Green tea polyphenols in drug discovery: a success or failure?

Green tea is made from unfermented dried leaves from Camellia sinensis and has been consumed by humans for thousands of years. For nearly as long, it has been used as a folk remedy for a wide array of diseases. More recently, a large number of in vitro and in vivo scientific studies have supported this ancient contention that the polyphenols from green tea can provide a number of health benefits. As these compounds are clearly safe for human consumption and ubiquitous in the food supply, they are highly attractive as lead compounds for drug discovery programs. However, as drugs, they are far from optimum. They are relatively unstable, poorly absorbed, and readily undergo a number of metabolic transformations by intestinal microbiota and human enzymes. Further, as these compounds target a wide array of biological systems, in vivo testing is rather difficult as effects on alternative pathways need to be carefully eliminated. The purpose of this review is to discuss some of the challenges and benefits of pursuing this family of compounds for drug discovery.     

Green Tea Polyphenols in drug discovery - a success or failure?

Green tea is made from unfermented dried leaves from Camellia sinensis and has been consumed by humans for thousands of years. For nearly as long, it has been used as a folk remedy for a wide array of diseases. More recently, a large number of in-vitro and in-vivo scientific studies have supported this ancient contention that the polyphenols from green tea can provide a number of health benefits. Since these compounds are clearly safe for human consumption and ubiquitous in the food supply, they are highly attractive as lead compounds for drug discovery programs. However, as drugs, they are far from optimum. They are relatively unstable, poorly absorbed, and readily undergo a number of metabolic transformations by intestinal microbiota and human enzymes. Further, since these compounds target a wide array of biological systems, in-vivo testing is rather difficult since effects on alternative pathways need to be carefully eliminated. The purpose of this review is to discuss some of the challenges and benefits of pursuing this family of compounds for drug discovery.     

Botanical ingredients in cosmeceuticals

During the last 10 to 15 years, complementary and alternative medicine (CAM) has become increasingly popular in the US. Within this realm of health care, oral and topical herbal supplements have become some of the most frequently used alternative therapies. Most herbal supplements are based on, or include, several botanical ingredients with long histories of traditional or folk medicine usage. Among the numerous botanical ingredients available on the market today, several are believed to confer dermatologic benefits. This article will focus on a select group of botanical compounds, many of which have long traditions in Asian medicine, with potential or exhibited dermatologic applications, including curcumin, Ginkgo biloba, ginseng, silymarin, soy, and tea tree oil. Other botanical agents, such as arnica, bromelain, chamomile, pomegranate, caffeine, green tea, licorice, and resveratrol, are also briefly considered. Some of these ingredients have been incorporated into topical formulations.     

Antioxidative and anti-carcinogenic activities of tea polyphenols

Tea (Camellia sinensis, Theaceace), a popular beverage consumed world-wide, has been studied for its preventive effects against cancer as well as cardiovascular, neurodegenerative, and other diseases. Most of the proposed beneficial effects have been attributed to the polyphenolic compounds in tea, but the nature of these activities and the molecular mechanisms of their actions remain unclear. Tea polyphenols are known to be strong antioxidants. Prevention of oxidative stress, modulation of carcinogen metabolism, and prevention of DNA damage have been suggested as possible cancer preventive mechanisms for tea and tea polyphenols. In this chapter, we discuss these topics in the light of biotransformation and bioavailability of tea polyphenols. We also review the preventive effects of tea polyphenols in animal models of carcinogenesis and some of the possible post-initiation mechanisms of action. Finally, we discuss the effects of tea consumption on cancer risk in humans. It is our aim to raise some of the unanswered questions regarding cancer prevention by tea and to stimulate further research in this area.     

Potential role of green tea catechins in various disease therapies: progress and promise

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Carbonic anhydrase inhibition as a cancer therapy: a review of patent literature, 2007 – 2009

Importance of the field: The functional contribution of membrane-bound extracellular carbonic anhydrases (CAs) to hypoxic tumor growth and progression has long been hypothesized; however, recent convergent evidence from a number of groups strongly implicates these CAs as key prosurvival enzymes during tumor hypoxia. From this perspective targeting the inhibition of cancer-associated CA enzymes, most notably CA IX and XII, has recently been identified as a mechanistically novel scientific opportunity with great potential as a new cancer drug target.

