Pomiferin, histone deacetylase inhibitor isolated from the fruits of Maclura pomifera

Pharmacological properties of extracts and prenylated isoflavonoids from the fruits of Osage orange (Maclura pomifera (Raf.) C.K.Schneid.)

Osage orange trees (Maclura pomifera (Raf.) C.K.Schneid.) are distributed worldwide, particularly in south-east states of the USA. They produce large quantities of strong yellow fruits, bigger than oranges, but these fruits are inedible, with an acid milky juice which is little consumed by birds and insects. Extracts prepared from Osage orange fruits (hedge apple) have revealed a range of pharmacological properties of interest in human and veterinary medicine. In addition, Osage orange extracts can be used in agriculture and aquaculture, and as dyeing agent for the textile industry. Extracts contain potent antioxidant compounds, notably the isoflavonoids pomiferin and auriculasin, together with other terpenoids and flavonoids. The structural characteristics and pharmacological properties of the major prenylated isoflavones isolated from M. pomifera are discussed here, with a focus on the two phenolic compounds osajin and warangalone, and the two catechol analogues pomiferin and auriculasin. The mechanisms at the origin of their potent antioxidant and anti-inflammatory effects are presented, notably inhibition of xanthine oxidase, phosphodiesterase 5A and kinases such as RKS2 and kRAS. Osajin and auriculasin display marked anticancer properties, owing to their ability to inhibit tumor cell proliferation, migration and tumor angiogenesis. Different molecular mechanisms are discussed, including osajin‑copper complexation and binding to quadruplex DNA. An overview of the mechanism of action of the prenylated isoflavones from Osage orange is presented, with the objective to promote their knowledge and to raise opportunities to better exploit the fruits of Osage orange, abundant but largely neglected at present.

Pomiferin targeting SLC9A9 based on histone acetylation modification pattern is a potential therapeutical option for gastric cancer with high malignancy

Changes in histone acetylation status are associated with gastric cancer (GC) progression. Pomiferin is a natural flavonoid, however, the specific role of pomiferin in the treatment of GC is still unclear, and its targets are not well clarified. In this work, the prognostic genes related with histone acetylation in GC were screened by univariate Cox analysis. Next, a risk model of was constructed using least absolute shrinkage and selection operator-Cox regression analyses, and multivariate Cox analysis was used for identifying the independent risk factor. Molecular docking was performed using AutoDock Vina to validate the interaction between solute carrier family 9 member A9 (SLC9A9) and pomiferin. In vitro and in vivo models were applied to investigate the tumor-suppressive role of pomiferin against GC. The inhibitory effects of pomiferin on EGFR/PI3K/AKT signaling were valdiated by Western blotting, immunofluorescence staining and qPCR. Here, a prognostic risk model based on histone acetylation regulators was established, and SLC9A9 was identified as a risk factor associated with histone acetylation status in GC. SLC9A9 expression was associated with abnormal immune microenvironment of tumor. Pomiferin had a high binding affinity with SLC9A9, and both pomiferin treatment and depletion of SLC9A9 repressed the malignant phenotypes of GC cells. Mechanistically, pomiferin inactivates EGFR/PI3K/AKT signaling in GC cells. In summary, SLC9A9, as a indicator of abnormal histone acetylation status of GC, functions as an oncogenic factor. Pomiferin binds with SLC9A9 to inactivate EGFR/PI3K/AKT pathway, to block GC progression, suggesting it is a promising drug for the patients with highly malignant GC.

Subtype-selective prenylated isoflavonoids disrupt regulatory drivers of MYCN-amplified cancers

Transcription factors have proven difficult to target with small molecules because they lack pockets necessary for potent binding. Disruption of protein expression can suppress targets and enable therapeutic intervention. To this end, we developed a drug discovery workflow that incorporates cell-line-selective screening and high-throughput expression profiling followed by regulatory network analysis to identify compounds that suppress regulatory drivers of disease. Applying this approach to neuroblastoma (NBL), we screened bioactive molecules in cell lines representing its MYC-dependent (MYCNA) and mesenchymal (MES) subtypes to identify selective compounds, followed by PLATESeq profiling of treated cells. This revealed compounds that disrupt a sub-network of MYCNA-specific regulatory proteins, resulting in MYCN degradation in vivo. The top hit was isopomiferin, a prenylated isoflavonoid that inhibited casein kinase 2 (CK2) in cells. Isopomiferin and its structural analogs inhibited MYC and MYCN in NBL and lung cancer cells, highlighting the general MYC-inhibiting potential of this unique scaffold.

Progress in discovery and development of natural inhibitors of histone deacetylases (HDACs) as anti-cancer agents

The study of epigenetic translational modifications had drawn great interest for the last few decades. These processes play a vital role in many diseases and cancer is one of them. Histone acetyltransferase (HAT) and histone deacetylases (HDACs) are key enzymes involved in the acetylation and deacetylation of histones and ultimately in post-translational modifications. Cancer frequently exhibits epigenetic changes, particularly disruption in the expression and activity of HDACs. It includes the capacity to regulate proliferative signalling, circumvent growth inhibitors, escape cell death, enable replicative immortality, promote angiogenesis, stimulate invasion and metastasis, prevent immunological destruction, and genomic instability. The majority of tumours develop and spread as a result of HDAC dysregulation. As a result, HDAC inhibitors (HDACis) were developed, and they today stand as a very promising therapeutic approach. One of the most well-known and efficient therapies for practically all cancer types is chemotherapy. However, the efficiency and safety of treatment are constrained by higher toxicity. The same has been observed with the synthetic HDACi. Natural products, owing to many advantages over synthetic compounds for cancer treatment have always been a choice for therapy. Hence, naturally available molecules are of particular interest for HDAC inhibition and HDAC has drawn the attention of the research fraternity due to their potential to offer a diverse array of chemical structures and bioactive compounds. This diversity opens up new avenues for exploring less toxic HDAC inhibitors to reduce side effects associated with conventional synthetic inhibitors. The review presents comprehensive details on natural product HDACi, their mechanism of action and their biological effects. Moreover, this review provides a brief discussion on the structure activity relationship of selected natural HDAC inhibitors and their analogues which can guide future research to discover selective, more potent HDACi with minimal toxicity.

