Five New Tamarixetin Glycosides from Astragalus thracicus Griseb. Including Some Substituted with the Rare 3-Hydroxy-3-methylglutaric Acid and Their Collagenase Inhibitory Effects In Vitro.

Along with the known kaempferol-3-O-α-l-rhamnopyranosyl-(1 → 2)-[6-O-(3-hydroxy-3-methylglutaryl)]-ß-d-galactopyranoside (1), five new flavonoids, containing the rarely isolated aglycon tamarixetin, were isolated from a methanolic extract of the endemic Balkan species Astragalus thracicus Griseb. Three of the new compounds are substituted with 3-hydroxy-3-methylglutaryl residue (HMG), untypical for the genus Astragalus. The compounds were identified as tamarixetin-3-O-α-l-rhamnopyranosyl-(1 → 2)-[6-O-(3-hydroxy-3-methylglutaryl)]-ß-d-galactopyranoside (2), tamarixetin-3-O-(2,6-di-O-α-l-rhamnopyranosyl)-ß-d-galactopyranoside (3), tamarixetin 3-O-ß-d-apiofuranosyl-(1 → 2)-ß-d-galactopyranoside (4), tamarixetin-3-O-ß-d-apiofuranosyl-(1 → 2)-[6-O-(3-hydroxy-3-methylglutaryl)]-ß-d-galactopyranoside (5), and tamarixetin-3-O-ß-d-apiofuranosyl-(1 → 2)-[α-l-rhamnopyranosyl-(1 → 6)]-ß-d-galactopyranoside (6). Selected compounds from A. thracicus were tested to evaluate their anticollagenase activity. The greatest effect was observed for quercetin-3-O-ß-d-apiofuranosyl-(1 → 2)-ß-d-galactopyranoside, possibly due to the presence of an ortho-dihydroxy arrangement of flavonoid ring B. The effect on collagenase and elastase was further evaluated also by in silico study, and the test compounds showed some level of in silico interaction.

Comparison of Metabolic Profiles of Fruits of Arctium lappa, Arctium minus, and Arctium tomentosum.

Metabolites of the edible and medicinal plant Arctium have been shown to possess beneficial activities. The phytochemical profile of Arctium lappa is well-explored and its fruits are known to contain mainly lignans, fatty acids, and sterols. But the fruits of other Arctium species have not been thoroughly investigated. Therefore, this study compares the metabolic profiles of the fruits of A. lappa, Arctium tomentosum, and Arctium minus. Targeted metabolomics led to the putative identification of 53 metabolites in the fruit extracts, the majority of these being lignans and fatty acids. Quantification of the major lignans showed that the year of collection had a significant effect on the lignan content. Furthermore, A. lappa fruits contained lesser amounts of arctigenin but greater amounts of arctigenin glycoside than A. minus fruits. Regarding the profile of fatty acids, A. minus fruits differed from the others in the presence of linolelaidic acid.

Enhancing Solubility and Bioefficacy of Stilbenes by Liposomal Encapsulation-The Case of Macasiamenene F.

Stilbenes in food and medicinal plants have been described as potent antiphlogistic and antioxidant compounds, and therefore, they present an interesting potential for the development of dietary supplements. Among them, macasiamenene F (MF) has recently been shown to be an effective anti-inflammatory and cytoprotective agent that dampens peripheral and CNS inflammation in vitro. Nevertheless, this promising molecule, like other stilbenes and a large percentage of drugs under development, faces poor water solubility, which results in trickier in vivo administration and low bioavailability. With the aim of improving MF solubility and developing a form optimized for in vivo administration, eight types of conventional liposomal nanocarriers and one type of PEGylated liposomes were formulated and characterized. In order to select the appropriate form of MF encapsulation, the safety of MF liposomal formulations was evaluated on THP-1 and THP-1-XBlue-MD2-CD14 monocytes, BV-2 microglia, and primary cortical neurons in culture. Furthermore, the cellular uptake of liposomes and the effect of encapsulation on MF anti-inflammatory effectiveness were evaluated on THP-1-XBlue-MD2-CD14 monocytes and BV-2 microglia. MF (5 mol %) encapsulated in PEGylated liposomes with an average size of 160 nm and polydispersity index of 0.122 was stable, safe, and the most promising form of MF encapsulation keeping its cytoprotective and anti-inflammatory properties.

