Structure-activity relationships of flavonoid-induced cytotoxicity on human leukemia cells

Simultaneous elimination mechanism of formaldehyde and acrolein by resveratrol in food and the cytotoxicity of the products

Polyphenols have been intensively investigated for scavenging single harmful aldehydes, such as formaldehyde (FA) and acrolein (ACR). However, there is a lack of studies on the effect and mechanism of eliminating co-existing harmful aldehydes by polyphenols. In this study, resveratrol (RV) was found to simultaneously scavenge FA and ACR by forming various adducts, with the RV-ACR adduct (RA, molecular formula: C17H16O4) and RV-ACR-FA adduct (RAF, molecular formula: C18H18O5) being the dominant ones. The elimination of co-existing FA and ACR by RV were further confirmed in real food systems. RA (IC50, 67.22 and 147.70 μM in GES-1 and Caco-2 cells, respectively) and RAF (127.50 and over 250 μM, respectively) showed significantly lower cytotoxicity than the co-existing FA and ACR (18.27 and 5.26 μM, respectively) in the gastrointestinal cell lines. This study provided data support for food safety control by employing RV as a dietary supplement to scavenge harmful aldehydes in foods.

Comparative Analysis of Acetylated Flavonoids' Chemopreventive Effects in Different Cancer Cell Lines

Flavonoids, a class of natural compounds with anticancer activity, exhibit varying biological activities and potencies based on their structural differences. Acylation, including acetylation of flavonoids, generally increases their structural diversity, which is closely related to the diversity of bioactivity within this group of compounds. However, it remains largely unknown how acetylation affects the bioactivity of many flavonoids. Based on our previous findings that O-acetylation enhances quercetin's bioactivity against various cancer cells, we synthesized 12 acetylated flavonoids, including seven novel compounds, to investigate their anticancer activities in the MDA-MB-231, HCT-116, and HepG2 cell lines. Our results showed that acetylation notably enhanced the cell proliferation inhibitory effect of quercetin and kaempferol across all cancer cell lines tested. Interestingly, while the 5,7,4'-O-triacetate apigenin (3Ac-A) did not show an enhanced the effect of inhibition of cell proliferation through acetylation, it exhibited significantly strong anti-migration activity in MDA-MB-231 cells. In contrast, the 7,4'-O-diacetate apigenin (2Ac-Q), which lacks acetylation at the 5-position hydroxy group, showed enhanced cell proliferation inhibitory effect but had weaker anti-migration effects compared to 3Ac-A. These results indicated that acetylated flavonoids, especially quercetin, kaempferol, and apigenin derivatives, are promising for anticancer applications, with 3Ac-A potentially having unique anti-migration pathways independent of apoptosis induction. This study highlights the potential application of flavonoids in novel chemopreventive strategies for their anti-cancer activity.

Using Flavonoid Substitution Status to Predict Anticancer Effects in Human Melanoma Cancers: An In Vitro Study

Skin cancers are a dominant type of cancer that impacts millions per year. Cancer is a heterogeneous disease triggered by the irreversible impairment of cellular homeostasis and function. In this study, we investigated the activity of 37 structurally diverse flavonoids to find potentially active substances using two melanoma cell lines: C32 and A375. First, the cytotoxic potential and DNA biosynthesis inhibition of flavonoids were tested to determine the most active compounds in cancer and normal cells. Second, the molecular mechanism of the anticancer activity of flavonoids was elucidated using Western blot and immunofluorescence analyses. Compounds 1, 6, 15, and 37 reduced the viability of A375 and C32 cell lines via the intrinsic and extrinsic pathways of apoptosis, whereas 16 and 17 acted in a higher degree via the inhibition of DNA biosynthesis. In our experiment, we demonstrated the anticancer activity of compound 15 (5,6-dihydroxyflavone) for the first time. The in vitro studies pointed out the importance of the flavonoid core in hydroxyl groups in the search for potential drugs for amelanotic melanoma.

Phylogenetic variations in a novel family of hyperstable apple snail egg proteins: insights into structural stability and functional trends

The relationship between protein stability and function evolution has not been explored in proteins from natural sources. Here, we investigate the phylogenetic differences of Perivitellin-1 (PV1) a novel family of hyperstable egg carotenoproteins crucial to the reproductive success of Pomacea snails, as they have evolved clade-specific protective functions. We studied P. patula PV1 (PpaPV1) from Flagellata clade eggs, the most basal of Pomacea and compared it with PV1s orthologs from derived clades. PpaPV1 stands as the most stable, with longer unfolding half-life, resistance to detergent unfolding, and therefore higher kinetic stability than PV1s from derived clades. In fact, PpaPV1 is among the most hyperstable proteins described in nature. In addition, its spectral characteristics providing a pale egg coloration, mild lectin activity and glycan specificity are narrower than derived clades. Our results provide evidence indicating large structural and functional changes along the evolution of the genus. Notably, the lectin binding of PpaPV1 is less pronounced, and its glycan specificity is narrower compared to PV1s in the sister Bridgesii clade. Our findings underscore the phylogenetic disparities in terms of structural and kinetic stability, as well as defensive traits like a potent lectin activity affecting the gut morphology of potential predators within the Bridgesii clade or a conspicuous, likely warning coloration, within the Canaliculata clade. This work provides a comprehensive comparison of the structural attributes, stability profiles, and functional roles of apple snail egg PV1s from multiple species within a phylogenetic context. Furthermore, it proposes an evolutionary hypothesis suggesting a trade-off between structural stability and the functional aspects of apple snail's major egg defense protein.

Potential Implications of Hyperoside on Oxidative Stress-Induced Human Diseases: A Comprehensive Review

Hyperoside is a flavonol glycoside mainly found in plants of the genera Hypericum and Crataegus, and also detected in many plant species such as Abelmoschus manihot, Ribes nigrum, Rosa rugosa, Agrostis stolonifera, Apocynum venetum and Nelumbo nucifera. This compound exhibits a multitude of biological functions including anti-inflammatory, antidepressant, antioxidative, vascular protective effects and neuroprotective effects, etc. This review summarizes the quantification, original plant, chemical structure and property, structure-activity relationship, pharmacologic effect, pharmacokinetics, toxicity and clinical application of hyperoside, which will be significant for the exploitation for new drug and full utilization of this compound.

A novel flavonol glycoside and six derivatives of quercetin and kaempferol from Clematis flammula with antioxidant and anticancer potentials

Clematis flammula leaves are traditionally used in Algeria to treat rheumatoid arthritis. Our aim was to identify the main compounds in this plant in order to characterize its antioxidant and anticancer activities. A new flavonol compound, kaempferol 3-O-[(6-O- caffeoyl)- glucosyl(1 → 2)]-(6-Ocaffeoyl) glucoside-7-O-rhamnoside (6) along with six known flavonol molecules were isolated from an ethanolic extract of Clematis flammula leaves. The chemical structures of these flavonols were elucidated using NMR and high resolution-MS spectroscopies. Antioxidant activities of the extract were revealed through its elimination of superoxide radical (O2.-) produced enzymatically (49.7 ± 1.52% at 50 μg/ml) and non-enzymatically (34 ± 1.2% at 100 μg/ml), probably related to its inhibition of the xanthine oxidase form of the xanthine oxidoreductase (XOR) enzyme (25.05 ± 2.33 μg/mL at 100 μg/mL), but mostly to that of the NADH oxidase form of the enzyme (69.16 ± 4.0%). Cytotoxicity tests of the extract on human hepatoma cell line HepG2 and ovarian cancer cell lines A2780 and OVCAR3 were promising especially regarding A2780 cell line (IC50: 77.0 μg/mL), which was comparable to taxol (IC50:76.9 μg/mL).

