7–17) were isolated from the stems and roots of W. nutans. The new structure including its absolute configuration was elucidated based on a combination of 1D and 2D NMR, UV, IR, HRESIMS spectroscopic data, as well as chemical transformation. Compounds 1–17 were first isolated from the plant species W. nutans, while compounds 1–3, 8, and 11 were reported from the genus Wikstroemia for the first time. All co-isolates were evaluated for their in vitro inhibitory effects on nitric oxide (NO) production induced by lipopolysaccharide (LPS) in murine RAW264.7 macrophage cells. The antibacterial activity of the selected compounds was also tested. Our work enriches the structure diversity of the secondary metabolites from the genus Wikstroemia.

Characteristic biflavonoids from Daphne kiusiana var. atrocaulis (Rehd.) F. Maekawa

Structurally diverse biflavonoids have attracted significant research interest for drug discovery over past decades. Biflavonoid oriented phytochemistry research on the stems of Daphne kiusiana var. atrocaulis (Rehd.) F. Maekawa was carried out, which resulted in the identification of ten major effective components (1-10), including the undescribed biflavonoids, daphnodorin Q (1), daphnodorin R (2) and flavane, daphnekiuslin A (10). The known structures were identified from this herb for the first time. Their structures were determined by combination of multiple spectroscopic data as well as calculated electronic circular dichroism (ECD). All the identified compounds were evaluated for the anti-neuroinflammatory effects. Compound 9 could inhibit the overactivation of BV-2 cells induced by lipopolysaccharide with IC₅₀ value at 26.32 μM.

Three new compounds from the dried root bark of Wikstroemia indica and their cytotoxicity against HeLa cells

Three new compounds (1-3) and twelve known compounds (4-15) were isolated from the n-butanol extraction of the 70% ethanol extract of the dried root barks of Wikstroemia indica. The structures of new compounds were identified by chemical evidence and extensive analysis of spectroscopic data (HR-ESI-MS, 1 D and 2 D NMR) and ECD calculations. All isolated compounds were evaluated for their cytotoxicity against HeLa cells using MTT assay and the results showed that daphnoretin (compound 5) owned the highest cytotoxicity against HeLa cells (IC₅₀=28.89 μmol/L).

3D-QSAR, molecular docking, molecular dynamics, and ADME/T analysis of marketed and newly designed flavonoids as inhibitors of Bcl-2 family proteins for targeting U-87 glioblastoma

Glioblastoma is the most common and destructive brain tumor with increasing complexity. Flavonoids are versatile natural compounds with the approved anticancer activity, which could be considered as a potential treatment for glioblastoma. A quantitative structure-activity relationship (QSAR) can provide adequate data for understanding the role of flavonoids structure against glioblastoma. The IC₅₀ of various flavonoids for the U-87 cell line was used to prepare an adequate three-dimensional QSAR (3D-QSAR) model. The validation of the model was carried out using some statistical parameters such as R² and Q² . Based on the QSAR model, the activities of other marketed and newly designed flavonoids were predicted. Molecular docking study and molecular dynamics (MD) simulation were conducted for better recognition of the interactions between the most active compounds and Bcl-2 family proteins. Moreover, an AMDE/T analysis was performed for the most active flavonoids. A reliable 3D-QSAR was performed with R² and Q² of 0.91 and 0.82. The molecular docking study revealed that BCL-XL has a higher binding affinity with the most active compounds, and the MD simulation showed that some residues of the BH3 domain, such as Phe97, Tyr101, Arg102, and Phe105 create remarkable hydrophobic interactions with the ligands. ADME/T analysis also showed the potential of the active compounds for further investigation. 3D-QSAR study is a beneficial method to evaluate and design anticancer compounds. Considering the results of the molecular docking study, MD simulation, and ADME/T analysis, the designed compound 54 could be considered as a potential treatment for glioblastoma.