Salvia officinalis L. exerts oncostatic effects in rodent and in vitro models of breast carcinoma.

Introduction: Based on extensive data from oncology research, the use of phytochemicals or plant-based nutraceuticals is considered an innovative tool for cancer management. This research aimed to analyze the oncostatic properties of Salvia officinalis L. [Lamiaceae; Salviae officinalis herba] using animal and in vitro models of breast carcinoma (BC). Methods: The effects of dietary administered S. officinalis in two concentrations (0.1%/SAL 0.1/and 1%/SAL 1/) were assessed in both syngeneic 4T1 mouse and chemically induced rat models of BC. The histopathological and molecular evaluations of rodent carcinoma specimens were performed after the autopsy. Besides, numerous in vitro analyses using two human cancer cell lines were performed. Results and Conclusion: The dominant metabolites found in S. officinalis propylene glycol extract (SPGE) were representatives of phenolics, specifically rosmarinic, protocatechuic, and salicylic acids. Furthermore, the occurrence of triterpenoids ursolic and oleanolic acid was proved in SPGE. In a mouse model, a non-significant tumor volume decrease after S. officinalis treatment was associated with a significant reduction in the mitotic activity index of 4T1 tumors by 37.5% (SAL 0.1) and 31.5% (SAL 1) vs. controls (set as a blank group with not applied salvia in the diet). In addition, salvia at higher doses significantly decreased necrosis/whole tumor area ratio by 46% when compared to control tumor samples. In a rat chemoprevention study, S. officinalis at a higher dose significantly lengthened the latency of tumors by 8.5 days and significantly improved the high/low-grade carcinomas ratio vs. controls in both doses. Analyses of the mechanisms of anticancer activities of S. officinalis included well-validated prognostic, predictive, and diagnostic biomarkers that are applied in both oncology practice and preclinical investigation. Our assessment in vivo revealed numerous significant changes after a comparison of treated vs. untreated cancer cells. In this regard, we found an overexpression in caspase-3, an increased Bax/Bcl-2 ratio, and a decrease in MDA, ALDH1, and EpCam expression. In addition, salvia reduced TGF-ß serum levels in rats (decrease in IL-6 and TNF-α levels were with borderline significance). Evaluation of epigenetic modifications in rat cancer specimens in vivo revealed a decline in the lysine methylations of H3K4m3 and an increase in lysine acetylation in H4K16ac levels in treated groups. Salvia decreased the relative levels of oncogenic miR21 and tumor-suppressive miR145 (miR210, miR22, miR34a, and miR155 were not significantly altered). The methylation of ATM and PTEN promoters was decreased after S. officinalis treatment (PITX2, RASSF1, and TIMP3 promoters were not altered). Analyzing plasma metabolomics profile in tumor-bearing rats, we found reduced levels of ketoacids derived from BCAAs after salvia treatment. In vitro analyses revealed significant anti-cancer effects of SPGE extract in MCF-7 and MDA-MB-231 cell lines (cytotoxicity, caspase-3/-7, Bcl-2, Annexin V/PI, cell cycle, BrdU, and mitochondrial membrane potential). Our study demonstrates the significant chemopreventive and treatment effects of salvia haulm using animal or in vitro BC models.

Dibenzocyclooctadiene Lignans from Schisandra chinensis with Anti-Inflammatory Effects.

Schisandra chinensis (Schisandraceae) is a medicinal plant widely used in traditional Chinese medicine. Under the name Wu Wei Zi, it is used to treat many diseases, especially as a stimulant, adaptogen, and hepatoprotective. Dibenzocyclooctadiene lignans are the main compounds responsible for the effect of S. chinensis. As a part of ongoing studies to identify and evaluate anti-inflammatory natural compounds, we isolated a series of dibenzocyclooctadiene lignans and evaluated their biological activity. Furthermore, we isolated new sesquiterpene 7,7-dimethyl-11-methylidenespiro[5.5]undec-2-ene-3-carboxylic acid. Selected dibenzocyclooctadiene lignans were tested to assess their anti-inflammatory potential in LPS-stimulated monocytes by monitoring their anti-NF-κB activity, antioxidant activity in CAA assay, and their effect on gap junction intercellular communication in WB-ras cells. Some S. chinensis lignans showed antioxidant activity in CAA mode and affected the gap junction intercellular communication. The anti-inflammatory activity was proven for (-)-gomisin N, (+)-γ-schisandrin, rubrisandrin A, and (-)-gomisin J.

