Triterpene derivatives as inhibitors of protein involved in the inflammatory process: molecules interfering with phospholipase A2, cycloxygenase, and lipoxygenase

Over the past years, there was an explosion in the knowledge of the protein target and molecular mechanism associated with various disease types and in the new research of drugs of natural origin. The key idea is to evaluate bioactive natural products interacting with protein domains of different genetic origin but structurally preserved to develop libraries of compounds biologically validated and selected from an evolutionistic point of view. Compared with synthetic compounds, natural products have a major number of unused scaffolds and not comparable to the libraries of synthetic compounds, and could represent a promising starting points for the discovery of new bioactive compounds. Many natural products are reported to interact with proteins involved in serious diseases, such as inflammation and cancer. Recently various chemical classes of plant secondary metabolites have emerged as potential therapeutic compounds in several inflammatory diseases. Owing to the findings that triterpenoids, a common class of plant secondary metabolites, have anti-inflammatory and anti-cancer effects on humans, the interest in their potential application in human health and disease is increasing. The present review describes anti-inflammatory triterpenes derivatives from plant and fungi reported during the last two decades in order to provide an account of this field of investigation, sorting compounds according to their targets, phospholipase A(2) (PLA(2)), cycloxygenase (COX), and lipoxygenase (LOX). The attempt is also being made to enumerate the possible leads for further synthetic and drug discovery program development.     

天然产物药物开发中资源问题的解决方案概述

天然产物是现代药物开发中先导结构的重要来源,但是天然活性先导化合物在天然生命体中往往含量微少,这严重限制了其临床前及临床研究,难以满足其后续的市场需求.本文通过具体案例剖析,归纳总结了源于结构复杂的天然产物在药物开发中资源问题的几种有效解决方案:①寻找量丰的核心天然骨架,再经半合成制备;②寻找其量丰的生源合成前体经仿生合成制备;③由量丰天然类似物经化学转化制备;④简化先导结构再全合成制备.希望为解决复杂天然产物药物开发中的资源供应提供借鉴.     

Current approaches to discover marine antileishmanial natural products

Leishmaniasis is a neglected infectious disease caused by kinetoplastid protozoans. An urgent need for novel chemotherapeutics exists. The current approaches to discover new antileishmanial compounds present many drawbacks, including high-cost and time-consuming bioassays. Thus, advances in leishmaniasis treatment are limited, and the development of screening assays is hindered. The combination of multidisciplinary approaches using standardised methods and synchronous projects could be an alternative to develop novel drugs for leishmaniasis treatment. In this review, we discuss the current status of leishmaniasis occurrence and treatment. In addition, we address the advantages and limitations of in vitro leishmaniasis bioassays and discuss the findings of drug discovery research using natural products. Finally, we comprehensively review the marine natural products that are active against Leishmania spp., including their natural sources and bioactivity profile.     

Lichenicolins A and B, new bisnaphthopyrones from an unidentified lichenicolous fungus, strain LL-RB0668

Lichenicolous fungus LL-RB0668 was isolated from a processed lichen thallus on a modified Lilly-Barnett solid medium. Two new bisnaphthopyrone compounds, lichenicolins A (1) and B (2), were isolated from the culture broth of this organism fermented on a rice-based solid medium. These results demonstrate that lichen-associated fungi potentially are a good resource for new bioactive natural products for current screening programs.     

Development and applications of new reactions for construction of basic structures of natural products]

