Natural resins and bioactive natural products thereof as potential antimicrobial agents

Natural products and their derivatives have historically been invaluable as a source of therapeutic agents and have contributed to the discovery of antimicrobial agents. However, today with the development of drug-resistant strains, new scaffolds and new sources of bioactive compounds are needed. To this end, plant derived natural resins are reviewed for their potential application as antimicrobial agents. Natural gums, extracts of the whole resins, as well as specific extracts, fractions, essential oils and isolated compounds from the above resins are discussed in terms of their antifungal, antibacterial, and antiprotozoal activity.     

Antibacterial agents: patent highlights January to June 2003

This review presents an overview of 38 patents published between January and June 2003 on different classes of antibacterial agents. Patent disclosures on novel oxazolidinone and macrolide derivatives with strong antibacterial activity continue to dominate patent publications in recent years. A use patent of a linezolid formulation for ear infections in infants and pre-operative procedure is highlighted. Disclosures on novel dual action oxazolidinone-quinolone hybrids designed to overcome bacterial resistance and new macrolide derivatives with antimycobacterial activity are also presented. Patents on beta-lactam and quinolone antibiotics focus on the development of new processes and formulations to improve cost, purity and stability of existing agents in clinical use. Novel antibacterial agents (DNA polymerase and D-glutamate racemase inhibitors) as potential lead compounds are also presented.     

Platinum group antitumor chemistry: design and development of new anticancer drugs complementary to cisplatin

In the next two decades, the world is expected to see around 20 million cases of cancer. Moreover, the types of cancer will vary considerably from country to other. Therefore, all efforts will be needed to face such a vast diversity of problems. With current annual sales of about $500 millions, the platinum(II) complex known as cisplatin [cis-(NH3)2PtCl2] is still one of the most effective drugs to treat testicular, ovarian, bladder and neck cancers. Since it was launched in 1978 there has been a rapid expansion in research to find new, more effective metal-based anticancer drugs and to study their interactions with biological systems. This study gives an up to date overview of the anticancer chemistry of the platinum group elements platinum, palladium, and nickel with an emphasis on the new strategies used in the development of new antitumor agents. Methodologies for application of bulky aromatic or aliphatic nitrogen ligands, chiral organic moieties, chelates containing other donor atoms than nitrogen, and biologically active ligands in the design of agents analogous to cisplatin are presented. The review also aims to highlight the class of the unconventional complexes that violate the empirical structure-activity rules (SAR) of platinum compounds and the common features and structural differences between the most successful anticancer complexes that are currently in human clinical trials.     

Salicylanilide ester prodrugs as potential antimicrobial agents--a review

Salicylanilides have been a subject of interest in medicinal chemistry as a group with a wide range of biological activities. The antibacterial (including antimycobacterial) and antifungal activities have come to be viewed as very significant. The synthesis of new prodrugs to counter a number of problematic properties of salicylanilides is a current trend. This article brings together the known basic facts about these prodrugs, particularly about the different mechanisms of the antimicrobial action of salicylanilides, including salicylanilide toxicity and undesired effects. The largest part of this group consists of antimicrobial salicylanilide esters with different organic acids, e.g. acetates, carbamates, esters with N-protected amino acids, and mutual antibacterial compounds with known antibacterial agents (β-lactames and linezolid), with the activity and structure-activity relationships of these compounds being of particular interest. This review summarizes the activity of salicylanilides as potential virulence inhibitors attributable to a blockade of the type III secretion pathway. Many salicylanilide ester derivatives have been demonstrated an effective and promising treatment against pathogenic fungi and bacteria (especially against Gram-positive, tuberculous and atypical mycobacterial strains), including strains such as methicillin-resistant Staphylococcus aureus and isoniazid-resistant mycobacteria which are resistant to one or more clinically used drugs.     

Preparation and biological evaluation of 6/7-trifluoromethyl(nitro)-, 6,7-difluoro-3-alkyl (aryl)-substituted-quinoxalin-2-ones. Part 3.

A new series of quinoxalinones 6/7-trifluoromethyl or nitro- and 6,7-difluoro substituted bearing various side-chains (alkyl, halogenoalkyl, benzyl and phenyl groups) at C-3 of the ring system was synthesized and submitted to preliminary in vitro evaluation for antibacterial, antifungal, antimycobacterial, anticancer and anti-HIV activities. Results of these screenings showed that compounds 23-28 exhibited a good inhibition activity against various strains of Candida. Compound 24 showed also an interesting in vitro anticancer activity.     