Significance of flavonoids targeting PI3K/Akt/HIF-1α signaling pathway in therapy-resistant cancer cells - A potential contribution to the predictive, preventive, and personalized medicine.

BACKGROUND: Cancer management faces multiple obstacles, including resistance to current therapeutic approaches. In the face of challenging microenvironments, cancer cells adapt metabolically to maintain their supply of energy and precursor molecules for biosynthesis and thus sustain rapid proliferation and tumor growth. Among the various metabolic adaptations observed in cancer cells, the altered glucose metabolism is the most widely studied. The aberrant glycolytic modification in cancer cells has been associated with rapid cell division, tumor growth, cancer progression, and drug resistance. The higher rates of glycolysis in cancer cells, as a hallmark of cancer progression, is modulated by the transcription factor hypoxia inducible factor 1 alpha (HIF-1α), a downstream target of the PI3K/Akt signaling, the most deregulated pathway in cancer. AIM OF REVIEW: We provide a detailed overview of current, primarily experimental, evidence on the potential effectiveness of flavonoids to combat aberrant glycolysis-induced resistance of cancer cells to conventional and targeted therapies. The manuscript focuses primarily on flavonoids reducing cancer resistance via affecting PI3K/Akt, HIF-1α (as the transcription factor critical for glucose metabolism of cancer cells that is regulated by PI3K/Akt pathway), and key glycolytic mediators downstream of PI3K/Akt/HIF-1α signaling (glucose transporters and key glycolytic enzymes). KEY SCIENTIFIC CONCEPTS OF REVIEW: The working hypothesis of the manuscript proposes HIF-1α - the transcription factor critical for glucose metabolism of cancer cells regulated by PI3K/Akt pathway as an attractive target for application of flavonoids to mitigate cancer resistance. Phytochemicals represent a source of promising substances for cancer management applicable to primary, secondary, and tertiary care. However, accurate patient stratification and individualized patient profiling represent crucial steps in the paradigm shift from reactive to predictive, preventive, and personalized medicine (PPPM / 3PM). The article is focused on targeting molecular patterns by natural substances and provides evidence-based recommendations for the 3PM relevant implementation.

Lipophilic Statins Eliminate Senescent Endothelial Cells by inducing Anoikis-Related Cell Death.

Pre-clinical studies from the recent past have indicated that senescent cells can negatively affect health and contribute to premature aging. Targeted eradication of these cells has been shown to improve the health of aged experimental animals, leading to a clinical interest in finding compounds that selectively eliminate senescent cells while sparing non-senescent ones. In our study, we identified a senolytic capacity of statins, which are lipid-lowering drugs prescribed to patients at high risk of cardiovascular events. Using two different models of senescence in human vascular endothelial cells (HUVECs), we found that statins preferentially eliminated senescent cells, while leaving non-senescent cells unharmed. We observed that the senolytic effect of statins could be negated with the co-administration of mevalonic acid and that statins induced cell detachment leading to anoikis-like apoptosis, as evidenced by real-time visualization of caspase-3/7 activation. Our findings suggest that statins possess a senolytic property, possibly also contributing to their described beneficial cardiovascular effects. Further studies are needed to explore the potential of short-term, high-dose statin treatment as a candidate senolytic therapy.

Treating Epilepsy with Natural Products: Nonsense or Possibility?

Epilepsy is a neurological disease characterized by recurrent seizures that can lead to uncontrollable muscle twitching, changes in sensitivity to sensory perceptions, and disorders of consciousness. Although modern medicine has effective antiepileptic drugs, the need for accessible and cost-effective medication is urgent, and products derived from plants could offer a solution. For this review, we have focused on natural compounds that have shown anticonvulsant activity in in vivo models of epilepsy at relevant doses. In some cases, the effects have been confirmed by clinical data. The results of our search are summarized in tables according to their molecular targets. We have critically evaluated the data we present, identified the most promising therapeutic candidates, and discussed these in the text. Their perspectives are supported by both pharmacokinetic properties and potential interactions. This review is intended to serve as a basis for future research into epilepsy and related disorders.