Curcumin and wikstroflavone B, a new biflavonoid isolated from Wikstroemia indica, synergistically suppress the proliferation and metastasis of nasopharyngeal carcinoma cells via blocking FAK/STAT3 signaling pathway

BACKGROUND

Curcumin (CUR) is a natural diarylheptanoid with marked anti-tumor activities. Recent investigations demonstrate that CUR combines with some other phytochemicals exerts advantages over its single application manifested as lower toxicity, higher efficacy or more significant reversal of multidrug resistance.

PURPOSE

This study aimed to elucidate a new biflavonoid (wikstroflavone B, WFB) isolated from Wikstroemia indica and to assess the synergistic inhibition of combined CUR and WFB (CUR/WFB) on human nasopharyngeal carcinoma (NPC) cell lines proliferation and metastasis.

METHODS

WFB was obtained through sequential chromatographic methods including silica gel, Sephadex LH-20 and preparative HPLC. Its structure was determined by HRESIMS, 1D and 2D NMR spectroscopic analysis. The absolute configuration of WFB was assigned through comparison of experimental and calculated optical rotation (OR) values. Changes in cellular viability, migration and invasion were assessed by MTT, colony formation, wound healing and Transwell assays. The nature of synergistic interaction of CUR/WFB was determined through the combination index (CI) method under the median-effect analysis. Expression levels of indicated mRNAs and proteins were measured by qRT-PCR and Western blotting assays, respectively.

RESULTS

WFB was isolated and structural elucidated. Compared with CUR or WFB used alone, CUR/WFB treatment inhibited more effectively on the cell viability, colony formation, cell migration and invasion. Both CI and dose reduction index (DRI) values indicated the significant synergistic effects existed between CUR and WFB. Besides, CUR/WFB showed the marked modulation on the genes involved in cell proliferation (survivin, cyclin D1, p53 and p21) and metastasis (MMP-2, MMP-9 and FAK). CUR/WFB treatment was also found to restrain the phosphorylation of FAK and STAT3 proteins. When pretreatment with a FAK inhibitor, the cell viability and metastasis were significantly attenuated.

CONCLUSION

The results indicate that WFB can synergistically increase the inhibitory effects of CUR on NPC cells proliferation and metastasis, and these findings may afford a rational approach for developing the antitumor medications.

Bioactive daphnane diterpenes from Wikstroemia chuii with their potential anti-inflammatory effects and anti-HIV activities

A phytochemical investigation on the stems and leaves of Wikstroemia chuii resulted in the isolation of three new daphnane diterpenes, wikstroechuins A-C (1-3), together with eight known analogues (4-11). The structures of new daphnane diterpenes (1-3) were determined on the basis of extensive spectroscopic methods and the known daphnane diterpenes (4-11) were identified by comparing their observable spectroscopic data with those reported spectral data in the literature. The anti-inflammatory effects as well as anti-HIV activities in vitro of all isolated daphnane diterpenes 1-11 were assessed. As a consequence, daphnane diterpenes 1-11 displayed remarkable inhibitory activities on NO (nitric oxide) production induced by lipopolysaccharide in mouse macrophage RAW 264.7 cells showing IC₅₀ values in the range of 0.12 ± 0.03 to 10.58 ± 0.16 µM. Meanwhile, daphnane diterpenes 1-11 displayed significant anti-HIV-1 reverse transcriptase (RT) effects showing EC₅₀ values ranging from 0.09509 to 8.62356 µM. These research results indicated that the discovery of these new daphnane diterpenes with remarkable anti-inflammatory and anti-HIV activities from W. chuii, especially these new ones, could be extremely meaningful to the discovery of new anti-inflammatory agents and anti-HIV drugs as well as their potential practical values in the health and pharmaceutical products.

Total synthesis of wikstrol A and wikstrol B

The first total synthesis of wikstrol A and wikstrol B was achieved by employing aldol reaction, Sharpless asymmetric dihydroxylation, regioselective iodination, Sonogashira coupling, and rhodium-catalyzed oxidative coupling as key steps. The structure of the key intermediate for wikstrol A was confirmed via its derivative by single-crystal X-ray analysis.