Chemistry and health effects of polymethoxyflavones and hydroxylated polymethoxyflavones

The chemopreventive effect of 5-demethylnobiletin, a unique citrus flavonoid, on colitis-driven colorectal carcinogenesis in mice is associated with its colonic metabolites

5-Demethylnobiletin (5DN) is a unique flavonoid mainly found in citrus fruits. In this study, we determined the chemopreventive effects of 5DN and its major colonic metabolites on both a colitis-driven colon carcinogenesis mouse model and a human colon cancer cell model. In azoxymethane/dextran sulfate sodium-treated mice, dietary 5DN (0.05% w/w in the diet) significantly decreased the tumor incidence, multiplicity and burden, and showed potent anti-proliferative, proapoptotic, and anti-inflammatory activities in mouse colon tissue. Three major metabolites of 5DN, named 5,3'-didemethylnobiletin (M1), 5,4'-didemethylnobiletin (M2) and 5,3',4'-tridemethylnobiletin (M3), were found in the colonic mucosa of 5DN-treated mice, and the combined level of these metabolites in mouse colonic mucosa was 1.56-fold higher than that of 5DN. Cell culture studies revealed that 5DN and its colonic metabolites profoundly inhibited the growth of human colon cancer cells by inducing cell cycle arrest, triggering apoptosis and modulating key signaling proteins related to cell proliferation and apoptosis. Importantly, the colonic metabolites, especially M1, showed much stronger effects than those produced by 5DN itself. Overall, our results demonstrated that dietary 5DN significantly inhibited colitis-driven colon carcinogenesis in mice, and this chemopreventive effect was associated with its metabolites in the colon.

Citrus Peel Flavonoids as Potential Cancer Prevention Agents

Citrus fruit and in particular flavonoid compounds from citrus peel have been identified as agents with utility in the treatment of cancer. This review provides a background and overview regarding the compounds found within citrus peel with putative anticancer potential as well as the associated in vitro and in vivo studies. Historical studies have identified a number of cellular processes that can be modulated by citrus peel flavonoids including cell proliferation, cell cycle regulation, apoptosis, metastasis, and angiogenesis. More recently, molecular studies have started to elucidate the underlying cell signaling pathways that are responsible for the flavonoids' mechanism of action. These growing data support further research into the chemopreventative potential of citrus peel extracts, and purified flavonoids in particular. This critical review highlights new research in the field and synthesizes the pathways modulated by flavonoids and other polyphenolic compounds into a generalized schema.

In-vivo biotransformation of citrus functional components and their effects on health

Citrus, one of the most popular fruits worldwide, contains various functional components, including flavonoids, dietary fibers (DFs), essential oils (EOs), synephrines, limonoids, and carotenoids. The functional components of citrus attract special attention due to their health-promoting effects. Food components undergo complex biotransformation by host itself and the gut microbiota after oral intake, which alters their bioaccessibility, bioavailability, and bioactivity in the host body. To better understand the health effects of citrus fruits, it is important to understand the in-vivo biotransformation of citrus functional components. We reviewed the biotransformation of citrus functional components (flavonoids, DFs, EOs, synephrines, limonoids, and carotenoids) in the body from their intake to excretion. In addition, we described the importance of biotransformation in terms of health effects. This review would facilitate mechanistic understanding of the health-promoting effect of citrus and its functional components, and also provide guidance for the development of health-promoting foods based on citrus and its functional components.

In Vitro and In Vivo Effects of Flavonoids on Peripheral Neuropathic Pain

Neuropathic pain is a common symptom and is associated with an impaired quality of life. It is caused by the lesion or disease of the somatosensory system. Neuropathic pain syndromes can be subdivided into two categories: central and peripheral neuropathic pain. The present review highlights the peripheral neuropathic models, including spared nerve injury, spinal nerve ligation, partial sciatic nerve injury, diabetes-induced neuropathy, chemotherapy-induced neuropathy, chronic constriction injury, and related conditions. The drugs which are currently used to attenuate peripheral neuropathy, such as antidepressants, anticonvulsants, baclofen, and clonidine, are associated with adverse side effects. These negative side effects necessitate the investigation of alternative therapeutics for treating neuropathic pain conditions. Flavonoids have been reported to alleviate neuropathic pain in murine models. The present review elucidates that several flavonoids attenuate different peripheral neuropathic pain conditions at behavioral, electrophysiological, biochemical and molecular biological levels in different murine models. Therefore, the flavonoids hold future promise and can be effectively used in treating or mitigating peripheral neuropathic conditions. Thus, future studies should focus on the structure-activity relationships among different categories of flavonoids and develop therapeutic products that enhance their antineuropathic effects.

Phenolic composition, antioxidant potential and health benefits of citrus peel

Citrus peel (CP) forms around 40-50% of the total fruit mass but is generally thought to be a waste. However, it is a substantial source of naturally occurring health enhancing compounds, particularly phenolic compounds and carotenoids. Phenolic compounds in CP mainly comprise phenolic acids (primarily caffeic, p-coumaric, ferulic and sinapic acid), flavanones (generally naringin and hesperidin) and polymethoxylated flavones (notably nobiletin and tangeretin). It has also been noted that CP's contain more amounts of these compounds than corresponding edible parts of the fruits. Phenolic compounds present in CP act as antioxidants (by either donation of protons or electrons) and protect cells against free radical damage as well as help in reducing the risk of many chronic diseases. Owing to the more abundance of polyphenols in CP's, their antioxidant activity is also higher than other edible fruit parts. Therefore, peels from citrus fruits can be used as sources of functional compounds and preservatives for the development of newer food products, that are not only safe but also have health-promoting activities. The present review provides in-depth knowledge about the phenolic composition, antioxidant potential and health benefits of CP.