Apoptosis-inducing anti-proliferative and quantitative phytochemical profiling with in silico study of antioxidant-rich Leea aequata L. leaves

Natural products have been important parts of traditional medicine since ancient times, with various promising health effects. Leea aequata (L. aequata), a natural product, has been widely used for treating several diseases due to its promising pharmacological activities. Therefore, the present study aimed to explore the phytochemical profiling and molecular docking of the antioxidant-rich part of L. aequata leaves and its antiproliferative activity. L. aequata leaves were extracted with methanol, followed by fractionation with the respective solvents to obtain the petroleum ether, chloroform, ethyl acetate, and aqueous fractions. The antioxidant activity was evaluated by spectrophotometric methods. The cytotoxic and antiproliferative activities were detected using MTT colorimetric and confocal microscopy methods, respectively. Phytochemical compositions were analyzed using gas chromatography‒mass spectrometry analysis. Computer aided (molecular docking SwissADME, AdmetSAR and pass prediction) analyses were undertaken to sort out the best-fit phytochemicals present in the plant responsible for antioxidant and anticancer effects. Among the fractions, the ethyl acetate fraction was the most abundant polyphenol-rich fraction and showed the highest antioxidant, reducing power, and free radical scavenging activities. Compared to untreated MCF-7 cells, ethyl acetate fraction-treated MCF-7 cells showed an increase in apoptotic characteristics, such as membrane blebbing, chromatin condensation, and nuclear fragmentation, causing apoptosis and decreased proliferation of HeLa and MCF-7 cells. Furthermore, gas chromatography mass spectrometry data revealed that the ethyl acetate fraction contained 16 compounds, including methyl esters of long-chain fatty acids, which are the major chemical constituents. Moreover, hexadecanoic acid, methyl ester; 9-octadecenoic acid (Z)-, methyl ester; 9,12-octadecadienoic acid, methyl ester (Z, Z) and phenol, 2,4-bis(1,1-dimethylethyl) are known to have antioxidant and cytotoxic activity, as confirmed by computer-aided models. A strong correlation was observed between the antioxidant and polyphenolic contents and the anticancer activity. In conclusion, we explored the possibility that L. aequata could be a promising source of antioxidants and anticancer agents with a high phytochemical profile.

Evaluation and molecular docking study of two flavonoids from Oroxylum indicum (L.) Kurz and their semi-synthetic derivatives as histone deacetylase inhibitors

Chrysin (5,7-dihydroxyflavone, 6) and galangin 3-methyl ether (5,7-dihydroxy-3-methoxy flavone, 7) were obtained from the leaves of Oroxylum indicum (L.) Kurz in 4% and 6% yields, respectively. Both compounds could act as pan-histone deacetylase (HDAC) inhibitors. Structural modification of these lead compounds provided thirty-eight derivatives which were further tested as HDAC inhibitors. Compounds 6b, 6c, and 6q were the most potent derivatives with the IC50 values of 97.29 ± 0.63 μM, 91.71 ± 0.27 μM, and 96.87 ± 0.45 µM, respectively. Molecular docking study indicated the selectivity of these three compounds toward HDAC8 and the test against HDAC8 showed IC50 values in the same micromolar range. All three compounds were further evaluated for the anti-proliferative activity against HeLa and A549 cell lines. Compound 6q exhibited the best activity against HeLa cell line with the IC50 value of 13.91 ± 0.34 μM. Moreover, 6q was able to increase the acetylation level of histone H3. These promising HDAC inhibitors deserve investigation as chemotherapeutic agents for treating cancer.

Antineoplastic activity of plant-derived compounds mediated through inhibition of histone deacetylase: a review

In the combat of treating cancer recent therapeutic approaches are focused towards enzymatic targets as they occupy a pivotal participation in the cascade of oncogenesis and malignancy. There are several enzymes that modulate the epigenetic pathways and chromatin structure related to cancer mutation. Among several epigenetic mechanisms such as methylation, phosphorylation, and sumoylation, acetylation status of histones is crucial and is governed by counteracting enzymes like histone acetyl transferase (HAT) and histone deacetylases (HDAC) which have contradictory effects on the histone acetylation. HDAC inhibition induces chromatin relaxation which forms euchromatin and thereby initiates the expression of certain transcription factors attributed with apoptosis, which are mostly correlated with the expression of the p21 gene and acetylation of H3 and H4 histones. Most of the synthetic and natural HDAC inhibitors elicit antineoplastic effect through activation of various apoptotic pathways and promoting cell cycle arrest at various phases. Due to their promising chemo preventive action and low cytotoxicity against normal host cells, bioactive substances like flavonoids, alkaloids, and polyphenolic compounds from plants have recently gained importance. Even though all bioactive compounds mentioned have an HDAC inhibitory action, some of them have a direct effect and others enhance the effects of the standard well known HDAC inhibitors. In this review, the action of plant derived compounds against histone deacetylases in a variety of in vitro cancer cell lines and in vivo animal models are articulated.

Biological Application of the Allopathic Characteristics of the Genus Maclura: A Review

Maclura is a plant genus little known and used, species of which have been mainly used in the recovery of soils, for medicinal purposes such as dental infection treatments, and as wood for making furniture and construction. The overexploitation of this genus has placed certain species in endangered extinction status in some countries, such as Brazil. In addition, the scarce research and information limit the development, cultivation, and management of its species regarding their biochemical composition, which includes bioactive compounds such as the phenolic and flavonoid compounds found in some species such as M. pomifera, M. cochinchinensis, and M. tinctoria. The plants' antioxidant, antimicrobial, anticancer, anti-inflammatory, and antiproliferative activities have been attributed to these compounds. Other biochemical components such as ashes, insoluble lignin, holocellulose, and the high content of lipids and carbohydrates have been identified to be used to produce biofuels, with characteristics very similar to fuels derived from petroleum. This review aims to analyze the current knowledge on the plant genus Maclura, exploring its biochemical compounds and potential applications, including as a food additive, antioxidant supplement, in agriculture, for therapeutic purposes, aquaculture, and the cosmetic and industrial sector.

The dual face of microglia (M1/M2) as a potential target in the protective effect of nutraceuticals against neurodegenerative diseases