三唑类抗真菌药物临床应用研究进展

近年来,随着免疫抑制治疗、化疗、实体器官移植的增多,中心静脉置管术以及心脏人工瓣膜植入术等介入性治疗的开展,发生侵袭性真菌感染（invasive fungal infection,IFI）的患者人数逐年上升。三唑类抗真菌药物抗菌谱广、毒性较小、耐受性较好,用于治疗侵袭性真菌感染最为广泛。但由于其本身也作用于哺乳动物细胞色素P450酶系,易与其他药物发生相互作用产生毒性。本文对目前国内外已广泛用于临床的三唑类药物及近年来研发的新型三唑类药物的作用及应用特点进行比较,并对相关研究进展进行综述。     

Multitarget ligands in antibacterial research: progress and opportunities

Introduction: Resistance to current antibacterial therapies is an inevitability that represents a significant global health concern. Bacteria have the capacity to render all current drug treatments ineffective, which places a demand on the drug discovery community to constantly develop new antibacterial agents. Compounds that inhibit multiple biological targets, often referred to as multitarget ligands, are an inviting prospect in antibacterial research because, although they will not solve the issue of resistance, they might help to delay the onset.

Areas covered: This review covers some of the recent progress in identifying new ligands that deliberately interact with more than one essential biological target in bacteria. The two principal areas covered are inhibitors of DNA replication and cell wall biosynthesis.

Expert opinion: Antibacterial programs for the design of multitarget ligands present an important opportunity for production of antibacterial agents. Their longevity, due to slow development of resistance, is comparable to that seen with other successful agents – but is much improved over single-targeted agents for which resistance can appear in vitro overnight. The preclinical development of these agents will have to overcome the standard problems of antibacterial discovery. Such problems include optimization of characteristics favoring cell entry and particularly the demonstration of selectivity of inhibition of the desired multiple targets without inhibition of other bacterial or any mammalian functions.     

美国市场30年(1980-2009)最热销的抗感染药品演变分析(Ⅰ)

该文所关注的是美国医院处方服务署(AHFS)编写的、每年出版一次的《药物信息》"Drug Information"以及每年公布一次的美国市场上最热销的前200位(200top drugs or 300 top drugs)。本文(Ⅰ)部分所关注的是2000年-2009年中10年间美国市场最热销的前200位药品(200 top drugs)中所涉及的抗感染药品(包括:抗微生物药、抗病毒药、抗真菌药和疫苗等),以及这些药物在临床使用中的演变。列入此10年间的Top200药物中的抗感染药品有35种:即大环内脂类有4种,磺胺类有1种,喹诺酮类有5种,青霉素类有2种,四环素类有3种,头孢菌素类有5种,抗病毒类有5种,抗真菌类有5种,氨基糖苷类1种,抗厌氧菌与原虫类等4种。这对于我国当前的医疗制度改革与促进抗菌药物的合理使用提供了可靠的参考依据。     

Antibacterial agents: patent highlights January to June 2004

This review presents highlights of 32 patents, published between January and June 2004, detailing different classes of antibacterial agents. Disclosures on novel oxazolidinone derivatives with antibacterial activity continue to dominate patent publications in recent years. Novel oxazolidinone derivatives active against linezolid-resistant cocci are reviewed. Patents on beta-lactam antibiotics focused mainly on developing new processes and formulations to improve cost, purity and pharmacokinetic parameters of existing clinical agents. Disclosures on novel potential dual-acting macrolide-quinolone hybrids designed to overcome erythromycin resistance, and new macrolide derivatives with antimycobacterial activity are described. Also presented are novel antibacterial agents, including peptide deformylase and cell-wall inhibitors, and those with undefined mechanisms of action as potential lead compounds, as well as quinolone and quinoline derivatives.     

Towards species-specific antifolates

Dihydrofolate reductase (DHFR) plays an essential role in cellular biochemistry and has been a well-recognized drug target for over fifty years. Antifolate inhibitors of DHFR, including clinically used therapeutics such as methotrexate, trimethoprim, and pyrimethamine have been successful as anticancer, antibacterial, antifungal and antiparasitic agents. As resistant strains of these microorganisms evolve and as new disease threats arise, the need for new antifolates that are potent and specific for infectious organisms becomes more pressing. Several new antifolates have been reported over the past decade; many of these are potent against a particular species of DHFR, but achieving the goal of potency and selectivity has proven to be more difficult. This review will describe recent advances in attaining species selectivity in developing new antifolates. Specifically, advances in developing inhibitors against Pneumocystis jirovecii and Plasmodium falciparum, the causative agents in pneumocystis pneumonia and malaria, respectively, will be presented.     