Preparation and evaluation of self-microemulsifying delivery system containing 5-demethyltangeretin on inhibiting xenograft tumor growth in mice

5-Demethyltangeretin (5-DTAN), a polymethoxylated flavone found in citrus peels, exhibits highly potent anti-cancer activity. However, 5-DTAN is a hydrophobic compound with poor aqueous solubility, which limits its oral bioavailability and efficacy. In this study, we aimed to develop and characterize an optimal self-microemulsifying delivery system (SMEDS) formulated for 5-DTAN and to assess its anticancer activity in a xenograft model. SMEDS is a lipid-based formulation and typically comprises oil, surfactant, and co-surfactant. The results from our solubility and compatibility test revealed that ethyl oleate and d-limonene were appropriate for use as an oil phases. The optimal formulation comprised ethyl oleate/d-limonene (10%/5%), Cremophor® EL (59.5%), and PEG 400 (25.5%). With this optimal formulation, the mean particle size was 97.1 ± 6.50 nm with the highest 5-DTAN loading (3.01 ± 0.38 mg/mL) determined by photon correlation spectroscopy. The transmission electron microscopy (TEM) morphology of 5-DTAN microemulsion droplets demonstrated a spherical shape and uniform size. Our findings suggest that using 5-DTAN loading SMEDS is an effective approach for inhibiting tumor growth in colon cancer xenograft mice. In summary, this study is the first to successfully demonstrate that oral administration of 5-DTAN-loaded SMEDS serves as a promising nutraceutical for cancer prevention.

Evaluation of Oral Bioaccessibility of Aged Citrus Peel Extracts Encapsulated in Different Lipid-Based Systems: A Comparison Study Using Different in Vitro Digestion Models

The oral delivery efficiency of aged citrus peel extract containing polymethoxyflavones and 5-demethylated polymethoxyflavones (PMFs) in three different systems, including a pure oil phase, a Tween 80-stabilized nanoemulsion, and a milled-cellulose-particles-stabilized Pickering emulsion, was investigated using two typical in vitro digestion models. The digestion profiles and release of PMFs in these emulsions and bulk oil in the human upper gastrointestinal (GI) tract were evaluated using the pH-stat lipolysis model and TNO's gastrointestinal model (TIM-1). Compared to the bulk oil sample, the bioaccessibilities of PMFs in the nanoemulsion and Pickering emulsion were both increased by around 14 fold when the pH-stat lipolysis model was used. However, the results from the TIM-1 system indicated that the bioaccessibilities of PMFs in the nanoemulsion and Pickering emulsion were around two and four times that in bulk oil, respectively. The results from this work would provide valuable information for the rational design and evaluation of lipid-based delivery systems for lipophilic bioactive compounds.

Drug Metabolite Cluster-Based Data-Mining Method for Comprehensive Metabolism Study of 5-hydroxy-6,7,3',4'-tetramethoxyflavone in Rats

The screening of drug metabolites in biological matrixes and structural characterization based on product ion spectra is among the most important, but also the most challenging due to the significant interferences from endogenous species. Traditionally, metabolite detection is accomplished primarily on the basis of predicted molecular masses or fragmentation patterns of prototype drug metabolites using ultra-high performance liquid chromatography coupled with high-resolution mass spectrometry (UHPLC-HRMS). Although classical techniques are well-suited for achieving the partial characterization of prototype drug metabolites, there is a pressing need for a strategy to enable comprehensive drug metabolism depiction. Therefore, we present drug metabolite clusters (DMCs), different from, but complementary to, traditional approaches for mining the information regarding drugs and their metabolites on the basis of raw, processed, or identified tandem mass spectrometry (MS/MS) data. In this paper, we describe a DMC-based data-mining method for the metabolite identification of 5-hydroxy-6,7,3′,4′-tetramethoxyflavone (HTF), a typical hydroxylated-polymethoxyflavonoid (OH-PMF), which addressed the challenge of creating a thorough metabolic profile. Consequently, eight primary metabolism clusters, sixteen secondary metabolism clusters, and five tertiary metabolism clusters were proposed and 106 metabolites (19 potential metabolites included) were detected and identified positively and tentatively. These metabolites were presumed to generate through oxidation (mono-oxidation, di-oxidation), methylation, demethylation, methoxylation, glucuronidation, sulfation, ring cleavage, and their composite reactions. In conclusion, our study expounded drug metabolites in rats and provided a reference for further research on therapeutic material basis and the mechanism of drugs.

Characterization of polymethoxyflavone demethylation during drying processes of citrus peels

Polymethoxyflavones (PMFs) are found almost exclusively in citrus peel and have attracted much attention due to their potential health benefits. Dried citrus peel is an important ingredient for applications in food and traditional Chinese medicine. However, the structural changes of PMFs during drying processes of citrus peel remain unknown. In this study, for the first time we discovered that four major permethoxylated PMFs, i.e. sinensetin, nobiletin, heptamethoxyflavone and tangeretin, underwent demethylation at the 5-position on the A ring of their flavonoid structures to yield corresponding 5-demethylated PMFs during the drying process of citrus peel. Our results further demonstrated that the aforementioned PMF demethylation was through two mechanisms: acid hydrolysis and enzyme-mediated catalysis. PMF demethylation in citrus peels was systematically characterized during hot-air drying (HAD), vacuum-freeze drying (VFD) and sun drying (SD). The highest PMF demethylation was obtained in SD followed by HAD and VFD. This study provided a solid scientific basis for rational control of PMF demethylation in citrus peels, which could facilitate the production of high-quality citrus peel and related products.

