Antitrypanosomal alkaloids from the marine bacterium Bacillus pumilus

Evaluation of Phenazine Derivatives from the Lichen-Associated Streptomyces flavidovirens as Potent Antineuroinflammatory Agents In Vitro and In Vivo

Eighteen nitrogen-containing compounds (1-18) were isolated from cultures of the lichen-associated Streptomyces flavidovirens collected from the Qinghai-Tibet Plateau, including seven phenazine derivatives with three new ones, named subphenazines A-C (2-4), two new furan pyrrolidones (8-9), and nine known alkaloids. The structures were elucidated by spectroscopic data analysis, and absolute configurations were determined by single-crystal X-ray diffraction and ECD calculations. The phenazine-type derivatives, in particular compound 3, exhibited significantly better antineuroinflammatory activity than other isolated compounds (8-18). Compound 3 inhibited the release of proinflammatory cytokines including IL-6, TNF-α, and PGE2, and the nuclear translocation of NF-κB; it also reduced the oxidative stress and activated the Nrf2 signaling pathway in LPS-induced BV2 microglia cells. In vivo anti-inflammatory activity in zebrafish indicated that 3 inhibited LPS-stimulated ROS generation. These findings suggested that compound 3 might be a potent antineuroinflammatory agent through the regulation of the NF-κB/Nrf2 signaling pathways.

Saturated Iso-Type Fatty Acids from the Marine Bacterium Mesoflavibacter zeaxanthinifaciens with Anti-Trypanosomal Potential

Chagas disease is a Neglected Tropical Disease with limited and ineffective therapy. In a search for new anti-trypanosomal compounds, we investigated the potential of the metabolites from the bacteria living in the corals and sediments of the southeastern Brazilian coast. Three corals, Tubastraea coccinea, Mussismilia hispida, Madracis decactis, and sediments yielded 11 bacterial strains that were fully identified by MALDI-ToF/MS or gene sequencing, resulting in six genera-Vibrio, Shewanella, Mesoflavibacter, Halomonas, Bacillus, and Alteromonas. To conduct this study, EtOAc extracts were prepared and tested against Trypanosoma cruzi. The crude extracts showed IC50 values ranging from 15 to 51 μg/mL against the trypomastigotes. The bacterium Mesoflavibacter zeaxanthinifaciens was selected for fractionation, resulting in an active fraction (FII) with IC50 values of 17.7 μg/mL and 23.8 μg/mL against the trypomastigotes and amastigotes, respectively, with neither mammalian cytotoxicity nor hemolytic activity. Using an NMR and ESI-HRMS analysis, the FII revealed the presence of unsaturated iso-type fatty acids. Its lethal action was investigated, leading to a protein spectral profile of the parasite altered after treatment. The FII also induced a rapid permeabilization of the plasma membrane of the parasite, leading to cell death. These findings demonstrate that these unsaturated iso-type fatty acids are possible new hits against T. cruzi.

A Marine Natural Product, Harzianopyridone, as an Anti-ZIKV Agent by Targeting RNA-Dependent RNA Polymerase

The Zika virus (ZIKV) is a mosquito-borne virus that already poses a danger to worldwide human health. Patients infected with ZIKV generally have mild symptoms like a low-grade fever and joint pain. However, severe symptoms can also occur, such as Guillain-Barré syndrome, neuropathy, and myelitis. Pregnant women infected with ZIKV may also cause microcephaly in newborns. To date, we still lack conventional antiviral drugs to treat ZIKV infections. Marine natural products have novel structures and diverse biological activities. They have been discovered to have antibacterial, antiviral, anticancer, and other therapeutic effects. Therefore, marine products are important resources for compounds for innovative medicines. In this study, we identified a marine natural product, harzianopyridone (HAR), that could inhibit ZIKV replication with EC50 values from 0.46 to 2.63 µM while not showing obvious cytotoxicity in multiple cellular models (CC50 > 45 µM). Further, it also reduced the expression of viral proteins and protected cells from viral infection. More importantly, we found that HAR directly bound to the ZIKV RNA-dependent RNA polymerase (RdRp) and suppressed its polymerase activity. Collectively, our findings provide HAR as an option for the development of anti-ZIKV drugs.