This review deals with the development of efficient methods to construct the basic structure of natural products and the versatile methods to control the stereochemistry, and these methods were applied to the synthesis of natural compounds. The photochemical spirodienone formation reaction was applied to the synthesis of proaporphine alkaloids. The alternative spirodienone formation reactions by the metal-catalyzed degradation reaction of phenolic alpha-diazoketones were applied to many natural spirocyclic compounds, such as chamigrane type sesquiterpenes, spirovetivane type phytoalexins, marine natural products, and so on. Lewis acid mediated spirocyclization reaction of cyclohexene bis-acetal derivative was developed, and this reaction was applied to the synthesis of aphidicolane and stemodane diterpenes. The regioselective cleavage reaction of the cyclopropane ring of tricyclooctanone derivatives was used for the syntheses of diquinane and triquinane compounds. A chiral pool synthesis of several aromadendrane sesquiterpenes was achieved via common tricyclic enone intermediates. The synthesis of macrocarpals, coupling products of aromadendrane skeleton and isopentylphloroglucinol dialdehyde, was also accomplished for the first time using an arene Cr(CO)3 complex as a chiral benzyl cation equivalent. The Fe(diene)(CO)3 complexes were used for the highly stereoselective asymmetric synthesis of several natural products, such as insect pheromones and alkaloid, as a versatile mobile chiral auxiliary.     

Sesquiterpenes: natural products that decrease cancer growth

Despite recent advances in our understanding of the biological processes leading to the development of cancer, there is still a need for new and effective agents to help bring this disease under control. One of the oldest and most effective strategies for developing new chemotherapeutics is the isolation and evaluation of chemicals of natural origin. The importance of natural products for drug discovery has been impressive: One has to only look at the number of clinically active drugs that are used in cancer therapy to see how many are either natural products or are based on natural products. It is also apparent that materials from natural sources are excellent probes (indicators) for cellular targets that, when modulated, may have a deleterious effect upon the survival or proliferation of tumor cells. And the search goes on. Sesquiterpenes are a class of naturally occurring molecules that have demonstrated therapeutic potential in decreasing the progression of cancer. These molecules are 15-carbon isoprenoid compounds that are typically found in plants and marine life. Although this class of compounds has frequently provided encouraging leads for chemotherapeutics, they have not been evaluated as potential anticancer agents. In this review, we provide a current overview of sesquiterpenoids that have potential as anticancer agents.     

Discovery,characterization, and structure-activity relationships studies of proapoptotic polyphenols targeting B-cell lymphocyte/leukemia-2 proteins

Among the most promising chemopreventive agents, certain natural polyphenols have recently received a great deal of attention because of their demonstrated inhibitory activity against tumorigenesis. In view of their anticancer properties, these compounds also hold great promise as potential chemotherapeutic agents. However, to translate these chemopreventive agents into chemotherapeutic compounds, their exact mechanisms of action must be delineated. By using a multidisciplinary approach guided by modern nuclear magnetic resonance spectroscopy techniques, fluorescence polarization displacement assays, and cell-based assays, we have begun to unravel the mechanisms of actions of certain polyphenols such as Gossypol (a compound from cotton seed extracts) and Purpurogallin (a natural compound extracted from Quercus sp. nutgall) and their derivatives. Our findings suggest that these natural products bind and antagonize the antiapoptotic effects of B-cell lymphocyte/leukemia-2 (Bcl-2) family proteins such as Bcl-x(L). Our in vitro and in vivo data not only open a window of opportunities for the development of novel cancer treatments with these compounds but also provide structural information that can be used for the design and development of novel and more effective analogues.     

Chemistry and biology of new marine alkaloids from the indole and annelated indole series

Chemistry and biology of marine natural products from the indole and annelated indole series have become an attractive research field for development of new pharmacological lead substances. In the past years some of the isolated natural organic compounds were synthesized by chemists and evaluated with great enthusiasm to find new lead natural compounds against different diseases. In this review the latest results for new compounds including isolation, biological evaluation, synthetic pathways and some retrosynthetic analyses are summarized.     

Antagonism of human formyl peptide receptor 1 with natural compounds and their synthetic derivatives

Formyl peptide receptor 1 (FPR1) regulates a wide variety of neutrophil functional responses and plays an important role in inflammation and the pathogenesis of various diseases. To date, a variety of natural and synthetic molecules have been identified as FPR1 ligands. Here, we review current knowledge on natural products and natural product-inspired small molecules reported to antagonize and/or inhibit the FPR1-mediated responses. Based on this literature, additional screening of selected commercially available natural compounds for their ability to inhibit fMLF-induced Ca^2 + mobilization in human neutrophils and FPR1 transfected HL-60 cells, and pharmacophore modeling, natural products with potential as FPR1 antagonists are considered and discussed in this review. The identification and characterization of natural products that antagonize FPR1 activity may have potential for the development of novel therapeutics to limit or alter the outcome of inflammatory processes.     