Areas covered in this review: This review covers world patent applications filed during the 2007 – 2009 period for small molecule approaches; non-small molecule approaches are not within the scope of this review.

What the reader will gain: The reader will be provided with a background of the biology of CAs as well as the recent research findings that have validated the crucial prosurvival role of CAs in hypoxic tumors. The review will highlight small molecule molecular methods that modulate CAs as an anti-cancer therapeutic strategy.

Take home message: Much of what has been reported in the patent literature during the period 2007 – 2009 is based on alleged therapeutic benefits of CA inhibitors in cancer. Recently appropriate CA-relevant cell and animal models of tumor hypoxia for the evaluation of compounds have become available and the verification of the ability of small molecules to modulate CA activity as a cancer therapy or as a diagnostic and/or prognostic tool is now possible and probable. The CA field will thus provide for a scientifically exciting and possibly rewarding next few years, accelerated by the growing interest in the potential clinical applications of this enzyme class in oncology.     

Lead finding from medicinal plants with hepatoprotective potentials

Background: Several lead compounds have been developed from natural resources as hepatoprotective. The hepatotoxic nature of the drugs, industrial toxins and drug-induced hepatotoxicity has been recognized as the major problem associated with liver diseases. Natural products including herbs have great potential in treating liver disorders. Objective: Botanicals have been used traditionally by herbalists and indigenous healers worldwide for several years for the prevention and treatment of liver disease and clinical research in this century has confirmed the efficacy of several plants in the treatment of liver disease. Many herbs used in several systems of alternative medicines have a long history of traditional use in revitalizing the liver and treating liver dysfunction and disease. Many of these herbs have been evaluated in clinical studies and are now being investigated phytochemically to understand their actions in a better way. Conclusion: An attempt has been made through this article to review the most potential medicinal plants with pharmacologically established hepatoprotective activity. Further, this article highlights their phytochemical profile and finds the effective leads from natural resources for the desired therapeutic benefit.     

Patents targeting γ-secretase inhibition and modulation for the treatment of Alzheimer's disease: 2004 – 2008

Background: Although Alzheimer's disease has been defined for over a century, at present there is no effective treatment. Amyloid deposition and plaque formation are widely believed to contribute to the pathology of the disease. As the etiology of plaque formation has become better understood, the search for therapies has bred small molecules capable of inhibiting or regulating the activity of γ-secretase. Objective: This paper reviews patents from the past 4 years claiming modulators or inhibitors of γ-secretase as a treatment for Alzheimer's disease. Method: One or two compounds from each patent were selected to represent the claimed chemical space. Compound selection was influenced by literature accounts, which are also discussed. Although an attempt has been made to include major contributions in the field, the list of patents reviewed should not be considered exhaustive. Conclusion: This review seeks to expand upon a previous review covering patents from 2000 – 2004. Since then there has been an increase in the number of structural and mechanistic approaches being pursued and several compounds have entered the clinic.     

Emerging drugs for lysosomal storage diseases

Importance of the field: Because orphan drug regulations encouraged development of drugs for rare disorders by granting marketing exclusivity for many years and other commercial benefits, treatment has become achievable for a few lysosomal storage disorders also. The presently available therapies, however, are not able to address all aspects of these multisystemic disorders and do not cure the patient. Therefore, there is a need for producing new drugs that are based on known pathophysiological mechanisms, such as enzyme replacement or inhibition of substrate synthesis, or which use new approaches to prevent the build-up of storage material.