Cytotoxic and Antifungal Staurosporine Derivatives from Marine-Derived Actinomycete Streptomyces sp. ZS-A121

A novel staurosporine derivate, streptomholyrine A (1), along with 6 known compounds were identified from the rice-based solid fermentation of marine-derived Streptomyces sp. ZS-A121. The planar structure and absolute configuration of streptomholyrine A were elucidated using a combination of 1D, 2D NMR, HRESIMS data analysis, chemical transformation, ECD and NMR calculations. Screening of all these compounds revealed their cytotoxic activity against HCT-116 cell lines, with IC50 values ranging from 0.012 to 11.67 μM, except for the known 1H-indole-3-hydroxyacetyl, which showed no inhibition activity. Furthermore, streptomholyrine A, along with two known staurosporine derivatives, k252d and staurosporine, exhibited activities against Candida albicans, with MICs of 12.5, 25.0 and 50.0 μg/ml, respectively.

The Genus Cladosporium: A Prospective Producer of Natural Products

Cladosporium, a genus of ascomycete fungi in the Dematiaceae family, is primarily recognized as a widespread environmental saprotrophic fungus or plant endophyte. Further research has shown that the genus is distributed in various environments, particularly in marine ecosystems, such as coral reefs, mangroves and the polar region. Cladosporium, especially the marine-derived Cladosporium, is a highly resourceful group of fungi whose natural products have garnered attention due to their diverse chemical structures and biological activities, as well as their potential as sources of novel leads to compounds for drug production. This review covers the sources, distribution, bioactivities, biosynthesis and structural characteristics of compounds isolated from Cladosporium in the period between January 2000 and December 2022, and conducts a comparative analysis of the Cladosporium isolated compounds derived from marine and terrestrial sources. Our results reveal that 34% of Cladosporium-derived natural products are reported for the first time. And 71.79% of the first reported compounds were isolated from marine-derived Cladosporium. Cladosporium-derived compounds exhibit diverse skeletal chemical structures, concentrating in the categories of polyketides (48.47%), alkaloids (19.21%), steroids and terpenoids (17.03%). Over half of the natural products isolated from Cladosporium have been found to have various biological activities, including cytotoxic, antibacterial, antiviral, antifungal and enzyme-inhibitory activities. These findings testify to the tremendous potential of Cladosporium, especially the marine-derived Cladosporium, to yield novel bioactive natural products, providing a structural foundation for the development of new drugs.

Indole alkaloids fusarindoles A-E from marine-derived fungus Fusarium equiseti LJ-1

Five undescribed indole alkaloids, fusarindoles A-E, together with seven known compounds were obtained from the marine-derived fungus Fusarium equiseti LJ-1. Their chemical structures and absolute configurations were determined by comprehensive analysis of the NMR, HRMS, UV, IR, ECD calculation and single-crystal X-ray diffraction data. The possible biosynthetic pathways of fusarindoles C-E were proposed. The cytotoxicities of eleven compounds, including fusarindoles A-E and six known compounds, against five human cancer cell lines A549, CNE2, SUNE1, HepG2 and QGY7701 were evaluated.

One new phenylpropanoid glycoside from Myxopyrum smilacifolium with α-glucosidase inhibitory activity

One new phenylpropanoid glycoside, myxosmoside I (1) and six known compounds, arenarioside (2), verbacoside (3), 3-formylindole (4), 5-hydroxymethyl furfural (5), D-manitol (6), and glycerol monooleate (7) were isolated from the roots of Myxopyrum smilacifolium (Wall.) Blume. Their chemical structures were determined by 1D-, 2D-NMR, and mass spectra, chemical methods, and compared with those reported in the literature. All compounds were evaluated for α-glucosidase inhibitory effect. Among them, phenylpropanoid glycosides 1-3 significantly inhibited α-glucosidase activity with IC₅₀ values of 30.0 ± 0.9, 66.6 ± 2.3, and 36.9 ± 2.0 µM, respectively.