The Current State of Knowledge in Biological Properties of Cirsimaritin

The search for natural plant-based products as new pharmacological alternatives to treat various human pathologies has taken on great importance for researchers and research laboratories. In this context, research has intensified to extract and identify natural molecules endowed with biological effects. The objective of this study is to review the source and pharmacological properties of cirsimaritin. The identification and isolation of this flavonoid from various natural sources, including medicinal plants such as Artemisia judaica, Cirsium japonicum, Lithocarpus dealbatus, Microtea debilis, and Ocimum sanctum, has been carried out and verified using different spectral techniques. Biological effect investigations are carried out with a wide variety of experimental models in vitro and in vivo and laboratory techniques. The results of these research works showed the biological properties of cirsimaritin including anticancer, antimicrobial, antidiabetic, antiparasitic, antioxidant, and anti-inflammatory effects. The mechanisms involved in the multiple activities of this molecule are diverse and include sub-cellular, cellular, and molecular levels. Indeed, this bioactive induces anti-inflammatory and antiproliferative effects by inhibiting cell membrane receptors, interference with signaling pathways, and inhibiting transcriptional factors such as Nf-κB involved in cell promotion and proliferation. In the light of these results, cirsimaritin appears as a promising and viable alternative natural bioactive drug to treat many pathological conditions.

In Vitro Induction of Apoptosis in Isolated Acute Myeloid Leukemia Cells: The Role of Anastatica hierochuntica Methanolic Extract

Anastatica hierochuntica L. (Cruciferae) has been known in Egyptian folk medicine as a remedy for gastrointestinal disorders, diabetes and heart diseases. Despite the wide usage, A. hierochuntica research provides insufficient data to support its traditional practice. The cytotoxicity of A. hierochuntica methanolic extract was investigated on acute myeloid leukemia blasts (AML) and normal human peripheral leucocytes (NHPL). The phytochemical identification of bioactive compounds using ¹H-NMR and LC-ESI-MS was also performed. A. hierochuntica extract caused non-significant cytotoxicity on NHPL, while the cytotoxicity on AML was significant (IC₅₀: 0.38 ± 0.02 μg/mL). The negative expression of p53, upregulation of Caspase-3 and increase in the BAX/BCL-2 ratio were reported at the protein and mRNA levels. The results suggest that A. hierochuntica extract induced AML cell death via the p53-independent mitochondrial intrinsic pathway and further attention should be paid to this plant as a promising natural anticancer agent.

Anticancer and antibacterial flavonoids from the callus of Ampelopsis grossedentata; a new weapon to mitigate the proliferation of cancer cells and bacteria

A new flavonoid angelioue (1) together with five known compounds cuminatanol (2), myricetin (3), epigallocatechin (4), taxifolin (5) and dihydromyricetin (6) was isolated from the callus extract of Ampelopsis grossedentata (Hand.-Mazz.) W. T. Wang and the structures were elucidated based on their detailed spectroscopic data. Among the compounds, the new compound angelioue (1) displayed significant antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) with the MIC value of 6.68 μg mL-1 and MBC value of 53.42 μg mL-1; in contrast the other compounds showed moderate to no antibacterial activity. In addition, known dihydromyricetin (6) exhibited potent cytotoxic activities against mouse breast cancer cells (4T1), human lung adenocarcinoma (A549) and human non-small cell lung cancer (NCI-H1975) tumor cell lines with GI50 values of 17.47, 18.91 and 20.50 μM mL-1, respectively. The compounds 1-5 exhibited low micro-molar inhibitory activities. Moreover, the structure-activity relationships of the most active compounds for antibacterial and cytotoxic activities are discussed. The present findings clearly suggest that the A. grossedentata callus is a good source of bioactive compounds.

Modification of flavonoids: methods and influences on biological activities

Flavonoids are important active ingredients in plant-based food, which have many beneficial effects on health. But the low solubility, poor oral bioavailability, and inferior stability of many flavonoids may limit their applications in the food, cosmetics, and pharmaceutical industries. Structural modification can overcome these shortcomings to improve and extend the application of flavonoids. The study of how to modify flavonoids and the influence of various modifications on biological activity have drawn great interest in the current literature. In this review, the working principles and operating conditions of modification methods were summarized along with their potential and limitations in terms of operational safety, cost, and productivity. The influence of various modifications on biological activities and the structure-activity relationships of flavonoids derivatives were discussed and highlighted, which may give guidance for the synthesis of highly effective active agents. In addition, the safety of flavonoids derivatives is reviewed, and future research directions of flavonoid modification research are discussed.

Effect of Hydroxyl Groups Esterification with Fatty Acids on the Cytotoxicity and Antioxidant Activity of Flavones

Flavonoids and polyunsaturated fatty acids due to low cytotoxicity in vitro studies are suggested as potential substances in the prevention of diseases associated with oxidative stress. We examined novel 6-hydroxy-flavanone and 7-hydroxy-flavone conjugates with selected fatty acids (FA) of different length and saturation and examined their cytotoxic and antioxidant potential. Our findings indicate that the conjugation with FA affects the biological activity of both the original flavonoids. The conjugation of 6-hydroxy-flavanone increased its cytotoxicity towards prostate cancer PC3 cells. The most noticeable effect was found for oleate conjugate. A similar trend was observed for 7-hydroxy-flavone conjugates with the most evident effect for oleate and stearate. The cytotoxic potential of all tested conjugates was not specific towards PC3 because the viability of human keratinocytes HaCaT cells decreased after exposure to all conjugates. Additionally, we showed that esterification of the two flavonoids decreased their antioxidant activity compared to that of the original compounds. Of all the tested compounds, only 6-sorbic flavanone showed a slight increase in antioxidant potential compared to that of the original compound. Our data show that conjugated flavonoids are better absorbed and enhance cytotoxic effects, but the presence of FA lowered the antioxidant potential.

Genoprotective Effect of Some Flavonoids against Genotoxic Damage Induced by X-rays In Vivo: Relationship between Structure and Activity

Flavonoids constitute a group of polyphenolic compounds characterized by a common gamma-benzo- pyrone structure considered in numerous biological systems to possess antioxidant capacity. Among the different applications of flavonoids, its genoprotective capacity against damage induced by ionizing radiation stands out, which has been related to antioxidant activity and its chemical structure. In this study, we determined the frequency of appearance of micronucleus in vivo by means of the micronucleus assay. This was conducted in mice treated with different flavonoids before and after exposure to 470 mGy X-rays; thereafter, their bone marrow polychromatophilic erythrocytes were evaluated to establish the structural factors enhancing the observed genoprotective effect. Our results in vivo show that the presence of a monomeric flavan-3-ol type structure, with absence of carbonyl group in position C4 of ring C, absence of conjugation between the carbons bearing the C2 = C3 double bond and the said ring, presence of a catechol group in ring B and characteristic hydroxylation in positions 5 and 7 of ring A are the structural characteristics that determine the highest degree of genoprotection. Additionally, a certain degree of polymerization of this flavonoid monomer, but maintaining significant levels of monomers and dimers, contributes to increasing the degree of genoprotection in the animals studied at both times of their administration (before and after exposure to X-rays).

Pharmacological investigation of antioxidant and anti-inflammatory activities of leaves and branches extracts from Plinia cauliflora (Jaboticaba)

ETHNOPHARMACOLOGICAL RELEVANCE

Among all native Brazilian plant species, Plinia cauliflora (DC.) Kausel (Jaboticaba), is well known for producing "superfruits", due to their high phenolic content and antioxidant property. The fruit has astringent characteristics, and it is popularly known for the treatment of diarrhea, rash, and intestinal inflammation. However, there are only a few studies on the use of leaves and branches of this species in the literature, mainly to treat oxidative stress and inflammation.