Areas covered in this review: New compounds that are being designed by different pharmaceutical companies can be divided in two groups, enzyme targeted and substrate targeted drugs. Enzyme targeted drugs include substances that modify the enzyme to make it more accessible to organs such as the bone or the brain, enhance enzyme activity (chaperones) or activate enzyme synthesis by small molecules that induce read-through of premature stop codons of genes that bear a nonsense mutation. To the group of substrate targeted drugs belong substances that inhibit the synthesis or modify the structure of the substrate (substrate deprivation or substrate optimization, respectively). For this review, a literature research has been undertaken that covers the years 1968 – 2010.

What the reader will gain: The reader of this paper will get an overview of drugs for lysosomal storage disorders that are on the market or are under development. This will help in the understanding of the pathophysiological mechanisms that underlie these rare metabolic diseases. In addition, the reader should realize that the increasing number of these very expensive drugs may lead to significant consequences for the health economic system.

Take home message: In the last years, the interest of scientists and pharmaceutical companies in lysosomal storage disorders has increased dramatically, leading to the production of a rising number of different drugs. These drugs act at several stages of the pathophysiological cascade, for example, at the level of the substrate (substrate deprivation) or of the enzyme (enzyme enhancement). The presently available treatments are not able to address all clinical manifestations of these disorders, and it will still take a long time until new drugs are developed that are capable of curing the patients.     

CCR3 antagonists: a survey of the patent literature

Background: Since the mid-1990s, there has been significant effort invested in the discovery and clinical development of CC chemokine receptor-3 (CCR3) antagonists as potential therapeutics for airway disease. Objectives/methods: A patent literature review is presented of small molecule CCR3 antagonists comprising the years 2004 to the present. The patent searches were conducted using Derwent Discovery (World patent index) and PCT publication databases. Results/conclusion: At least two small molecule compounds have been reported to advance into clinical trials. However, data that support a definitive proof-of-concept in humans have yet to be disclosed. Nevertheless, patents from various pharmaceutical companies have continued to emerge, revealing diverse chemical classes of potent CCR3 antagonists and reflecting a continued broad interest in this area.     

Glycosidase inhibitors: a patent review (2008 – 2013)

Introduction: In the recent decades, the interest on glycosidases has dramatically increased, mainly because these enzymes play a key role in many biological processes. The importance of these enzymes is also reflected by a number of diseases, which result from the lack or dysfunction of a given glycosidase, as well as by the use of glycosidase inhibitors in the treatment of metabolic disorders or viral infections. Based on the biological potential associated to these enzymes, several glycosidase inhibitors have been developed. In this review, the most important inhibitors targeting these enzymes, including the disaccharides, iminosugars, carbasugars, thiosugars and other non-glycosidic compounds will be discussed and special attention will be given to the ones that are currently used clinically.

Areas covered: This review summarizes and characterizes the current knowledge regarding the classes of glycosidase inhibitors that have therapeutic potential in a wide range of diseases. It highlights the relevant research, patents and patent applications filed in the past years on the field.

Expert opinion: Since the glycosidase inhibitors are involved in several chronic diseases and possibly pandemic, the pharmaceutical research toward developing new generations of these molecules is very important to public health in the world. The unique combination of these compounds – for example, they share many properties with natural carbohydrates and also possess distinct specific characteristics – makes them precious for pharmaceutical companies in an attempt to search for potential new drugs. Currently, the most promising compounds are the iminosugars and thiosugars due to their better oral bioavailability.     

A subacute toxicity evaluation of green tea (Camellia sinensis) extract in mice

Green tea is believed to be beneficial to health because it possesses antioxidant, antiviral and anticancer properties. The potential toxicity of green tea when administered at high doses via concentrated extracts, however, has not been completely investigated. The objective of the present study was to evaluate the safety of green tea extract in ICR mice using a subacute exposure paradigm. In this study, mice were orally administered (gavage) green tea extract at doses of 0 (as normal group), 625, 1250 and 2500 mg/kg body weight/day for 28 days. The results showed that oral administration of green tea extract did not cause adverse effects on body weight, organ weights, hematology, serum biochemistry, urinalysis or histopathology. Additionally, administering green tea extract via gavage significantly reduced triglyceride and cholesterol levels. These observed effects could be attributed to the high levels of catechins present in green tea as these compounds have been reported to have beneficial health effects. The no-observed-adverse-effect level for green tea extract derived from the results of the present study was 2500 mg/kg body weight/day.     