临床试验中的天然产物：抗寄生虫、抗病毒和神经系统药物

本文综述了从1998年到2005年底进行临床试验或注册的抗寄生虫、抗病毒和作用于神经系统的天然产物、半合成天然产物及天然产物衍生药物。     

Sleeping sickness pathogen (Trypanosoma brucei) and natural products: therapeutic targets and screening systems

Trypanosoma brucei is the causative agent of human African trypanosomiasis (sleeping sickness) which is fatal if left untreated. This disease occurs in 36 African countries, south of the Sahara, where 60 million people are at risk of acquiring infection. The current chemotherapy relies on only four drugs, three of which were developed more than 60 years ago. These drugs have many limitations, ranging from oral inabsorption, acute toxicities, short duration of action and the emergence of trypanosomal resistance. Despite decades of use of most of the current trypanocides, little is known about their mode of action. That being said, African trypanosomes continue to be among the most extensively studied parasitic protists to date. Many of their intriguing biological features have been well documented and can be viewed as attractive targets for antitrypanosomal chemotherapy. A considerable number of natural products with diverse molecular structures have revealed antiparasitic potency in the laboratory and represent interesting lead compounds for the development of new and urgently needed antiparasitics. The major validated drug targets in T. brucei are discussed with particular emphasis on those known to be attacked by natural compounds.     

海洋卤化天然产物研究进展

卤化天然产物是一类常见的次级代谢产物,在医药研发领域占有重要地位。卤素的存在通常可以增强化合物的生物活性。海洋是卤化天然产物的主要来源。这些卤化物由海绵、海藻、珊瑚、真菌和细菌等生物产生。文章按照化合物中卤素原子的不同综述了近十年（2012年-2022年3月）181个海洋来源卤化天然产物及其抗菌、抗抗肿瘤和抗污等生物活性的研究进展。     

Activation of antioxidant activity in natural medicinal products by heating, brewing and lipophilization. A new drug delivery system

On the basis of the authors' previous hypothesis (1) that treatment of natural plant products with heating and gastric juice results in liberation of low molecular weight compounds with antioxidant activity that exist in the native products as repeating subunits of high molecular weight polymers, they have developed specially treated natural health or medicinal products in which several identifiable low molecular weight compounds with antioxidant activity are liberated and activated. The principal features of the treatment protocol included heating at 80-95 degrees C with continuous manual stirring in an oriental pottery vessel over a Japanese traditional oven, subsequent brewing with Koji (Aspergillus oryzae), and final emulsification in sesame oil. These products were named AOA (antioxidant analogues) or B-H (Bio-harmony). AOA and B-H were markedly effective both in scavenging the reactive oxygen species (ROS) generated and in inhibiting lipid peroxidation; they also significantly reduced both adjuvant- and adriamycin-induced paw oedema in rats. These agents were strikingly effective in ameliorating a variety of inflammatory diseases in patients and caused a fall in their serum lipid peroxide levels. Significant levels of several low molecular weight antioxidant compounds such as flavoprotein and carotene were directly detected by analysis of the treated products. The authors conclude that the procedures are useful and effective for potentiating the bioavailability of pharmacologically active natural products.     