AIM OF THE STUDY

The present study aimed to investigate the antioxidant and anti-inflammatory potential of leaves and branches extracts from P. cauliflora.

MATERIAL AND METHODS

The phytochemical analysis of P. cauliflora extracts was performed by the total phenolic, flavonoid, and tannin dosage method. Moreover, the compounds were identified by HPLC-MS-Q-TOF. Antioxidant capacity was determined by DPPH, β-carotene/linoleic acid system, MDA formation, and phosphomolybdenum assays. In vitro and in vivo anti-inflammatory activities of P. cauliflora were evaluated by the reduction of nitric oxide in the J774A.1 cell line and inhibition of ear edema in mice, respectively.

RESULTS

The ethanolic extract of the leaves exhibited greater flavonoid content whereas the ethanolic extract of the branches showed higher tannins content. Twenty-two and seventeen compounds were identified by HPLC-MS-Q-TOF in the leaves and branches, respectively, being tellimagrandin I, castalagin, and valoneic acid dilactone reported for the first time in P. cauliflora. The antioxidant potential of extracts was confirmed through different oxidation pathways from oxidizing radicals, which might be related to the presence of phenolic compounds. For the anti-inflammatory assay, the leaves and branches extracts showed promising results, with a reduction of nitric oxide ear edema inhibition around 95% and 80%, respectively.

CONCLUSIONS

Herein, the great biological potential of leaves and branches extracts from P. cauliflora was highlighted. These parts of the plant are underused and poorly reported in the literature, especially for the antioxidant and anti-inflammatory activities.

Santin and cirsimaritin from Betula pubescens and Betula pendula buds induce apoptosis in human digestive system cancer cells

Flavonoids are bioactive secondary metabolites of plants, which exert anti‐cancer effects. However, metabolism in enterocytes and the liver can influence the biological activity of flavonoids contained in the diet. Therefore, results from in vitro studies on cancer cells from the digestive tract and liver may reflect the real effects in the human body. Previously, we have found that the extract from birch buds exerts antiproliferative activity in a panel of cancer cells. In the present study, the anti‐cancer activity of ten flavonoids isolated from the buds of Betula pubescens and Betula pendula was characterized. Among them, santin and cirsimaritin significantly reduced viability, proliferation and clonogenicity of gastric (AGS), colon (DLD‐1) and liver (HepG2) cancer cells. Both flavonoids induced apoptosis, accompanied by activation of caspase‐3, caspase‐7, caspase‐8 and caspase‐9. Moreover, upregulation of p53 was detected only in wild‐type p53 harbouring cells. Together, our results suggest that santin and cirsimaritin exhibit promising anti‐cancer activity in cultures of digestive system cancer cells.

Biotransformation of Flavonoids Improves Antimicrobial and Anti-Breast Cancer Activities In Vitro

Coarse cereals are rich in flavonoids, which are bioactive substances with a wide range of functions. Biotransformation is considered an emerging approach to methylate flavonoids, displaying prominent regio- and stereoselectivity. In the current study, liquiritigenin, naringenin, and hesperidin flavonoids were biotransformed using O-methyltransferases that were heterologously expressed in Saccharomyces cerevisiae BJ5464-NpgA. Nuclear magnetic resonance (NMR) spectroscopy was used together with high-resolution mass spectroscopy analysis to determine the structures of the resulting methylated transformants, and their antimicrobial and antiproliferation activities were also characterized. Among the five methylated flavonoids obtained, 7-methoxy-liquiritigenin had the strongest inhibitory effect on Candida albicans SC5314 (C. albicans SC5314), Staphylococcus aureus ATCC6538 (S. aureus ATCC6538), and Escherichia coli ATCC25922 (E. coli ATCC25922), which increased 7.65-, 1.49-, and 0.54-fold in comparison to the values of their unmethylated counterparts at 200, 250, and 400 μM, respectively. The results suggest that 3′-methoxyhesperetin showed the best antiproliferative activity against MCF-7 cells with IC₅₀ values of 10.45 ± 0.45 µM, which was an increase of more than 14.35-fold compared to that of hesperetin. These results indicate that methylation enhances the antimicrobial activities and antiproliferative effects of flavonoids. The current study provides an experimental basis for further research on flavonoids as well as flavonoid-containing crops in the development of antimicrobial and anti-breast cancer drugs in addition to supplementary and health foods. The biotransformation method is ideal, as it represents a means for the sustainable production of bioactive flavonoids.

Chemopreventive effect of troxerutin against hydrogen peroxide-induced oxidative stress in human leukocytes through modulation of glutathione-dependent enzymes

Troxerutin is a natural flavonoid present abundantly in tea, coffee, olives, wheat, and a variety of fruits and vegetables. Due to its diverse pharmacological properties, this flavonoid has aroused interest for treatment of various diseases, and consequently prompted investigation into its toxicological characteristics. The aim of this study was to evaluate the genotoxic and mutagenic effects and chemoprotective activity attributed to troxerutin using human peripheral blood leukocytes (PBLs) through several well-established experimental protocols based upon different parameters. Data demonstrated that troxerutin (100 to 1000 µM) induced no marked cytotoxic effect on PBLs after 24 hr, and did not produce strand breaks and mutagenicity. Regarding chemoprevention, this flavonoid attenuated cytotoxicity, genotoxicity, and mutagenicity initiated by hydrogen peroxide (H₂O₂) in human PBLs. Further, troxerutin demonstrated no marked cytotoxic effect on PBLs and exerted a protective effect against oxidative stress induced by H₂O₂ through modulation of GSH-dependent enzymes.

From Ethnomedicine to Plant Biotechnology and Machine Learning: The Valorization of the Medicinal Plant Bryophyllum sp

The subgenus Bryophyllum includes about 25 plant species native to Madagascar, and is widely used in traditional medicine worldwide. Different formulations from Bryophyllum have been employed for the treatment of several ailments, including infections, gynecological disorders, and chronic diseases, such as diabetes, neurological and neoplastic diseases. Two major families of secondary metabolites have been reported as responsible for these bioactivities: phenolic compounds and bufadienolides. These compounds are found in limited amounts in plants because they are biosynthesized in response to different biotic and abiotic stresses. Therefore, novel approaches should be undertaken with the aim of achieving the phytochemical valorization of Bryophyllum sp., allowing a sustainable production that prevents from a massive exploitation of wild plant resources. This review focuses on the study of phytoconstituents reported on Bryophyllum sp.; the application of plant tissue culture methodology as a reliable tool for the valorization of bioactive compounds; and the application of machine learning technology to model and optimize the full phytochemical potential of Bryophyllum sp. As a result, Bryophyllum species can be considered as a promising source of plant bioactive compounds, with enormous antioxidant and anticancer potential, which could be used for their large-scale biotechnological exploitation in cosmetic, food, and pharmaceutical industries.

Antiprotozoal Activity against Entamoeba histolytica of Flavonoids Isolated from Lippia graveolens Kunth

Amebiasis caused by Entamoeba histolytica is nowadays a serious public health problem worldwide, especially in developing countries. Annually, up to 100,000 deaths occur across the world. Due to the resistance that pathogenic protozoa exhibit against commercial antiprotozoal drugs, a growing emphasis has been placed on plants used in traditional medicine to discover new antiparasitics. Previously, we reported the in vitro antiamoebic activity of a methanolic extract of Lippia graveolens Kunth (Mexican oregano). In this study, we outline the isolation and structure elucidation of antiamoebic compounds occurring in this plant. The subsequent work-up of this methanol extract by bioguided isolation using several chromatographic techniques yielded the flavonoids pinocembrin (1), sakuranetin (2), cirsimaritin (3), and naringenin (4). Structural elucidation of the isolated compounds was achieved by spectroscopic/spectrometric analyses and comparing literature data. These compounds revealed significant antiprotozoal activity against E. histolytica trophozoites using in vitro tests, showing a 50% inhibitory concentration (IC₅₀) ranging from 28 to 154 µg/mL. Amebicide activity of sakuranetin and cirsimaritin is reported for the first time in this study. These research data may help to corroborate the use of this plant in traditional Mexican medicine for the treatment of dyspepsia.

