Pteleifolols A-E, acetophenone di-C-glycosides and a benzopyran dimer from the leaves of Melicope pteleifolia

Natural-derived acetophenones: chemistry and pharmacological activities

Acetophenones are naturally occurring phenolic compounds which have found in over 24 plant families and also fungi strains. They are exist in both free or glycosides form in nature. The biological activities of these compounds have been assayed and reported including cytotoxicity, antimicrobial, antimalarial, antioxidant and antityrosinase activities. Herein, we review the chemistry and biological activity of natural acetophenone derivatives that have been isolated and identified until January 2024. Taken together, it was reported 252 acetophenone derivatives in which the genera Melicope (69) and Acronychia (44) were the principal species as producers of acetophenones.

Molecular networking-based discovery of anti-inflammatory chromene dimers from Melicope pteleifolia

With the aid of a feature-based molecular networking strategy, five undescribed C₂ and C₁ symmetric chromene dimers, namely, melptelchromenes A-E, were isolated from the leaves of Melicope pteleifolia. Four asymmetric dimers were found to be racemates and were resolved by chiral phase HPLC analyses. Their structures, including absolute configurations, were elucidated by HRMS, NMR spectroscopy, and quantum mechanical calculations of ECD spectra and NMR chemical shifts. Melptelchromenes A-D possess a unique ethylidene linkage via two 2H-chromene cores, while melptelchromene E represents the first example of a dimeric chromene featuring a 1,3-diarylbutan-1-ol moiety. Of these compounds, 6,6'-linked dimeric chromenes showed nitric oxide inhibitory activities on lipopolysaccharide-induced RAW 264 cells, and (-)- and (+)-melptelchromene E were the two most potent compounds (IC₅₀, 3.0 and 5.1 μM, respectively).

Advances in plant-derived C-glycosides: Phytochemistry, bioactivities, and biotechnological production

C-glycosides represent a large group of natural products with a C-C bond between the aglycone and the sugar moiety. They exhibit great structural diversity, wide natural distribution, and significant biological activities. By the end of 2021, at least 754 C-glycosides and their derivatives have been isolated and characterized from plants. Thus far, 66 functional C-glycosyltransferases (CGTs) have been discovered from plants, and provide green and efficient approaches to synthesize C-glycosides. Herein, advances in plant-derived C-glycosides are comprehensively summarized from aspects of structural diversity and identification, bioactivities, and biotechnological production. New strategies to discover novel C-glycosides and CGTs, as well as the applications of biotechnological methods to produce C-glycosides in the future are also discussed.

The phytochemistry, pharmacology and applications of Melicope pteleifolia: A review

ETHNOPHARMACOLOGY RELEVANCE

The leaves, stems and roots of Melicope pteleifolia (Champ. ex Benth.) T.Hartley (MP; Rutaceae, called sanyaku in Chinese; syn.: Euodia lepta), have been used traditionally for the treatment of sore throat, rheumatism, eczema, dermatitis, bruises, and insect, rat, snake bites based on traditional Chinese medicine concepts.

AIM OF THIS STUDY

This paper aims to provide a comprehensive and critical analysis of studies on MP and focusing on potential relationships between traditional uses and pharmacological effects, assessing the therapeutic potential as a medicine.

MATERIALS AND METHODS

Relevant data on MP were retrieved using the keywords "Melicope pteleifolia", "pharmacology", "toxicity" and "applications" in databases including "Pubmed", "SciFinder", "Springer", "Elsevier", "Wiley", "Web of Science", "Google Scholar", "China Knowledge Resource Integrated databases (CNKI)", "PhD" and "MSc dissertations", and a hand-search.

RESULTS AND DISCUSSION

The heat-clearing, dampness-removing and gallbladder-normalizing actions of MP have been linked to biomedical concepts like anti-inflammatory, antioxidant and hepatoprotective activities. The latter is potentially based on the presence of furaquinoline alkaloids, phenylpropanoids and flavonoids. Analgesic, antimicrobial and anti-tumor effects have also been reported. Currently limited evidence is available relating to potential toxicological risks especially of aqueous extracts with so far no reports signalling specific risks. Although some studies on the pharmacodynamics of MP have been reported, studies on action mechanisms of MP are still rare.

CONCLUSIONS

In the future and prior to initiating clinical trials, the safety, in vitro and in vivo pharmacology, and mechanism of action of MP needs to be assessed, including a focus on the link between traditional uses and modern applications. In addition, phytochemical and biological studies need to conduct on flowers and fruits of MP. Furthermore, strict quality control measures are needed in the studies investigating any aspect of the pharmacology, chemistry and biology of MP.

(±)-Meliviticines A and B: Rearranged prenylated acetophenone derivatives from Melicope viticina and their antimicrobial activity

Two new prenylated acetophenone derivatives racemates, meliviticines A (1) and B (2) with unprecedented rearranged skeletons, were isolated from Melicope viticina. Subsequent chiral resolution led to the separation of two pairs of enantiomers, (±)-meliviticines A (1a/1b) and (±)-meliviticines B (2a/2b). Their structures including absolute configurations were elucidated by extensive spectroscopic data, electronic circular dichroism analysis, and X-ray crystallography. A plausible biosynthetic pathway of 1 and 2, involving ring cleavage and rearrangement of the prenylated acetophenone backbone was proposed. All the isolates showed moderate antimicrobial activities with MIC values of 25-50 μg/mL against several bacterial and fungal strains.

Acetophenone derivatives from the roots of Melicope ptelefolia

Five new prenylated acetophenones, melicoptelins A-E (1-5), along with one known congener (6) were isolated from the roots of Melicope ptelefolia. Among them, compounds 2a/2b, 3a/3b, and 4a/4b were obtained as inseparable interconverting mixtures of keto and enol tautomers. Their structures were elucidated on the basis of extensive spectroscopic methods, including 1D, 2D NMR and HRESIMS. Compouds 2a/2b, 4a/4b and 5 exhibit protein tyrosine phosphatase 1B (PTP1B) inhibitory activity with IC₅₀ values of 34.4, 55.2 and 66.6 μM, respectively.