Evaluation of the Marine Bacterial Population in the Great Bitter Lake, Egypt, as a Source of Antimicrobial Secondary Metabolites

The ecological uniqueness of the Great Bitter Lake ecosystem makes its bacterial population interesting for investigation. Here, we present the first trial to evaluate the biosynthetic capacity of the bacterial population at the lake as a source of novel antimicrobials. We collected different samples from various locations throughout the lake including the oxic sediment, anoxic sediment, shore water, and off-shore water. We modified a molecular approach to compare and choose the samples with the highest bacterial biosynthetic capacity by quantifying the polyketide synthase gene clusters in their total community DNA. Furthermore, we screened the bacterial isolates recovered from these samples and their metabolic extracts for antimicrobial activity. We tried to tentatively investigate the identity of the active metabolites by PCR screening and LC–MS. The bacterial population in the oxic sediment had the highest biosynthetic capacity compared to other sample types. Four active Bacillus isolates were identified. The isolated Bacillus species were expected to produce numerous probable bioactive metabolites encoded by biosynthetic gene clusters related to the polyketide synthases (either individual or hybrid with non-ribosomal peptide synthetase), such as Bacillomycin D, Iturin A, Bacilosarcin B, Bacillcoumacin G and Macrolactin (N and G). These results suggest that the under-explored bacterial community of the Great Bitter Lake has a prospective biosynthetic capacity and can be a promising source for novel antibiotics.

Metabolites From the Mangrove-Derived Fungus Cladosporium sp. HNWSW-1

Two new benzoic acids, cladoslide A (1) and cladoslide B (2); one new β-carboline derivative, cladospomine (3); and one new pyridin-2(1H)-one, cladoslide C (4), were isolated from the fermentation cultures of the mangrove-derived fungus Cladosporium sp. HNWSW-1, along with the previously reported N-acetyl-β-oxotryptamine (5), (4S,5S,11R)-iso-cladospolide B (6), (4S,5S,11S)-iso-cladospolide B (7), and (4R,5S,11R)-iso-cladospolide B (8). Their structures were elucidated by spectroscopic analysis, Rh₂(OCOCF₃)₄-induced ECD experiments, and Marfey’s method. Compound 1 showed cytotoxicity against the K562 cell line with IC₅₀ values of 13.10 ± 0.08 μM. Moreover, compounds 1 and 5 exhibited inhibitory activity against α-glycosidase with IC₅₀ values of 0.32 ± 0.01 mM and 0.17 ± 0.01 mM, respectively.

Marine alkaloids as bioactive agents against protozoal neglected tropical diseases and malaria

Covering: 2000 up to 2021Natural products are an important resource in drug discovery, directly or indirectly delivering numerous small molecules for potential development as human medicines. Among the many classes of natural products, alkaloids have a rich history of therapeutic applications. The extensive chemodiversity of alkaloids found in the marine environment has attracted considerable attention for such uses, while the scarcity of these natural materials has stimulated efforts towards their total synthesis. This review focuses on the biological activity of marine alkaloids (covering 2000 to up to 2021) towards Neglected Tropical Diseases (NTDs) caused by protozoan parasites, and malaria. Chemotherapy represents the only form of treatment for Chagas disease, human African trypanosomiasis, leishmaniasis and malaria, but there is currently a restricted arsenal of drugs, which often elicit severe adverse effects, show variable efficacy or resistance, or are costly. Natural product scaffolds have re-emerged as a focus of academic drug discovery programmes, offering a different resource to discover new chemical entities with new modes of action. In this review, the potential of a range of marine alkaloids is analyzed, accompanied by coverage of synthetic efforts that enable further studies of key antiprotozoal natural product scaffolds.

Characterization of a mercury tolerant strain of Staphylococcus arlettae from Darjeeling hills with an account of its antibiotic resistance pattern and metabolome

Mercury (Hg) is a ubiquitous heavy metal grouped with the top ten most toxic pollutants affecting both human and environmental health. Consequently, mercury contamination due to anthropogenic interference has become a rising global concern. The bacterial strain MTD10A was isolated from soil samples collected over the Darjeeling hills. Heavy metal tolerance study conducted exhibited considerable tolerance to mercury by this bacterial isolate at unprecedented concentrations of up to 0.1 mg/mL of HgCl₂. Biochemical characterization and molecular identification via 16S rRNA sequencing identified this highly tolerant bacteria as a strain of a Coagulase Negative Staphylococcus arlettae. This study also maps the resistance pattern of MTD10A against clinically relevant antibiotics and contains a broad assessment of the metabolomic profile of the bacteria achieved via GC-MS. Tolerance of MTD10A to such excessive levels of mercury shown in our study suggests the possibility of a promising candidate for bioremediation in heavily mercury contaminated areas.

