Yedukondalu Nalli

Bioactive metabolites from an endophytic Cryptosporiopsis sp. inhabiting Clidemia hirta

An endophytic Cryptosporiopsis sp. was isolated from Clidemia hirta and analyzed for its secondary metabolites that lead to the isolation of three bioactive molecules. The compounds were purified from the culture broth of the fungus and their structures were determined by spectroscopic methods as (R)-5-hydroxy-2-methylchroman-4-one (1), 1-(2,6-dihydroxyphenyl)pentan-1-one (2) and (Z)-1-(2-(2-butyryl-3-hydroxyphenoxy)-6-hydroxyphenyl)-3-hydroxybut-2-en-1-one (3). Compound 1 exhibited significant cytotoxic activity against the human leukemia cell line, HL-60 with an IC50 of 4 μg/ml. This compound induced G2 arrest of the HL-60 cell cycle significantly. In addition, out of these compounds, 2 and 3 were active against several bacterial pathogens. Compound 2 was active against Bacillus cereus, Escherichia coli and Staphylococcus aureus with IC50 values varying from 18 to 30 μg/ml, and compound 3 displayed activity against Pseudomonas fluorescens with an IC50 value of 6 μg/ml. Compounds 2 and 3 are novel whereas compound 1 was reported earlier but the stereochemistry of its C-2 methyl is established for the first time.

Phialomustin A–D, new antimicrobial and cytotoxic metabolites from an endophytic fungus, Phialophora mustea

Phialomustin A–D (1–4), four new bioactive metabolites, with an unprecedented azaphilone derived skeleton, were isolated and characterized from an endophytic fungus isolated from Crocus sativus. The ITS-5.8S-ITS2 ribosomal gene sequence of the endophyte displayed a sequence similarity of more than 99% with Phialophora mustea. The structural determinations of compounds (1–4) were authenticated by spectroscopic and chemical analysis. The absolute configuration of the stereogenic centers of 1, 3 and 4 were determined by electronic circular dichroism spectroscopy. Compounds 3 and 4 showed promising antifungal activities against Candida albicans, with IC50 values of 14.3 and 73.6 μM, whereas compound 2 exhibited remarkable cytotoxic activity against the human breast cancer cell line, T47D, with an IC50 of 1 μM.

An Insight into the Secondary Metabolism of Muscodor yucatanensis: Small-Molecule Epigenetic Modifiers Induce Expression of Secondary Metabolism-Related Genes and Production of New Metabolites in the Endophyte

Muscodor spp. are proficient producers of bioactive volatile organic compounds (VOCs) with many potential applications. However, all members of this genus produce varying amounts and types of VOCs which suggests the involvement of epigenetics as a possible explanation. The members of this genus are poorly explored for the production of soluble compounds (extrolites). In this study, the polyketide synthase (PKS) and non-ribosomal peptide synthetase (NRPS) genes from an endophyte, Muscodor yucatanensis Ni30, were cloned and sequenced. The PKS genes belonged to reduced, partially reduced, non-reduced, and highly reduced subtypes. Strains over-expressing PKS genes were developed through the use of small-molecule epigenetic modifiers (suberoylanilide hydroxamic acid (SAHA) and 5-azacytidine). The putative epigenetic variants of this organism differed considerably from the wild type in morphological features and cultural characteristics as well as metabolites that were produced. Each variant produced a different set of VOCs distinct from the wild type, and several VOCs including methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)hexane-2,4-diol and 2-carboxymethyl-3-n-hexylmaleic appeared in the variant strains, the production of which could be attributed to the activity of otherwise silent PKS genes. The bioactive extrolite brefeldin A was isolated and characterized from the wild type. However, this metabolite was not detected in EV-1, but instead, two other products were isolated and characterized as ergosterol and xylaguaianol C. Hence, M. yucatanensis has the genetic potential to produce several previously undetectable VOCs and organic solvent soluble products. It is also the case that small-molecule epigenetic modifiers can be used to produce stable variant strains of fungi with the potential to produce new molecules. Finally, this work hints to the prospect that the epigenetics of an endophytic microorganism can be influenced by any number of environmental and chemical factors associated with its host plant which may help to explain the enormous chemical diversity of secondary metabolic products found in Muscodor spp.

TNF-α and IL-6 inhibitory effects of cyclic dipeptides isolated from marine bacteria Streptomyces sp

Inflammation is mediated by a variety of soluble factors, including a group of secreted polypeptides known as cytokines. The anti-inflammatory cytokines are a series of immune regulatory molecules that control the pro inflammatory cytokine response. Cytokines act in concert with specific cytokine inhibitors and soluble cytokine receptors to regulate the human immune response. The aim of the present study is to probe the anti-inflammatory potential of the crude extract and the bioactive metabolite isolated from marine bacteria Streptomyces sp. on key inflammatory mediators like tumor necrosis factor-α and interleukin-6. Here, we isolated ten known pyrazine-1,4-dione substituted cyclic dipeptide by semi-preparative HPLC and studied their anti-inflammatory activities against tumor necrosis factor-α and interleukin-6. Compound 3, 4, 5, 7 and 8 showed good inhibition of the both the cytokines in lipopolysaccharide-stimulated macrophages. The study reveal that compound 7 was to be specific inhibitor for tumor necrosis factor-α which efficiently inhibited tumor necrosis factor-α release in a dose-dependent manner and decreased lipopolysaccharide induced tumor necrosis factor-α production in human peripheral blood mononuclear cells in both the in vitro and in vivo experiments.