The Gold(I) Complex with Plant Hormone Kinetin Shows Promising In Vitro Anticancer and PPARγ Properties.

Motivated by the clinical success of gold(I) metallotherapeutic Auranofin in the effective treatment of both inflammatory and cancer diseases, we decided to prepare, characterize, and further study the [Au(kin)(PPh3)] complex (1), where Hkin = kinetin, 6-furfuryladenine, for its in vitro anti-cancer and anti-inflammatory activities. The results revealed that the complex (1) had significant in vitro cytotoxicity against human cancer cell lines (A2780, A2780R, PC-3, 22Rv1, and THP-1), with IC50 ≈ 1-5 µM, which was even significantly better than that for the conventional platinum-based drug Cisplatin while comparable with Auranofin. Although its ability to inhibit transcription factor NF-κB activity did not exceed the comparative drug Auranofin, it has been found that it is able to positively influence peroxisome-proliferator-activated receptor-gamma (PPARγ), and as a consequence of this to have the impact of moderating/reducing inflammation. The cellular effects of the complex (1) in A2780 cancer cells were also investigated by cell cycle analysis, induction of apoptosis, intracellular ROS production, activation of caspases 3/7 and disruption of mitochondrial membrane potential, and shotgun proteomic analysis. Proteomic analysis of R2780 cells treated with complex (1) and starting compounds revealed possible different places of the effect of the studied compounds. Moreover, the time-dependent cellular accumulation of copper was studied by means of the mass spectrometry study with the aim of exploring the possible mechanisms responsible for its biological effects.

Could temporary external fixation after reduction of displaced acetabular fractures prevent posttraumatic heterotopic ossification?

OBJECTIVES: To recommend appropriate immobilization after the initial reduction of acetabular displaced fractures in order to minimize the risk of heterotopic ossification formation. DESIGN: Retrospective study of patients treated in our surgical department during the years 2005-2018. MATERIALS AND METHODS: There were 94 patients included in statistical analysis. The factors of injury severity, course of surgery and hospitalization and incidence of complications were recorded. The functional and X-ray results were evaluated at least one year after surgery. RESULTS: The patients were divided into the two groups according to the type of fixation after closed reduction, the external fixation (EF) and the skeletal traction (ST) group. According to the type of fracture there were 33 patients with central displacement and 61 patients with posterior displacement. Ossification grade III. And IV. Occur in 20% of our sample. There was greater incidence of Brooker grade III. And IV. Ossification in the ST group, but statistically insignificant, p = 0.57. There was no statistically significant difference in the occurrence of ossifications regarding the severity of the head injury, p = 0.11, or to the severity of the injury p = 0.54. The combination of posterior displacement and ST results in higher risk for ossifications, specifically in our group at 11.48% compared to the combination of posterior displacement and EF where it is 8.2%. CONCLUSION: Skeletal traction for posterior displaced acetabular fracture appears to be a more risky procedure for the development of ossifications than external fixation.

Antithrombotic and antiplatelet effects of plant-derived compounds: a great utility potential for primary, secondary, and tertiary care in the framework of 3P medicine.

Thromboembolism is the third leading vascular disease, with a high annual incidence of 1 to 2 cases per 1000 individuals within the general population. The broader term venous thromboembolism generally refers to deep vein thrombosis, pulmonary embolism, and/or a combination of both. Therefore, thromboembolism can affect both - the central and peripheral veins. Arterial thromboembolism causes systemic ischemia by disturbing blood flow and oxygen supply to organs, tissues, and cells causing, therefore, apoptosis and/or necrosis in the affected tissues. Currently applied antithrombotic drugs used, e.g. to protect affected individuals against ischemic stroke, demonstrate significant limitations. For example, platelet inhibitors possess only moderate efficacy. On the other hand, thrombolytics and anticoagulants significantly increase hemorrhage. Contextually, new approaches are extensively under consideration to develop next-generation antithrombotics with improved efficacy and more personalized and targeted application. To this end, phytochemicals show potent antithrombotic efficacy demonstrated in numerous in vitro, ex vivo, and in vivo models as well as in clinical evaluations conducted on healthy individuals and persons at high risk of thrombotic events, such as pregnant women (primary care), cancer, and COVID-19-affected patients (secondary and tertiary care). Here, we hypothesized that specific antithrombotic and antiplatelet effects of plant-derived compounds might be of great clinical utility in primary, secondary, and tertiary care. To increase the efficacy, precise patient stratification based on predictive diagnostics is essential for targeted protection and treatments tailored to the person in the framework of 3P medicine. Contextually, this paper aims at critical review toward the involvement of specific classes of phytochemicals in antiplatelet and anticoagulation adapted to clinical needs. The paper exemplifies selected plant-derived drugs, plant extracts, and whole plant foods/herbs demonstrating their specific antithrombotic, antiplatelet, and fibrinolytic activities relevant for primary, secondary, and tertiary care. One of the examples considered is antithrombotic and antiplatelet protection specifically relevant for COVID-19-affected patient groups.