Geldanamycin, radicicol, and chimeric inhibitors of the Hsp90 N-terminal ATP binding site

Natural products have continued to drive the development of new chemotherapeutics and elucidation of new biological targets for the treatment of disease. Since Whitesell and Neckers' original discovery that geldanamycin does not directly inhibit v-Src, but instead manifests its biological activity through inhibition of the Hsp90 molecular chaperone, additional natural products and natural product derivatives have been identified and developed to inhibit the Hsp90 protein folding machinery. 17-AAG, a geldanamycin analogue, is currently in clinical trials for the treatment of several types of cancer. Recent work has produced improved radicicol analogues that show promising Hsp90 inhibitory activity in vitro. In addition, chimeric molecules of these two natural products are active in vitro and represent a novel class of Hsp90 inhibitors for cancer treatment. In addition to their chemotherapeutic uses, natural product inhibitors and their derivatives have been utilized to probe the biological mechanisms by which Hsp90 inhibition regulates tumor cell growth. As a consequence of these studies, the molecular chaperones have emerged as an exciting new class of therapeutic targets. This review will highlight the utility of the natural products, geldanamycin and radicicol, as well as improved analogues and the activities exhibited by these compounds against various cancer cell lines.     

Natural products – antifungal agents derived from plants

A new spectrum of human fungal infections is increasing due to increased cancer, AIDS, and immunocompromised patients. The increased use of antifungal agents also resulted in the development of resistance to the present drugs. It makes necessary to discover new classes of antifungal compounds to cure fungal infections. Plants are rich source of bioactive secondary metabolites of wide variety such as tannins, terpenoids, saponins, alkaloids, flavonoids, and other compounds, reported to have in vitro antifungal properties. Since the plant kingdom provides a useful source of lead compounds of novel structure, a wide-scale investigation of species from the tropics has been considered. Therefore, the research on natural products and compounds derived from natural products has accelerated in recent years due to their importance in drug discovery. A series of molecules with antifungal activity against different strains of fungus have been found in plants, which are of great importance to humans. These molecules may be used directly or considered as a precursor for developing better molecules. This review attempts to summarize the current status of important antifungal compounds from plants.     

抗分枝杆菌植物天然产物研究进展

由分枝杆菌引起的感染是人类健康的巨大威胁。目前,多种结核分枝杆菌和非结核分枝杆菌对临床抗分枝杆菌药物具有较高的耐药性。中药治疗分枝杆菌感染具有悠久历史。例如,中药材狼毒已应用于抗结核分枝杆菌的治疗。非中药来源的植物中,也蕴含丰富的抗分枝杆菌成分。这些植物来源的天然产物具有较好的结构多样性,是开发抗分枝杆菌药物的潜在来源。本文综述了近年来在中药和其他非中药来源植物中发现的,具有良好抗分枝杆菌活性的化合物或提取物,并介绍了它们的作用机制。这些活性植物天然产物为新抗分枝杆菌药物的发现提供了化合物库。同时,这些植物天然产物结构与现有抗分枝杆菌药物具有显著的差别,研究其作用机制,也可发现新的抗分枝杆菌靶标。     

Natural-product-library-based screening for discovery of capsid C-terminal domain targeted HIV-1 inhibitors

Antiretroviral therapy (ART) can effectively suppress replication of human immunodeficiency virus type 1 (HIV-1) and limit disease progression. However, ART is unable to eradicate the virus, and the requirement for lifelong treatment may have side effects and may lead to the development of resistance. New approaches to prevent and treat HIV-1 infection should therefore be developed. HIV-1 capsid (CA) protein is an unexploited but attractive target for antiviral drug development. The hydrophobic cavity of the C-terminal domain of CA (CA CTD) has been validated as a potential target for antiviral drugs. Binding of compounds to this conserved non-polar groove in CA CTD allosterically disrupts the CA assembly. This study screened 2080 natural products to identify potential antiviral agents for further development to combat HIV-1 infection. From the primary screen at a fixed concentration of 50 µM, 16 compounds were found to be effective against this target. Six compounds observed in the primary screen were confirmed in dose–response experiments, and were tested against HIV-1-induced cytopathic effects. Two compounds were found to inhibit HIV-1 replication, and the most active compound – rubranol – inhibited viral replication at a moderate micromolar concentration (EC₅₀ = 15.85 μM). The binding modes of rubranol and hirsutanonol to CA CTD were analysed by molecular docking, providing insight for the design of drugs targeting HIV-1 CA. This study reports, for the first time, identification of natural products that showed potential as anti-HIV-1 agents by targeting the conserved hydrophobic cavity of HIV-1 CA CTD.