The pathophysiology of different neurodegenerative illnesses is significantly influenced by the polarization regulation of microglia and macrophages. Traditional classifications of macrophage phenotypes include the pro-inflammatory M1 and the anti-inflammatory M2 phenotypes. Numerous studies demonstrated dynamic non-coding RNA modifications, which are catalyzed by microglia-induced neuroinflammation. Different nutraceuticals focus on the polarization of M1/M2 phenotypes of microglia and macrophages, offering a potent defense against neurodegeneration. Caeminaxin A, curcumin, aromatic-turmerone, myricetin, aurantiamide, 3,6'-disinapoylsucrose, and resveratrol reduced M1 microglial inflammatory markers while increased M2 indicators in Alzheimer's disease. Amyloid beta-induced microglial M1 activation was suppressed by andrographolide, sulforaphane, triptolide, xanthoceraside, piperlongumine, and novel plant extracts which also prevented microglia-mediated necroptosis and apoptosis. Asarone, galangin, baicalein, and a-mangostin reduced oxidative stress and pro-inflammatory cytokines, such as interleukin (IL)-1, IL-6, and tumor necrosis factor-alpha in M1-activated microglia in Parkinson's disease. Additionally, myrcene, icariin, and tenuigenin prevented the nod-like receptor family pyrin domain-containing 3 inflammasome and microglial neurotoxicity, while a-cyperone, citronellol, nobiletin, and taurine prevented NADPH oxidase 2 and nuclear factor kappa B activation. Furthermore, other nutraceuticals like plantamajoside, swertiamarin, urolithin A, kurarinone, Daphne genkwa flower, and Boswellia serrata extracts showed promising neuroprotection in treating Parkinson's disease. In Huntington's disease, elderberry, curcumin, iresine celosia, Schisandra chinensis, gintonin, and pomiferin showed promising results against microglial activation and improved patient symptoms. Meanwhile, linolenic acid, resveratrol, Huperzia serrata, icariin, and baicalein protected against activated macrophages and microglia in experimental autoimmune encephalomyelitis and multiple sclerosis. Additionally, emodin, esters of gallic and rosmarinic acids, Agathisflavone, and sinomenine offered promising multiple sclerosis treatments. This review highlights the therapeutic potential of using nutraceuticals to treat neurodegenerative diseases involving microglial-related pathways.

Pomiferin targets SERCA, mTOR, and P-gp to induce autophagic cell death in apoptosis-resistant cancer cells, and reverses the MDR phenotype in cisplatin-resistant tumors in vivo

Drug resistance in cancer has been classified as innate resistance or acquired resistance, which were characterized by apoptotic defects and ABC transporters overexpression respectively. Therefore, to preclude or reverse these resistance mechanisms could be a promising strategy to improve chemotherapeutic outcomes. In this study, a natural product from Osage Orange, pomiferin, was identified as a novel autophagy activator that circumvents innate resistance by triggering autophagic cell death via SERCA inhibition and activation of the CaMKKβ-AMPK-mTOR signaling cascade. In addition, pomiferin also directly inhibited the P-gp (MDR1/ABCB1) efflux and reversed acquired resistance by potentiating the accumulation and efficacy of the chemotherapeutic agent, cisplatin. In vivo study demonstrated that pomiferin triggered calcium-mediated tumor suppression and exhibited an anti-metastatic effect in the LLC-1 lung cancer-bearing mouse model. Moreover, as an adjuvant, pomiferin potentiated the anti-tumor effect of the chemotherapeutic agent, cisplatin, in RM-1 drug-resistant prostate cancer-bearing mouse model by specially attenuating ABCB1-mediated drug efflux, but not ABCC5, thereby promoting the accumulation of cisplatin in tumors. Collectively, pomiferin may serve as a novel effective agent for circumventing drug resistance in clinical applications.

Epibrassinolide impaired colon tumor progression and induced autophagy in SCID mouse xenograft model via acting on cell cycle progression without affecting endoplasmic reticulum stress observed in vitro

Epibrassinolide is a member of brassinosteroids with a polyhydroxysteroid structure similar to steroid hormones of vertebrates. It was shown that EBR decreased cell proliferation and induced apoptosis in different colon cancer cell lines without exerting a cytotoxic effect in epithelial fetal human colon cells. This finding highlighted the potential of epibrassinolide in clinical therapeutic setup. In our previous studies, we showed that epibrassinolide was able to induce apoptosis via endoplasmic reticulum stress. Recently, we also showed that endoplasmic reticulum and apoptotic stresses can be prevented via autophagic induction in non-cancerous epithelial or aggressive forms of cancer cells. Therefore, here in this study, we evaluated the anti-tumoral effect of epibrassinolide as well as the autophagy involvement in the aggressive forms of colon cancer cell lines as well as in vivo SCID mouse xenograft colon cancer model for the first time. For this purpose, SCID mouse model was used for subcutaneous injection of colon cancer cells in matrigel formulation. We found that autophagy is induced in both in vitro and in vivo models. Following tumor formation, SCID mice were treated daily with increasing concentrations of epibrassinolide for two weeks. Our findings showed that EBR inhibited the volume and diameter of the tumor in a dose-dependent manner by causing cell cycle arrest. Therefore our data suggest that epibrassinolide exerts a cytostatic effect on the agrressive form of colon cancer model in vivo, without affecting endoplasmic reticulum stress and the induction of autophagy might have role in this effect of epibrassinolide.

Therapeutic Potential of CKD-504, a Novel Selective Histone Deacetylase 6 Inhibitor, in a Zebrafish Model of Neuromuscular Junction Disorders

The neuromuscular junction (NMJ), which is a synapse for signal transmission from motor neurons to muscle cells, has emerged as an important region because of its association with several peripheral neuropathies. In particular, mutations in GARS that affect the formation of NMJ result in Charcot-Marie-Tooth disease and distal hereditary motor neuropathy. These disorders are mainly considered to be caused by neuronal axon abnormalities; however, no treatment is currently available. Therefore, in order to determine whether the NMJ could be targeted to treat neurodegenerative disorders, we investigated the NMJ recovery effect of HDAC6 inhibitors, which have been used in the treatment of several peripheral neuropathies. In the present study, we demonstrated that HDAC6 inhibition was sufficient to enhance movement by restoring NMJ impairments observed in a zebrafish disease model. We found that CKD-504, a novel HDAC6 inhibitor, was effective in repairing NMJ defects, suggesting that treatment of neurodegenerative diseases via NMJ targeting is possible.

Heteroleptic copper(II) complexes of prenylated flavonoid osajin behave as selective and effective antiproliferative and anti-inflammatory agents

