Biological Activities of Two Major Copaiba Diterpenoids and Their Semi-synthetic Derivatives

The oleoresin of Copaifera reticulata Ducke, Fabaceae, is a traditional Brazilian remedy used for a wide range of applications. Commonly named copaiba, the oleoresin has been found to exhibit strong antimicrobial effects in our previous study, which could be attributed to some of its diterpenoid constituents. In order to find new biological activities and to eventually enhance the before observed effects, (−)-polyalthic acid (1) and kaurenoic acid (2), together with eight prepared semi-synthetic derivatives (1a–1c and 2a–2e) were evaluated for their cytotoxic, antibacterial and antifungal properties. Regarding the gram-positive bacteria Enterococcus faecium and methicillin-resistant Staphylococcus aureus, we found that both the exocylic methylene group and the carboxyl group were crucial for the activity against these two clinically relevant bacterial strains. Investigation of the antifungal activity, in contrast, showed that the carboxyl group is unnecessary for the effect against the dermatophytes Trichophyton rubrum and Cryptococcus neoformans, indicated by low micromolar IC50 values for both (−)-polyalthic acid diethylamide (1a) as well as (−)-polyalthic acid methyl ester (1b). Apart from studying the biological activity, the structure of one semi-synthetic derivative, compound 1c, is being reported for the first time. During the course of the structure elucidation of the new compound, we discovered inconsistencies regarding the stereochemistry of polyalthic acid and its stereoisomers, which we clarified in the present work. [Figure not available: see fulltext.]PeerReviewe

Malettinin E, an antibacterial and antifungal tropolone produced by a marine Cladosporium strain

The isolation and structure elucidation of malettinins A–C (1–3) along with the new malettinin E (4) are described. The compounds were produced by the fungus Cladosporium sp. strain KF501, which was isolated from the German Wadden Sea. The malettinins are built up of tropolone/dihydropyran ring structures linked to a furan ring. The structure elucidation of the isolated compounds was achieved by means of one- and two-dimensional NMR spectroscopy supported by mass and UV data. The relative configuration of 4 was determined on the basis of single-crystal X-ray diffraction analysis. 1–4 exhibited antibacterial and antifungal activities when profiled against Xanthomonas campestris and Trichophyton rubrum. The influence of the chemical structure of the furan ring and of configurational changes on biological activities was observed

Comparative Metabolite Profile, Biological Activity and Overall Quality of Three Lettuce (Lactuca sativa L., Asteraceae) Cultivars in Response to Sulfur Nutrition

The main objective of the present study was to assess the effects of sulfur (S) nutrition on plant growth, overall quality, secondary metabolites, and antibacterial and radical scavenging activities of hydroponically grown lettuce cultivars. Three lettuce cultivars, namely, Pazmanea RZ (green butterhead, V1), Hawking RZ (green multi-leaf lettuce, V2), and Barlach RZ (red multi-leaf, V3) were subjected to two S-treatments in the form of magnesium sulfate (+S) or magnesium chloride (−S). Significant differences were observed under −S treatments, especially among V1 and V2 lettuce cultivars. These responses were reflected in the yield, levels of macro- and micro-nutrients, water-soluble sugars, and free inorganic anions. In comparison with the green cultivars (V1 and V2), the red-V3 cultivar revealed a greater acclimation to S starvation, as evidenced by relative higher plant growth. In contrast, the green cultivars showed higher capabilities in production and superior quality attributes under +S condition. As for secondary metabolites, sixteen compounds (e.g., sesquiterpene lactones, caffeoyl derivatives, caffeic acid hexose, 5-caffeoylquinic acid (5-OCQA), quercetin and luteolin glucoside derivatives) were annotated in all three cultivars with the aid of HPLC-DAD-MS-based untargeted metabolomics. Sesquiterpene lactone lactucin and anthocyanin cyanidin 3-O-galactoside were only detected in V1 and V3 cultivars, respectively. Based on the analyses, the V3 cultivar was the most potent radical scavenger, while V1 and V2 cultivars exhibited antibacterial activity against Staphylococcus aureus in response to S provision. Our study emphasizes the critical role of S nutrition in plant growth, acclimation, and nutritional quality. The judicious-S application can be adopted as a promising antimicrobial prototype for medical applications

Seasonal Variations in the Metabolome and Bioactivity Profile of Fucus vesiculosus Extracted by an Optimised, Pressurised Liquid Extraction Protocol

