Ferroptosis inhibitory constituents from the fruits of Cullen corylifolium

Polymethoxyflavone from Citrus depressa as an inhibitor against various variants of SARS-CoV-2 spike protein

ETHNOPHARMACOLOGICAL RELEVANCE

In traditional Taiwanese medicine, Citrus depressa Hayata serves as the raw material of Chen-Pi which has been widely used to treat respiratory ailments. Scientific investigations have validated the attributes of C. depressa, elucidating its valuable properties, including antioxidative, anti-inflammatory, anticancer, neuroprotion, hepatoprotection, and hypolipidemic effects.

AIM OF THE STUDY

This study aims to isolate a universal inhibitor of the SARS-CoV-2 spike protein from C. depressa and confirm the mechanism by which these inhibitors disrupt the binding of the spike protein to hACE2.

MATERIALS AND METHODS

The whole fruit of C. depressa was subjected to ethanol extraction, following by partitioning to obtain water, butanol, and ethyl acetate fractions. To identify the inhibitory components in citrus fruits, we performed both the SPR assay and the SARS-CoV-2 pseudo-virus assays. Subsequently, we employed a bioassay-guided approach to efficiently isolate and characterize the bioactive constituents that hindered the interaction between the SARS-CoV-2 spike protein and hACE2, using a combination of MPLC and Semi-preparative HPLC for compound isolation. ELISA based spike protein binding assay evaluate the inhibitory activities of the extract and potential constituents against multiple spike protein variants. To further shed light on the inhibitory mechanism, candidate inhibitors were validated through the SPR assay and molecular docking.

RESULTS

The crude extract and ethyl acetate layer derived from C. depressa showed significant inhibitory activity on SARS-CoV-2 Omicron BA.4/5, with IC50 of 77.4 μg/mL and 100 μg/mL, respectively. Ten potential compounds from C. depressa have been identified with inhibitory activity against various SARS-CoV-2 spike proteins. 2'-hydroxy-4,4',5',6'-tetramethoxychalcone (Cd3) and 5-hydroxy-3',4',6,7,8-pentamethoxyflavone (Cd8) also showed good inhibitory activity to the spike protein, with KD of 0.79 μM and 37.3 nM, respectively. These findings are in line with prior study, indicating Cd3 and Cd8 can bind to key amino acid residue, disrupting the formation of the spike protein and h-ACE2 complex.

CONCLUSION

This study presents the initial evidence showcasing the inhibitory effect of polymethoxyflavones (PMFs) on the spike protein of SARS-CoV-2. Moreover, the inhibitory activity of C. depressa extracts indicates their potential to prevent infections of different SARS-CoV-2 variants.

Farnesane sesquiterpenoids from Rubus delavayi and their anti-Trichinella spiralis activities

Two new farnesane sesquiterpenoid glycosides, rubusdelosides A and B (1 and 4), together with five known farnesane sesquiterpenoids (2, 3, and 5-7), and two known meroterpenoids (8 and 9), were isolated from water extract of the herbs of R. delavayi. Their structures were identified by the comprehensive analyses of physicochemical properties and spectroscopic data (NMR and HR-ESI-MS). Compounds 1-8 showed moderate in vivo anti-T. spiralis activities.

Alkaloids and Coumarins with Adiponectin-Secretion-Promoting Activities from the Leaves of Orixa japonica

Fractionation of a methanol extract of Orixa japonica leaves led to the identification of five new quinoline alkaloids (1, 2, 4, 8, and 9), three new coumarins (15, 17, and 19), and 20 known compounds. The structures were determined by analysis of 1D and 2D NMR spectroscopic data. The absolute configuration of 19 was proposed by electronic circular dichroism calculation. Among the compounds tested in the phenotypic screening to measure adiponectin secretion in human bone marrow mesenchymal stem cells, metabolites 4 and 12 stimulated adiponectin secretions with EC₅₀ values of 13.8 and 25.8 μM, respectively. Further PPARγ binding assay and molecular modeling suggested that compounds 4 and 12 are selective PPARγ agonists.