Heteroleptic copper(II) complexes, containing prenylated flavonoid osajin isolated from the fruits of Maclura pomifera Schneid., were prepared and thoroughly characterized, including single crystal X-ray analysis. Some of the following complexes of the general composition [Cu(L)(bpy)]NO₃ (1), [Cu(L)(dimebpy)]NO₃·2MeOH (2) [Cu(L)(phen)]NO₃·H₂O (3), [Cu(L)(bphen)]NO₃ (4) and [Cu(L)(dppz)]NO₃ (5), where HL stands for 3-(4-hydroxyphenyl)-5-hydroxy-8,8-dimethyl-6-(3-methylbut-2-ene-1-yl)-4H,8H-benzo[1,2-b:3,4-b']dipyran-4-one (osajin), bpy = 2,2'-bipyridine, dimebpy = 4,4'-dimethyl-2,2'-bipyridine, phen = 1,10-phenanthroline, bphen = 4,7-diphenyl-1,10-phenanthroline and dppz = dipyrido[3,2-a:2',3'-c]phenazine, were also monitored for their solution stability and interactions with cysteine and glutathione by mass spectrometry. The in vitro cytotoxicity of the complexes was evaluated against a panel of eight human cancer cell lines: (MCF-7, HOS, A549, PC-3, A2780, A2780R, Caco-2, and THP-1). The results revealed high antiproliferative activity of the complexes with the best IC₅₀ values of 0.5-3.4 μM for complexes (4) and (5), containing the bulkier N,N'-donor ligands (bphen, and dppz, respectively). The complexes also revealed a relatively low toxicity towards human hepatocytes (IC₅₀ values are higher than 100 μM in some cases), and thus proved to be highly selective towards the cancer cells. On the other hand, the complexes showed a strong in vitro nuclease effect using the model pUC-19 plasmid. In the model of lipopolysaccharide-stimulated (LPS) THP-1 monocytes, the complexes revealed ability to lower the activity of nuclear factor kappa-B/activator protein 1 (NF-κB /AP-1) system and decrease the secretion of tumor necrosis factor alpha (TNF-α). Thus, the complexes have been identified as strong antiproliferative and anti-inflammatory compounds.

Copper(II) Complexes Containing Natural Flavonoid Pomiferin Show Considerable In Vitro Cytotoxicity and Anti-inflammatory Effects

A series of new heteroleptic copper(II) complexes of the composition [Cu(L)(bpy)]NO₃·2MeOH (1), [Cu(L)(dimebpy)]NO₃·2H₂O (2), [Cu(L)(phen)]NO₃·2MeOH (3), [Cu(L)(bphen)]NO₃·MeOH (4), [Cu(L)(dppz)]NO₃·MeOH (5) was prepared, where HL = 3-(3,4-dihydroxyphenyl)-5-hydroxy-8,8-dimethyl-6-(3-methylbut-2-ene-1-yl)-4H,8H-benzo[1,2-b:3,4-b′]dipyran-4-one, (pomiferin) and bpy = 2,2′-bipyridine, dimebpy = 4,4′-dimethyl-2,2′-bipyridine, phen = 1,10-phenanthroline, bphen = 4,7-diphenyl-1,10-phenanthroline, and dppz = dipyrido[3,2-a:2′,3′-c]phenazine. The complexes were characterized using elemental analysis, infrared and UV/Vis spectroscopies, mass spectrometry, thermal analysis and conductivity measurements. The in vitro cytotoxicity, screened against eight human cancer cell lines (breast adenocarcinoma (MCF-7), osteosarcoma (HOS), lung adenocarcinoma (A549), prostate adenocarcinoma (PC-3), ovarian carcinoma (A2780), cisplatin-resistant ovarian carcinoma (A2780R), colorectal adenocarcinoma (Caco-2) and monocytic leukemia (THP-1), revealed the complexes as effective antiproliferative agents, with the IC₅₀ values of 2.2–13.0 μM for the best performing complexes 3 and 5. All the complexes 1–5 showed the best activity against the A2780R cells (IC₅₀ = 2.2–6.6 μM), and moreover, the complexes demonstrated relatively low toxicity on healthy human hepatocytes, with IC₅₀ > 100 μM. The complexes were evaluated by the Annexin V/propidium iodide apoptosis assay, induction of cell cycle modifications in A2780 cells, production of reactive oxygen species (ROS), perturbation of mitochondrial membrane potential, inhibition of apoptosis and inflammation-related signaling pathways (NF-κB/AP-1 activity, NF-κB translocation, TNF-α secretion), and tested for nuclease mimicking activity. The obtained results revealed the corresponding complexes to be effective antiproliferative and anti-inflammatory agents.

Targeting allosteric sites of human aromatase: a comprehensive in-silico and in-vitro workflow to find potential plant-based anti-breast cancer therapeutics

Recent findings suggested several allosteric pockets on human aromatase that could be utilised for the development of new modulators able to inhibit this enzyme in a new mechanism. Herein, we applied an integrated in-silico-based approach supported by in-vitro enzyme-based and cell-based validation assays to select the best leads able to target these allosteric binding sites from a small library of plant-derived natural products. Chrysin, apigenin, and resveratrol were found to be the best inhibitors targeting the enzyme’s substrate access channel and were able to produce a competitive inhibition with IC₅₀ values ranged from 1.7 to 15.8 µM. Moreover, they showed a more potent antiproliferative effect against ER+ (MCF-7) than ER- one (MDA-MB-231) cell lines. On the other hand, both pomiferin and berberine were the best hits for the enzyme’s haem-proximal cavity producing a non-competitive inhibition (IC₅₀ 15.1 and 21.4 µM, respectively) and showed selective antiproliferative activity towards MCF-7 cell lines.

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.

Anticancer activity of Nigerian medicinal plants: a review

Background

Cancer is currently the leading cause of death globally and the number of deaths from cancer is on the rise daily. Medicinal plants have been in continuous use over the years for the management of cancer, particularly, in most developing countries of the world including Nigeria. The use of synthetic drugs for the treatment of cancer is often accompanied by toxic side effects. Thus, the alternative use of readily available and inexpensive medicinal plants is the panacea to the toxic side effects associated with synthetic drugs.

Main body

The present review summarized the anticancer activity of 51 medicinal plants that are widespread in all regions of Nigeria. Furthermore, the proposed anticancer pharmacological actions as well as the anticancer bioactive compounds, the type of cancer cell inhibited, the plant parts responsible for the anticancer activity, and the nature of the extracts used for the studies were discussed in this review. The 51 Nigerian medicinal plants were reported to exhibit anticancer activities of the prostate, cervices, lung, skin, colon, esophagus, blood, ovary, central nervous system/brain, breast, stomach, pancreas, larynx, and kidney. The major classes of bioactive compounds indicated to be responsible for the anticancer activity include the polyphenols, flavonoids, alkaloids, saponins, triterpenes, tannins, and quinones. The major anticancer pharmacological actions of these bioactive compounds were antiproliferative, cytotoxic, cytostatic, antimetastatic, apoptotic, and antioxidative as well as provoked cell cycle arrest, inhibition of angiogenesis and reduction of cancer cell viability.

Conclusion

The Nigerian medicinal plants can be harnessed to provide for readily available and inexpensive anticancer drugs in the future because the plants reported in this review showed promising anticancer activity.