Potent Cytotoxic Natural Flavonoids: The Limits of Perspective

BACKGROUND

Besides the numerous biologic and pharmacologic functions in the human body that act as potent antioxidants, flavonoids (flavones, flavanones, flavonols, flavanols and isoflavones) are noted as cancer preventive or therapeutic agents.

METHODS

This review summarizes the published data using PubMed, Science Direct, and Scopus.

RESULTS

In this context, recognition and introduction of the most active cytotoxic flavonoids as promising agents for cancer therapy gives insight for further evaluations. However, there are some critical points that may affect the entering of flavonoids as active cytotoxic phytochemicals in the clinical phase. Issues such as the abundance of active species in nature, the methods of extraction and purification, solubility, pharmacokinetic profile, presence of the chiral moieties, method of synthesis, and structure modification may limit the entry of a selected compound for use in humans. Although plenty of basic evidence exists for cytotoxic/antitumor activity of the versatility of flavonoids for entry into clinical trials, the above-mentioned concerns must be considered.

CONCLUSION

This review is an effort to introduce cytotoxic natural flavonoids (IC50< 10 µM) that may have the potential to be used against various tumor cells. Also, active constituents, molecular mechanisms, and related clinical trials have been discussed as well as the limitations and challenges of using flavonoids in clinic.

Plinia cauliflora (Mart.) Kausel: A comprehensive ethnopharmacological review of a genuinely Brazilian species

ETHNOPHARMACOLOGICAL RELEVANCE

Plinia cauliflora (Mart.) Kausel is widespread in alluvial plains and open forests in Brazil, Argentina, and Paraguay. The fruits of P. cauliflora are used as food, and almost all parts of this species have long been used as a traditional Brazilian medicine for the treatment of skin irritations, flu, diarrhea, labyrinthitis, genito-urinary problems, and asthma.

THE AIM OF THE REVIEW

This review provides comprehensive and up-to-date information on P. cauliflora with regard to its ethnopharmacological uses, constituents, biological activities, and toxicology, all of which are useful for future research and the development of new drugs.

MATERIALS AND METHODS

The information and data on P. cauliflora were collected from ethnobotanical textbooks and scientific databases, such as PubMed, Scopus, EBSCO, Science Direct, Google, and Google Scholar.

RESULTS

The main chemical constituents in P. cauliflora preparations were depsides, flavonoids, and hydrolysable tannins. The main medicinal use of the species in Brazil is for the treatment of diarrhea. Although antimicrobial potential of this species has been demonstrated, data on gastrointestinal motility are still incipient and need further investigation. Studies that indicate the efficacy of its traditional use for sore throat, pelvic hemorrhage, uterine wounds, vaginal discharge, and flu are nonexistent. The scientific literature does not describe any toxic effects of its popular use. However, the available data do not allow us to conclude that the ethnomedicinal use of this species is safe, with a lack of well-designed preclinical tests and randomized clinical trials.

CONCLUSION

This review summarizes research on the traditional use, phytochemistry, biological activities, and toxicology of P. cauliflora. Although P. cauliflora possesses significant biological activities, much of its ethnomedicinal use has not been scientifically evaluated. Well-designed pharmacological and toxicological assays and randomized clinical trials are still needed to validate its ethnopharmacological use as an herbal medicine.

Ionic Liquid-Like Pharmaceutical Ingredients and Applications of Ionic Liquids in Medicinal Chemistry: Development, Status and Prospects

Background:

As a new kind of green media and bioactive compounds with special structure, Ionic Liquids (ILs) are attracting much attention and applied widely in many fields. However, their roles and potential have not been fully recognized by many researchers of medicinal chemistry. Because of obvious differences from other traditional drugs and reagents, their uses and performance together with advantages and disadvantages need to be explored and reviewed in detail.

Methods:

For a systematic and explicit description of the relationship between ILs and medicinal chemistry, all of the contents were elucidated and summarized in a series of independent parts. In each part, it started from the research background or a conceptual framework and then specific examples were introduced to illustrate the theme. Finally, the important conclusions were drawn and its future was outlooked after the discussion about related key problems appearing in each mentioned research. Meanwhile, methodologies such as empirical analysis, comparison and induction were applied in different sections to exposit our subject.

Results:

The whole review was composed of five parts, and 148 papers were cited in total. Related basic information of ionic liquids was provided on the basis of representative references, including their concepts and important characters. Then 82 papers outlined ionic liquid-like active pharmaceutical ingredients, which unfolded with their major biological activities (antimicrobial activity, antibiofilm activity, antitumor activity, anticholinesterase activity and so on). Applications of ionic liquids in the synthesis of drugs and pharmaceutical intermediates were elaborated in 92 papers to illustrate the important roles of ILs and their extraordinary properties in this field. Moreover, new technologies (such as immobilization of IL, microwave reaction, solventfree synthesis, microreactor, etc) were introduced for further innovation. Finally, 26 papers were included to expound the status of the IL-assisted derivatization of various natural lead compounds.

Conclusion:

This review placed emphasis on chemical structures of ILs and their structureactivity relationships in a specific manner, leading to meaningful and valuable related information to some related fields and thus promotes further development and application of various ILs for medicinal chemistry. The deep exploration for key scientific problems is the driving force to propel their theoretical breakthrough and industrial production.

Molecular Targets of Genistein and Its Related Flavonoids to Exert Anticancer Effects

Increased health awareness among the public has highlighted the health benefits of dietary supplements including flavonoids. As flavonoids target several critical factors to exert a variety of biological effects, studies to identify their target-specific effects have been conducted. Herein, we discuss the basic structures of flavonoids and their anticancer activities in relation to the specific biological targets acted upon by these flavonoids. Flavonoids target several signaling pathways involved in apoptosis, cell cycle arrest, mitogen-activated protein kinase (MAPK), phosphoinositide 3-kinase (PI3K)/AKT kinase, and metastasis. Polo-like kinase 1 (PLK1) has been recognized as a valuable target in cancer treatment due to the prognostic implication of PLK1 in cancer patients and its clinical relevance between the overexpression of PLK1 and the reduced survival rates of several carcinoma patients. Recent studies suggest that several flavonoids, including genistein directly inhibit PLK1 inhibitory activity. Later, we focus on the anticancer effects of genistein through inhibition of PLK1.