Review and Chemoinformatic Analysis of Ferroptosis Modulators with a Focus on Natural Plant Products

Ferroptosis is a regular cell death pathway that has been proposed as a suitable therapeutic target in cancer and neurodegenerative diseases. Since its definition in 2012, a few hundred ferroptosis modulators have been reported. Based on a literature search, we collected a set of diverse ferroptosis modulators and analyzed them in terms of their structural features and physicochemical and drug-likeness properties. Ferroptosis modulators are mostly natural products or semisynthetic derivatives. In this review, we focused on the abundant subgroup of polyphenolic modulators, primarily phenylpropanoids. Many natural polyphenolic antioxidants have antiferroptotic activities acting through at least one of the following effects: ROS scavenging and/or iron chelation activities, increased GPX4 and NRF2 expression, and LOX inhibition. Some polyphenols are described as ferroptosis inducers acting through the generation of ROS, intracellular accumulation of iron (II), or the inhibition of GPX4. However, some molecules have a dual mode of action depending on the cell type (cancer versus neural cells) and the (micro)environment. The latter enables their successful use (e.g., apigenin, resveratrol, curcumin, and EGCG) in rationally designed, multifunctional nanoparticles that selectively target cancer cells through ferroptosis induction.

Emerging Mechanisms and Disease Implications of Ferroptosis: Potential Applications of Natural Products

Ferroptosis, a newly discovered form of regulatory cell death (RCD), has been demonstrated to be distinct from other types of RCD, such as apoptosis, necroptosis, and autophagy. Ferroptosis is characterized by iron-dependent lipid peroxidation and oxidative perturbation, and is inhibited by iron chelators and lipophilic antioxidants. This process is regulated by specific pathways and is implicated in diverse biological contexts, mainly including iron homeostasis, lipid metabolism, and glutathione metabolism. A large body of evidence suggests that ferroptosis is interrelated with various physiological and pathological processes, including tumor progression (neuro)degenerative diseases, and hepatic and renal failure. There is an urgent need for the discovery of novel effective ferroptosis-modulating compounds, even though some experimental reagents and approved clinical drugs have been well documented to have anti- or pro-ferroptotic properties. This review outlines recent advances in molecular mechanisms of the ferroptotic death process and discusses its multiple roles in diverse pathophysiological contexts. Furthermore, we summarize chemical compounds and natural products, that act as inducers or inhibitors of ferroptosis in the prevention and treatment of various diseases. Herein, it is particularly highlighted that natural products show promising prospects in ferroptosis-associated (adjuvant) therapy with unique advantages of having multiple components, multiple biotargets and slight side effects.

Can Polyphenols Inhibit Ferroptosis?

Polyphenols, a diverse group of naturally occurring molecules commonly found in higher plants, have been heavily investigated over the last two decades due to their potent biological activities—among which the most important are their antioxidant, antimicrobial, anticancer, anti-inflammatory and neuroprotective activities. A common route of polyphenol intake in humans is through the diet. Since they are subjected to excessive metabolism in vivo it has been questioned whether their much-proven in vitro bioactivity could be translated to in vivo systems. Ferroptosis is a newly introduced, iron-dependent, regulated mode of oxidative cell death, characterized by increased lipid peroxidation and the accumulation of toxic lipid peroxides, which are considered to be toxic reactive oxygen species. There is a growing body of evidence that ferroptosis is involved in the development of almost all chronic diseases. Thus, ferroptosis is considered a new therapeutic target for offsetting many diseases, and researchers are putting great expectations on this field of research and medicine. The aim of this review is to critically analyse the potential of polyphenols to modulate ferroptosis and whether they can be considered promising compounds for the alleviation of chronic conditions.

The Regulatory Effects and the Signaling Pathways of Natural Bioactive Compounds on Ferroptosis

Natural bioactive compounds abundantly presented in foods and medicinal plants have recently received a remarkable attention because of their various biological activities and minimal toxicity. In recent years, many natural compounds appear to offer significant effects in the regulation of ferroptosis. Ferroptosis is the forefront of international scientific research which has been exponential growth since the term was coined. This type of regulated cell death is driven by iron-dependent phospholipid peroxidation. Recent studies have shown that numerous organ injuries and pathophysiological processes of many diseases are driven by ferroptosis, such as cancer, arteriosclerosis, neurodegenerative disease, diabetes, ischemia-reperfusion injury and acute renal failure. It is reported that the initiation and inhibition of ferroptosis plays a pivotal role in lipid peroxidation, organ damage, neurodegeneration and cancer growth and progression. Recently, many natural phytochemicals extracted from edible plants have been demonstrated to be novel ferroptosis regulators and have the potential to treat ferroptosis-related diseases. This review provides an updated overview on the role of natural bioactive compounds and the potential signaling pathways in the regulation of ferroptosis.

Toward improved human health: Nrf2 plays a critical role in regulating ferroptosis

Ferroptosis is a recently defined type of regulated cell death caused by an excess iron-dependent accumulation of lipid peroxides and is morphologically and biochemically distinct from other types of cell death. Notably, Nrf2 is identified to exquisitely modulate ferroptosis due to its ability to target a host of ferroptosis cascade genes, which places Nrf2 in the pivotal position of ferroptosis. This paper reviews the regulation effect of Nrf2 on ferroptosis, different activation mechanisms of Nrf2 as well as the relevance of the Nrf2-ferroptosis axis in diseases, and finally summarizes foods with beneficial effects in ferroptosis via the Nrf2 pathway and aims to serve as a reference for follow-up studies of food functions related to Nrf2, ferroptosis, and human health.

