Phenolic Constituents of Wikstroemia retusa

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.

Retusone A, a Guaiane-Type Sesquiterpene Dimer from Wikstroemia retusa and Its Inhibitory Effects on Histone Acetyltransferase HBO1 Expression

Retusone A (1), a new sesquiterpene dimer consisting of two guaiane-type sesquiterpenoids, and oleodaphnal (2) were isolated from heartwood of Wikstroemia retusa (Thymelaeaceae). The planar structure of 1 was elucidated on the basis of HRESIMS and NMR spectroscopic data, and the relative stereochemistry was established by X-ray diffraction analysis. The absolute configuration of 1 was determined by electronic circular dichroism. Compound 1 suppressed luciferase reporter gene expression driven by the HBO1 (histone acetyltransferase binding to ORC1) gene promoter in human breast cancer MCF7 cells. Compound 1 also decreased the expression of endogenous HBO1 mRNA and protein, and inhibited proliferation of the cells. These results suggest that retusone A (1), which has a unique dimeric sesquiterpenoid structure with inhibitory activity against HBO1 expression, may contribute to the development of a novel therapeutic candidate for the treatment of breast cancer.

Two new triterpenoid saponins from Ardisia crenata

Two new triterpenoid saponins, ardisicrenoside K (1) and ardisicrenoside L (2), have been isolated from the roots of Ardisia crenata Sims. Their structures have been determined as 3beta-O-[alpha-L-rhamnopyranosyl-(1 --> 2)-beta-D-glucopyranosyl-(1 --> 4)-[beta-D-glucopyranosyl-(1 --> 2)]-alpha-L-arabinopyranosyl]-13beta,28-epoxy-16-oxo-30,30-dimethoxyoleanane and 3beta-O-[beta-D-xylopyranosyl-(1 --> 2)-beta-D-glucopyranosyl-(1 --> 4)-[beta-D-glucopyranosyl-(1 --> 2)]-alpha-L-arabinopyranosyl]-13beta,28-epoxy-16alpha,20-dihydroxyoleanane by means of chemical evidences and spectral analysis. Their weak anti-fungal activity against the plant pathogenic fungus Pyricularia oryzae was evaluated in vitro.

Triterpenoid saponins from Ardisia crenata

Two novel triterpenoid saponins, ardisicrenoside A [3 beta-O-(alpha-L-rhamnopyranosyl-(1-->2)-[beta-D-glucopyranosyl- (1-->4)-[beta-D-glucopyranosyl-(1-->2)]-alpha-L-arabinopyranosyl)- 13 beta,28-epoxy-16 alpha,30-oleananediol] and ardisicrenoside B [3 beta-O-(beta-D-xylopyranosyl-(1-->2)-[beta-D- glucopyranosyl-(1-->4)-[beta-D-glucopyranosyl-(1-->2)]- alpha-L-arabinopyranosyl)-13 beta,28-epoxy-16 alpha,30-oleananediol] were isolated from the roots of Ardisia crenata. Two known triterpenoid saponins, ardisiacrispins A and B were also isolated from this source. Their structures were determined mainly by 2D NMR (COSY, HOHAHA, HETCOR, HMBC and ROESY) experiments. The aglycones are the new 13 beta,28-epoxy-3 beta,16 alpha,30-oleananetriol for ardisicrenosides A and B.