Lichens as a potential natural source of bioactive compounds: a review

Biological activity of material whether known in folk medicine or observed in planned screening program has been the starting point in the drug research. The general pattern is the isolation of active principles, elucidation their structures, followed by attempts for modulation of its activity potential by chemical modification. Lichens are valuable plant resources and are used as medicine, food, fodder, perfume, spice, dyes and for miscellaneous purposes throughout the world. Lichens are well known for the diversity of secondary metabolites that they produce. Compounds isolated from various lichen species have been reported to display diverse biological activities. Here we review the medicinal efficacy of lichen substances, which intends to explore the pharmaceutical potential of lichen substances.     

Diels–Alder adducts from Celastraceae species

Celastraceae species are a rich source of adducts whose biosynthesis has been hypothesized as involving a Diels–Alder reaction. The co-occurrence of these natural terpenoids adducts with their corresponding precursors, and the reported regio- and stereoisomers support that their biosynthesis may occur via a Diels–Alderase. Triterpene dimers, composed of a quinonemethide and a phenolic nor-triterpene, are the most numerous group of adducts and are all restricted to the Celastraceae family. This review covers natural Diels–Alder adducts from Celastraceae species, providing an overview of the reported terpenoid adducts classified by their monomer nature. In addition, synthetic efforts on the chemical feasibility of the biosynthetic Diels–Alder reactions involved and the biological activities of these metabolites are discussed.     

Chrysobalanaceae: secondary metabolites, ethnopharmacology and pharmacological potential

Many Chrysobalanaceae species, in special Licania and Parinari, are widely used in folk medicine to treat several diseases. This review describes some aspects of their ethnopharmacology potential, biological activities and the secondary metabolites reported so far for Chrysobalanaceae. The chemical constituents of this family include triterpenoids, diterpenoids, steroids and phenylpropanoids like flavonoids as well as chromones derivatives.     

Secondary Metabolites of Plants from the Genus Chloranthus: Chemistry and Biological Activities

Chloranthus, a genus of the family Chloranthaceae, which is mainly distributed in eastern and southern Asia, has been used in Chinese folk medicine due to its antitumor, antifungal, and anti‐inflammatory activities. This review compiles the research on isolation, structure elucidation, structural diversity, and bioactivities of Chloranthus secondary metabolites reported between 2007 and 2013. The metabolites listed encompass 82 sesquiterpenoids, 50 dimeric sesquiterpenoids, 15 diterpenoids, one coumarin, and five other compounds. Among them, dimeric sesquiterpenoids, the characteristic components of plants from the genus Chloranthus, have attracted considerable attention due to their complex structures and significant biological features, e.g., antitumor, antibacterial, antifungal, anti‐inflammatory, and hepatoprotective activities, and potent and selective inhibition of the delayed rectifier (IK) K⁺ current and tyrosinase.     

我国卫矛科杀虫植物研究进展

卫矛科植物由于具有独特的生物活性而受到广泛关注。作者主要综述了我国对卫矛科杀虫植物的研究进展。迄今为止,该科植物中发现的主要杀虫成分均是以二氢沉香呋喃为骨架的多元醇酯和生物碱。就杀虫活性而言,主要是对昆虫拒食作用的测定,仅对苦皮藤(Celastrus angulatus)和雷公藤(Tripterygium wilfordii)杀虫成分的毒杀、麻醉等胃毒作用的研究比较系统深入。此外,也对当前这些研究中存在的问题及前景进行了分析。     

Metabolomic Profile of the Genus Inula

Plants have a long history as therapeutics in the treatment of human diseases and have been used as source of medicines for ages. Searching for new biologically active natural products, many plants and herbs are screened for natural products with pharmacological activities. In this field, the genus Inula, which comprises more than 100 species, several of them being used in traditional medicine, is very important, especially due to the finding that several of the isolated pure secondary metabolites proved to possess important biological activities. Inula species have been reported as rich sources of sesquiterpene lactones, including eudesmanes, germacranes, guaianes, and dimeric structures, and since 2006 ca. 400 secondary metabolites, including more than 100 new natural products, some of them with relevant pharmacological activities, have been identified. Herein, we critically compile and update the information regarding the types of secondary metabolites found in the genus Inula and the progress in their isolation.     

Diterpenoids of Gorgonian Corals: Chemistry and Bioactivity

During the past seven years, many complex and structurally unique secondary metabolites have been isolated from gorgonian corals. In this review, 244 diterpenoids isolated from gorgonian corals complete with their structures, names, references, and biological activities are reported. The article covers the literature published during the period from 2008 to 2014 with 95 citations.     