Genomic and Metabolomic Investigation of a Rhizosphere Isolate Streptomyces netropsis WLXQSS-4 Associated with a Traditional Chinese Medicine

Rhizosphere microorganisms play important ecological roles in promoting herb growth and producing abundant secondary metabolites. Studies on the rhizosphere microbes of traditional Chinese medicines (TCMs) are limited, especially on the genomic and metabolic levels. In this study, we reported the isolation and characterization of a Steptomyces netropsis WLXQSS-4 strain from the rhizospheric soil of Clematis manshurica Rupr. Genomic sequencing revealed an impressive total of 40 predicted biosynthetic gene clusters (BGCs), whereas metabolomic profiling revealed 13 secondary metabolites under current laboratory conditions. Particularly, medium screening activated the production of alloaureothin, whereas brominated and chlorinated pimprinine derivatives were identified through precursor-directed feeding. Moreover, antiproliferative activities against Hela and A549 cancer cell lines were observed for five compounds, of which two also elicited potent growth inhibition in Enterococcus faecalis and Staphylococcus aureus, respectively. Our results demonstrated the robust secondary metabolism of S. netropsis WLXQSS-4, which may serve as a biocontrol agent upon further investigation.

Microorganisms as a Potential Source of Molecules to Control Trypanosomatid Diseases

Trypanosomatids are the causative agents of leishmaniasis and trypanosomiasis, which affect about 20 million people in the world’s poorest countries, leading to 95,000 deaths per year. They are often associated with malnutrition, weak immune systems, low quality housing, and population migration. They are generally recognized as neglected tropical diseases. New drugs against these parasitic protozoa are urgently needed to counteract drug resistance, toxicity, and the high cost of commercially available drugs. Microbial bioprospecting for new molecules may play a crucial role in developing a new generation of antiparasitic drugs. This article reviews the current state of the available literature on chemically defined metabolites of microbial origin that have demonstrated antitrypanosomatid activity. In this review, bacterial and fungal metabolites are presented; they originate from a range of microorganisms, including cyanobacteria, heterotrophic bacteria, and filamentous fungi. We hope to provide a useful overview for future research to identify hits that may become the lead compounds needed to accelerate the discovery of new drugs against trypanosomatids.

Ecological and biotechnological importance of secondary metabolites produced by coral-associated bacteria

Symbiotic relationships between corals and their associated micro-organisms are essential to maintain host homeostasis. Coral-associated bacteria (CAB) can have different beneficial roles in the coral metaorganism, such as metabolizing essential nutrients for the coral host and protecting the coral from pathogens. Many CAB exert these functions via secondary metabolites, which include antibacterial, antifouling, antitumour, antiparasitic and antiviral compounds. This review describes how analysis of CAB has led to the discovery of secondary metabolites with potential biotechnological applications. The most commonly found types of secondary metabolites, antimicrobial and antibiofilm compounds, are emphasized and described. Recently developed methods that can be applied to enhance the culturing of CAB from shallow-water reefs and the less-studied deep-sea coral reefs are also discussed. Last, we suggest how the combined use of meta-omics and innovative growth-diffusion techniques can vastly improve the discovery of novel compounds in coral environments.

Marine Invertebrate Extracts Induce Colon Cancer Cell Death via ROS-Mediated DNA Oxidative Damage and Mitochondrial Impairment

Marine compounds are a potential source of new anticancer drugs. In this study, the antiproliferative effects of 20 invertebrate marine extracts on three colon cancer cell models (HGUE-C-1, HT-29, and SW-480) were evaluated. Extracts from two nudibranchs (Phyllidia varicosa, NA and Dolabella auricularia, NB), a holothurian (Pseudocol ochirus violaceus, PS), and a soft coral (Carotalcyon sp., CR) were selected due to their potent cytotoxic capacities. The four marine extracts exhibited strong antiproliferative effects and induced cell cycle arrest at the G2/M transition, which evolved into early apoptosis in the case of the CR, NA, and NB extracts and necrotic cell death in the case of the PS extract. All the extracts induced, to some extent, intracellular ROS accumulation, mitochondrial depolarization, caspase activation, and DNA damage. The compositions of the four extracts were fully characterized via HPLC-ESI-TOF-MS analysis, which identified up to 98 compounds. We propose that, among the most abundant compounds identified in each extract, diterpenes, steroids, and sesqui- and seterterpenes (CR); cembranolides (PS); diterpenes, polyketides, and indole terpenes (NA); and porphyrin, drimenyl cyclohexanone, and polar steroids (NB) might be candidates for the observed activity. We postulate that reactive oxygen species (ROS) accumulation is responsible for the subsequent DNA damage, mitochondrial depolarization, and cell cycle arrest, ultimately inducing cell death by either apoptosis or necrosis.