Recent patenting activities in the discovery and development of vasopressin V2 receptor agonists

Introduction: Vasopressin V₂ agonists are well known as effective therapies in the treatment of central diabetes insipidus and nocturnal enuresis. Furthermore, given their mode of action, these particular agonists have more recently been considered, in both the pharmaceutical industry and in academia, as viable therapies for urological conditions such as nocturia.

Areas covered: For the past 10 years, significant progress has been made in the discovery and development of vasopressin V₂ agonists. This article provides the reader with information on the recent progress in the discovery and development of these compounds based on patents published from 2002 onward. Specifically, the article looks at the discovery of new non-peptide agonists as well as well as novel formulations of the vasopressin V₂ agonist desmopressin.

Expert opinion: The V₂ receptor is currently one of the hottest therapeutic targets investigated for the treatment of urinary disorders such as nocturia and central diabetes. Over the past 10 years, significant progress has been made in the discovery and development of vasopressin V₂ receptor agonists, for the treatment of these disorders. The author anticipates that these agonists will be launched to market in the not-too-distant future.     

Metabolism,Genotoxicity, annd Carcinogenicity of Comfrey

Comfrey has been consumed by humans as a vegetable and a tea and used as an herbal medicine for more than 2000 years. Comfrey, however, produces hepatotoxicity in livestock and humans and carcinogenicity in experimental animals. Comfrey contains as many as 14 pyrrolizidine alkaloids (PA), including 7-acetylintermedine, 7-acetyllycopsamine, echimidine, intermedine, lasiocarpine, lycopsamine, myoscorpine, symlandine, symphytine, and symviridine. The mechanisms underlying comfrey-induced genotoxicity and carcinogenicity are still not fully understood. The available evidence suggests that the active metabolites of PA in comfrey interact with DNA in liver endothelial cells and hepatocytes, resulting in DNA damage, mutation induction, and cancer development. Genotoxicities attributed to comfrey and riddelliine (a representative genotoxic PA and a proven rodent mutagen and carcinogen) are discussed in this review. Both of these compounds induced similar profiles of 6,7-dihydro-7-hydroxy-1-hydroxymethyl-5H-pyrrolizine (DHP)-derived DNA adducts and similar mutation spectra. Further, the two agents share common mechanisms of drug metabolism and carcinogenesis. Overall, comfrey is mutagenic in liver, and PA contained in comfrey appear to be responsible for comfrey-induced toxicity and tumor induction.     

Green tea in chemoprevention of cancer

The concept of prevention of cancer using naturally occurring substances that could be included in the diet consumed by the human population is gaining increasing attention. Tea, next to water, is the most popularly consumed beverage in the world and it is grown in about 30 countries. Abundant data, amassed from several laboratories around the world in the last ten years, provided convincing evidence that polyphenolic antioxidants present in tea afford protection against cancer risk in many animal-tumor bioassay systems. The epidemiological studies, though inconclusive, have also suggested that the consumption of tea is associated with a lowered risk of cancer. Much of this work has been done on green tea; less is known about black tea. Green tea contains many polyphenolic antioxidants, and (-)-epigallocatechin-3- gallate (EGCG) is the key polyphenolic antioxidant believed to be responsible for most of the cancer chemopreventive properties of green tea. This review will discuss these effects and the molecular mechanisms associated with the biological response to green-tea polyphenols.      

Terpenes and derivatives as a new perspective for pain treatment: a patent review

Introduction: Terpenes are natural compounds found in several organisms belonging to the animal and plant kingdoms. They constitute the largest class of natural products with > 55,000 known compounds structurally diversified. Several studies have attributed to this big family of compounds a range of pharmacological properties, such as anticancer, antimicrobial, antifungal, antiviral, antihyperglycemic, analgesic, anti-inflammatory and antiparasitic.