C-geranylated flavonoids from Paulownia tomentosa Steud. fruit as potential anti-inflammatory agents.

ETHNOPHARMACOLOGICAL RELEVANCE: Paulownia tomentosa Steud., a traditional Chinese medicinal plant, was used for many centuries in Chinese herbal medicine as a component of remedies for many illnesses, including inflammatory diseases. It is a rich source of phenolic compounds, mainly geranylated flavonoids, which are currently studied for their promising biological activities. AIM OF THE STUDY: The study aimed to isolate minor geranylated flavanones and flavones from P. tomentosa fruit and evaluate their cytotoxicity and possible anti-inflammatory effects in a cell-based model of inflammation. MATERIALS AND METHODS: Chromatographic separation of chloroform portion of the ethanolic extract of P. tomentosa fruit led to the isolation of twenty-seven flavonoids (1-27), twenty-six of them geranylated with different modifications and one non-geranylated flavanone, and two phenolic compounds. Compounds were identified using UV, IR, HRMS, NMR, and CD spectroscopy. Ten of these compounds (7-10, 12, 21, 22, 24, 25, and 27) were determined to be new flavonoid derivatives obtained from a natural source for the first time. Selected compounds were analyzed for cytotoxicity and anti-inflammatory potential to affect the activation of nuclear factor κB/activator protein 1 (NF-κB/AP-1) after lipopolysaccharide (LPS) stimulation. RESULTS: All the test compounds (1-21 and 23-26) reduced the activation of NF-κB/AP-1 24 h after the addition of LPS. Eight compounds (5, 14-18, 21, and 26) were more active than prednisone, a widely used anti-inflammatory drug. However, this effect was not seen significantly on the level of TNF-α and IL-1ß, which can be explained by the plurality of possible outcomes of activation of the NF-κB pathway in cells. CONCLUSIONS: Results of the presented study confirmed that constituents from traditional Chinese medicinal plant P. tomentosa Steud. have promising anti-inflammatory activities and can serve as a potential source of inspiration for new anti-inflammatory medications.

Synthesis of C-prenylated analogues of stilbenoid methyl ethers and their cyclic dihydrobenzopyranyl derivatives as potential anti-inflammatory agents.

An efficient and versatile synthesis of the naturally occurring C-prenylated stilbenoid methyl ethers and their synthetic analogues is presented. The synthesis represents a six step convergent process including an optimised C-prenylation method. Furthermore, during the demethylation process, six new dihydro-benzopyranyl derivatives were obtained and isolated.

Anti-breast cancer effects of phytochemicals: primary, secondary, and tertiary care.

Breast cancer incidence is actually the highest one among all cancers. Overall breast cancer management is associated with challenges considering risk assessment and predictive diagnostics, targeted prevention of metastatic disease, appropriate treatment options, and cost-effectiveness of approaches applied. Accumulated research evidence indicates promising anti-cancer effects of phytochemicals protecting cells against malignant transformation, inhibiting carcinogenesis and metastatic spread, supporting immune system and increasing effectiveness of conventional anti-cancer therapies, among others. Molecular and sub-/cellular mechanisms are highly complex affecting several pathways considered potent targets for advanced diagnostics and cost-effective treatments. Demonstrated anti-cancer affects, therefore, are clinically relevant for improving individual outcomes and might be applicable to the primary (protection against initial cancer development), secondary (protection against potential metastatic disease development), and tertiary (towards cascading complications) care. However, a detailed data analysis is essential to adapt treatment algorithms to individuals' and patients' needs. Consequently, advanced concepts of patient stratification, predictive diagnostics, targeted prevention, and treatments tailored to the individualized patient profile are instrumental for the cost-effective application of natural anti-cancer substances to improve overall breast cancer management benefiting affected individuals and the society at large.