The destruxins: synthesis, biosynthesis, biotransformation, and biological activity

Destruxins, secondary metabolites first reported in 1961, are cyclic hexadepsipeptides composed of an alpha-hydroxy acid and five amino acid residues. The name "destruxin" is derived from "destructor" from the species Oospora destructor, the entomopathogenic fungus from which these metabolites were first isolated. Individual destruxins differ on the hydroxy acid, N-methylation, and R group of the amino acid residues; where established, the configurations of the amino acid residues are S, and those of the hydroxy acids are R. Destruxins exhibit a wide variety of biological activities, but are best known for their insecticidal and phytotoxic activities. The great interest in destruxins derives from their potential role as virulence factors in fungi, whether such microorganisms are useful insect biocontrol agents or detrimental, causing great plant disease epidemics. Reports on isolation, chemical structure determination, total synthesis, transformation by diverse organisms, and biological activity of destruxins and related metabolites are reviewed for the first time.     

Antifouling Brominated Diterpenoids from Japanese Marine Red Alga Laurencia venusta Yamada

The marine red algal genus Laurencia has abundant halogenated secondary metabolites, which exhibit novel structural types and possess various unique biological potentials, including antifouling activity. In this study, we report the isolation, structure elucidation, and antifouling activities of two novel brominated diterpenoids, aplysin-20 aldehyde ( 1 ), 13-dehydroxyisoaplysin-20 ( 2 ), and its congeners. We screened marine red alga Laurencia venusta Yamada for their antifouling activity against the mussel Mytilus galloprovincialis. Ethyl acetate extracts of L. venusta from Hiroshima and Chiba, Japan, were isolated and purified, and the compound structures were identified using 1D and 2D NMR, HR-APCI-MS, IR, and chemical synthesis. Seven secondary metabolites were identified, and their antifouling activities were evaluated. Compounds 1 , 2 , and aplysin-20 ( 3 ) exhibited strong activities against M. galloprovincialis. Therefore, these compounds can be explored as natural antifouling drugs.     

Anticancer evaluation of structurally diverse Amaryllidaceae alkaloids and their synthetic derivatives

Plants of the Amaryllidaceae family have been under intense scrutiny for the presence of the specific metabolites responsible for the medicinal properties associated with them. The study began in 1877 with the isolation of alkaloid lycorine from Narcissus pseudonarcissus and since then more than 100 alkaloids, exhibiting diverse biological activities, have been isolated from the Amaryllidaceae plants. Based on the present scientific evidence, it is likely that isocarbostyril constituents of the Amaryllidaceae, such as narciclasine, pancratistatin and their congeners, are the most important metabolites responsible for the therapeutic benefits of these plant species in the folk medical treatment of cancer. Notably, Narcissus poeticus L., used by the ancient Greek physicians, is now known to contain about 0.12 g of narciclasine per kg of fresh bulbs. The focus of the present research work is the chemistry and biology of these compounds as specifically relevant to their potential use in medicine. In particular, the anticancer evaluation of lycorine, narciclasine as well as of other Amaryllidaceae alkaloids and their synthetic derivatives are presented in this paper. The structure–activity relationships among some groups of Amaryllidaceae alkaloids will be discussed.     

天然二萜酚类化合物研究进展

本文从来源、结构类型和生物活性三方面,对近８年来新发现的９８种天然二萜酚类化合物进行了综述。这些化合物主要来源于唇形科、灯心草科、卫预先科等科植物,以唇形科鼠属草属最多,结构类型以脱氢松香酸型及重排脱氢松香酸型三环二萜酚类为主。生物活必玉要为抗氧化、抗微生物及抗肿瘤活性。     

Rare actinomycete bacteria from the shallow water sediments of the Trondheim fjord, Norway: isolation, diversity and biological activity

Actinomycete bacteria produce a wide variety of secondary metabolites with diverse biological activities, some of which have been developed for human medicine. Rare actinomycetes are promising sources in search for new drugs, and their potential for producing biologically active molecules is poorly studied. In this work, we have investigated the diversity of actinomycetes in the shallow water sediments of the Trondheim fjord (Norway). Due to the use of different selective isolation methods, an unexpected variety of actinomycete genera was isolated. Although the predominant genera were clearly Streptomyces and Micromonospora, representatives of Actinocorallia, Actinomadura, Knoellia, Glycomyces, Nocardia, Nocardiopsis, Nonomuraea, Pseudonocardia, Rhodococcus and Streptosporangium genera were isolated as well. To our knowledge, this is the first report describing isolation of Knoellia and Glycomyces species from the marine environment. 35 selected actinomycete isolates were characterized by 16S rDNA sequencing, and were shown to represent strains from 11 different genera. In addition, these isolates were tested for antimicrobial activity and the presence of polyketide synthase and non-ribosomal peptide synthetase genes. This study confirms the significant biodiversity of actinobacteria in the Norwegian marine habitats, and their potential for producing biologically active compounds.     