Cytotoxic Flavonoids from the Aerial Parts of Stachys lavandulifolia Vahl

Background: Stachys lavandulifolia Vahl is a herbaceous plant distributed in the west and south western Asia. Despite of the wide medicinal uses, there are some reports on toxicity potential of this plant. In present study we attempted to evaluate the toxicity and to characterize the cytotoxic principles of S. lavandulifolia. Methods: Brine shrimp lethality test (BSLT) was used to evaluate the general toxicity of the extracts and essential oil obtained from the aerial parts of S. lavandulifolia. Phytochemical constituents of the active extract were investigated using various chromatographic and spectroscopic methods. GC and GC-MS were also used to analyze the plant essential oil. GC and GC-MS were used to analyze the plant essential oil. Cytotoxic activities of the isolated compounds were also evaluated using MTT assay method. Results: In brine shrimp lethality test (BSLT), chloroform extract and the plant essential oil exhibited the most toxicity against Artemia salina larvae (LD50: 121.8±5.6 and 127.6±14.7 µg ml-1, respectively). GC and GC-MS analyses of essential oil led to the characterization of forty compounds of which α-bisabolol (23.85%) and thymol (17.88%) were identified as the main constituents. Nine flavonoids, Pachypodol (1), chrysosplenetin (2), kumatakenin (3), velutin (4), penduletin (5), viscosine (6), chrysoeriol (7), hydroxygenkwanin (8) and apigenin (9) were isolated from the chloroform extract of S. lavandulifolia. Among the isolated compounds, chrysosplenetin (2), a polymethoxylated flavonoid, was found as the most toxic compound toward MDA-MB-23 and HT-29 cells, with IC50 values of 88.23 and 116.50 µg ml-1, respectively. Furthermore, chrysosplenetin (2), kumatakenin (3) and viscosine (6) with selectivity indices of 2.70, 2.59 and 3.33, respectively, showed higher preferential toxicity against MDA-MB-23 cells in comparison with tamoxifen (SI:2.45). Conclusion: This study reports methoxylated flavonoids as compounds which could be involved in toxicity of S. lavandulifolia. The results of MTT assay also suggest some of these compounds as appropriate candidates for anti-cancer drug development research.

An In Vitro Estimation of the Cytotoxicity and Genotoxicity of Root Extract from Leonurus sibiricus L. Overexpressing AtPAP1 against Different Cancer Cell Lines

As the current cancer treatment success rate is not sufficient, interest has grown in plants as possible sources of anti-cancer compounds. One such plant with a broad spectrum of activity is Lenourus sibiricus of the family Lamiaceae. This study investigates for the first time both the genotoxic and cytotoxic activities of TR (transformed) and AtPAP1 TR (with over-expression of transcriptional factor) root extracts of Lenourus sibiricus against various cancer cell lines (CCRF-CEM, K-562 and A549). Both tested extracts showed a cytotoxic effect on CCRF-CEM and K-562 cell lines, but strongest activity was observed for the AtPAP1 TR extract. No cytotoxic effect was observed against the A549 cell line in the tested concentration range, and it was found that both tested extracts may induce apoptosis by decreasing mitochondrial membrane potential and inducing nDNA damage lesion in the TP53 region and mtDNA in ND1 (mitochondrially encoded NADH: ubiquinone oxidoreductase core subunit 1) and ND5 (mitochondrially encoded NADH:ubiquinone oxidoreductase core subunit 5) regions in K-562 and CCRF-CEM. Our results confirmed that TR and AtPAP1 TR root extracts from L. sibiricus are cytotoxic and genotoxic against different model cell lines (CCRF-CEM and K-562). However, the observed genotoxicity of both extracts needs to be confirmed by additional studies. These preclinical observations support the use of L. sibiricus with other pharmacological purposes.

Cytotoxicity of white birch bud extracts: Perspectives for therapy of tumours

Birch buds (Gemmae Betulae) are widely used in Russian and Chinese traditional medicine mainly as a diuretic and diaphoretic agent but also as an antiseptic, anti-inflammatory and analgesic. Despite the long history of therapeutic use of birch buds in folk medicine, the existing information on their chemical composition and pharmacological effects is insufficient. This circumstance warrants further study of the chemistry and pharmacology of birch buds. The present study was designed to investigate (a) the chemical composition of buds from two species of white birch and (b) the in vitro cytotoxic effect of extracts from these sources on selected tumour cells. Extracts from Betula pubescens Ehrh. and Betula pendula Roth. buds were obtained using three different methods: carbon dioxide supercritical fluid extraction (SFE), washing of exudate covering whole buds, and extraction of milled buds with diethyl ether. The chemical composition of extracts was investigated by GC-MS. Cytotoxicity was determined by MTT assay, and cell proliferation was determined by [³H]thymidine uptake in cancer cells and normal skin fibroblasts. The GC-MS investigation identified a total of 150 substances of different classes. The chemical composition of B. pubescens and B. pendula buds differed, with bud extracts from the former containing a relatively high quantity of sesquiterpenoids and flavonoids, while the main components of extracts from the latter were triterpenoids. The results of the biological assay indicated that birch bud extracts demonstrated time- and concentration-dependent and differential cytotoxicity. The highest cytotoxic activity demonstrated bud exudates and SFE extracts obtained from both Betula species. The rich chemical composition of birch buds suggests the possibility of a wider spectrum of biological activity than previously thought. Birch bud extracts could be a promising source of compounds with cytotoxic activity against various cancers.

Cytotoxic Activity of Extracts from Plants of Central Argentina on Sensitive and Multidrug-Resistant Leukemia Cells: Isolation of an Active Principle from Gaillardia megapotamica

Plants are a significant reservoir of cytotoxic agents, including compounds with the ability to interfere with multidrug-resistant (MDR) cells. With the aim of finding promising candidates for chemotherapy, 91 native and naturalized plants collected from the central region of Argentina were screened for their cytotoxic effect toward sensitive and MDR P-glycoprotein (P-gp) overexpressing human leukemia cells by means of MTT assays. The ethanol extracts obtained from Aldama tucumanensis, Ambrosia elatior, Baccharis artemisioides, Baccharis coridifolia, Dimerostemma aspilioides, Gaillardia megapotamica, and Vernonanthura nudiflora presented outstanding antiproliferative activity at 50 μg/mL, with inhibitory values from 93 to 100%, when tested on the acute lymphoblastic leukemia (ALL) cell line CCRF-CEM and the resistant derivative CEM-ADR5000, while 70-90% inhibition was observed against the chronic myelogenous leukemia (CML) cell K562 and its corresponding resistant subline, Lucena 1. Subsequent investigation showed these extracts to possess marked cytotoxicity with IC50 values ranging from 0.37 to 29.44 μg/mL, with most of them being below 7 μg/mL and with ALL cells, including the drug-resistant phenotype, being the most affected. G. megapotamica extract found to be one of the most effective and bioguided fractionation yielded helenalin (1). The sesquiterpene lactone displayed IC50 values of 0.63, 0.19, 0.74, and 0.16 μg/mL against K562, CCRF-CEM, Lucena 1, and CEM/ADR5000, respectively. These results support the potential of these extracts as a source of compounds for treating sensitive and multidrug-resistant leukemia cells and support compound 1 as a lead for developing effective anticancer agents.

Effect of diosmin on apoptotic signaling molecules in N-nitrosodiethylamine-induced hepatocellular carcinoma in experimental rats

The aim of the present study was to evaluate the antioxidant and chemopreventive efficiency of diosmin against N-nitrosodiethylamine (NDEA)-induced hepatocarcinogenesis in adult male rats. Rats were classified into four groups as follows: Group I: Control, Group II: NDEA-induced hepatocellular carcinogenic rats, Group III: Cancer-bearing animals treated with diosmin (200 mg/kg/body weight/day) orally for 28 days, Group IV: Control animals treated with diosmin (200 mg/kg/body weight/day) alone for 28 days. The model of NDEA-induced HCC rats elicited significant increases in alpha-fetoprotein (AFP), lipid peroxidation (LPO) and increase in anti-apoptotic proteins (Bcl-2, Bcl-xL and Mcl-1) with a concomitant significant decline in liver antioxidant enzymes, pro-apoptotic (Bax and Bad) and caspase-3 &-9 proteins. The oral administration of diosmin as a protective agent normalized the altered levels of AFP, LPO, antioxidant enzymes, pro- and anti-apoptotic proteins as well as caspase-3 and -9 proteins. Transmission electron microscopical studies also revealed that treatment of diosmin has a perspective anti-cancer activity by rearranging hepatic cell structure and its integrity. Results of this study suggest that diosmin may be one of a pharmacological and therapeutic representative against hepatocellular carcinoma.