Oolong Tea Extract and Citrus Peel Polymethoxyflavones Reduce Transformation of l-Carnitine to Trimethylamine-N-Oxide and Decrease Vascular Inflammation in l-Carnitine Feeding Mice

Carnitine, a dietary quaternary amine mainly from red meat, is metabolized to trimethylamine (TMA) by gut microbiota and subsequently oxidized to trimethylamine-N-oxide (TMAO) by host hepatic enzymes, flavin monooxygenases (FMOs). The objective of this study aims to investigate the effects of flavonoids from oolong tea and citrus peels on reducing TMAO formation and protecting vascular inflammation in carnitine-feeding mice. The results showed that mice treated with 1.3% carnitine in drinking water significantly (p < 0.05) increased the plasma levels of TMAO compared to control group, whereas the plasma TMAO was remarkedly reduced by flavonoids used. Meanwhile, these dietary phenolic compounds significantly (p < 0.05) decreased hepatic FMO3 mRNA levels compared to carnitine only group. Additionally, oolong tea extract decreased mRNA levels of vascular inflammatory markers such as tissue necrosis factor-alpha (TNF-α), vascular cell adhesion molecule-1 (VCAM-1) and E-selectin. Polymethoxyflavones significantly lowered the expression of VCAM-1 and showed a decreasing trend in TNF-α and E-selectin mRNA expression compared to the carnitine group. Genus-level analysis of the gut microbiota in the cecum showed that these dietary phenolic compounds induced an increase in the relative abundances of Bacteroides. Oolong tea extract-treated group up-regulated Lactobacillus genus, compared to the carnitine only group. Administration of polymethoxyflavones increased Akkermansia in mice.

Nobiletin and Derivatives: Functional Compounds from Citrus Fruit Peel for Colon Cancer Chemoprevention

The search for effective methods of cancer treatment and prevention has been a continuous effort since the disease was discovered. Recently, there has been increasing interest in exploring plants and fruits for molecules that may have potential as either adjuvants or as chemopreventive agents against cancer. One of the promising compounds under extensive research is nobiletin (NOB), a polymethoxyflavone (PMF) extracted exclusively from citrus peel. Not only does nobiletin itself exhibit anti-cancer properties, but its derivatives are also promising chemopreventive agents; examples of derivatives with anti-cancer activity include 3'-demethylnobiletin (3'-DMN), 4'-demethylnobiletin (4'-DMN), 3',4'-didemethylnobiletin (3',4'-DMN) and 5-demethylnobiletin (5-DMN). In vitro studies have demonstrated differential efficacies and mechanisms of NOB and its derivatives in inhibiting and killing of colon cancer cells. The chemopreventive potential of NOB has also been well demonstrated in several in vivo colon carcinogenesis animal models. NOB and its derivatives target multiple pathways in cancer progression and inhibit several of the hallmark features of colorectal cancer (CRC) pathophysiology, including arresting the cell cycle, inhibiting cell proliferation, inducing apoptosis, preventing tumour formation, reducing inflammatory effects and limiting angiogenesis. However, these substances have low oral bioavailability that limits their clinical utility, hence there have been numerous efforts exploring better drug delivery strategies for NOB and these are part of this review. We also reviewed data related to patents involving NOB to illustrate the extensiveness of each research area and its direction of commercialisation. Furthermore, this review also provides suggested directions for future research to advance NOB as the next promising candidate in CRC chemoprevention.

Skullcapflavone II Inhibits Degradation of Type I Collagen by Suppressing MMP-1 Transcription in Human Skin Fibroblasts

Skullcapflavone II is a flavonoid derived from the root of Scutellaria baicalensis, a herbal medicine used for anti-inflammatory and anti-cancer therapies. We analyzed the effect of skullcapflavone II on the expression of matrix metalloproteinase-1 (MMP-1) and integrity of type I collagen in foreskin fibroblasts. Skullcapflavone II did not affect the secretion of type I collagen but reduced the secretion of MMP-1 in a dose- and time-dependent manner. Real-time reverse transcription-PCR and reporter gene assays showed that skullcapflavone II reduced MMP-1 expression at the transcriptional level. Skullcapflavone II inhibited the serum-induced activation of the extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) signaling pathways required for MMP-1 transactivation. Skullcapflavone II also reduced tumor necrosis factor (TNF)-α-induced nuclear factor kappa light chain enhancer of activated B cells (NF-κB) activation and subsequent MMP-1 expression. In three-dimensional culture of fibroblasts, skullcapflavone II down-regulated TNF-α-induced MMP-1 secretion and reduced breakdown of type I collagen. These results indicate that skullcapflavone II is a novel biomolecule that down-regulates MMP-1 expression in foreskin fibroblasts and therefore could be useful in therapies for maintaining the integrity of extracellular matrix.

Supercritical fluid CO2 extraction of three polymethoxyflavones from Citri reticulatae pericarpium and subsequent preparative separation by continuous high-speed counter-current chromatography

Polymethoxyflavones (PMFs) are widely found in Citri Reticulatae Pericarpium (CRP) and have been investigated with a broad spectrum of biological activities as well as health promoting properties. However, separation of the PMFs from a complex sample, especially preparative separation of these PMFs with high purity, remains challenging. In the present study, an efficient method based on supercritical fluid extraction (SFE) and continuous high-speed counter-current chromatography (HSCCC) has been developed for extracting and preparative purification PMFs from CRP. Various experimental conditions were investigated to optimize the SFE and HSCCC processes. Under these optimized conditions, crude extract of CRP (extract I) was obtained with a maximum contents of nobiletin, 3,5,6,7,8,3',4'-heptamethoxyflavone and tangeretin. Further extraction of crude extract I was carried out to obtain crude extract II, which was further isolated and purified by HSCCC. It was worth mentioned that continuous injection HSCCC process were realized without lost of separation efficiency, which allowed for multiple purification cycles and therefore saved a lot of labor and time. Furthermore, high-performance liquid chromatography (HPLC) was employed to analyze the fractions separated by HSCCC, which revealed that the purities of the three PMFs were all above 98%. The structures of the three PMFs were identified by LC-MS and ¹H NMR spectroscopy.