Metabolism of Selected 2-Arylbenzofurans in a Colon In Vitro Model System.

2-arylbenzofurans represent a small group of bioactive compounds found in the plant family Moraceae. As it has not been investigated whether these substances are stable during passage through the gastrointestinal tract, their biological effects may be altered by the metabolism of intestinal microbiota or cells. The aim of the present study was to investigate and compare mulberrofuran Y (1), moracin C (2), and mulberrofuran G (3) in an in vitro model of human intestinal bacterial fermentation and in an epithelial model using the Caco-2 cell line. The analysis of compounds by LC-MS-Q-TOF showed sufficient stability in the fermentation model, with no bacterial metabolites detected. However, great differences in the quantity of permeation were observed in the permeability assay. Moreover, mulberrofuran Y (1) and moracin C (2) were observed to be transformed into polar metabolites by conjugation. Among the test compounds, mulberrofuran Y (1) was mostly stable and accumulated in endothelial cells (85.3%) compared with mulberrofuran G (3) and moracin C (2) (14% and 8.2%, respectively). Thus, only a small amount of mulberrofuran Y (1) was conjugated. Moracin C (2) and mulberrofuran G (3) were metabolized almost completely, with only traces of the unchanged molecule being found on the apical and cellular sides of the system. Only conjugates of mulberrofuran Y (1) and moracin C (2) were able to reach the basolateral side. Our results provide the basic description of bioavailability of these three compounds, which is a necessary characteristic for final evaluation of bio-efficacy.

Direct and Indirect Antioxidant Effects of Selected Plant Phenolics in Cell-Based Assays.

Background: Oxidative stress is a key factor in the pathophysiology of many diseases. This study aimed to verify the antioxidant activity of selected plant phenolics in cell-based assays and determine their direct or indirect effects. Methods: The cellular antioxidant assay (CAA) assay was employed for direct scavenging assays. In the indirect approach, the influence of each test substance on the gene and protein expression and activity of selected antioxidant enzymes was observed. One assay also dealt with activation of the Nrf2-ARE pathway. The overall effect of each compound was measured using a glucose oxidative stress protection assay. Results: Among the test compounds, acteoside showed the highest direct scavenging activity and no effect on the expression of antioxidant enzymes. It increased only the activity of catalase. Diplacone was less active in direct antioxidant assays but positively affected enzyme expression and catalase activity. Morusin showed no antioxidant activity in the CAA assay. Similarly, pomiferin had only mild antioxidant activity and proved rather cytotoxic. Conclusions: Of the four selected phenolics, only acteoside and diplacone demonstrated antioxidant effects in cell-based assays.

Antiproliferative and cytotoxic activities of C-Geranylated flavonoids from Paulownia tomentosa Steud. Fruit.

Prenylated or geranylated flavonoids have been studied for their promising antiproliferative and cytotoxic activities. Twelve natural geranylated flavonoids (1-12) were isolated from the fruit of Paulownia tomentosa Steud. Their structures were elucidated using UV and IR spectroscopy, mass spectrometry, and 1D and 2D NMR spectroscopy. The absolute configurations were determined using NMR and circular dichroism. Seven of the compounds were characterized as new geranylated derivatives isolated from a natural source for the first time, namely 3'-O-methyl-5'-hydroxyisodiplacone (3), paulodiplacone A (5), tomentone II (6), tomentone B (7), tomentodiplacone P (8), paulodiplacone B (9), and tomentoflavone A (12). After 24 h of incubation at concentrations in the range 1-30 µM, the isolated compounds were tested for their antiproliferative and cytotoxic potentials against the human monocytic leukaemia cell line THP-1, using WST-1 and LDH assays, respectively. Almost all of the test compounds induced a concentration-dependent reduction in the metabolic activity of THP-1 cells and a concentration-dependent reduction in the cell viability. Diplacone (1) was the most potent antiproliferative and cytotoxic agent (IC50 9.31 ± 0.72 µM, LC50 18.01 ± 1.19 µM). 3'-O-Methyl-5'-hydroxydiplacone (2) showed relatively strong antiproliferative effect (IC50 12.61 ± 0.90 µM) and weaker cytotoxic activity (LC50 > 30 µM), indicating that it may serve as a potential lead compound for further testing. The structure-activity relationship for the 12 isolated compounds is discussed.