Green synthesis palladium nanoparticles mediated by white tea (Camellia sinensis) extract with antioxidant, antibacterial, and antiproliferative activities toward the human leukemia (MOLT-4) cell line

Among nanoparticles used for medical applications, palladium nanoparticles (PdNPs) are among the least investigated. This study was undertaken to develop PdNPs by green synthesis using white tea (W.tea; Camellia sinensis) extract to produce the Pd@W.tea NPs. The Pd@W.tea NPs were characterized by UV–vis spectroscopy and X-ray diffractometry, and evaluated with transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The Pd@W.tea NPs were spherical (size 6–18 nm) and contained phenols and flavonoids acquired from the W.tea extract. Pd@W.tea NPs has good 1-diphenyl-2-picrylhydrazyl (DPPH), OH, and NO-scavenging properties as well as antibacterial effects toward Staphylococcus epidermidis and Escherichia coli. MTT assay showed that Pd@W.tea NPs (IC₅₀ =0.006 μM) were more antiproliferative toward the human leukemia (MOLT-4) cells than the W.tea extract (IC₅₀ =0.894 μM), doxorubicin (IC₅₀ =2.133 μM), or cisplatin (IC₅₀ =0.013 μM), whereas they were relatively innocuous for normal human fibroblast (HDF-a) cells. The anticancer cell effects of Pd@W.tea NPs are mediated through the induction of apoptosis and G2/M cell-cycle arrest.

Leaf and Root Extracts from Campomanesia adamantium (Myrtaceae) Promote Apoptotic Death of Leukemic Cells via Activation of Intracellular Calcium and Caspase-3

Phytochemical studies are seeking new alternatives to prevent or treat cancer, including different types of leukemias. Campomanesia adamantium, commonly known as guavira or guabiroba, exhibits pharmacological properties including antioxidant, antimicrobial, and antiproliferative activities. Considering the anticancer potential of this plant species, the aim of this study was to evaluate the antileukemic activity and the chemical composition of aqueous extracts from the leaves (AECL) and roots (AECR) of C. adamantium and their possible mechanisms of action. The extracts were analyzed by LC-DAD-MS, and their constituents were identified based on the UV, MS, and MS/MS data. The AECL and AECR showed different chemical compositions, which were identified as main compounds glycosylated flavonols from AECL and ellagic acid and their derivatives from AECR. The cytotoxicity promoted by these extracts were evaluated using human peripheral blood mononuclear cells and Jurkat leukemic cell line. The cell death profile was evaluated using annexin-V-FITC and propidium iodide labeling. Changes in the mitochondrial membrane potential, the activity of caspases, and intracellular calcium levels were assessed. The cell cycle profile was evaluated using propidium iodide. Both extracts caused concentration-dependent cytotoxicity only in Jurkat cells via late apoptosis. This activity was associated with loss of the mitochondrial membrane potential, activation of caspases-9 and -3, changes in intracellular calcium levels, and cell cycle arrest in S-phase. Therefore, the antileukemic activity of the AECL and AECR is mediated by mitochondrial dysfunction and intracellular messengers, which activate the intrinsic apoptotic pathway. Hence, aqueous extracts of the leaves and roots of C. adamantium show therapeutic potential for use in the prevention and treatment of diseases associated the proliferation of tumor cell.

Modifications of dietary flavonoids towards improved bioactivity: An update on structure-activity relationship

Over the past two decades, extensive studies have revealed that inflammation represents a major risk factor for various human diseases. Chronic inflammatory responses predispose to pathological progression of chronic illnesses featured with penetration of inflammatory cells, dysregulation of cellular signaling, excessive generation of cytokines, and loss of barrier function. Hence, the suppression of inflammation has the potential to delay, prevent, and to treat chronic diseases. Flavonoids, which are widely distributed in humans daily diet, such as vegetables, fruits, tea and cocoa, among others, are considered as bioactive compounds with anti-inflammatory potential. Modification of flavonoids including hydroxylation, o-methylation, and glycosylation, can alter their metabolic features and affect mechanisms of inflammation. Structure-activity relationships among naturally occurred flavonoids hence provide us with a preliminary insight into their anti-inflammatory potential, not only attributing to the antioxidant capacity, but also to modulate inflammatory mediators. The present review summarizes current knowledge and underlies mechanisms of anti-inflammatory activities of dietary flavonoids and their influences involved in the development of various inflammatory-related chronic diseases. In addition, the established structure-activity relationships of phenolic compounds in this review may give an insight for the screening of new anti-inflammatory agents from dietary materials.

Assessment of antioxidant, antitumor and pro-apoptotic effects of Salvia fruticosa Mill. subsp. thomasii (Lacaita) Brullo, Guglielmo, Pavone & Terrasi (Lamiaceae)

The aim of the present study was to investigate the in vitro antioxidant and antitumor effects of Salvia fruticosa Mill subsp. thomasii (Lacaita) Brullo, Guglielmo, Pavone & Terrasi (Lamiaceae). The aerial parts were extracted by maceration with methanol. This extract was partitioned with methanol and n-hexane. Luteolin, luteolin 7-O-glucoside, rutin and salvigenin were isolated from the methanol-soluble fraction. n-Hexane fraction showed viridiflorol, β-pinene, 1,8-cineole, as main components. The methanol-soluble fraction exerted antitumor activity against human breast cancer (MCF-7 and MDA-MB-231) and human colorectal carcinoma (RKO and Caco-2) cells. TUNEL test revealed that S. fruticosa subsp. thomasii leads to cells death by apoptosis, with low cytotoxic effects on non-tumoral 3T3-L1 cells. Moreover, it exerted the highest protection of lipid peroxidation and reduced the oxidative stress induced by menadione treatment in 3T3-L1 murine fibroblasts. S. fruticosa subsp. thomasii bioactivity could promote its use not only as food but also in nutraceutical/pharmaceutical industries.

Natural and Synthetic Flavonoids: Structure-Activity Relationship and Chemotherapeutic Potential for the Treatment of Leukemia

Flavonoids and their derivatives are polyphenolic secondary metabolites with an extensive spectrum of pharmacological activities, including antioxidants, antitumor, anti-inflammatory, and antiviral activities. These flavonoids can also act as chemopreventive agents by their interaction with different proteins and can play a vital role in chemotherapy, suggesting a positive correlation between a lower risk of cancer and a flavonoid-rich diet. These agents interfere with the main hallmarks of cancer by various individual mechanisms, such as inhibition of cell growth and proliferation by arresting the cell cycle, induction of apoptosis and differentiation, or a combination of these mechanisms. This review is an effort to highlight the therapeutic potential of natural and synthetic flavonoids as anticancer agents in leukemia treatment with respect to the structure-activity relationship (SAR) and their molecular mechanisms. Induction of cell death mechanisms, production of reactive oxygen species, and drug resistance mechanisms, including p-glycoprotein efflux, are among the best-described effects triggered by the flavonoid polyphenol family.