The metabolism of seaweeds depends on environmental parameters, the availability of nutrients, and biotic/abiotic stresses; therefore, their chemical composition fluctuates throughout the year. This study investigated seasonal variations in the metabolome of the Baltic Sea brown alga Fucus vesiculosus and its potential relation to the bioactivity profile. By using a definitive screening design (DSD) combined with pressurised liquid extraction (PLE), an optimised protocol was developed to extract algal biomass monthly for a full calendar year. An untargeted metabolomics approach using ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MSn)-based molecular networking and manual dereplication was employed. The extracts were simultaneously screened for their in vitro antimicrobial, anticancer/apoptotic, and free radical scavenging activities. 44 compounds were putatively dereplicated in the metabolome. Many compounds were found to vary with the sampling month; phlorotannin total ion count (TIC) was highest in summer, whilst chlorophylls, lipids, and carotenoids peaked in winter and spring. The greatest radical scavenging and apoptotic activities against pancreas cancer cells observed in the summer months were attributed to high phlorotannin TIC. Methicillin-resistant Staphylococcus aureus (MRSA) inhibitory activity was produced year-round without a clear seasonal trend. This is the first study applying DSD-based optimised PLE extraction combined with a metabolome analysis of F. vesiculosus for the identification of seasonal variations in both metabolome and bioactivity

Diversity and antimicrobial potential of bacterial isolates associated with the soft coral Alcyonium digitatum from the Baltic Sea

It is well recognized that microorganisms associated with marine invertebrates, in particular sponges and hard corals, are an excellent source of new natural products. Therefore, the diversity of bacteria associated with marine invertebrates and their potential to produce bioactive compounds have received much attention in recent years. We report here for the first time on the biodiversity of bacteria associated with the soft coral Alcyonium digitatum, which is abundant in the Baltic Sea. In order to increase the cultured diversity, bacteria were isolated using four different media, identified with support of 16S rRNA gene sequences and screened for antimicrobial activity using two different media. Activity of crude extracts was tested against Bacillus subtilis, Staphylococcus epidermidis, Escherichia coli, and the yeast Candida albicans. A total of 251 coral-associated bacterial isolates were classified and found to belong to 41 species in 14 genera of the Firmicutes, Actinobacteria, Gammaproteobacteria, and Alphaproteobacteria. The genus Bacillus was most abundant and diverse with 17 recognized species. Forty-eight percent of all 251 isolates exhibited antimicrobial activity. All isolates of Bacillus methylotrophicus and Bacillus amyloliquefaciens displayed inhibition of at least three out of the four tested microorganisms. It became obvious during this study that the production of antibiotic substances not only is strain-specific, but in many cases also depends on the media composition and growth conditions. In addition, the antimicrobial potential of bacteria associated with A. digitatum may represent a promising source for antimicrobial substances

Chemical and biological screening of deep-water sponges from Antarctic regions

The majority of marine natural products (MNPs) originate from tropical and temperate shallow water invertebrates, such as sponges [1]. Recent studies indicate the presence of great genetic diversity in deep-waters that may be linked to unprecedented chemistry due to evolution/adaptation to extremely harsh environmental conditions. However, only less than 2% of MNPs derive from the deep-sea organisms [2]. Antarctic ecosystems are rich in biodiversity [3] and exposed to unique environmental characteristics resulting in communities structured both by biotic interactions (e.g. predation, competition) and abiotic factors (e.g. seasonality, ice-scouring) [4], suggesting a high chemical diversity. In this work, we investigated 39 deep-water sponges collected from the Antarctic Weddell Sea and adjacent areas (depths -100 – 600 m). The freeze-dried sponge samples were extracted with water, followed by MeOH and CH2Cl2 separately. The combined organic extracts were tested for activity against cancer cells [HepG2 (liver) and HT29 (bowel) cancer cell lines], bacteria [ESKAPE panel: Enterococcus faecalis, Staphylococcus aureus (MRSA), Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Escherichia coli) and fungi (yeasts Candida albicans, Cryptococcus neoformans). Several Latrunculia sponge extracts displayed high anticancer activity against both cell lines (IC50 values 0.50 – 3.16 µg/ml). The organic extract of the glass sponge Rossella cf. antarctica showed moderate antibiotic activity towards MRSA and E. faecalis with IC50 values of 96 and 213 µg/ml, respectively. All extracts have undergone chemical profiling/dereplication studies by HPLC-DAD-MS and 1H NMR spectroscopy. The results of chemical and biological screening will assist in selection and activity-guided isolation of Antarctic deep-water sponge metabolites

Bioactivity profile of dissolved organic matter and its relation to molecular composition