Screening of Natural Compounds as P-Glycoprotein Inhibitors against Multidrug Resistance.

Multidrug resistance (MDR) is a common problem when fighting cancer with chemotherapy. P-glycoprotein (P-gp, or MDR1) is an active pump responsible for the efflux of xenobiotics out of the cell, including anti-cancer drugs. It is a validated target against MDR. No crystal structure of the human P-gp is available to date, and only recently several cryo-EM structures have been solved. In this paper, we present a comprehensive computational approach that includes constructing the full-length three-dimensional structure of the human P-gp and its refinement using molecular dynamics. We assessed its flexibility and conformational diversity, compiling a dynamical ensemble that was used to dock a set of lignan compounds, previously reported as active P-gp inhibitors, and disclose their binding modes. Based on the statistical analysis of the docking results, we selected a system for performing the structure-based virtual screening of new potential P-gp inhibitors. We tested the method on a library of 87 natural flavonoids described in the literature, and 10 of those were experimentally assayed. The results reproduced the theoretical predictions only partially due to various possible factors. However, at least two of the predicted natural flavonoids were demonstrated to be effective P-gp inhibitors. They were able to increase the accumulation of doxorubicin inside the human promyelocytic leukemia HL60/MDR cells overexpressing P-gp and potentiate the antiproliferative activity of this anti-cancer drug.

Flavonoids Targeting HIF-1: Implications on Cancer Metabolism.

Tumor hypoxia is described as an oxygen deprivation in malignant tissue. The hypoxic condition is a consequence of an imbalance between rapidly proliferating cells and a vascularization that leads to lower oxygen levels in tumors. Hypoxia-inducible factor 1 (HIF-1) is an essential transcription factor contributing to the regulation of hypoxia-associated genes. Some of these genes modulate molecular cascades associated with the Warburg effect and its accompanying pathways and, therefore, represent promising targets for cancer treatment. Current progress in the development of therapeutic approaches brings several promising inhibitors of HIF-1. Flavonoids, widely occurring in various plants, exert a broad spectrum of beneficial effects on human health, and are potentially powerful therapeutic tools against cancer. Recent evidences identified numerous natural flavonoids and their derivatives as inhibitors of HIF-1, associated with the regulation of critical glycolytic components in cancer cells, including pyruvate kinase M2(PKM2), lactate dehydrogenase (LDHA), glucose transporters (GLUTs), hexokinase II (HKII), phosphofructokinase-1 (PFK-1), and pyruvate dehydrogenase kinase (PDK). Here, we discuss the results of most recent studies evaluating the impact of flavonoids on HIF-1 accompanied by the regulation of critical enzymes contributing to the Warburg phenotype. Besides, flavonoid effects on glucose metabolism via regulation of HIF-1 activity represent a promising avenue in cancer-related research. At the same time, only more-in depth investigations can further elucidate the mechanistic and clinical connections between HIF-1 and cancer metabolism.

Polyketide Derivatives in the Resistance of Gerbera hybrida to Powdery Mildew.

Powdery mildew is a common disease affecting the commercial production of gerbera flowers (Gerbera hybrida, Asteraceae). Some varieties show a certain degree of resistance to it. Our objective was to identify biomarkers of resistance to powdery mildew using an 1H nuclear magnetic resonance spectroscopy and chemometrics approach in a complex, fully factorial experiment to suggest a target for selection and breeding. Resistant varieties were found to differ from those that were susceptible in the metabolites of the polyketide pathway, such as gerberin, parasorboside, and gerberinside. A new compound probably involved in resistance, 5-hydroxyhexanoic acid 3-O-ß-D-glucoside, was described for the first time. A decision tree model was built to distinguish resistant varieties, with an accuracy of 57.7%, sensitivity of 72%, and specificity of 44.44% in an independent test. Our results suggest the mechanism of resistance to powdery mildew in gerbera and provide a potential tool for resistance screening in breeding programs.