Antiplasmodial flavanones and a stilbene from Carpha glomerata

Phytochemical Investigation of Carex praecox Schreb. and ACE-Inhibitory Activity of Oligomer Stilbenes of the Plant

Phenolic compounds are the main special metabolites of Cyperaceae species from phytochemical, pharmacological, and chemotaxonomical points of view. The present study focused on the isolation, structure determination, and pharmacological investigation of constituents from Carex praecox. Twenty-six compounds, including lignans, stilbenes, flavonoids, megastigmanes, chromenes, and phenylpropanoids, were identified from the methanol extract of the plant. Five of these compounds, namely, carexines A-E, are previously undescribed natural products. All compounds were isolated for the first time from C. praecox. The ACE-inhibitory activity of seven stilbenoid compounds was tested, and (-)-hopeaphenol proved to be the most active (IC50 7.7 ± 0.9 μM). The enzyme-kinetic studies revealed a mixed-type inhibition; therefore, domain-specific studies were also conducted. The in silico docking of (-)-hopeaphenol to the ACE affirmed some favorable interactions. In addition, the antiproliferative and antibacterial effects of some compounds were also evaluated.

Isolation and Identification of Flavanone Derivative Eriodictyol from the Methanol Extract of Afzelia africana Bark and Its Antimicrobial and Antioxidant Activities

Background

Afzelia africana is a plant species with well-documented ethnobotanical and medicinal properties. The plant is reported to have various secondary metabolites and had been applied for the treatment of various diseased conditions.

Objectives

The study objectives include fractionation, isolation, purification, and characterization of eriodictyol from the bark of A. africana, and the determination of its antimicrobial and antioxidant activities. Methodology. The series of methodologies that were employed include fractionations and purification (column chromatography), characterization (HPLC, LC-MS, IR, ¹H, ¹³C, DEPT-135, HSQC, and HMBC), antimicrobial assays (microbroth dilution and checkerboard assay), and antioxidant activities assays (ABTS and DPPH scavenging capacity).

Results

The study reports the identification and characterization of eriodictyol from the bark of A. africana which exhibited potent antioxidant activities against ABTS and DPPH radicals with scavenging capacities (SC₅₀) of 2.14 ± 0.05 and 2.51 ± 0.06 µg/mL, respectively. The compound exhibited its antimicrobial activity by reporting good bacteriostatic activities (MBC/MIC > 4) against Staphylococcus aureus (SA), methicillin-resistant Staphylococcus aureus (MRSA), and fluconazole-resistant Candida albicans (CA2). Moreover, a broad spectrum of bactericidal effects (MBC/MIC ≤ 4) was reported against Streptococcus mutans (SM), Escherichia coli (EC), Bacillus subtilis (BS), Klebsiella pneumonia (KP), Pseudomonas aeruginosa (PA), Salmonella typhi (ST), and standard Candida albicans (CA1). The compound further exhibited synergistic effects against EC, KP, ST, and MRSA; ST; and CA2 when combined with ciprofloxacin, tetracycline, and nystatin, respectively. However, antagonistic effects were observed against PA and CA1 when combined with ciprofloxacin and ketoconazole, respectively.

Conclusion

The study reports for the first time the identification of eriodictyol from the bark of A. africana which exhibited significant antioxidant and antimicrobial properties.

Naturally occurring prenylated stilbenoids: food sources, biosynthesis, applications and health benefits

Prenylated stilbenoids are a unique class of natural phenolic compounds consisting of C6-C2-C6 skeleton with prenyl substitution. They are potential nutraceuticals and dietary supplements presented in some edible plants. Prenylated stilbenoids demonstrate promising health benefits, including antioxidant, anti-cancer, anti-inflammatory, anti-microbial activities. This review reports the structure, bioactivity and potential application of prenylated stilbeniods in food industry. Edible sources of these compounds are compiled and summarized. Structure-activity relationship of prenylated stilbenoids are also highlighted. The biosynthesis strategies of prenylated stilbenoids are reviewed. The findings of these compounds as food preservative, nutraceuticals and food additive are discussed. This paper combines the up-to-date information and gives a full image of prenylated stilbenoids.