Prenylated flavonoids in foods and their applications on cancer prevention

Functional foods play an important role in health care and chronic diseases prevention, particularly cancer. Prenylated flavonoids are presented in many food resources. They are recognized as neutraceuticals due to their diverse health benefits. Up to now, more than 1000 prenylated flavonoids have been identified in plants. Their food resources are reviewed in this paper. Due to the good safety and cancer prevention effect of prenylated flavonoids, this paper reviews the cancer prevention activities and mechanisms reported in last decade. The structure-activity relationship is discussed. Due to the limited availability in nature, the heterologously biosynthetic technique of prenylated flavonoids is discussed in this review. Inclusion of dietary prenylated flavonoids into human diet is highly desirable. This paper combines the up-to-date information and give a clear image regarding prenylated flavonoids as neutraceuticals.

Chemical composition and antimicrobial activity of Osage orange (Maclura pomifera) leaf extracts

The main goal of this study was to establish the chemical profile of Osage orange (Maclura pomifera) leaf extracts, obtained by conventional maceration technique, and to examine its antimicrobial activity. The identification and quantification of the extract compounds were done using ultra-high-performance liquid chromatography, with a diode array detector coupled with triple-quadrupole mass spectrometer and gas chromatography-mass spectrometry techniques. Thirty-one polyphenolic compounds were detected and identified in the ethanolic extracts, whereby 5-O-caffeoylquinic acid was found to be the dominant compound. Among other compounds, pentacosane and palmitic acid were the most abundant compounds in the dichloromethane extract. The preliminary antimicrobial activity screening shows that Gram-positive bacteria tend to be more sensitive to the investigated extracts. The highest antimicrobial activity was determined against Enterococcus faecalis ATCC 19433 and Listeria monocytogenes ATCC 35152. From these results, Osage orange leaves can be considered as plant material with significant antimicrobial properties.

Osajin displays potential antiprostate cancer efficacy via impairment of fatty acid synthase and androgen receptor expression

BACKGROUND

Currently, antiprostate cancer (PCa) drugs, including androgen deprivation therapy (ADT), are initially effective; however, most patients with PCa who receive ADT eventually progress to deadly aggressiveness. There is an urgent need to seek alternative strategies to cure this lethal disease. Activation of lipogenesis has been demonstrated to lead to PCa progression. Therefore, targeting the aberrant lipogenic activity could be developed therapeutically in PCa. The aim of this study is to investigate the molecular basis and efficacy of osajin, a bioactive prenylated isoflavonoid, in PCa.

METHODS

PCa cells, LNCaP (androgen-sensitive) and C4-2 (androgen-insensitive/castration-resistant), were used in this study. Proliferation, migration, and invasion analyses were conducted by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method, a wound healing assay, and the transwell method. Lipogenesis was determined by a Fatty Acid Quantification Kit and oil red O staining. Apoptosis was assessed by annexin V-fluorescein isothiocyanate/propidium iodide staining, caspase enzymatic activity, and Western blot analyses.

RESULTS

Osajin inhibited fatty acid synthase (FASN) expression, a key enzyme for lipogenesis, in PCa cells. By inhibiting FASN, osajin decreased the fatty-acid levels and lipid accumulation. Significantly, osajin downregulated androgen receptor (AR) and prostate-specific antigen (PSA) in PCa cells. Moreover, osajin suppressed PCa cell growth, migration, and invasion. Through activation of the caspase-dependent pathway, osajin induced apoptosis in PCa cells.

CONCLUSIONS

These data provide a novel molecular basis of osajin in PCa cells, and cotargeting lipogenesis and the AR axis via impairment of FASN and AR expression by osajin could be applied as a new and promising approach for the treatment of malignant PCa.

Natural Products and Chemical Biology Tools: Alternatives to Target Epigenetic Mechanisms in Cancers

DNA methylation and histone acetylation are widely studied epigenetic modifications. They are involved in numerous pathologies such as cancer, neurological disease, inflammation, obesity, etc. Since the discovery of the epigenome, numerous compounds have been developed to reverse DNA methylation and histone acetylation aberrant profile in diseases. Among them several were inspired by Nature and have a great interest as therapeutic molecules. In the quest of finding new ways to target epigenetic mechanisms, the use of chemical tools is a powerful strategy to better understand epigenetic mechanisms in biological systems. In this review we will present natural products reported as DNMT or HDAC inhibitors for anticancer treatments. We will then discuss the use of chemical tools that have been used in order to explore the epigenome.

In silico approaches for investigating the binding propensity of apigenin and luteolin against class I HDAC isoforms

AIM

Aberrant activity of class I histone deacetylases (HDACs) has strong implications for various cancers. Targeting these HDACs with synthetic HDAC inhibitors has shown significant side effects such as atrial fibrillation and QT prolongation emphasizing the need of natural inhibitors as substitutes to synthetic ones.

RESULTS

The binding propensity of the two plant-derived inhibitors apigenin and luteolin towards class I HDAC isoforms was checked using extra-precision molecular docking and implicit solvation MMGBSA. Apigenin showed a superior binding affinity against these isoforms as compared to luteolin. Both inhibitors docked stable to the binding pocket of these HDACs as determined by molecular dynamics simulation study.

CONCLUSION

Apigenin and luteolin may serve as substitutes to synthetic inhibitors for effective HDAC based anticancer therapy.

Methanolic Extract of Costus pictus D. DON Induces Cytotoxicity in Liver Hepatocellular Carcinoma Cells Mediated by Histone Deacetylase Inhibition

Background

Leaves of Costus pictus D. Don, (insulin plant) are used as dietary supplement for the treatment of diabetes.

Objective

The antidiabetic activity of this plant is well documented, but its activity on different cell types and mechanism remains unknown. Thus, the present study evaluates the cytotoxicity of C. pictus methanolic extract (CPME) against various cancer and normal cells.

Materials and Methods

Dried leaves of C. pictus were extracted using methanol and were subjected to histone deacetylase (HDAC) inhibition and toxicity studies.

Results

The CPME displayed a selective toxicity toward tested cancer cells in a dose- and time-dependent manner. CPME exhibited significant cytotoxicity on Liver hepatocellular carcinoma cells (Hep G2) (half maximal inhibitory concentration IC₅₀ = 6.7 mg/ml). Since CPME demonstrates both antidiabetic, anticancer activity, and HDAC enzyme play a detrimental role in both the complications, we have evaluated the CPME-induced HDAC regulation on Hep G2 cell lines. CPME showed a notable HDAC inhibition (55%). Furthermore, CPME did not show any genotoxicity or membrane instability at the tested concentrations.

Conclusion

CPME demonstrates selective cytotoxicity toward tumor cells at a lower concentration through HDAC inhibition.