Recent advances in antifungal drug development targeting lanosterol 14α-demethylase (CYP51): A comprehensive review with structural and molecular insights

Fungal infections are posing serious threat to healthcare system due to emerging resistance among available antifungal agents. Among available antifungal agents in clinical practice, azoles (diazole, 1,2,4-triazole and tetrazole) remained most effective and widely prescribed antifungal agents. Now their associated side effects and emerging resistance pattern raised a need of new and potent antifungal agents. Lanosterol 14α-demethylase (CYP51) is responsible for the oxidative removal of 14α-methyl group of sterol precursors lanosterol and 24(28)-methylene-24,25-dihydrolanosterol in ergosterol biosynthesis hence an essential component of fungal life cycle and prominent target for antifungal drug development. This review will shed light on various azole- as well as non-azoles-based derivatives as potential antifungal agents that target fungal CYP51. Review will provide deep insight about structure activity relationship, pharmacological outcomes, and interactions of derivatives with CYP51 at molecular level. It will help medicinal chemists working on antifungal development in designing more rational, potent, and safer antifungal agents by targeting fungal CYP51 for tackling emerging antifungal drug resistance.     

Polyoxins and nikkomycins: progress in synthetic and biological studies

Polyoxins and nikkomycins are naturally-occurring peptidyl nucleoside antibiotics. As inhibitors of chitin synthetase, they exhibit antifungal activity, but lack antibacterial activity. Since they also lack mammalian toxicity, they represent potentially useful models for the development of effective agents for the treatment of opportunistic fungal infections. Direct clinical application of the natural peptidyl nucleosides is compromised by their attenuated in vivo activity, apparently due to their hydrolytic lability and inefficient fungal cell wall permeability. Thus, extensive efforts have focused on syntheses of natural peptidyl nucleosides, their components and analogs in anticipation of establishing useful structure-activity-relationships (SAR) for the development of new antifungal agents. A comprehensive and critical review of the synthetic effort and subsequent biological studies reveals that while much has been accomplished, ideal antifungal agents have not yet been developed from the natural peptidyl nucleoside leads. The need for continued study of agents with novel modes of action is emphasized by the realization that other structurally varied antifungal agents currently used clinically have limitations and often severe side effects, including nephrotoxicity.     

Antibacterial,antifungal, and antimycobacterial activity of Ilex aquifolium leaves

The objective of this study was to examine antibacterial, antifungal, and antimycobacterial properties of Ilex aquifolium L. (Aquifoliaceae) growing in Turkey. The ethanol, ethyl acetate, chloroform, and n-hexane extracts prepared from the leaves of I. aquifolium were tested against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Enterobacter aerogenes, Proteus vulgaris, Salmonella typhimurium, and Candida albicans for antibacterial and antifungal evaluation using the microdilution broth susceptibility assay. In addition, antimycobacterial activity of the crude extracts of I. aquifolium was evaluated by microplate Alamar blue assay. The results showed that the extracts tested, except n-hexane, possessed moderate antibacterial and antifungal activity varying from 62.5 to 250?μg/mL. On the other hand, the ethanol extract of the leaves exhibited a minimum inhibitory concentration value (MIC) against Mycobacterium tuberculosis H₃₇Ra strain of 200 μg/mL.     

三唑类抗真菌药物致肝损伤的研究进展

药物性肝损伤是临床常见的药源性疾病之一,也是药物临床试验失败和撤市的主要原因之一。三唑类抗真菌药物是治疗侵袭性真菌感染的主要药物,对多种临床常见真菌具有良好的抗菌活性,临床应用广泛。但随着三唑类抗真菌药物临床应用的日益增多,其肝损伤不良反应的报道也越来越多,给该类药物的临床应用带来一定挑战。三唑类抗真菌药物致肝损伤的影响因素包括药物浓度、年龄、基因多态性、炎症等,发生机制包括氧化应激、胆汁淤积、调节细胞色素P450的表达及脂质代谢异常等多个方面。本文将对三唑类抗真菌药物致肝损伤的临床特点、影响因素及发生机制的研究进展进行综述,以期为该类药物肝损伤的深入研究及临床安全合理应用提供参考。     