Nanoencapsulation of functional food ingredients

Many functional food ingredients are poorly soluble in water, susceptible to chemical degradation, and incompatible with surrounding food matrix. Other issues are related to limited oral bioavailability, unpleasant sensory properties, and poor release profiles. Nanoencapsulation of functional food ingredients can help increase their water solubility/dispersibility in foods and beverages, improve their bioavailability by exhibiting good dose-dependent functionalities, mask undesired flavors/tastes to reduce the adverse effect on mouth-feel, enhance shelf-life and compatibility during production, storage, transportation and utilization of food products, and control release rate or specific delivery environment for better performance on their functionalities. This chapter provides an overview of different delivery systems for different functional food ingredients, the types of materials suitable for wall materials or building blocks of nanocapsules, the fabrication methods to assemble different delivery systems and release these active ingredients under different physiological conditions.

Simultaneous separation of six pure polymethoxyflavones from sweet orange peel extract by high performance counter current chromatography

Successful isolation of polymethoxyflavones (PMFs) from citrus peels has led to numerous evaluations of PMFs in a broad spectrum of biological activities, such as inhibition of chronic inflammation, cancer prevention and anti-atherogenic properties. Recent reports associated with the health promoting properties of PMFs in citrus fruits have dramatically increased. However, the limiting factor in animal and human study of PMFs is still the supply of pure PMFs, such as tangeretin, nobiletin, sinensetin and 3,5,6,7,3',4'-hexamethoxyflavone. Herein, we introduce the newly developed efficient separation method using high-performance counter-current chromatography (HPCCC) in isolating multiple pure single PMFs simultaneously in one cycle process. With the smallest preparation loop on the semi-preparative HPCCC instrument, the optimized solvent system of hexanes/ethyl acetate/methanol/water resulted in the isolation of pure sinensetin, tangeretin, nobiletin, 3,5,6,7,3',4'-hexamethoxyflavone, 5,6,7,4'-tetramethoxyflavone and 3,5,6,7,8,3',4'-heptamethoxyflavone directly from crude sweet orange peel extract in one cycle of separation process by HPCCC in the mode of reverse phase. The purity of each of the six isolated PMFs is greater than 96.6% analyzed by high-performance liquid chromatography and proton nuclear magnetic resonance. Scale-up and high purity of individual PMFs can be separated by using a large separation loop in preparative HPCCC model. The renovated HPCCC methodology can be practically used in natural product isolation and consequent biological property evaluation.

Effectiveness of a Novel Nutraceutical Compound Containing Red Yeast Rice, Polymethoxyflavones and Antioxidants in the Modulation of Cholesterol Levels in Subjects With Hypercholesterolemia and Low-Moderate Cardiovascular Risk: The NIRVANA Study

Background: Red yeast rice supplements are broadly accepted as treatment for dyslipidaemia in subjects without high cardiovascular (CV) risk. Their effect on lipid profile is well known, but few data are available on their effect on endothelial function. Objectives: To study the effect of a novel nutraceutical compound (NC) containing low monacolin K dose, polymethoxyflavones and antioxidants on lipid profile, endothelial function and oxidative stress. Methods: Fifty-two subjects with low-moderate CV risk and dyslipidaemia (according to European guidelines) were enrolled and treated for 8 weeks with the NC. Blood samples were collected at baseline and at the end of treatment to assess changes in lipid profile, endothelial function and oxidative stress. The primary endpoint was the reduction of low density lipoprotein (LDL) cholesterol. Endothelial function was assessed through measurement of rate of apoptosis and nitric oxide (NO) production in human umbilical vein endothelial cells (HUVECs) treated with subject's serum. High-sensitivity C-reactive protein, 4-hydroxynonenal (HNE) and oxidized LDL (oxLDL) were markers of oxidative stress. Results: Fifty subjects completed the study. The treatment caused a significant decrease in LDL (-15.6%, p < 0.001), oxLDL (-21.5%, p < 0.001), total cholesterol (TC), triglycerides, and ApoB. Apoptosis rate of HUVECs significantly decreased (-15.9%, p < 0.001). No changes were noted for NO levels and 4-HNE protein adducts. The reduction of the apoptosis rate was correlated to the reduction of oxLDL. Conclusion: An 8-week treatment based on a novel NC containing low manocolin K dose, polymethoxyflavones and antioxidants improved lipid profile in subjects with dyslipidaemia and low-moderate CV risk. Secondarily, we observed an improvement in surrogate markers of endothelial function that may result from the reduction of oxLDL (Registered at www.clinicaltrials.gov, NCT03216811).

Antinociceptive effect of flavonol and a few structurally related dimethoxy flavonols in mice

Previous reports suggest flavonoids as potent analgesic compounds. Based on these observations, the present study investigated the antinociceptive action of flavonol, 3', 4'-dimethoxy flavonol, 6, 3'-dimethoxy flavonol, 7, 2'-dimethoxy flavonol, and 7, 3'-dimethoxy flavonol and the possible mechanisms involved in these effects. The antinociceptive effect of the investigated compounds in doses of 25, 50, 100, and 200 mg/kg was evaluated in male Swiss albino mice using the acetic acid test, formalin-induced nociception, and hot water tail immersion test. The role of opioid, tryptaminergic, adrenergic, dopaminergic, GABAergic, and K⁺_ATP channels in producing the antinociceptive effect was also studied using appropriate interacting agents. Treatment with flavonol and dimethoxy flavonols resulted in a significant reduction in the number of abdominal constrictions in the acetic acid test, a significant inhibition of the paw-licking/biting response time in both the phases of formalin nociception and also a significant increase in mean reaction time in the hot water tail immersion test. These observations revealed the antinociceptive effect of dimethoxy flavonols. The role of opioid, serotonergic (5HT₃), and dopaminergic system was identified in the antinociceptive effect of flavonol and all dimethoxy derivatives investigated. In addition, the role of GABAergic, K⁺_ATP channel, and α-2 adrenergic mechanisms were also observed in the antinociceptive action of some of the investigated compounds. The present study identified the antinociceptive effect of flavonol and dimethoxy flavonols in mice acting through different neuronal pathways.