SUMMARY

C. pictus is used as munching supplementary food for the treatment of diabetesCPME selectively induces cytotoxicity in cancer cells leaving normal cells healthySelective toxicity to cancer cells are attributed by the inhibition of HDAC enzymeCPME did not show any genotoxicity and membrane instability in blood cellsCPME could be potential source of HDAC inhibitor. Abbreviations used: A549: Human lung carcinoma cells, CPME: Costus pictus methanolic extract, DMEM: Dulbecco's modified eagle's medium, DMSO: Dimethyl sulfoxide, ELISA: Enzyme-linked immunosorbent assay, 5-FU: 5-Fluorouracil, Hep G2: Liver hepatocellular carcinoma cells, HEK-293: Human embryonic kidney cells, Hela: Human cervical carcinoma cells, HT-29: Human colorectal adenocarcinoma cells, HDAC: Histone deacetylase, IC₅₀: Half maximal inhibitory concentration, MCF-7: Human breast adenocarcinoma cells, MDA-MB-435S: Human breast cancer cells, MTT: 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide, NFF: Neonatal foreskin fibroblasts, PHA: Phytohemagglutinin, PBS: Phosphate buffer saline, RPMI-1640: Roswell Park Memorial Institute Medium.

Natural product inhibitors of carbonic anhydrase I and II isoenzymes: osajin and pomiferin

The aim of this study is to purify carbonic anhydrase I and II isoenzymes from human erythrocyte, isolate two natural products osajin (OSJ) and pomiferin (PMF) from Maclura pomifera fruits, and evaluate the in vitro effect of these natural metabolites on these isoenzymes. These natural products may be used as starting points for drug discovery (like drugs used in several therapeutic applications, including antiglaucoma activity). For the purification procedure, the Sepharose-4B-l-tyrosine-sulphonamide affinity chromatography was used. Column chromatography and thin layer chromatography methods were used for isolation of OSJ and PMF from M. pomifera fruits and their chemical structures were elucidated by IR, 1D, and 2D NMR methods. We compared inhibitory effects of these natural products with inhibitory effects of phenolic compounds and found that these products demonstrated average inhibition effects. We thought that this study will give inspiration to scientists interested in this issue.

Antioxidant, Cytotoxic and α-Glucosidase Inhibitory Activities of Compounds isolated from the Twig Extracts of Maclura fruticosa

The first phytochemical investigation of the twig extracts of Maclura fruticosa led to the isolation and identification of a new xanthone, maclurafruticosone (1), together with 14 known compounds (2–15). All compounds were elucidated using spectroscopic methods as well as through comparisons made with data reported in the literature. Some isolated compounds were evaluated for their antioxidant, α-glucosidase inhibitory and cytotoxic activities. Compound 4, 6 and 7 showed significant antioxidant activity against DPPH radicals with IC50 values ranging from 7.45–16.12 μM. Compound 4 also exhibited potent activity against ABTS•+ scavenging activity with an IC50 value of 0.55 ± 0.01 μM which was better than positive control (ascorbic acid, IC50 2.35 ± 0.17 μM). Compound 12 showed significant α-glucosidase inhibitory activity with an IC50 value of 0.02 ± 0.37 mM. Compounds 5, 6 and 12 showed weak cytotoxic activities against a colon cancer cell line with IC50 values ranging from 22.35–47.62 μM.

Targeting Glioblastoma with the Use of Phytocompounds and Nanoparticles

Glioblastoma multiforme (GBM) are extremely lethal and still poorly treated primary brain tumors, characterized by the presence of highly tumorigenic cancer stem cell (CSC) subpopulations, considered responsible for tumor relapse. In order to successfully eradicate GBM growth and recurrence, new anti-cancer strategies selectively targeting CSCs should be designed. CSCs might be eradicated by targeting some of their cell surface markers and transporters, inducing their differentiation, impacting their hyper-glycolytic metabolism, inhibiting CSC-related signaling pathways and/or by targeting their microenvironmental niche. In this regard, phytocompounds such as curcumin, isothiocyanates, resveratrol and epigallocatechin-3-gallate have been shown to prevent or reverse cancer-related epigenetic dysfunctions, reducing tumorigenesis, preventing metastasis and/or increasing chemotherapy and radiotherapy efficacy. However, the actual bioavailability and metabolic processing of phytocompounds is generally unknown, and the presence of the blood brain barrier often represents a limitation to glioma treatments. Nowadays, nanoparticles (NPs) can be loaded with therapeutic compounds such as phytochemicals, improving their bioavailability and their targeted delivery within the GBM tumor bulk. Moreover, NPs can be designed to increase their tropism and specificity toward CSCs by conjugating their surface with antibodies specific for CSC antigens, with ligands or with glucose analogues. Here we discuss the use of phytochemicals as anti-glioma agents and the applicability of phytochemical-loaded NPs as drug delivery systems to target GBM. Additionally, we provide some examples on how NPs can be specifically formulated to improve CSC targeting.

A grape seed procyanidin extract inhibits HDAC activity leading to increased Pparα phosphorylation and target-gene expression

SCOPE

Histone deacetylases (HDACs) have emerged as epigenetic regulators of risk factors associated with the metabolic syndrome (MetS), and certain botanical extracts have proven to be potent HDAC inhibitors. Understanding the role of dietary procyanidins in HDAC inhibition is important in exploring the therapeutic potential of natural products.

METHODS

C57BL/6 mice were gavaged with vehicle (water) or grape seed procyanidin extract (GSPE, 250 mg/kg) and terminated 14 h later. Liver and serum were harvested to assess the effect of GSPE on HDAC activity, histone acetylation, Pparα activity and target-gene expression, and serum lipid levels.

RESULTS

GSPE increased histone acetylation and decreased Class I HDAC activity in vivo, and dose-dependently inhibited recombinant HDAC2 and 3 activities in vitro. Accordingly, Pparα gene and phosphorylated protein expression were increased, as were target genes involved in fatty acid catabolism, suggesting increased Pparα activity. Serum fibroblast growth factor 21 (Fgf21) was elevated, and triglyceride levels were reduced by 28%.

CONCLUSION

GSPE regulates HDAC and Pparα activities to modulate lipid catabolism and reduce serum triglycerides in vivo.

Histone deacetylase inhibitor sulforaphane: The phytochemical with vibrant activity against prostate cancer

Epigenetic modifications are closely involved in the patho-physiology of prostate cancer. Histone deacetylases (HDACs), the transcriptional corepressors have strong crosstalk with prostate cancer progression as they influence various genes related to tumour suppression. HDACs play a marked role in myriad of human cancers and as such are emerging as striking molecular targets for anticancer drugs and therapy. Histone deacetylase inhibitors (HDACi), the small-molecules interfering HDACs are emerging as promising chemotherapeutic agents. These inhibitors have shown multiple effects including cell growth arrest, differentiation and apoptosis in prostate cancer. The limited efficacy of HDACi as single agents in anticancer therapy has been strongly improved via novel therapeutic strategies like doublet therapy (combined therapy). More than 20HDACi have already entered into the journey of clinical trials and four have been approved by FDA against diverse cancers. This review deals with plant derived HDACi sulphoraphane (SFN; 1-isothiocyanato-4-(methylsulfinyl)-butane) and its potential role in prostate cancer therapy along with the underlying molecular mechanism being involved. The article further highlights the therapeutic strategy that can be utilized for sensitizing conventional therapy resistant cases and for acquiring the maximum therapeutic benefit from this promising inhibitor in the upcoming future.