Synthesis, Structure and Antimicrobial Activity of Novel Metabolites from a Marine Actinomycete in Vietnam's East Sea

A naturally new ester, 2,4-dichlorophenyl 2,4-dichloro benzoate (1) and a new compound, 4,5-dihydroxy-7-methylphthalide (2), along with eight known compounds were isolated from the fermentation broth of the marine-derived actinomycete Streptomyces sp. (strain G212). The structures of these compounds were established by their spectral data analysis, including MS, and 2D-NMR. To confirm the structures of the two new compounds 1 and 2, their total syntheses were achieved. These syntheses also allow obtaining enough quantities of 1 and 2 for their biological screening. The isolated compounds and synthetic samples were evaluated for their antimicrobial activity against a panel of clinically significant microorganisms. Except for 8 and 10, the remaining compounds were active against at least one tested microbial strain with the MIC values in range of 32-256 μg/mL. Compounds 5, 6, 17 and 2a were found to have a broad-spectrum of antimicrobial activity.

Neuroprotective Activity of Some Marine Fungal Metabolites in the 6-Hydroxydopamin- and Paraquat-Induced Parkinson's Disease Models

A new melatonin analogue 6-hydroxy-N-acetyl-β-oxotryptamine (1) was isolated from the marine-derived fungus Penicillium sp. KMM 4672. It is the second case of melatonin-related compounds isolation from microfilamentous fungi. The neuroprotective activities of this metabolite, as well as 3-methylorsellinic acid (2) and 8-methoxy-3,5-dimethylisochroman-6-ol (3) from Penicillium sp. KMM 4672, candidusin A (4) and 4″-dehydroxycandidusin A (5) from Aspergillus sp. KMM 4676, and diketopiperazine mactanamide (6) from Aspergillus flocculosus, were investigated in the 6-hydroxydopamine (6-OHDA)- and paraquat (PQ)-induced Parkinson's disease (PD) cell models. All of them protected Neuro2a cells against the damaging influence of 6-OHDA to varying degrees. This effect may be realized via a reactive oxygen species (ROS) scavenging pathway. The new melatonin analogue more effectively protected Neuro2A cells against the 6-OHDA-induced neuronal death, in comparison with melatonin, as well as against the PQ-induced neurotoxicity. Dehydroxylation at C-3″ and C-4″ significantly increased free radical scavenging and neuroprotective activity of candidusin-related p-terphenyl polyketides in both the 6-OHDA- and PQ-induced PD models.

Pumilacidins from the Octocoral-Associated Bacillus sp. DT001 Display Anti-Proliferative Effects in Plasmodium falciparum

Chemical examination of the octocoral-associated Bacillus species (sp.) DT001 led to the isolation of pumilacidins A (1) and C (2). We investigated the effect of these compounds on the viability of Plasmodium falciparum and the mechanism of pumilacidin-induced death. The use of inhibitors of protein kinase C (PKC) and phosphoinositide 3-kinase (PI3K) was able to prevent the effects of pumilacidins A and C. The results indicated also that pumilacidins inhibit parasite growth via mitochondrial dysfunction and decreased cytosolic Ca²⁺.