Phytochemical Composition and Chronic Hypoglycemic Effect of Bromelia karatas on STZ-NA-Induced Diabetic Rats

Oral administration of an aqueous extract of the aerial parts of Bromelia karatas to STZ-NA rats showed a significant hypoglycemic effect in a chronic trial lasting 42 days. Chromatographic profiles of the active extract (WE) and an organic extract (OE) of B. karatas were obtained by high-performance liquid chromatography (HPLC) and used to identify their major components. Isolation and identification of the compounds present in the extracts were accomplished by means of various conventional chromatographic and spectroscopic techniques. This process led to the identification of β-sitosterol-3-O-β-D-glucopyranoside (1) and ρ-coumaric acid (3) as the major compounds present in the extracts. During the isolation of 1 and 3, seven additional metabolites not previously reported for the plant were obtained, namely, cirsiliol 4'-O-β-D-glucopyranoside (2), stigmasterol (4), β-sitosterol (5), 1-O-feruloyl-3-O-ρ-coumaroylglycerol (6), β-D-(1-O-acetyl-3,6-O-trans-diferuloyl) fructofuranosyl-α-D-2',4',6'-O-triacetylglucopyranoside (7), 1-O-p-coumaroyl-3-O-caffeoylglycerol (8), and 2-propyl-β-glucopyranoside (9).

Bioaccessibility of polymethoxyflavones encapsulated in resistant starch particle stabilized Pickering emulsions: role of fatty acid complexation and heat treatment

Digestion of Pickering emulsions stabilized by starch-fatty acid complexes.

Effect of flavonol and its dimethoxy derivatives on paclitaxel-induced peripheral neuropathy in mice

Background:

Peripheral neuropathy is the dose limiting side effect of many anticancer drugs. Flavonoids exhibit good antinociceptive effect in animal models. Their efficacy against different types of nociception has been documented. The present study investigated the effect of flavonol (3-hydroxy flavone), 3′,4′-dimethoxy flavonol, 6,3′-dimethoxy flavonol, 7,2′-dimethoxy flavonol and 7,3′-dimethoxy flavonol against paclitaxel-induced peripheral neuropathy in mice.

Methods:

A single dose of paclitaxel (10 mg/kg, i.p.) was administered to induce peripheral neuropathy in mice and the manifestations of peripheral neuropathy such as tactile allodynia, cold allodynia and thermal hyperalgesia were assessed 24 h later by employing Von Frey hair aesthesiometer test, acetone bubble test and hot water tail immersion test, respectively. The test compounds were prepared as a suspension in 0.5% carboxymethyl cellulose and were administered s.c. in various doses (25, 50, 100 and 200 mg/kg). The above behavioral responses were assessed prior to and 30 min after drug treatment. In addition, the effect of test compounds on proinflammatory cytokines like tumor necrosis factor-alpha (TNF-α), interleukin-1-beta (IL-1β) and free radicals was investigated by using suitable in vitro assays.

Results:

A dose-dependent attenuation of tactile allodynia, cold allodynia and thermal hyperalgesia was evidenced in mice treated with flavonol derivatives. The test compounds inhibited TNF-α, IL-1β and free radicals in a concentration-dependent manner.

Conclusions:

These results revealed that flavonol and its dimethoxy derivatives ameliorated the manifestations of paclitaxel-induced peripheral neuropathy in mice. The inhibition of proinflammatory cytokines and free radicals could contribute to this beneficial effect.

Analysis of Fluorescence Spectra of Citrus Polymethoxylated Flavones and Their Incorporation into Mammalian Cells

Citrus polymethoxylated flavones (PMFs) influence biochemical cascades in human diseases, yet little is known about how these compounds interact with cells and how these associations influence the actions of these compounds. An innate attribute of PMFs is their ultraviolet-light-induced fluorescence, and the fluorescence spectra of 14 PMFs and 7 PMF metabolites were measured in methanol. These spectra were shown to be strongly influenced by the compounds' hydroxy and methoxy substituents. For a subset of these compounds, the fluorescence spectra were measured when bound to human carcinoma Huh7.5 cells. Emission-wavelength maxima of PMF metabolites with free hydroxyl substituents exhibited 70-80 nm red shifts when bound to the Huh7.5 cells. Notable solvent effects of water were observed for nearly all these compounds, and these influences likely reflect the effects of localized microenvironments on the resonance structures of these compounds when bound to human cells.

Pharmacokinetics, bioavailability, tissue distribution and excretion of tangeretin in rat

Tangeretin, 4′,5,6,7,8-pentamethoxyflavone, is one of the major polymethoxyflavones (PMFs) existing in citrus fruits, particularly in the peels of sweet oranges and mandarins. Tangeretin has been reported to possess several beneficial bioactivities including anti-inflammatory, anti-proliferative and neuroprotective effects. To achieve a thorough understanding of the biological actions of tangeretin in vivo, our current study is designed to investigate the pharmacokinetics, bioavailability, distribution and excretion of tangeretin in rats. After oral administration of 50 mg/kg bw tangeretin to rats, the C_max, T_max and t_1/2 were 0.87 ± 0.33 μg/mL, 340.00 ± 48.99 min and 342.43 ± 71.27 min, respectively. Based on the area under the curves (AUC) of oral and intravenous administration of tangeretin, calculated absolute oral bioavailability was 27.11%. During tissue distribution, maximum concentrations of tangeretin in the vital organs occurred at 4 or 8 h after oral administration. The highest accumulation of tangeretin was found in the kidney, lung and liver, followed by spleen and heart. In the gastrointestinal tract, maximum concentrations of tangeretin in the stomach and small intestine were found at 4 h, while in the cecum, colon and rectum, tangeretin reached the maximum concentrations at 12 h. Tangeretin excreted in the urine and feces was recovered within 48 h after oral administration, concentrations were only 0.0026% and 7.54%, respectively. These results suggest that tangeretin was mainly eliminated as metabolites. In conclusion, our study provides useful information regarding absorption, distribution, as well as excretion of tangeretin, which will provide a good base for studying the mechanism of its biological effects.

