The Role of Flavanones as Scaffolds for the Development of New Treatments against Malaria and African and American Trypanosomiases.

Parasitic infections are diseases transmitted by parasites usually found in contaminated food, water, or insect bites. Generally classified as neglected tropical diseases, malaria and trypanosomiases are some of the most prominent parasitic diseases that cause significant loss of life annually. In 2020, an estimated 241 million malaria cases were reported, with 627,000 deaths worldwide. An estimated 6 to 7 million people are infected with Trypanosoma cruzi worldwide, whereas an estimated 1000 global cases of African human trypanosomiasis were reported in 2020. Flavanones are a group of compounds that belong to the flavonoid family and are chemically obtained by direct cyclization of chalcones. Recent pharmacological studies have demonstrated the effectiveness of plant flavanones in inhibiting the growth of the parasites responsible for malaria and trypanosomiases. The present work aims to summarize up-to-date and comprehensive literature information on plant flavanones with antimalarial and antitrypanosomal activities. The mechanisms of action of the antiparasitic flavanones are also discussed. A literature search was performed for naturally occurring flavanones and antimalarial and antitrypanosomal activities by referencing textbooks and scientific databases (SciFinder, Wiley, American Chemical Society, Science Direct, National Library of Medicine, Scientific Electronic Library Online, Web of Science, etc.) from their inception until April 2022. Based on in vitro experiments, more than sixty flavanones were reported to exhibit antimalarial, anti-T. cruzi, and anti-T. brucei activities. Previous studies demonstrated that these compounds bind to PGP-like transporters of P. falciparum to reverse the parasite's resistance. Other reports pinpointed the direct effect of these compounds on the mitochondria of the malaria parasite. Moreover, flavanones have shown strong docking to several validated T. cruzi and T. brucei protein targets, including adenosine kinase, pteridine reductase 1, dihydrofolate reductase, and trypanothione reductase, among others. Flavanones, isolated and characterized from diverse plant parts, were reported to exhibit moderate to high activity against P. falciparum, T. cruzi, and T. brucei in in vitro studies. These potentially active flavanones can be used as scaffolds for the development of new antiparasitic agents. However, more studies on the cytotoxicity, pharmacokinetics, and mechanisms of action of potent flavanones should be performed.

Protective Roles and Mechanism of Action of Plant Flavonoids against Hepatic Impairment: Recent Developments.

BACKGROUND: The liver is one of the crucial organs in humans and is responsible for the regulation of diverse processes, including metabolism, secretion, and detoxification. Ingestion of alcohol and drugs, environmental pollutants, and irradiation are among the risk factors accountable for oxidative stress in the liver. Plant flavonoids have the potential to protect the liver from damage caused by a variety of chemicals. OBJECTIVE: The present study aims to summarize up-to-date information on the protective roles of plant flavonoids against liver damage. METHODOLOGY: The literature information on the hepatoprotective plant flavonoids was assessed through various databases, which were searched from their respective inception until March 2022. RESULTS: More than 70 flavonoids with hepatoprotective activity against a variety of models of liver toxicity have been reported across the literature. Among these are flavones (19), flavonols (30), flavanones (9), isoflavonoids (5), and biflavonoids (2). Several hepatoprotective mechanisms of action were reported in various classes of flavonoids, including flavones and flavonols (upregulation of the pro-survival ERK1/2 pathway; downregulation of apoptotic proteins, including Bax, Bcl-2, Bax, BH3, caspase-3, 8, 9, etc.), flavanones (downregulation of NF-κB, TNF-α, IL-1 ß, IL-6, iNOS, etc.), isoflavonoids (downregulation of lipogenesis genes, such as SREBP-1c, LXRα, RXRα, PPARγ and ACC2, with concomitant upregulation of genes involved in ß-oxidation, including AMPK and PPARα; inhibition of CYPs, such as CYP1A1, CYP1A2, CYP2B1, CYP2D6, CYP2E1 and CYP3A1/2). CONCLUSION: The present work demonstrated the effectiveness of plant flavonoids against hepatic damage. However, more studies need to be performed regarding the cytotoxicity, pharmacokinetics, and mechanisms of action of these very important cytoprotective flavonoids.

Antibacterial flavonoids from the fruits of Macaranga hurifolia.

As part of our search for new secondary metabolites from Macaranga hurifolia Beille, a phytochemical investigation was carried out on the fruits that led to the isolation and characterization of two new prenylated flavonol derivatives named macafolias A (1) and B (2), along with five known compounds. Their chemical structures were established on the basis of extensive analysis of their 1-D and 2-D NMR (1H, 13C, APT, COSY, HSQC and HMBC) in conjunction with mass spectroscopy and by comparison with data from the literature. The in vitro assay of the antibacterial potency of the crude extract, fractions and some pure compounds were evaluated against a wide range of bacteria strains.

Chemical constituents of two Cameroonian medicinal plants: Sida rhombifolia L. and Sida acuta Burm. f. (Malvaceae) and their antiplasmodial activity.

An extensive phytochemical investigation of the EtOH/H2O (7:3) extracts of Sida rhombifolia L. and Sida acuta Burm. f., yielded a previously undescribed ceramide named rhombifoliamide (1) and a xylitol dimer (2), naturally isolated here for the first time, as well as the thirteen known compounds viz, oleanolic acid (3), ß-amyrin glucoside (4), ursolic acid (5), ß-sitosterol glucoside (6), tiliroside (7), 1,6-dihydroxyxanthone (8), a mixture of stigmasterol (9) and ß-sitosterol (10), cryptolepine (11), 20-Hydroxyecdysone (12), (E)-suberenol (13), thamnosmonin (14) and xanthyletin (15). Their structures were elucidated by the analyses of their spectroscopic and spectrometric data (1 D and 2 D NMR, and HRESI-MS) and by comparison with the previously reported data. The crude extracts, fractions, and some isolated compounds were tested against chloroquine-sensitive (3D7) and chloroquine-resistant (Dd2) Plasmodium falciparum strains. All the tested samples demonstrated moderate and/or significant activities against 3D7 (IC50 values: 0.18-20.11 µg/mL) and Dd2 (IC50 values: 0.74-63.09 µg/mL).[Formula: see text].

Antimalarial activity of the aqueous extract of Euphorbia cordifolia Elliot in Plasmodium berghei-infected mice

Objective: To evaluate the antimalarial activity of the aqueous extract of Euphorbia (E.) cordifolia Elliot against Plasmodium (P.) berghei-infected mice. Methods: Thirty healthy Swiss mice were intraperitoneally inoculated with 200 μL of P. berghei parasitized-erythrocytes and divided into five groups, and then daily treated for 5 d with single dose of 10 mL/kg of distilled water for malaria control, 10 mg/kg of chloroquine for the chloroquine control and 100, 200 and 400 mg/kg of the aqueous extract of E. cordifolia for the three test groups. Parasitaemia was monitored by Giemsa-staining. At the end of the treatment, animals were sacrificed, and blood was collected for haematological and biochemical analyses. Organs were collected for biochemical and histopathological analyses. Statistical significance (P<0.05) was evaluated by analysis of variance followed by the Tukey post-test using Graphpad prism 7.0. Results: E. cordifolia extract decreased the parasite load to 2.46%, with an effective dose (ED