Repurposing of the gold drug auranofin and a review of its derivatives as antibacterial therapeutics

Multidrug resistance (MDR) is a significant issue associated with the clinical application of antibiotics. It is also challenging to discover and develop new antibiotics with novel scaffolds. Therefore, the repurposing of existing drugs has become a promising strategy for antibiotic drug discovery. Auranofin, an approved gold metallic drug, has been used for the treatment of rheumatoid arthritis (RA) for many years. Recent research revealed that auranofin has strong antibacterial activity against multiple Gram-positive bacteria by inhibiting thioredoxin reductase (TrxR). These results inspired the development of gold complexes as antibacterial agents. Herein, we discuss recent advances in the development of auranofin and other gold complexes as antibacterial agents, providing a new viewpoint for the treatment of bacterial infection.     

Semisynthetic cephalosporins with antifungal activity: laboratory studies on 2-pyridinethiol 1-oxide cephalosporins

Cephalosporins are chemotherapeutic agents whose spectrum and use are limited to antibacterial activity. Therefore, it was of interest to find several new semisynthetic cephalosporins which possess in vitro antifungal activity against Trichophyton mentagrophytes, Candida albicans and certain other yeasts. Five new cephalosporins containing the 2-pyridinethiol 1-oxide grouping were examined. Four with this heterocyclic moiety in the 3-position were found to have activity. One with the grouping in the 7-acyl-side chain was inactive. The degree of the antifungal activity was influenced by the substituent at the 7-position. The cephalosporin with a p-hydroxyphenylglycyl side chain was the most potent against the fungal strains studied. Despite this in vitro antifungal activity, none of the compounds protected mice against a systemic Candida albicans infection. All of these cephalosporins had broad spectrum in vitro and in vivo antibacterial activity.     

中药协同抗真菌药物抗念珠菌的研究进展

侵袭性念珠菌感染已成为备受关注的公共卫生问题,而现行治疗念珠菌感染的药物有限,联合用药是一种实用有效的新药开发策略。从天然植物（尤其是药用植物）中提取的化合物及其衍生物与传统的抗真菌剂联合使用对杀灭念珠菌具有显著的协同作用。归纳了念珠菌对传统抗真菌药物的耐药情况,并总结了中药协同传统抗真菌药物的抑菌活性和抑菌机制,以期为抗念珠菌新型治疗策略的研究提供参考依据。     

含三唑的抗微生物药物研究进展

含三唑的化合物是目前抗微生物药物研究开发中的热点领域之一。本文结合国内外文献简述了在抗菌、抗真菌、抗结核、抗病毒方面已经上市及正在进行临床试验的含三唑的药物,着重强调了含三唑的抗微生物药物及其构效关系的研发近况。随着研究的进一步发展,有望成功地开发出更多具有显著生物学活性的新药。     

戊二酰亚胺类抗生素的研究进展*

戊二酰亚胺娄抗生素从链霉菌发酵液提取分离得到,具有抗真菌、抗细菌、抗原虫、抗病毒、抗肿瘤及免疫抑制等多种生物活性。本类抗生素包括具有经过多年发展的环己酰亚胺、S-632类以及斩近发现的具有明显抑制肿瘤细胞迁移的大环内酯结构的migrastatin家族等。现对戊二酰亚胺类抗生素及其类似物的结构、活性和构效关系进行综述,并简单介绍了几个非微生物来源及化学合成的酰亚胺类物质。     

Peptide deformylase – a promising therapeutic target for tuberculosis and antibacterial drug discovery

Background: Tuberculosis (TB) remains the most important infectious disease causing morbidity and death, due to the human pathogen Mycobacterium tuberculosis. The emergence of multi-drug-resistant and extensively-drug-resistant forms of TB have resulted in an increase in the number of TB cases. Thus, there is an urgent need to identify new drugs with novel targets to ensure future therapeutic success. Studies have indicated that peptide deformylase is an interesting potential candidate for discovering antimicrobial agents. Objective: To explore the role of peptide deformylase, a highly conserved metalloprotease and an essential enzyme in bacterial life cycle, as a target for antibacterial as well as antimycobacterial drug development. Methods: This review is based on recent published literature and online resources related to peptide deformylase inhibitors and their anbacterial potential. Results/conclusion: Peptide deformylase is an emerging therapeutic target for the treatment of tuberculosis and peptide deformylase inhibitors can act as potential future antibacterial agents.