Polymethoxyflavones from Nicotiana plumbaginifolia (Solanaceae) Exert Antinociceptive and Neuropharmacological Effects in Mice

Polymethoxylavones (PMFs) are known to exhibit significant anti-inflammatory and neuroprotective properties. Nicotiana plumbaginifolia, an annual Bangladeshi herb, is rich in polymethoxyflavones that possess significant analgesic and anxiolytic activities. The present study aimed to determine the antinociceptive and neuropharmacological activities of polyoxygenated flavonoids namely- 3,3′,5,6,7,8-hexamethoxy-4′,5′-methylenedioxyflavone (1), 3,3′,4′,5′,5,6,7,8-octamethoxyflavone (exoticin) (2), 6,7,4′,5′-dimethylenedioxy-3,5,3′-trimethoxyflavone (3), and 3,3′,4′,5,5′,8-hexamethoxy-6,7-methylenedioxyflavone (4), isolated and identified from N. plumbaginifolia. Antinociceptive activity was assessed using the acetic-acid induced writhing, hot plate, tail immersion, formalin and carrageenan-induced paw edema tests, whereas neuropharmacological effects were evaluated in the hole cross, open field and elevated plus maze test. Oral treatment of compounds 1, 3, and 4 (12.5–25 mg/kg b.w.) exhibited dose-dependent and significant (p < 0.01) antinociceptive activity in the acetic-acid, formalin, carrageenan, and thermal (hot plate)-induced pain models. The association of ATP-sensitive K⁺ channel and opioid systems in their antinociceptive effect was obvious from the antagonist effect of glibenclamide and naloxone, respectively. These findings suggested central and peripheral antinociceptive activities of the compounds. Compound 1, 3, and 4 (12.5 mg/kg b.w.) demonstrated significant (p < 0.05) anxiolytic-like activity in the elevated plus-maze test, while the involvement of GABA_A receptor in the action of compound 3 and 4 was evident from the reversal effects of flumazenil. In addition, compounds 1 and 4 (12.5–25 mg/kg b.w) exhibited anxiolytic activity without altering the locomotor responses. The present study suggested that the polymethoxyflavones (1–4) from N. Plumbaginifolia could be considered as suitable candidates for the development of analgesic and anxiolytic agents.

Antiobesity Efficacy of Quercetin-Rich Supplement on Diet-Induced Obese Rats: Effects on Body Composition, Serum Lipid Profile, and Gene Expression

The antiobesity effects of quercetin-rich supplement (QRS), which contain quercetin, lycopene, taurine, and litchi flower extract, on a high-fat diet (HFD)-induced obese rats were investigated. The rats that consume HFD with QRS (185 mg/kg rat) have significantly modulated the final body weights [490 ± 11 (HFD) → 441 ± 11 (HFD+QRS) g], total body fat [112.9 ± 4.5 (HFD) → 86.6 ± 5.7 (HFD+QRS) g], liver weights [14.8 ± 0.4 (HFD) → 12.6 ± 0.4 (HFD+QRS) g/rat], and the serum TG [102.5 ± 7.3 (HFD) → 90.7 ± 6.5 (HFD+QRS) mg/dL] to a level that resembled the regular diet-consumed rats (p < 0.05). The excretion of lipid in the faeces augmented in QRS groups as compared with the nonsupplemented HFD group [faecal total lipid: 62.43 ± 2.80 (HFD) → 73.15 ± 0.88 (HFD+QRS) mg/g dried faeces, p < 0.05]. In the histological analysis, quercetin-rich formulation supplemented groups presented a much less lipid accumulation and smaller size of adipocytes. Moreover, a decreased serum thiobarbituric acid reactive substances [1.55 ± 0.17 (HFD) → 0.78 ± 0.04 (HFD+QRS) nmol MDA eq/mL serum] increased levels of serum Trolox equivalent antioxidant capacity [3.89 ± 0.08 (HFD) → 6.46 ± 0.20 (HFD+QRS) μmol/mL serum], and more active hepatic antioxidant enzymes were observed in the supplemented groups (p < 0.05). The result of this work is a good demonstration of how a combination of bioactive compounds could work synergistically and become very effective in disease prevention.

Polymethoxylated Flavones from Orange Peels Inhibit Cell Proliferation in a 3D Cell Model of Human Colorectal Cancer

Polymethoxylated flavones (PMFs) have been recognized to inhibit colorectal cancer proliferation through various mechanisms, however most of these studies have been performed on cells grown as monolayers that present limitations in mimicking the 3D tumor architecture and microenvironment. The main aim of this study was to investigate the anticancer potential of an orange peel extract (OPE) enriched in PMFs in a 3D cell model of colorectal cancer. The OPE was developed by supercritical fluid extraction and the anticancer effect was evaluated in HT29 spheroids cultures in a stirred-tank based system. Results showed that OPE inhibited cell proliferation, induced cell cycle arrest (G2/M phase), promoted apoptosis, and reduced ALDH⁺ population on HT29 spheroids. The antiproliferative activity was significantly lower than that obtained for 2D model (EC50 value of 0.43 ± 0.02 mg/mL) and this effect was dependent on diameter and cell composition/phenotype of spheroids derived from different culture days (day 3 - 0.53 ± 0.05 mg/mL; day 5 - 0.55 ± 0.03 mg/mL; day 7 - 1.24 ± 0.15 mg/mL). HT29 spheroids collected at day 7 presented typical characteristics of in vivo solid tumors including a necrotic/apoptotic core, hypoxia regions, presence of cancer stem cells, and a less differentiated invasive front. Nobiletin, sinesentin, and tangeretin were identified as the main compounds responsible for the anticancer activity.