Medicinal Plants: Their Use in Anticancer Treatment

Globally cancer is a disease which severely effects the human population. There is a constant demand for new therapies to treat and prevent this life-threatening disease. Scientific and research interest is drawing its attention towards naturally-derived compounds as they are considered to have less toxic side effects compared to current treatments such as chemotherapy. The Plant Kingdom produces naturally occurring secondary metabolites which are being investigated for their anticancer activities leading to the development of new clinical drugs. With the success of these compounds that have been developed into staple drugs for cancer treatment new technologies are emerging to develop the area further. New technologies include nanoparticles for nano-medicines which aim to enhance anticancer activities of plant-derived drugs by controlling the release of the compound and investigating new methods for administration. This review discusses the demand for naturally-derived compounds from medicinal plants and their properties which make them targets for potential anticancer treatments.

The role of dietary histone deacetylases (HDACs) inhibitors in health and disease

Modification of the histone proteins associated with DNA is an important process in the epigenetic regulation of DNA structure and function. There are several known modifications to histones, including methylation, acetylation, and phosphorylation, and a range of factors influence each of these. Histone deacetylases (HDACs) remove the acetyl group from lysine residues within a range of proteins, including transcription factors and histones. Whilst this means that their influence on cellular processes is more complex and far-reaching than histone modifications alone, their predominant function appears to relate to histones; through deacetylation of lysine residues they can influence expression of genes encoded by DNA linked to the histone molecule. HDAC inhibitors in turn regulate the activity of HDACs, and have been widely used as therapeutics in psychiatry and neurology, in which a number of adverse outcomes are associated with aberrant HDAC function. More recently, dietary HDAC inhibitors have been shown to have a regulatory effect similar to that of pharmacological HDAC inhibitors without the possible side-effects. Here, we discuss a number of dietary HDAC inhibitors, and how they may have therapeutic potential in the context of a whole food.

Aurones as histone deacetylase inhibitors: identification of key features

In this study, a total of 22 flavonoids were tested for their HDAC inhibitory activity using fluorimetric and BRET-based assays. Four aurones were found to be active in both assays and showed IC50 values below 20 μM in the enzymatic assay. Molecular modelling revealed that the presence of hydroxyl groups was responsible for good compound orientation within the isoenzyme catalytic site and zinc chelation.

Flavonoids from each of the six structural groups reactivate BRM, a possible cofactor for the anticancer effects of flavonoids

Flavonoids have been extensively studied and are well documented to have anticancer effects, but it is not entirely known how they impact cellular mechanisms to elicit these effects. In the course of this study, we found that a variety of different flavonoids readily restored Brahma (BRM) in BRM-deficient cancer cell lines. Flavonoids from each of the six different structural groups were effective at inducing BRM expression as well as inhibiting growth in these BRM-deficient cancer cells. By blocking the induction of BRM with shRNA, we found that flavonoid-induced growth inhibition was BRM dependent. We also found that flavonoids can restore BRM functionality by reversing BRM acetylation. In addition, we observed that an array of natural flavonoid-containing products both induced BRM expression as well as deacetylated the BRM protein. We also tested two of the BRM-inducing flavonoids (Rutin and Diosmin) at both a low and a high dose on the development of tumors in an established murine lung cancer model. We found that these flavonoids effectively blocked development of adenomas in the lungs of wild-type mice but not in that of BRMnull mice. These data demonstrate that BRM expression and function are regulated by flavonoids and that functional BRM appears to be a prerequisite for the anticancer effects of flavonoids both in vitro and in vivo.

Characterization of pomiferin triacetate as a novel mTOR and translation inhibitor

Deregulation of the phosphatidylinositol 3-kinase (PI3K)-Akt-mammalian target of rapamycin (mTOR)-70kDa ribosomal protein S6 kinase 1 (p70(S6K)) pathway is commonly observed in many tumors. This pathway controls proliferation, survival, and translation, and its overactivation is associated with poor prognosis for tumor-associated survival. Current efforts focus on the development of novel inhibitors of this pathway. In a cell-based high-throughput screening assay of 15,272 pure natural compounds, we identified pomiferin triacetate as a potent stabilizer of the tumor suppressor programmed cell death 4 (Pdcd4). Mechanistically, pomiferin triacetate appeared as a general inhibitor of the PI3K-Akt-mTOR-p70(S6K) cascade. Interference with this pathway occurred downstream of Akt but upstream of p70(S6K). Specifically, mTOR kinase emerged as the molecular target of pomiferin triacetate, with similar activities against mTOR complexes 1 and 2. In an in vitro mTOR kinase assay pomiferin triacetate dose-dependently inhibited mTOR with an IC50 of 6.2 μM. Molecular docking studies supported the interaction of the inhibitor with the catalytic site of mTOR. Importantly, pomiferin triacetate appeared to be highly selective for mTOR compared to a panel of 17 lipid and 50 protein kinases tested. As a consequence of the mTOR inhibition, pomiferin triacetate efficiently attenuated translation. In summary, pomiferin triacetate emerged as a novel and highly specific mTOR inhibitor with strong translation inhibitory effects. Thus, it might be an interesting lead structure for the development of mTOR- and translation-targeted anti-tumor therapies.

The fruits of Maclura pomifera extracts inhibits glioma stem-like cell growth and invasion

Glioma is the most common primary intracranial tumour. Recently, growing evidence showed that glioma possesses stem-like cells, which are thought to be chemo- and radio-resistant and believed to contribute to the poor clinical outcomes of these tumours. In this study, we found that stem-like glioma cells (CD133+) were significantly increased in neurosphere cells, which are highly invasive and resistant to multiple chemotherapeutic agents. From our natural products library, we screened 48 natural products and found one compound, Pomiferin, which was of particular interest. Our results showed that Pomiferin could inhibit cell viability, CD133+ cell population, sphere formation, and invasion ability of glioma neurosphere cells. We also found that multiple stemness-associated genes (BIM1, Nestin, and Nanog) were down-regulated by Pomiferin treatment of glioma neurosphere cells. Taken together, our results suggest that Pomiferin could kill the cancer stem-like cells in glioma and may serve as a potential therapeutic agent in the future.