Chemical analysis of the Alphaproteobacterium strain MOLA1416 associated with the marine lichen Lichina pygmaea

Alphaproteobacterium strain MOLA1416, related to Mycoplana ramosa DSM 7292 and Chelativorans intermedius CC-MHSW-5 (93.6% 16S rRNA sequence identity) was isolated from the marine lichen, Lichina pygmaea and its chemical composition was characterized by a metabolomic network analysis using LC-MS/MS data. Twenty-five putative different compounds were revealed using a dereplication workflow based on MS/MS signatures available through GNPS (https://gnps.ucsd.edu/). In total, ten chemical families were highlighted including isocoumarins, macrolactones, erythrinan alkaloids, prodiginines, isoflavones, cyclohexane-diones, sterols, diketopiperazines, amino-acids and most likely glucocorticoids. Among those compounds, two known metabolites (13 and 26) were isolated and structurally identified and metabolite 26 showed a high cytotoxic activity against B16 melanoma cell lines with an IC₅₀ 0.6 ± 0.07 μg/mL.

American trypanosomiasis, or Chagas disease, in Panama: a chronological synopsis of ecological and epidemiological research

American trypanosomiasis, or Chagas disease, is a growing public health problem in Panama, and further forest degradation due to human population growth is expected to worsen the situation. Most people infected with the parasite Trypanosoma cruzi are silently ill, and their life expectancy is severely compromised, which contributes to further deterioration of living conditions in endemic regions. Here, we review the outcomes of nearly 100 years of ecological and epidemiological investigation about Chagas disease in Panama, in an attempt to highlight progress, identify needs, and re-orient future efforts. Rhodnius pallescens and Triatoma dimidiata are both primary vectors of T. cruzi in Panama, but R. pallescens seems more efficient in human-altered forest ecosystems due to a greater degree of association with Attalea butyracea. In contrast, T. dimidiata transmits T. cruzi efficiently under more sylvatic conditions (e.g. settlements inside old-growth or secondary forest patches), where its populations reach considerable numbers irrespective of the absence of A. butyracea. A trend of increasing forest degradation, suburbanization, and development of tourism in Panama favoring the establishment of A. butyracea and other palm tree species (Acrocomia sp.) suggests that a colonist species like R. pallescens will continue to play a more prominent role in the transmission of T. cruzi than a forest specialist like T. dimidiata. However, studies about the taxonomic status and ecology of these vectors are still needed in Panama to address their transmission potential fully. The implementation of an active surveillance system and education programs could greatly minimize the risk of Chagas disease transmission in Panama, preventing fatal infections in children from endemic areas.

Imaging mass spectrometry and MS/MS molecular networking reveals chemical interactions among cuticular bacteria and pathogenic fungi associated with fungus-growing ants

The fungus-growing ant-microbe symbiosis is an ideal system to study chemistry-based microbial interactions due to the wealth of microbial interactions described, and the lack of information on the molecules involved therein. In this study, we employed a combination of MALDI imaging mass spectrometry (MALDI-IMS) and MS/MS molecular networking to study chemistry-based microbial interactions in this system. MALDI IMS was used to visualize the distribution of antimicrobials at the inhibition zone between bacteria associated to the ant Acromyrmex echinatior and the fungal pathogen Escovopsis sp. MS/MS molecular networking was used for the dereplication of compounds found at the inhibition zones. We identified the antibiotics actinomycins D, X2 and X_0β, produced by the bacterium Streptomyces CBR38; and the macrolides elaiophylin, efomycin A and efomycin G, produced by the bacterium Streptomyces CBR53.These metabolites were found at the inhibition zones using MALDI IMS and were identified using MS/MS molecular networking. Additionally, three shearinines D, F, and J produced by the fungal pathogen Escovopsis TZ49 were detected. This is the first report of elaiophylins, actinomycin X_0β and shearinines in the fungus-growing ant symbiotic system. These results suggest a secondary prophylactic use of these antibiotics by A. echinatior because of their permanent production by the bacteria.

Isolation and Structure Identification of Novel Brominated Diketopiperazines from Nocardia ignorata-A Lichen-Associated Actinobacterium

Actinobacteria are well known for their potential in biotechnology and their production of metabolites of interest. Lichens are a promising source of new bacterial strains, especially Actinobacteria, which afford a broad chemical diversity. In this context, the culture medium of the actinobacterium Nocardia ignorata, isolated from the terrestrial lichen Collema auriforme, was studied. The strain was cultivated in a BioFlo 115 bioreactor, and the culture medium was extracted using an XAD7HP resin. Five known diketopiperazines: cyclo (l-Pro-l-OMet) (1), cyclo (l-Pro-l-Tyr) (2), cyclo (d-Pro-l-Tyr) (3), cyclo (l-Pro-l-Val) (4), cyclo (l-Pro-l-Leu) (5), and one auxin derivative: indole-carboxaldehyde (8) were isolated, along with two new brominated diketopiperazines: cyclo (d-Pro-l-Br-Tyr) (6) and cyclo (l-Pro-l-Br-Tyr) (7). Structure elucidation was performed using HRMS and 1D and 2D NMR analysis, and the synthesis of compounds 6 and 7 was carried out in order to confirm their structure.