Evaluation of Cytotoxic and Genotoxic Effects of Euphorbia Triaculeata Forssk. Extract

Objective: To evaluate the cytotoxic and genotoxic activity of Euphorbia triaculeata Forssk. plant extract from Jazan region, Saudi Arabia, in an in vitro cancer model, which could be beneficial in anticancer therapy against human breast cancer cell line (MCF-7), prostate cell line (PC-3), human hepatocellular carcinoma cell line (HEPG2) and normal breast epithelial cell line (MCF-10A). The human foreskin fibroblast cell line, (Hs68), was also included in the cell panel. Doxorubicin and 5-Flurouracil, broad-spectrum anticancer drugs, were used as the positive control. Methods: Cytotoxicity of Euphorbia triaculeata plant extract was investigated by employing MTT assay and the genotoxicity was assessed by using comet assay. Results: Both toxicity tests exhibited significant toxicity results. In the comet assay, the Euphorbia triaculeata extract exhibited genotoxic effects against MCF-7 DNA and PC 3 but not on HEPG2 cell lines in a time-dependent manner by increasing the mean percentage of DNA damage. Euphorbia triaculeata extract showed significant toxicity against cancer cells. Comparison with positive control signifies that cytotoxicity exhibited by methanol extract might have moderate activity. Conclusion: The present work confirmed the cytotoxicity and genotoxicity of Euphorbia triaculeata plant. However, the observed toxicity of this plant extract needs to be confirmed by additional studies. Based on our results, further examination of the potential anticancer properties of Euphorbia triaculeata plant species and the identification of the active ingredients of these extracts is warranted.

Established Human Cell Lines as Models to Study Anti-leukemic Effects of Flavonoids

Despite the extensive work on pathological mechanisms and some recent advances in the treatment of different hematological malignancies, leukemia continues to present a significant challenge being frequently considered as incurable disease. Therefore, the development of novel therapeutic agents with high efficacy and low toxicity is urgently needed to improve the overall survival rate of patients. In this comprehensive review article, the current knowledge about the anticancer activities of flavonoids as plant secondary polyphenolic metabolites in the most commonly used human established leukemia cell lines (HL-60, NB4, KG1a, U937, THP-1, K562, Jurkat, CCRF- CEM, MOLT-3, and MOLT-4) is compiled, revealing clear anti-proliferative, pro-apoptotic, cell cycle arresting, and differentiation inducing effects for certain compounds. Considering the low toxicity of these substances in normal blood cells, the presented data show a great potential of flavonoids to be developed into novel anti-leukemia agents applicable also in the malignant cells resistant to the current conventional chemotherapeutic drugs.

The Val158Met polymorphism in COMT gene and cancer risk: role of endogenous and exogenous catechols

Catechol-O-methyltransferase, COMT, is an important phase II enzyme catalyzing the transfer of a methyl-group from S-adenosylmethionine to a catechol-containing substrate molecule. A genetic variant Val158Met in the COMT gene leads to a several-fold decrease in the enzymatic activity giving rise to the accumulation of potentially carcinogenic endogenous catechol estrogens and their reactive intermediates and increasing thus the risk of tumorigenesis. However, numerous association studies between the COMT genotype and susceptibility to various malignancies have shown inconsistent and controversial findings indicating that additional gene-gene and gene-environment interactions might be crucial in modulating the physiological role of the COMT. In this review article, the important contribution of dietary catechol-containing flavonoids to modification of the relationships between the COMT genotype and cancer risk is discussed. Whereas, the diverse anticancer activities of common phytochemicals, such as green tea polyphenols, quercetin, fisetin or luteolin, can be markedly changed (both decreased or increased) by the COMT-mediated O-methylation of these exogenous substrates, flavonoids can also behave as potent inhibitors of the COMT enzyme slowing detoxification of endogenous catechol estrogens. Such a many-featured functioning of the COMT and its complex regulation by several different genetic and environmental factors, including plant-based food ingredients, emphasizes the necessity to further stratify the association studies between the COMT genotype and tumor risk by consumption of catechol-containing dietary flavonoids. Currently, it can be only speculated that some of the possible associations might be masked by the regular intake of specific food polyphenols, taking effect in certain communities or populations.

Flavonoids of Calligonum polygonoides and their cytotoxicity

Context Calligonum polygonoides L. subsp. comosum L' Hér. (Polygonaceae), locally known as "arta", is a slow-growing small leafless desert shrub. Objective Isolation, structure elucidation and evaluation of cytotoxic activity of flavonoids from C. polygonoides aerial parts. Materials and methods Flavonoids in the hydroalcoholic extract of the of C. polygonoides were isolated and purified using column chromatography and preparative HPLC. The structures of the isolated flavonoids were elucidated on the basis of spectroscopic data including 2D NMR techniques. The cytotoxic activity of the isolated flavonoids (6.25, 25, 50 and 100 μg/mL) was evaluated against liver HepG2 and breast MCF-7 cancer cell lines using sulphorhodamine-B assay. Results A new flavonoid, kaempferol-3-O-β-D-(6″-n-butyl glucuronide) (1), and 13 known flavonoids, quercetin 3-O-β-D-(6″-n-butyl glucuronide) (2), kaempferol-3-O-β-D-(6″-methyl glucuronide) (3), quercetin-3-O-β-D-(6″-methyl glucuronide) (4), quercetin-3-O-glucuronide (5), kaempferol-3-O-glucuronide (6), quercetin-3-O-α-rhamnopyranoside (7), astragalin (8), quercetin-3-O-glucopyranoside (9), taxifolin (10), (+)-catechin (11), dehydrodicatechin A (12), quercetin (13), and kaempferol (14), were isolated from the aerial parts of C. polygonoides. Quercetin showed significant cytotoxic activity against HepG2 and MCF-7 cell lines with IC50 values of 4.88 and 0.87 μg/mL, respectively. Structure-activity relationships were analyzed by comparing IC50 values of several pairs of flavonoids differing in one structural element. Discussion and conclusion The activity against breast cancer cell lines decreased by glycosylation at C-3. The presence of 2,3-double bond in ring C, carbonyl group at C-4 and 3',4'-dihydroxy substituents in ring B are essential structural requirements for the cytotoxic activity against breast cancer cells.

Comparative Developmental Toxicity of Flavonoids Using an Integrative Zebrafish System

Flavonoids are a large, structurally diverse class of bioactive naturally occurring chemicals commonly detected in breast milk, soy based infant formulas, amniotic fluid, and fetal cord blood. The potential for pervasive early life stage exposures raises concerns for perturbation of embryogenesis, though developmental toxicity and bioactivity information is limited for many flavonoids. Therefore, we evaluated a suite of 24 flavonoid and flavonoid-like chemicals using a zebrafish embryo-larval toxicity bioassay-an alternative model for investigating developmental toxicity of environmentally relevant chemicals. Embryos were exposed to 1-50 µM of each chemical from 6 to 120 h postfertilization (hpf), and assessed for 26 adverse developmental endpoints at 24, 72, and 120 hpf. Behavioral changes were evaluated in morphologically normal animals at 24 and 72 hpf, at 120 hpf using a larval photomotor response (LPR) assay. Gene expression was comparatively evaluated for all compounds for effects on biomarker transcripts indicative of AHR (cyp1a) and ER (cyp19a1b, esr1, lhb, vtg) pathway bioactivity. Overall, 15 of 24 flavonoids elicited adverse effects on one or more of the developmental or behavioral endpoints. Hierarchical clustering and principle component analyses compared toxicity profiles and identified 3 distinct groups of bioactive flavonoids. Despite robust induction of multiple estrogen-responsive biomarkers, co-exposure with ER and GPER antagonists did not ameliorate toxicity, suggesting ER-independence and alternative modes of action. Taken together, these studies demonstrate that development is sensitive to perturbation by bioactive flavonoids in zebrafish that are not related to traditional estrogen receptor mode of action pathways. This integrative zebrafish platform provides a useful framework for evaluating flavonoid developmental toxicity and hazard prioritization.