In vitro antiplasmodial activity, targeted LC-MS metabolite profiling, and identification of major natural products in the bioactive extracts of Palicourea and Psychotria species from the Amazonia and Atlantic Forest biomes, Brazil

INTRODUCTION

A great variety of bioactive natural products has been reported for different Palicourea and Psychotria species (Rubiaceae). However, few of them as well as few of species of these botanical genera have been evaluated for antiplasmodial activity.

OBJECTIVE

To assess the antiplasmodial activity of 24 extracts from Palicourea and Psychotria genera, along with the targeted LC-MS metabolite profiling, as well as identification of the main metabolites in the bioactive extracts.

METHODS

Twenty four ethanol and acid-base extracts from Palicourea and Psychotria genera collected in the Amazonia and Atlantic Forest, Brazil, were evaluated against chloroquine-resistant Plasmodium falciparum W2 strain by PfLDH. The metabolite profiling and putative identification of metabolites from bioactive extracts were determined by LC-DAD-ESI-MS and LC-HRMS, respectively.

RESULTS

The ethanol extracts disclosed low antiplasmodial activity (% GI < 50%). High antiplasmodial effect was observed for the acid-base extracts from Psychotria apoda and Psychotria colorata with 100% inhibition of parasite growth inhibition. Fragment ions related to pyrrolidinoindoline alkaloids were observed by LC-DAD-ESI-MS mainly in the most bioactive extracts. The results of the in vitro screening associated with the LC-DAD-ESI-MS and LC-HRMSⁿ data allowed to predict, for the first time, the pyrrolidinoindoline alkaloids as possible antiplasmodial representing, then, new potential natural antimalarial hits. In addition, other metabolite classes such as flavanones, lignans and chalcones were also putatively identified in the bioactive extracts of Psychotria apoda, Psychotria capitata, and Psychotria poeppigiana.

CONCLUSION

The present results point to Palicourea and Psychotria species as sources of new antimalarial hits.

Chemistry and Pharmacology of Cyperaceae Stilbenoids: A Review

Cyperaceae is a cosmopolitan plant family with approx. 5000 species distributed worldwide. Several members of this family are used in traditional medicines for the treatment of different diseases. In the last few decades, constituents with great chemical diversity were isolated from sedges, and a wide range of biological activities were detected either for crude extracts or for pure compounds. Among the isolated compounds, phenolic derivatives are the most important, especially stilbenoids, and flavonoids. To date, more than 60 stilbenoids were isolated from 28 Cyperaceae species. Pharmacological investigation of Cyperaceae stilbenoids revealed that several compounds possess promising activities; mainly antiproliferative, antibacterial, antioxidant and anthelmintic effects. Isolation, synthesis and pharmacological investigation of stilbenes are increasing constantly. As Cyperaceae species are very good sources of a wide variety of stilbenes, and several of them occur in large amount worldwide, they are worthy for phytochemical and pharmacological investigations. Moreover, stilbenes are important from chemotaxonomical point of view, and they play a key role in plant defense mechanisms as well. This review summarizes the stilbenoids isolated from sedges, and their biological activities.

Bio- and chemo- transformations of glabranin and 7-O-methylglabranin and cytotoxic evaluations of the transformed products

The biotransformation of glabranin (1) with Aspergillus niger and Cunninghamella blakesleeana favoured the formation of benzofuran derivatives (3 and 4), while in contrast, its acid-catalysed chemical transformation favoured the formation of benzopyran derivatives (6 and 7). Compound 6 was further biooxidised at C-4'. Biotransformation of 7-O-methylglabranin (2) proceeded via oxidation of the prenyl group and C-4' by the same fungi, and the obtention of 11 mimics the biosynthesis of this last compound. Some compounds displayed moderate antiproliferative activity against selected human cancer cell lines, with glabranin being the most active, suggesting that the prenyl group and the phenol at C-7 are important structural determinants for cytotoxicity.