Leveraging plant exine capsules as pH-responsive delivery vehicles for hydrophobic nutraceutical encapsulation

Plant exine capsules are natural microscale capsules that are highly physically robust and chemically resilient.

Citrus peel extracts attenuated obesity and modulated gut microbiota in mice with high-fat diet-induced obesity

Polymethoxyflavones (PMFs) and hydroxyl PMFs (HOPMFs) are mainly found in citrus peel and have shown anti-obesity potential in in vitro and in vivo studies.

Combination of citrus polymethoxyflavones, green tea polyphenols, and Lychee extracts suppresses obesity and hepatic steatosis in high-fat diet induced obese mice

SCOPE

SlimTrym^® is a formulated product composed of citrus polymethoxyflavones (PMFs), green tea extract, and lychee extract. We investigated the effect of dietary SlimTrym^® on diet-induced obesity and associated non-alcoholic fatty liver disease (NAFLD) in mice.

METHODS AND RESULTS

Male C57BL/6 mice were fed a normal diet (ND), high fat diet (HFD) or HFD containing 0.1% or 0.5% SlimTrym^® for 16 weeks. Dietary SlimTrym^® significantly reduced weight gain and relative perigonadal, retroperitoneal, mesenteric fat weight as well as the size of adipocyte in HFD-fed mice. SlimTrym^® supplementation also effectively diminished hepatic steatosis and the serum levels of glutamate oxaloacetate transaminase (GOT), glutamate pyruvate transaminase (GPT), triacylglycerol (TG), and total cholesterol (TCHO). Down-regulation of peroxisome proliferator-activated receptor (PPAR)γ, sterol regulatory element-binding protein (SREBP)-1, and the activation of AMP-activated protein kinase (AMPK) signaling by SlimTrym^® in both adipose tissue and liver may be responsible for the observed anti-obesity effects.

CONCLUSION

SlimTrym^® supplementation potentially diminished diet-induced obesity and hepatic steatosis via regulating AMPK signaling and molecules involved in lipid metabolism.

Dietary 5-demethylnobiletin inhibits cigarette carcinogen NNK-induced lung tumorigenesis in mice

5-Demethylnobiletin (5DN) is a unique citrus flavonoid with various beneficial bioactivities. In this study, we determined the inhibitory effects of 5DN and its two major metabolites in the 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung tumorigenesis mouse model as well as in human and mouse lung cancer cell models. In NNK-treated female A/J mice, dietary administration of 5DN (0.025% or 0.05% w/w in the diet) significantly decreased both lung tumor multiplicity and tumor volume. Immunohistochemical analysis showed strong anti-proliferative effects of 5DN in lung tumors. Two major metabolites of 5DN, named 5,3'-didemethylnobiletin (M1) and 5,4'-didemethylnobiletin (M2), were found in the lung tissue of 5DN-fed mice. Cell culture studies demonstrated that 5DN, M1 and M2 significantly inhibited the growth of human and mouse lung cancer cells by causing cell cycle arrest, inducing apoptosis and modulating key signaling proteins related to cell proliferation and cell death. Interestingly, the metabolites of 5DN, especially M1 produced much stronger inhibitory effects on both human and mouse lung cancer cells than those produced by 5DN itself. Our results demonstrated that dietary administration of 5DN significantly inhibited NNK-induced tumorigenesis in mice, and this effect may be partially associated with the metabolites of 5DN in lung tissues.

Edible leaf extract of Ipomoea aquatica Forssk. (Convolvulaceae) attenuates doxorubicin-induced liver injury via inhibiting oxidative impairment, MAPK activation and intrinsic pathway of apoptosis

Ipomoea aquatica Forssk. (Convolvulaceae) is an aquatic vegetable traditionally employed against toxic effects of xenobiotics. The present study has been designed to investigate the molecular mechanism underlying the beneficial role of the edible (aqueous) leaf extract of I. aquatica (AEIA) against doxorubicin (Dox)-induced liver injury. AEIA exhibited a dose-dependent (∼400 μg/ml) increase in cell viability against Dox (1 μM) in isolated rodent hepatocytes. AEIA (400 μg/ml) prevented the Dox-induced increase in ROS, redox imbalance, and activation of mitogen activated protein kinases (MAPK) and intrinsic pathway of apoptosis in hepatocytes. In the in vivo assay, administration of AEIA (100 mg/kg, p.o.) against Dox (3 mg/kg, i.p.) also reduced the oxidative impairment, DNA fragmentation, ATP formation, and up-regulated the mitochondrial co-enzymes Qs in the liver tissues of Wistar rats. Histological assessments were in agreement with the biochemical findings. Substantial quantities of phyto-antioxidants in AEIA may mediate its beneficial function against Dox-induced liver injury.

Synergistic chemopreventive effects of nobiletin and atorvastatin on colon carcinogenesis

Different cancer chemopreventive agents may act synergistically and their combination may produce enhanced protective effects against carcinogenesis than each individual agent alone. Herein, we investigated the chemopreventive effects of nobiletin (NBT, a citrus polymethoxyflavone) and atorvastatin (ATST, a lipid-lowering drug) in colon cancer cells/macrophages and an azoxymethane (AOM)-induced colon carcinogenesis rat model. The results demonstrated that co-treatments of NBT/ATST produced enhanced growth inhibitory and anti-inflammatory effects on the colon cancer cells and macrophages, respectively. Isobologram analysis confirmed that these interactions between NBT and ATST were synergistic. NBT/ATST co-treatment also synergistically induced extensive cell cycle arrest and apoptosis in colon cancer cells. Oral administration of NBT (0.1%, w/w in diet) or ATST (0.04%, w/w in diet) significantly decreased colonic tumor incidence and multiplicity in AOM-treated rats. Most importantly, co-treatment of NBT/ATST at their half doses (0.05% NBT + 0.02% ATST, w/w in diet) resulted in even stronger inhibitory effects on colonic tumor incidence and multiplicity than did NBT or ATST alone at higher doses. Statistical analysis confirmed that the enhanced chemopreventive activities against colon carcinogenesis in rats by the NBT/ATST combination were highly synergistic. Our results further demonstrated that NBT/ATST co-treatment profoundly modulated key cellular signaling regulators associated with inflammation, cell proliferation, cell cycle progression, apoptosis, angiogenesis and metastasis in the colon of AOM-treated rats. In conclusion, for the first time, our results demonstrated a strong synergy in inhibiting colon carcinogenesis produced by the co-treatment of NBT and ATST, which provided a scientific basis for using NBT in combination with ATST for colon cancer chemoprevention in humans.