Flavonoids from Artemisia sacrorum Ledeb. and their cytotoxic activities against human cancer cell lines

Flavonoids have been demonstrated to have cytotoxic activities toward numerous human cancer cells, whereas they have little or no effect on normal cells. The numerous flavonoids in traditional Chinese herbs may be promising candidates for the development of novel anti-cancer drugs. Our previous study demonstrated that CH₂Cl₂ and 95% ethanol eluate (EE) fractions have the strongest cytotoxic activities against human cancer cell lines of the 9 fractions separated from Artemisia sacrorum Ledeb., which is widely used to prevent and treat diverse diseases in Northeast China. In the present study, 8 flavonoids were isolated from the 95% EE fraction of Artemisia sacrorum Ledeb. The chemical structures of the compounds were elucidated by extensive spectroscopic analyses. The following 5 flavonoids were isolated for the first time from this plant: Jaceosidin, kaempferol, quercetin, luteolin and quercitrin. A total of 2 flavonoids from the CH₂Cl₂ fraction and 8 flavonoids from the 95% EE fraction were examined to evaluate their cytotoxic activities against human SK-HEP-1 hepatoma cancer cells and human HeLa cervical cancer cells, respectively. The results revealed that 2 flavonoids had marked cytotoxic activities against HeLa cells.

Baicalin and Baicalein Inhibit Src Tyrosine Kinase and Production of IL-6

Flavonoids play an important role in the treatment of various diseases, as they are able to inhibit reactive oxygen species, which cause damage to cells and tissues which may lead to increased risk of inflammatory diseases. Baicalin and baicalein, two flavonoids found in the roots ofScutellaria baicalensis, in the leaves ofThymus vulgarisandOroxylum indicum, were tested for their anti-inflammatory activity as well as for their cytotoxicity. Thereby the two compounds were investigated on Src tyrosine kinase inhibition and inhibition of production of interleukin (IL-6) in lipopolysaccharide- (LPS-) stimulated THP-1 cells. Additionally, the THP-1 cell line was used for the determination of the cytotoxicity. Both baicalin and baicalein showed some anti-inflammatory properties, while baicalein turned out to be the more active compound with higher inhibitory activities on both Src tyrosine kinase and production of cytokine IL-6. Baicalin and baicalein showed no signs of cytotoxicity in the MTS cytotoxicity assay in THP-1 cells.

Flavonoids as a scaffold for development of novel anti-angiogenic agents: An experimental and computational enquiry

Relationship between structural diversity and biological activities of flavonoids has remained an important discourse in the mainstream of flavonoid research. In the current study anti-angiogenic, cytotoxic, antioxidant and cyclooxygenase (COX) inhibitory activities of diverse class of flavonoids including hydroxyl and methoxy substituted flavones, flavonones and flavonols have been evaluated in the light of developing flavonoids as a potential scaffold for designing novel anti-antiangiogenic agents. We demonstrate anti-angiogenic potential of flavonoids using in vivo chorioallantoic membrane model (CAM) and further elaborate the possible structural reasoning behind observed anti-angiogenic effect using in silico methods. Additionally, we report antioxidant potential and kinetics of free radical scavenging activity using DPPH and SOR scavenging assays. Current study indicates that selected flavonoids possess considerable COX inhibition potential. Furthermore, we describe cytotoxicity of flavonoids against selected cancer cell lines using MTT cell viability assay. Structural analysis of in silico docking poses and predicted binding free energy values are not only in accordance with the experimental anti-angiogenic CAM values from this study but also are in agreement with the previously reported literature on crystallographic data concerning EGFR and VEGFR inhibition.

Signaling proteins and pathways affected by flavonoids in leukemia cells

Flavonoids are a class of plant secondary metabolites that are found ubiquitously in plants and in the human diet. Our objective is to investigate the antiproliferative effects of flavonoids (baicalein, luteolin, genistein, apigenin, scutellarin, galangin, chrysin, and naringenin) toward leukemia cells (HL-60, NB4, U937, K562, Jurkat) as well as the relationship between their antileukemic potencies and molecular structures. At the proteomic level, we evaluate the effects of different flavonoids on the expression levels of various proteins using Protein Pathway Array (PPA) technology. Our results showed a dose-dependent cytotoxicity of flavonoids toward various types of leukemia cells. The results of PPA illustrated that flavonoids, such as baicalein, genistein, and scutellarin affected different proteins in different leukemia cell lines. Cell cycle regulatory proteins, such as CDK4, CDK6, Cyclin D1, Cyclin B1, p-CDC2, and p-RB were affected in different leukemia cells. Furthermore, we found that baicalein suppresses CDK4 and activates p-ERK in most leukemia cells; genistein mainly affects CDK4, p-ERK, p-CDC2, while scutellarin dysregulated the proteins, cell division control protein 42, Notch4, and XIAP. Collectively, a wide variety of dysregulation of key signaling proteins related to apoptosis and cell-cycle regulation contributes to the antileukemic properties of these flavonoids.

Cytotoxicity of dietary flavonoids on different human cancer types

Flavonoids are ubiquitous in nature. They are also in food, providing an essential link between diet and prevention of chronic diseases including cancer. Anticancer effects of these polyphenols depend on several factors: Their chemical structure and concentration, and also on the type of cancer. Malignant cells from different tissues reveal somewhat different sensitivity toward flavonoids and, therefore, the preferences of the most common dietary flavonoids to various human cancer types are analyzed in this review. While luteolin and kaempferol can be considered as promising candidate agents for treatment of gastric and ovarian cancers, respectively, apigenin, chrysin, and luteolin have good perspectives as potent antitumor agents for cervical cancer; cells from main sites of flavonoid metabolism (colon and liver) reveal rather large fluctuations in anticancer activity probably due to exposure to various metabolites with different activities. Anticancer effect of flavonoids toward blood cancer cells depend on their myeloid, lymphoid, or erythroid origin; cytotoxic effects of flavonoids on breast and prostate cancer cells are highly related to the expression of hormone receptors. Different flavonoids are often preferentially present in certain food items, and knowledge about the malignant tissue-specific anticancer effects of flavonoids could be purposely applied both in chemoprevention as well as in cancer treatment.

Kaempferol suppresses bladder cancer tumor growth by inhibiting cell proliferation and inducing apoptosis

The effects of the flavonoid compound, kaempferol, which is an inhibitor of cancer cell proliferation and an inducer of cell apoptosis have been shown in various cancers, including lung, pancreatic, and ovarian, but its effect has never been studied in bladder cancer. Here, we investigated the effects of kaempferol on bladder cancer using multiple in vitro cell lines and in vivo mice studies. The MTT assay results on various bladder cancer cell lines showed that kaempferol enhanced bladder cancer cell cytotoxicity. In contrast, when analyzed by the flow cytometric analysis, DNA ladder experiment, and TUNEL assay, kaempferol significantly was shown to induce apoptosis and cell cycle arrest. These in vitro results were confirmed in in vivo mice studies using subcutaneous xenografted mouse models. Consistent with the in vitro results, we found that treating mice with kaempferol significant suppression in tumor growth compared to the control group mice. Tumor tissue staining results showed decreased expressions of the growth related markers, yet increased expressions in apoptosis markers in the kaempferol treated group mice tissues compared to the control group mice. In addition, our in vitro and in vivo data showed kaempferol can also inhibit bladder cancer invasion and metastasis. Further mechanism dissection studies showed that significant down-regulation of the c-Met/p38 signaling pathway is responsible for the kaempferol mediated cell proliferation inhibition. All these findings suggest kaempferol might be an effective and novel chemotherapeutic drug to apply for the future therapeutic agent to combat bladder cancer.