Areas covered: In this review, the authors summarize therapeutic patent applications concerning the employment of terpenes for pain relief, focusing on the perspective for these compounds to become candidates for new drugs intended to control painful syndromes.

Expert opinion: Over years of tremendous academic and industrial investment in the characterization of the analgesic action of terpenes, there was the development of a successful product that has been well-accepted clinically. Furthermore, there is still hope that new therapeutic options for the control of painful syndromes will be developed from terpenes, which have been shown to be great candidates for this purpose because of the range of pharmacological mechanisms in important target sites.     

A case of poppy tea dependence in an octogenarian lady

While poppy seed and poppy tea dependence has been described, it is unusual to see such patients actively seek treatment in India. We report the case of an 82‐year‐old client with dependent use of poppy for 55 years. She was brought for treatment as access to poppy became difficult following legal restrictions. She was successfully maintained on buprenorphine maintainence.[Subodh BN, Murthy P, Chand PK, Arun K, Bala SN, Benegal V, Madhusudhan S. A case of poppy tea dependence in an octogenarian lady. Drug Alcohol Rev 2009]     

Inhibitors of cathepsin K: a patent review (2004 – 2010)

Introduction: Cathepsin K is a lysosomal cysteine protease involved in osteoclast-mediated bone resorption. Inhibition of cathepsin K represents a potentially attractive therapeutic approach for treating diseases characterized by excessive bone resorption, such as osteoporosis.

Areas covered: The present review provides an overview of low molecular weight cathepsin K inhibitors published in the patent literature from July 2004 to 2010. Different chemotypes are surveyed and listed according to electrophilic warhead type. Relevant information from original research articles in peer-reviewed journals and clinical investigations is also described.

Expert opinion: Between 2004 and 2010, more than 50 patent applications have appeared, underlining the continued interest in small molecule cathepsin K inhibition for therapeutic intervention. Most compounds claimed are peptide-derived inhibitors displaying a reversible binding nitrile or ketone warhead. The success of these compounds in the clinic will be determined by the selectivity that can be achieved against other off-target cathepsin. In this respect, eliminating lysosomotropic characteristics may prove to be crucial in the design of selective cathepsin K inhibitors. During the review period, ONO-5334 and odanacatib have progressed to Phase II and Phase III clinical trials, respectively. The results of these studies are eagerly awaited and may determine the future of these agents as disease-modifying therapeutics.     

Analysis of urinary metabolites of tea catechins by liquid chromatography/electrospray ionization mass spectrometry.

Tea has been proposed to have beneficial health effects which have been attributed to the polyphenolic compounds known as catechins. The bioavailability and biotransformation of these compounds, however, are not clearly understood. In this study, we used liquid chromatography/electrospray ionization-mass spectrometry (LC/ESI-MS) to determine urinary glucuronidated and sulfated tea catechins and their metabolites (including methylated and ring-fission metabolites) based on the detection of deprotonated molecular ions and aglycone fragment ions. The compound resolution was achieved both chromatographically and mass spectroscopically. After green tea administration, the major conjugates appeared in human, mouse, and rat urine samples were identified as monoglucuronides and monosulfates of (-)-epigallocatechin (EGC) and (-)-epicatechin. We also found O-methyl-EGC-O-glucuronides and -O-sulfates and O-methyl-epicatechin-O-sulfates in human urine. (-)-5-(3',4',5'-Trihydroxyphenyl)-gamma-valerolactone (M4) and (-)-5-(3',4'-dihydroxyphenyl)-gamma-valerolactone (M6), the ring-fission metabolites of EGC and (-)-epicatechin, respectively, were also predominantly in monoglucuronide and monosulfate forms in the urine. In comparison to rats, the urinary metabolite profiles of tea catechins in mice resemble more closely to those in humans. This is the first report describing direct simultaneous analysis of multiple tea catechin conjugates in urine samples. This method will allow more thorough investigations of the biotransformation of tea polyphenols.