Kaurane and pimarane-type diterpenes from the Viguiera species inhibit vascular smooth muscle contractility

The research, development and use of natural products as therapeutic agents, especially those derived from plants, have been increasing in recent years. Despite the fact that plants provide a rich source of novel biologically active compounds, only a small percentage have been phytochemically investigated and studied for their medical potential. Viguiera is a genus that belongs to the family Asteraceae and to the sunflower tribe Heliantheae, which is widespread mostly in Mexico and in other areas of the Andes and upland areas of Brazil. A review on the secondary metabolites pointed out that sesquiterpene lactones and diterpenes, of the kaurane and pimarane-type, are the main compounds produced by these plants. Some reports have shown that kaurane- and pimarane-type diterpenes exert several biological activities such as anti-inflammatory action, antimicrobial and antispasmodic activities. Kaurenoic and pimaradienoic acids, which are the main secondary metabolites isolated by our research group from the roots of Viguiera robusta and V. arenaria, respectively, have been evaluated on vascular smooth muscle contractility. We showed that these diterpenoids are able to inhibit the vascular contractility mainly by blocking extracellular Ca(2+) influx. Additionally, in this review we discuss the structure-activity relationship of the diterpenes regarding their inhibitory activity on vascular contractility.     

Achievements in the Study of Marine Low‐Molecular Weight Biologically Active Metabolites from the Vietnamese Territorial Waters as a Result of Expeditions aboard the Research Vessel ‘Akademik Oparin’ (2004–2017)

Until 2004, the secondary metabolites of marine organisms of the Vietnamese territorial waters had been studied very poorly. Only four new compounds were isolated from 1977 to 2003. Joint Russian‐Vietnamese expeditions aboard the research vessel ‘Akademik Oparin’ made it possible to study in detail the chemical diversity of marine micro‐ and macroorganisms. As a result of five expeditions, more than 250 low‐molecular weight natural compounds, including 117 new metabolites, were isolated from marine invertebrates and microfilamentous fungi. Their biological activities, such as cytotoxic, cytoprotective, and antioxidant activities, were investigated. Information about the structure and biological activity of the compounds, the source for their isolation and the geographical location of the objects is summarized in this review.     

The endophytic Aspergillus strains: A bountiful source of natural products

Fungi that invade plant inner tissues without inducing disease symptoms are known as fungal endophytes. They represent a promising and tremendous reservoir of natural products with valuable biological potentials for application in medicine, agriculture and industry. Among the numerous existing endophytic fungi, Aspergillus strains constitute one of the most prolific sources of secondary metabolites with diverse chemical classes and interesting biological activities. This review covers the literature of the year 2020, reporting the isolation of 202 compounds obtained from more than 10 different endophytic Aspergillus species associated with different host plants. Analysis and interpretation of the collected data revealed that chemical investigation of endophytes belonging to the genus Aspergillus may greatly contribute to the discovery of potential drug leads. The isolated metabolites were chemically various and exhibited diverse biological activities such as antibacterial, anti-cancer, anti-plasmodial, anti-inflammatory, antioxidant, immunosuppressive and antifungal activities. Moreover, adoption of advanced technology in molecular biology together with modern chemical tools is anticipated to improve the discovery of new biopharmaceuticals from this valuable microbial world in the future.     

鼠尾草属植物二萜类化学成分的研究进展

鼠尾草属植物富含二萜类化合物,该类成分不仅具有结构的多变性,而且具有广泛的生物活性。该综述就近十年来从鼠尾草属植物中发现的新二萜类化合物及其生物活性进行总结。     

Diterpenoid metabolites from pacific marine algae of the order Caulerpales (Chlorophyta)

Chemical investigations of two new species of Udotea, reinvestigation of Tydemania expeditionis and Chlorodesmis fastigiata from Guam and Saipan, Marianas Islands, as well as studies of Caulerpa brownii from Southern Australia, have led to the isolation of four new related diterpenoids and several previously described metabolites. These metabolites possess antimicrobial activities and inhibit cell division in the fertilized sea urchin egg bioassay.     

Recent Advances in Isolation,Synthesis and Biological Evaluation of Terrein

Terrein is a small-molecule polyketide compound with a simple structure mainly isolated from fungi. Since its discovery in 1935, many scholars have conducted a series of research on its structure identification, isolation source, production increase, synthesis and biological activity. Studies have shown that terrein has a variety of biological activities, not only can inhibit melanin production and epidermal hyperplasia, but also has anti-cancer, anti-inflammatory, anti-angiopoietic secretion, antibacterial, insecticidal activities, and so on. It has potential application prospects in beauty, medicine, agriculture and other fields. This article reviews the process of structural identification of terrein since 1935, and summarizes the latest advances in its isolation, source, production increase, synthesis, and biological activity evaluation, with a view to providing a reference and helping for the in-depth research of terrein.     

ent-Rosane and abietane diterpenoids as cancer chemopreventive agents

Two ent-rosane- (cuzcol, 1 and 6-dehydroxycuzcol, 2) and a abietatriene- (salvadoriol, 3) type diterpenoids have been isolated from Maytenus cuzcoina and Crossopetalum uragoga, respectively, along with five known diterpene compounds (4-8). Their stereostructures have been elucidated on the basis of spectroscopic analysis, including 1D and 2D NMR techniques, and computational data. The absolute configuration of cuzcol was determined by application of Riguera ester procedure. This is the first instance of isolation of ent-rosane diterpenoids from species of the Celastraceae. The isolated diterpenes were found to be potent anti-tumour-promoter agents, and carnosol (7) also showed a remarkable chemopreventive effect in an in vivo two-stage carcinogenesis model.