Abstract Dissolved organic matter (DOM) occupies a huge and uncharted molecular space. Given its properties, DOM can be presented as a promising biotechnological resource. However, research into bioactivities of DOM is still in early stages. In this study, the biotechnological potential of terrestrial and marine DOM, its molecular composition and their relationships are investigated. Samples were screened for their in vitro antibacterial, antifungal, anticancer and antioxidant activities. Antibacterial activity was detected against Staphylococcus aureus in almost all DOM samples, with freshwater DOM showing the lowest IC50 values. Most samples also inhibited Staphylococcus epidermidis, and four DOM extracts showed up to fourfold higher potency than the reference drug. Antifungal activity was limited to only porewater DOM towards human dermatophyte Trichophyton rubrum. No significant in vitro anticancer activity was observed. Low antioxidant potential was exerted. The molecular characterization by FT-ICR MS allowed a broad compositional overview. Three main distinguished groups have been identified by PCoA analyses. Antibacterial activities are related to high aromaticity content and highly-unsaturated molecular formulae (O-poor). Antifungal effect is correlated with highly-unsaturated molecular formulae (O-rich). Antioxidant activity is positively related to the presence of double bonds and polyphenols. This study evidenced for the first time antibacterial and antifungal activity in DOM with potential applications in cosmeceutical, pharmaceutical and aquaculture industry. The lack of cytotoxicity and the almost unlimited presence of this organic material may open new avenues in future marine bioprospecting efforts. Graphical abstrac

Structure and biosynthesis of desmamides A-C, lipoglycopeptides from the endophytic cyanobacterium Desmonostoc muscorum LEGE 12446

Certain cyanobacteria of the secondary metabolite-rich order Nostocales can establish permanent symbioses with a large number of cycads, by accumulating in their coralloid roots and shifting their metabolism to dinitrogen fixa-tion. Here, we report the discovery of two novel lipoglycopeptides, desmamides A (1) and B (2), together with their aglycone desmamide C (3), from the nostocalean cyanobacterium Desmonostoc muscorum LEGE 12446 isolated from a cycad (Cycas revoluta) coralloid root. The chemical structures of the compounds were elucidated using a combination of 1D and 2D Nuclear Magnetic Resonance (NMR) spectroscopy and Mass Spectrometry (MS). The desmamides are decapeptides, featuring O-glycosylation of tyrosine (in 1 and 2) and an unusual 3,5-dihydroxy-2-methyldecanoic acid residue. The biosynthesis of the desmamides was studied by substrate feeding experiments and bioinformatics. We describe herein the dsm biosynthetic gene cluster (BGC) and propose it to be associated with desmamide production. The discovery of this class of very abundant (>1.5% d.w.) bacterial lipoglycopeptides paves the way for exploration of their potential role in root endosymbiosis

Bioactivity Screening of Microorganisms Isolated from Arctic Ocean Deep-Sea Sediment

Oceans cover >70% of the earth and encompass variable habitats concerning salinity, temperature, pressure, light availability. The deep sea (>1000 m water depth) constitutes more than 60% of the ocean´s biosphere and harbors an unparalleled biodiversity. It constitutes an extreme habitat due to high pressure, darkness and often low nutrient and oxygen concentrations. In order to ensure their survival, microorganisms thriving in such environments have to develop unique metabolic adaptations, thus represent an interesting resource for the discovery of new molecules. However, due to access difficulties to deep-sea habitats and the lack of suitable and affordable sampling techniques, deep-sea microorganisms have remained untapped for their potential in marine biodiscovery. In this study, we obtained deep-sea sediment samples from Arctic Ocean (-2432 m), sampled by an ROV during RV Polarstern expedition 108. Isolation of microorganisms has been performed using two specific media for bacteria and fungi, respectively. Isolates were identified by amplification of the 16S rRNA gene (bacteria) and ITS1-2 region (fungi) followed by Sanger sequencing. In total, 70 bacterial isolates were identified covering four phyla (52 Firmicutes, 1 Actinobacteria, 11 Proteobacteria and 6 Bacteroidetes) and seven fungal strains from two different phyla (6 Ascomycota and 1 Basidiomycota). Selected isolates were cultivated in two different media, followed by solvent (EtOAc) extraction and bioactivity screenings against a panel of clinically relevant microbial pathogens and six cancer cell lines. At 100 µg/mL concentration, three bacterial extracts showed antitumor activity (>70%), whereas 17 exhibited activity (>65%) against methicillin-resistant Staphylococcus aureus (MRSA). Notably, only one fungus showed a cultivation medium dependent-high antifungal activity (>90%), highlighting the impact of culture media on the production of bioactive secondary metabolites