HPLC determination of isoflavone levels in osage orange from the Midwest and southern United States

The fruit of the Maclura pomifera tree is a sustainable source for the pharmacologically interesting isoflavones, osajin and pomiferin. A reversed-phase HPLC method was developed to identify osage orange samples with high isoflavone content and to determine the optimum conditions for sample preparation. Analytical run time was 8 min at a flow rate of 1 mL/min using a gradient of acetonitrile in H2O (0.1% formic acid) and UV peak detection at 274 nm. The method was validated for specificity, accuracy, precision, and limits of detection and quantitation (LOD/LOQ). The method was applied to determine the levels of osajin and pomiferin in extracts prepared from different samples of osage orange growing in the Midwest and southern United States. Results demonstrated the effect of different variables, such as sample preparation, geographical location, and growth stage, on the levels of osajin and pomiferin in analyzed samples.

Epigenetic mechanisms underlying diet-sourced compounds in the prevention and treatment of gastrointestinal cancer

The development of colon cancer, the third most diagnosed cancer and third leading cause of cancer deaths in the United States, can be influenced by genetic predispositions and environmental exposures. As 80% of colon cancer cases are sporadic in nature, much interest lies in determining risk factors that may foster its development, as well as identifying compounds that could inhibit colon cancer development or halt progression. A major risk factor for sporadic colon cancer is a high fat, Western diet which has been linked to a cancer-prone, pro-inflammatory state. Cultures which place an emphasis on fresh fruits and vegetables demonstrate lower colon cancer incidences. Diet not only has the potential to encourage colon cancer development, but recent evidence demonstrates that certain dietary natural products can halt colon cancer development and progression via epigenetic regulation. Epigenetic dysregulation may contribute to inflammation-driven diseases, such as cancer, and can lead to the inappropriate silencing of genes necessary to inhibit cancer development. Natural compounds have shown the ability to reverse epigenetic dysregulation in in vitro and in vivo models. As current allopathic medicines aimed at reversing epigenetic silencing are accompanied with the risk of toxicity and side effects, much interest lies in being able to harness the disease preventing properties in natural products. Here, we discuss the epidemiology of colon cancer, describe the need for natural approaches to inhibit disease development and highlight natural products which have been shown to inhibit gastrointestinal cancer initiation and progression in vitro or in vivo through epigenetic modulation.

Influence of natural and synthetic histone deacetylase inhibitors on chromatin

SIGNIFICANCE

Histone deacetylase inhibitors (HDACIs) have emerged as a new class of anticancer therapeutics. The hydroxamic acid, suberoylanilide hydroxamic acid (Vorinostat, Zolinza™), and the cyclic peptide, depsipeptide (Romidepsin, Istodax™), were approved by the U.S. Food and Drug Administration (FDA) for the treatment of cutaneous T-cell lymphoma in 2006 and 2009, respectively. At least 15 HDACIs are currently undergoing clinical trials either alone or in combination with other therapeutic modalities for the treatment of numerous hematological and solid malignancies.

RECENT ADVANCES

The potential utility of HDACIs has been extended to nononcologic applications, including autoimmune disorders, inflammation, diseases of the central nervous system, and malaria.

CRITICAL ISSUES

Given the promise of HDACIs, there is growing interest in the potential of dietary compounds that possess HDAC inhibition activity. This review is focused on the identification of and recent findings with HDACIs from dietary, medicinal plant, and microbial sources. We discuss the mechanisms of action and clinical potential of natural HDACIs.

FUTURE DIRECTIONS

Apart from identification of further HDACI compounds from dietary sources, further research will be aimed at understanding the effects on gene regulation on lifetime exposure to these compounds. Another important issue that requires clarification.

Regulation of immune responses by histone deacetylase inhibitors

Both genetic and epigenetic factors are important regulators of the immune system. There is an increasing body of evidence attesting to epigenetic modifications that influence the development of distinct innate and adaptive immune response cells. Chromatin remodelling via acetylation, methylation, phosphorylation, and ubiquitination of histone proteins as well as DNA, methylation is epigenetic mechanisms by which immune gene expression can be controlled. In this paper, we will discuss the role of epigenetics in the regulation of host immunity, with particular emphasis on histone deacetylase inhibitors. In particular, the role of HDAC inhibitors as a new class of immunomodulatory therapeutics will also be reviewed.

Histone deacetylase modulators provided by Mother Nature

Protein acetylation status results from a balance between histone acetyltransferase and histone deacetylase (HDAC) activities. Alteration of this balance leads to a disruption of cellular integrity and participates in the development of numerous diseases, including cancer. Therefore, modulation of these activities appears to be a promising approach for anticancer therapy. Histone deacetylase inhibitors (HDACi) are epigenetically active drugs that induce the hyperacetylation of lysine residues within histone and non-histone proteins, thus affecting gene expression and cellular processes such as protein-protein interactions, protein stability, DNA binding and protein sub-cellular localization. Therefore, HDACi are promising anti-tumor agents as they may affect the cell cycle, inhibit proliferation, stimulate differentiation and induce apoptotic cell death. Over the last 30 years, numerous synthetic and natural products, including a broad range of dietary compounds, have been identified as HDACi. This review focuses on molecules from natural origins modulating HDAC activities and presenting promising anticancer activities.

Antiproliferative activity of pomiferin in normal (MCF-10A) and transformed (MCF-7) breast epithelial cells

Pomiferin and osajin are prenylated isoflavones from Osage orange fruit that both have potent antioxidant activity in a variety of assays. Pomiferin, in particular, has strong activity against the superoxide anion in a photochemiluminescence (PCL) assay system. In vitro, pomiferin, but not osajin, demonstrated selective antiproliferative activity against the tumorigenic breast epithelial cell line MCF-7 (IC(50) = 5.2 μM) with limited toxicity toward nontumorigenic breast epithelial cells (MCF-10A). The differential sensitivity of normal and tumorigenic cells to the antiproliferative action of pomiferin was examined further by using cDNA microarrays. With a stringent cutoff of p < 0.01, a total of 94 genes were significantly differentially expressed between MCF-7 and MCF-10A cells; 80 up-regulated and 14 down-regulated when cells were exposed to 5 μM pomiferin for 24 h. Fold changes by microarray analysis were confirmed using RT-qPCR, and the most significant changes were found with genes related to antioxidant enzymes. Genes involved in mitotic inhibition and apoptotic regulations were also found to be up-regulated. Pomiferin is therefore a good anticancer candidate agent that may be useful either alone or in combination with other therapeutic agents and, because of its selectivity toward tumor cells, likely to have fewer side effects that classic chemotherapy drugs.