Phytochemical analysis, biological activities of methanolic extracts and an isolated flavonoid from Tunisian Limoniastrum monopetalum (L.) Boiss: an in vitro and in silico investigations.

In recent years, due to the dramatic increase of the bacteria resistance to antibiotics and chemotherapeutic drugs, an increasing importance is given to the discovery of novel bioactive molecules, more potent than those in use. In this contest, methanol extracts of different parts of the medicinal plant Limoniastrum monopetalum (L.) Boiss. (Plumbaginaceae), widely occurring in Tunisia, were prepared to evaluate the antimicrobial and antiproliferative activities. The methanol extract of the roots showed the highest antibacterial activity against E. coli, S. aureus and E. faecalis, whereas the stem extract exhibited the highest antiproliferative effects towards a Hela cell line. Analysis of volatile fractions, using gas chromatography-mass spectrometry (GC-MS) and gas chromatography-flame ionization detector (GC-FID) techniques, led to the identification of camphor as the most abundant constituent, which represented from 84.85 to 99.48% of the methanol extracts. Multiple chromatographic separation of the methanol leaf extract afforded the flavonoid maeopsin-6-O-glucoside (S1) and a few fractions that were subjected to biological activity assays. One fraction exhibited interesting antibacterial activity against E. coli and E. faecalis (MIC values of 62.5 and 78.12 µg/mL, respectively), and antiproliferative effects against Hela and A549 cells (IC50 = 226 and 242.52 µg/mL, respectively). In addition, in silico studies indicated that maesopsin-6-O-glucoside, which was moderately active against Staphylococcus aureus, strongly interacted with the active site of the accessory gene regulator protein A (AgrA) of Staphylococcus aureus.

Characterization of Silver Carbonate Nanoparticles Biosynthesized Using Marine Actinobacteria and Exploring of Their Antimicrobial and Antibiofilm Activity.

Bacterial resistance to different antimicrobial agents is growing with alarming speed, especially when bacterial cells are living in biofilm. Hybrid nanoparticles, synthesized through the green method, hold promise as a potential solution to this challenge. In this study, 66 actinomycete strains were isolated from three distinct marine sources: marine sediment, the algae Codium bursa, and the marine sponge Chondrosia reniformis. From the entirety of the isolated strains, one strain, S26, identified as Saccharopolyspora erythrea, was selected based on its taxonomic position and significant antimicrobial activity. Using the biomass of the selected marine Actinobacteria, the green synthesis of eco-friendly silver carbonate nanoparticles (BioAg2CO3NPs) is reported for the first time in this pioneering study. The BioAg2CO3NPs were characterized using different spectroscopic and microscopic analyses; the synthesized BioAg2CO3NPs primarily exhibit a triangular shape, with an approximate size of 100 nm. Biological activity evaluation indicated that the BioAg2CO3NPs exhibited good antimicrobial activity against all tested microorganisms and were able to remove 58% of the biofilm formed by the Klebsiella pneumoniae kp6 strain.

Taxonomic Characterization, Antiviral Activity and Induction of Three New Kenalactams in Nocardiopsis sp. CG3.

Exploration of secondary metabolites secreted by new Actinobacteria taxa isolated from unexplored areas, can increase the possibility to obtain new compounds which can be developed into new drugs for the treatment of serious diseases such as hepatitis C. In this context, one actinobacterial strain, CG3, has been selected based on the results of polyphasic characterization, which indicate that it represents a new putative species within the genus Nocardiopsis. Two fractions (F2 and F3), prepared from the culture of strain CG3 in soybean medium, exhibited a pronounced antiviral activity against the HCV strain Luc-Jc1. LC-HRESIMS analysis showed different bioactive compounds in both active fractions (F2 and F3), including five polyenic macrolactams (kenalactams A-E), three isoflavone metabolites, along with mitomycin C and one p-phenyl derivative. Furthermore, feeding with 1% of methionine, lysine or alanine as a unique nitrogen source, induced the production of three novel kenalactam derivatives.

Metabolic Profile, Biotransformation, Docking Studies and Molecular Dynamics Simulations of Bioactive Compounds Secreted by CG3 Strain.

Actinobacteria isolated from untapped environments and exposed to extreme conditions such as saltpans are a promising source of novel bioactive compounds. These microorganisms can provide new molecules through either the biosynthetic pathway or the biotransformation of organic molecules. In the present study, we performed a chemical metabolic screening of secondary metabolites secreted by the new strain CG3, which was isolated from a saltpan located in the Sahara of Algeria, via high-performance liquid chromatography coupled with high-resolution mass spectrometry (HPLC-ESI-HRMS). The results indicated that this strain produced five new polyene macrolactams, kenalactams A-E, along with two known compounds, mitomycin C and 6″-hydroxy-4,2',3',4″ tetramethoxy-p-terphenyl. Furthermore, the CG3 isolate could have excellent properties for converting the aglycone isoflavone glycitein to the compounds 6,7-dimethoxy-3-(4-methoxyphenyl)chromen-4-one (50) and 6,7-dimethoxy-3-phenylchromen-4-one (54), and the isoflavone genistein can be converted to 5,7-dimethoxy-3-(4-methoxyphenyl)chromen-4-one (52). Docking studies and molecular dynamics simulations indicated that these three isoflavones, generated via biotransformation, are potent inhibitors of the target protein aromatase (CYP19A1); consequently, they can be used to prevent breast cancer risk in postmenopausal women.

Diversity of Actinobacteria Isolated from Date Palms Rhizosphere and Saline Environments: Isolation, Identification and Biological Activity Evaluation.

The diversity of cultural Actinobacteria in two types of Algerian Sahara environments, including saline environments and date palms rhizosphere, was investigated. In this study, a total of 40 strains of actinomycetes was isolated from different soil samples, using a rehydration and centrifugation method. Molecular identification, based on 16S rRNA gene sequence analysis, revealed that these isolates were affiliated to six clusters corresponding to eight genera, including Streptomyces, Nocardiopsis, Saccharopolyspora, Actinomadura, Actinocorallia, Micromonospora, Couchioplanes, and Planomonospora. A taxonomic analysis, based on the morphological, physiological, biochemical, and molecular investigation, of selected strains, which belong to the rare Actinobacteria, was undertaken. Four strains (CG3, A111, A93, and A79) were found to form distinct phyletic lines and represent new actinobacterial taxa. An assessment of antimicrobial proprieties of the 40 obtained actinomycetes strains, showed moderate to strong antimicrobial activities against fungi and bacteria. This study demonstrated the richness of Algerian Sahara with rare Actinobacteria, which can provide novel bioactive metabolites, to solving some of the most challenging problems of the day, such as multi-drug resistance.

Kenalactams A-E, Polyene Macrolactams Isolated from Nocardiopsis CG3.

In our screening program for new biologically active secondary metabolites, a new strain, Nocardiopsis CG3 (DSM 106572), isolated from the saltpan of Kenadsa, was found to produce five new polyene macrolactams, the kenalactams A-E (1-5). Their structures were elucidated by spectral methods (NMR and HRESIMS), and the absolute configuration was derived by chemical derivatization (Mosher's method). Through a feeding experiment, alanine was proven to be the nitrogen-bearing starter unit involved in biosynthesis of the polyketide kenalactam A (1). Kenalactam E (5) was cytotoxic against human prostate cancer PC-3 cells with an IC50 value of 2.1 µM.