Encapsulation of Polymethoxyflavones in Citrus Oil Emulsion-Based Delivery Systems

The purpose of this work was to elucidate the effects of citrus oil type on polymethoxyflavone (PMF) solubility and on the physicochemical properties of PMF-loaded emulsion-based delivery systems. Citrus oils were extracted from mandarin, orange, sweet orange, and bergamot. The major constituents were determined by GC/MS: sweet orange oil (97.4% d-limonene); mandarin oil (72.4% d-limonene); orange oil (67.2% d-limonene); and bergamot oil (34.6% linalyl acetate and 25.3% d-limonene). PMF-loaded emulsions were fabricated using 10% oil phase (containing 0.1% w/v nobiletin or tangeretin) and 90% aqueous phase (containing 1% w/v Tween 80) using high-pressure homogenization. Delivery systems prepared using mandarin oil had the largest mean droplet diameters (386 or 400 nm), followed by orange oil (338 or 390 nm), bergamot oil (129 or 133 nm), and sweet orange oil (122 or 126 nm) for nobiletin- or tangeretin-loaded emulsions, respectively. The optical clarity of the emulsions increased with decreasing droplet size due to reduced light scattering. The viscosities of the emulsions (with or without PMFs) were similar (1.3 to 1.4 mPa·s), despite appreciable differences in oil phase viscosity. The loading capacity and encapsulation efficiency of the emulsions depended on carrier oil type, with bergamot oil giving the highest loading capacity. In summary, differences in the composition and physical characteristics of citrus oils led to PMF-loaded emulsions with different encapsulation and physicochemical characteristics. These results will facilitate the rational design of emulsion-based delivery systems for encapsulation of PMFs and other nutraceuticals in functional foods and beverages.

Label-free Imaging and Characterization of Cancer Cell Responses to Polymethoxyflavones Using Raman Microscopy

We determined the cellular responses of human colon cancer HT29 and HCT116 cells to the treatments of nobiletin (NBT) and 5-demethylnobiletin (5DN) using Raman microscopy. Evaluation at both single cell and cell population levels revealed found that NBT induced more changes in the peak intensity of nucleic acid than 5DN, whereas 5DN induced more changes in the peak intensity of localized lipid than NBT. This result indicates the different modes of inhibitory action of these two PMFs against colon cancer cells. Between the two colon cancer cells tested, HCT116 cells were more sensitive to both PMFs than HT29 cells. The Raman data were generally in a good agreement with the flow cytometry data. Our results demonstrate that Raman microscopy is able to provide macromolecular information on cellular responses to anticancer treatments.

Suppression of Adipogenesis by 5-Hydroxy-3,6,7,8,3',4'-Hexamethoxyflavone from Orange Peel in 3T3-L1 Cells

We reported previously that hydroxylated polymethoxyflavones (HPMFs) effectively suppressed obesity in high-fat-induced mouse. In this study, we further investigated the molecular mechanism of action of 5-hydroxy-3,6,7,8,3',4'-hexamethoxyflavone (5-OH-HxMF), one of major HPMFs in orange peel. Treatment of 5-OH-HxMF effectively inhibited lipid accumulation by 55-60% in a dose-dependent manner. The 5-OH-HxMF attenuated adipogenesis through downregulating adipogenesis-related transcription factors such as peroxisome proliferator-activated receptor gamma (PPARγ) and CCAAT/enhancer-binding proteins (C/EBPs), as well as downstream target fatty acid synthase and acetyl-CoA carboxylase (ACC). 5-OH-HxMF activated adenosine monophosphate-activated protein kinase signaling and silent mating type information regulation 1 (SIRTUIN 1 or SIRT1) in 3T3-L1 adipocytes to decrease lipid accumulation. In addition, the inhibition rate of lipid accumulation was compared between 5-OH-HxMF and 3,5,6,7,8,3',4'-heptamethoxyflavone (HpMF). 5-OH-HxMF inhibited lipid accumulation 15-20% more than HpMF did, indicating that hydroxyl group at position 5 can be a key factor in the suppression of adipogenesis.

Inhibitory Effects of Metabolites of 5-Demethylnobiletin on Human Nonsmall Cell Lung Cancer Cells

5-Demethylnobiletin is a unique flavonoid found in citrus fruits with potential chemopreventive effects against human cancers. We previously identified three metabolites of 5DN, namely 5,4'-didemethylnobiletin (M1), 5,3',4'- tridemethylnobiletin (M2), and 5,3'-didemethylnobiletin (M3) in mice fed 5DN. Herein, we investigated the inhibitory effects of these three metabolites on NSCLC cells. Our results demonstrated that M1, M2, and especially M3 showed stronger inhibition on the growth and colony formation of H460 and H1299 cells compared to 5DN. Three metabolites significantly inhibited the tumorsphere formation of A549 cells. Flow cytometry analysis showed that all metabolites induced cell cycle arrest and cellular apoptosis, and these effects were also stronger than that of 5DN. The inhibitory effects of these metabolites were associated with their ability to modulate the key signaling proteins related to cell proliferation and apoptosis. Overall, our results provided a basis for utilizing 5DN and its metabolites for chemoprevention of lung cancer.