Porostereum sp., Associated with Saffron ( Crocus sativus L.), is a Latent Pathogen Capable of Producing Phytotoxic Chlorinated Aromatic Compounds

Saffron (Crocus sativus L.) is one of the most expensive spices in the world due to its medicinal and aromatic value. However, saffron production is severely affected by the corm rot disease throughout the saffron producing countries. In this study, we report a basidiomycetous latent pathogen of saffron, designated as CSE26, capable of producing phytotoxic compounds. CSE26 is a highly odorous basidiomycete with monomitic hyphal system. Molecular phylogeny of ITS and 28S ribosomal gene sequence of CSE26 assigned it as Porostereum spadiceum. It was found to produce corm rot in C. sativus under in vivo and field conditions, with a disease severity index of 0.7 and 0.5, respectively. CSE26 was found to produce chlorinated aromatic compounds (CAMs) having phytotoxic activity against Arabidopsis plants. Therefore, these compounds may be acting as pathogenic determinants of CSE26. However, there is a need to study the level of production of these CAMs by this fungus in the natural environment and their effects on plant health.

Murrayanine Attenuates Lipopolysaccharide-induced Inflammation and Protects Mice from Sepsis-Associated Organ Failure

Murrayanine (MK) is the main compound isolated from Murraya koenigii, an aromatic plant belonging to the Rutaceae family, also known as curry leaf tree. Murrayanine was reported to possess potential antioxidant, antimycobacterial and antifungal effects. However, its effect in sepsis remains unclear. This study was designed to investigate the anti‐inflammatory effect of MK using both in vitro and in vivo assay. Results of this study indicated that MK decreased NO, TNF‐α and IL‐6 production in both lipopolysaccharide (LPS)‐stimulated RAW 264.7 cells and murine peritoneal macrophages. Moreover, iNOS and COX‐2 protein expression as well as their downstream product, PGE2, was also decreased effectively in RAW 264.7 cells. Furthermore, MK decreased the phosphorylation of IKB and repressed NF‐kB activity in LPS‐activated RAW 264.7 cells. Additionally, we evaluated MK efficacy in vivo using LPS‐induced sepsis, a systemic inflammation model in mice. Administration of MK inhibits pro‐inflammatory cytokines (TNF‐α and IL‐6) secretion; decreases AST, ALT, BUN and CRE level in mouse sera; mitigates lung, liver and kidney injuries; and also increases LPS‐challenged mice survival rate. Collectively, our results suggest that MK exerts potential as a new anti‐inflammatory and immunosuppressive drug in sepsis treatment.

POCl3-mediated cyclization of (+)-S-mahanimbine led to the divergent synthesis of natural product derivatives with antiplasmodial activity

(+)-Mahanimbine (1) is a carbazole alkaloid isolated from Murraya koenigii. It undergoes rearrangements under thermal, photolytic, or acidic conditions and is transformed into diverse structural motifs; most of its derivatives have also been reported as natural products with distinct biological activities. Herein, we report the POCl3-mediated reaction of (+)-S-mahanimbine, which rearranged and transformed into seven new and five known natural products viz. isocyclomahanimbine (3), curryanin (5), bicyclomahanimbine (9), curryangin (10) and murrayazolinine (13), which includes previously undisclosed chemistry. The compounds’ (1–13) structural assignments were authenticated by extensive 1D and 2D NMR experiments, HRESIMS, and comparison with the literature data. Compound 3 was unambiguously confirmed by X-ray crystal diffraction analysis. Compounds 1–13 were screened for the first time for anti-parasitic activity against Plasmodium falciparum, in which the new compounds 2, 6 and 7 were proven to be the most potent and exhibited the highest antiplasmodial activity with IC50 values of 2.7, 4.5 and 3.2 μM, respectively. These findings may provide new insights into the design of new pyrano carbazole alkaloid derivatives with promising antiplasmodial potential.

Isolation of three new metabolites and intervention of diazomethane led to separation of compound 1 & 2 from an endophytic fungus, Cryptosporiopsis sp. depicting cytotoxic activity

The discovery of three new natural products (1, 4, and 5), one semi-synthetic derivative (3) along with two known compounds (2 and 6) were isolated from an endophytic fungus Cryptosporiopsis sp. The structural elucidations of 1–6 were authenticated by one-dimensional and two-dimensional nuclear magnetic resonance, mass spectroscopy, and X-ray diffraction analysis. Herein, we intervention of diazomethane as tool that help in the crystallization and isolation of inseparable mixtures of compounds 1 and 2. Compounds (1–6) were screened for cytotoxic activity against six cancer cell lines in which the 4-epi-ethisolide (2) exhibited moderate activity with IC50 values 11 µM in HL-60, whereas the compound 3 lost its cytotoxic potentiality, but it displayed moderate antimicrobial activity. The result illustrates that the methylene moiety in 2 plays significant role in cytotoxic potential.