Bioactive natural products from Pseudonocardia endophytica VUK-10

Two proline containing cyclic dipeptides (CDPs), cyclo (L-Pro-L-Tyr) (1) and cyclo (L-Pro-L-Phe) (2) were isolated from the fermentation broth of Pseudonocardia endophytica VUK-10 originating from the Nizampatnam mangrove ecosystem on the south coast of Andhra Pradesh, India. The structures of the compounds were established by 1H NMR and 13C NMR spectroscopy, FTIR and EIMS. The antimicrobial and cytotoxic activities of the compounds were tested against a variety of medicinally and agriculturally important bacteria and fungi as well as on the MDA-MB-231, OAW-42, HeLa and MCF-7 human cell lines. Xanthomonas malvacearum was most sensitive toward 1 (MIC 4 μg/ml), whereas compound 2 had good antibacterial activity against Xanthomonas campestris (MIC 8 μg/ml). Fusarium solani was highly sensitive toward 1 (MIC 16 μg/ml). The compounds were cytotoxic against the human cell lines at micro molar concentrations; the highest activity (IC50 < 10 μM) of 1 was recorded against the MDA-MB-231 cancer cell line.

Phytochemical composition, antiparasitic and α-glucosidase inhibition activities from Pelliciera rhizophorae

BACKGROUND

Panama has an extensive mangrove area and it is one of the countries with the highest biodiversity in America. Mangroves are widely used in traditional medicine, nevertheless, there are very few studies that validates their medicinal properties in America. Given the urgent need for therapeutic options to treat several diseases of public health importance, mangrove ecosystem could be an interesting source of new bioactive molecules. This study was designed to evaluate the potential of Pelliciera rhizophorae as a source of bioactive compounds.

RESULTS

The present investigation was undertaken to explore the possible antiparasitic potential and α-glucosidase inhibition by compounds derived from the Panamanian mangrove Pelliciera rhizophorae. Bioassay-guided fractionation of the crude extract led to the isolation of ten chemical compounds: α-amyrine (1), β-amyrine (2), ursolic acid (3), oleanolic acid (4), betulinic acid (5), brugierol (6) iso-brugierol (7), kaempferol (8), quercetin (9), and quercetrin (10). The structures of these compounds were established by spectroscopic analyses including APCI-HR-MS and NMR. Compounds 4 (IC50 = 5.3 µM), 8 (IC50 = 22.9 µM) and 10 (IC50 = 3.4 µM) showed selective antiparasitic activity against Leishmania donovani, while compounds 1 (IC50 = 19.0 µM) and 5 (IC50 = 18.0 µM) exhibited selectivity against Tripanosoma cruzi and Plasmodium falciparum, respectively. Moreover, compounds 1-5 inhibited α-glucosidase enzyme in a concentration-dependent manner with IC50 values of 1.45, 0.02, 1.08, 0.98 and 2.37 µM, respectively. Their inhibitory activity was higher than that of antidiabetic drug acarbose (IC50 217.7 µM), used as a positive control. Kinetic analysis established that the five compounds acted as competitive inhibitors. Docking analysis predicted that all triterpenes bind at the same site that acarbose in the human intestinal α-glucosidase (PDB: 3TOP).

CONCLUSIONS

Three groups of compounds were isolated in this study (triterpenes, flavonols and dithiolanes). Triterpenes and flavones showed activity in at least one bioassay (antiparasitic or α-glucosidase). In addition, only the pentacyclic triterpenes exhibited a competitive type of inhibition against α-glucosidase.