Targetting ferroptosis for blood cell-related diseases

Ferroptosis is an iron-dependent cell death pathway and participates in various diseases. Current evidence suggests that ferroptosis can obviously affect the function of blood cells. This paper aims to elaborate the role of ferroptosis in blood cells and related diseases. First, abnormal ferroptosis damages the developing red blood cells by breaking systemic iron homeostasis, leading to erythropoiesis suppression and anaemia. Ferroptosis mediates neutrophils recruitment and neutrophil extracellular trap formation (NETosis). In T-cells, ferroptosis induces a novel point of synergy between immunotherapy and radiotherapy. Additionally, ferroptosis may mediate B cells differentiation, antibody responses and lymphoma. Nevertheless, increased ferroptosis can ameliorate acute myeloid leukaemia and T-cell leukaemia/lymphoma by inducing iron-dependent cancer cells death. Besides, ferroptosis activates platelets by increasing P-selectin, thus causing thromboembolism. Ferroptosis mediates virus infection and parasite infection by driving T-cell death and preventing T-cell immunity. Interestingly, ferroptosis is also considered as a critical player in COVID-19 infections, while targetting ferroptosis may also improve thromboembolism and prognosis in patients with COVID-19 infection. Overall, the crucial role of ferroptosis in blood cells will show a new therapeutic potential in blood cell-related diseases.HighlightsFerroptosis shows a new therapeutic potential for blood cell-related diseases.Ferroptosis damages erythropoiesis and thus induces anaemia.Ferroptosis induces platelet activation and leads to thromboembolism.Ferroptosis regulates T-cell and B-cell immunity, which participant in infectious diseases.Inversely, ferroptosis ameliorates acute myeloid leukaemia and T-cell leukaemia.

Regulation of ferroptosis by bioactive phytochemicals: Implications for medical nutritional therapy

Ferroptosis is an iron- and lipotoxicity-dependent regulated cell death that has been implicated in various diseases, such as cancer, neurodegeneration and stroke. The biosynthesis of phospholipids, coenzyme Q₁₀, and glutathione, and the metabolism of iron, amino acids and polyunsaturated fatty acid, are tightly associated with cellular sensitivity to ferroptosis. Up to now, only limited drugs targeting ferroptosis have been documented and exploring novel effective ferroptosis-modulating compound is needed. Natural bioactive products are conventional resources for drug discovery, and some of them have been clinically used against cancers and neurodegenerative diseases as dietary supplements or pharmaceutic agents. Notably, increasing evidence demonstrates that natural compounds, such as saponins, flavonoids and isothiocyanates, can either induce or inhibit ferroptosis, further expanding their therapeutic potentials. In this review, we highlight current advances of the emerging molecular mechanisms and disease relevance of ferroptosis. We also systematically summarize the regulatory effects of natural phytochemicals on ferroptosis, and clearly indicate that saponins, terpenoids and alkaloids induce ROS- and ferritinophagy-dependent ferroptosis, whereas flavonoids and polyphenols modulate iron metabolism and nuclear factor erythroid 2-related factor 2 (NRF2) signaling to inhibit ferroptosis. Finally, we explore their clinical applications in ferroptosis-related diseases, which may facilitate the development of their dietary usages as nutraceuticals.

Direct Keap1-kelch inhibitors as potential drug candidates for oxidative stress-orchestrated diseases: A review on In silico perspective

The recent outcry in the search for direct keap1 inhibitors requires a quicker and more effective drug discovery process which is an inherent property of the Computer Aided Drug Discovery (CADD) to bring drug candidates into the clinic for patient's use. This Keap1 (negative regulator of ARE master activator) is emerging as a therapeutic strategy to combat oxidative stress-orchestrated diseases. The advances in computer algorithm and compound databases require that we highlight the functionalities that this technology possesses that can be exploited to target Keap1-Nrf2 PPI. Therefore, in this review, we uncover the in silico approaches that had been exploited towards the identification of keap1 inhibition in the light of appropriate fitting with relevant amino acid residues, we found 3 and 16 other compounds that perfectly fit keap1 kelch pocket/domain. Our goal is to harness the parameters that could orchestrate keap1 surface druggability by utilizing hotspot regions for virtual fragment screening and identification of hotspot residues.