Biodiversity, Anti-Trypanosomal Activity Screening, and Metabolomic Profiling of Actinomycetes Isolated from Mediterranean Sponges

Marine sponge–associated actinomycetes are considered as promising sources for the discovery of novel biologically active compounds. In the present study, a total of 64 actinomycetes were isolated from 12 different marine sponge species that had been collected offshore the islands of Milos and Crete, Greece, eastern Mediterranean. The isolates were affiliated to 23 genera representing 8 different suborders based on nearly full length 16S rRNA gene sequencing. Four putatively novel species belonging to genera Geodermatophilus, Microlunatus, Rhodococcus and Actinomycetospora were identified based on a 16S rRNA gene sequence similarity of < 98.5% to currently described strains. Eight actinomycete isolates showed bioactivities against Trypanosma brucei brucei TC221 with half maximal inhibitory concentration (IC₅₀) values <20 μg/mL. Thirty four isolates from the Milos collection and 12 isolates from the Crete collection were subjected to metabolomic analysis using high resolution LC-MS and NMR for dereplication purposes. Two isolates belonging to the genera Streptomyces (SBT348) and Micromonospora (SBT687) were prioritized based on their distinct chemistry profiles as well as their anti-trypanosomal activities. These findings demonstrated the feasibility and efficacy of utilizing metabolomics tools to prioritize chemically unique strains from microorganism collections and further highlight sponges as rich source for novel and bioactive actinomycetes.

Indole diketopiperazines from endophytic Chaetomium sp 88194 induce breast cancer cell apoptotic death

Diketopiperazines are important secondary metabolites of the fungi with variety bioactivities. Several species belonging to genus Chaetomium produce compounds of this class, such as chetomin. To identify new antitumor agents, secondary metabolites of fungus Chaetomium sp 88194 were investigated and three new indole diketopiperazines, Chaetocochins G (1), Oidioperazines E (2) and Chetoseminudin E (3), along with two known compounds Chetoseminudins C (4) and N-acetyl-β-oxotryptamine (5), were obtained. Chaetocochins G and Chetoseminudin E were recrystallized in CHCl₃ containing a small amount of MeOH, and their structures with absolute configuration were established by spectroscopic data interpretation and single-crystal X-ray diffraction analysis. The absolute configuration of Oidioperazines E was defined by comparing of experimental and calculated electronic circular dichroism spectra. These isolates were also evaluated the anticancer activity, and Chaetocochins G displayed more potent cytotoxicity in MCF-7 cells than the common chemotherapeutic agent (5-fluorouracil) associated with G2/M cell cycle arrest. More importantly, Chaetocochins G induced cell apoptotic death via caspase-3 induction and proteolytic cleavage of poly (ADP-ribose) polymerase, concomitantly with increased Bax and decreased Bcl-2 expression. Our findings suggested that indole diketopiperazines from endophytic Chaetomium sp 88194 may be potential resource for developing anti-cancer reagents.

Indole alkaloids from marine sources as potential leads against infectious diseases

Indole alkaloids comprise a large and complex class of natural products found in a variety of marine sources. Infectious diseases remain a major threat to public health, and in the absence of long-term protective vaccines, the control of these infectious diseases is based on a small number of chemotherapeutic agents. Furthermore, the emerging resistance against these drugs makes it urgently necessary to discover and develop new, safe and, effective anti-infective agents. In this regard, the aim of this review is to highlight indole alkaloids from marine sources which have been shown to demonstrate activity against infectious diseases.

Marine natural products

This review covers the literature published in 2012 for marine natural products, with 1035 citations (673 for the period January to December 2012) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1241 for 2012), together with the relevant biological activities, source organisms and country of origin. Biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.

Trypanocidal activity of marine natural products

Marine natural products are a diverse, unique collection of compounds with immense therapeutic potential. This has resulted in these molecules being evaluated for a number of different disease indications including the neglected protozoan diseases, human African trypanosomiasis and Chagas disease, for which very few drugs are currently available. This article will review the marine natural products for which activity against the kinetoplastid parasites; Trypanosoma brucei brucei, T.b. rhodesiense and T. cruzi has been reported. As it is important to know the selectivity of a compound when evaluating its trypanocidal activity, this article will only cover molecules which have simultaneously been tested for cytotoxicity against a mammalian cell line. Compounds have been grouped according to their chemical structure and representative examples from each class were selected for detailed discussion.