Nanoemulsions have small droplet size and are kinetically stable colloidal systems. They have enhanced functional properties in comparison to conventional emulsions. The composition and structure of ...the nanoemulsions can be controlled for the encapsulation and effective delivery of bioactive lipophilic compounds. Nanoemulsions have potential application in the food industry for the delivery of nutraceuticals, coloring and flavoring agents, and antimicrobials. The nanoemulsion formulations of active ingredients can be used for developing biodegradable coating and packaging films to enhance the quality, functional properties, nutritional value, and shelf life of foods. This review focuses on preparation of food grade nanoemulsions using high-energy methods and low-energy approaches and their characterization for physical properties, stability, and microstructure. The application of nanoemulsion formulations for sustainable food processing and improving the delivery of functional compounds, such as colorants, flavoring agents, nutraceuticals, and preservatives or antimicrobial agents in foods has been discussed.
The essential oil (EO) from the roots of
Plectranthus
barbatus
Andr. (Syn.
Coleus forskohlii
Briq.) was evaluated for quorum sensing (QS) inhibitory activity.
P. barbatus
EO was screened for ...inhibition of QS regulated violacein production in
Chromobacterium violaceum
(ATCC 12472) wild-type strain. At inhibitory (6.25% v/v) and sub-inhibitory concentrations (3.125% v/v) of the EO, dose-dependent response in the inhibition of violacein production was observed in
C. violaceum
. Similarly, sub-MIC (6.25% v/v) of
P. barbatus
EO disrupted QS regulated biofilm formation by 27.87% and inhibited swarming and twitching motility in
Pseudomonas aeruginosa
PA01 implying its anti-infective and QS modulatory activity. Fluorescence microscopy studies confirmed the disruption of biofilm formation by EO in
P. aeruginosa
PAO1. Promising antibacterial activity was recorded at concentrations as low as 3.12% v/v for
Listeria monocytogenes
(ATCC 13932) and at 6.25% v/v for both
Salmonella enterica
subsp
. enterica
serovar Typhimurium (ATCC 25241) and
Escherichia coli
(ATCC 11775). Furthermore, significant dose-dependent inhibition was observed for biofilm formation and motility in all the tested pathogens in different treated concentrations. GC–MS analysis revealed α-pinene, endo-borneol, bornyl acetate, 1-Hexyl-2-Nitrocyclohexane as the major phytoconstituents.
P. barbatus
EO or its constituent compounds with QS modulatory, antimicrobial and biofilm inhibitory property could be potential new-age dietary source based intervention and preservation technologies.
Marine actinobacteria are less explored than their terrestrial counterparts as potential source of natural products. The present study was aimed to elucidate the bioactive potential of metabolites ...produced by marine-derived actinobacterial strain
Streptomyces
sp.SCA29 isolated from Havelock Island, Andaman and Nicobar Islands, India. The potential isolate SCA29 was identified as
Streptomyces
sp. by phenotypic, genotypic (16S-rRNA) and phylogenetic analyses. The crude bioactive compound was extracted using organic solvents. The compounds were subjected to separation and purification by column chromatography which yielded six fractions. Each fraction was assayed for inhibition of α-glucosidase and α-amylase enzymes, antagonistic activity against bacterial pathogens, and cytotoxic activity against various cell lines. The fraction F3c was considered to be highly active owing to its significant inhibition potential against α-glucosidase and α-amylase enzymes with IC
50
values as 44.26 and 53.19 µg/mL, respectively. The active fraction showed antibacterial activity against test bacterial pathogens with the MIC value ranged from 3.90 to 31.25 µg/mL. The compound also exhibited concentration-dependent cytotoxicity on various cell lines without significant effect against human normal cells. The bioassay-guided fractionation of extract led to the identification of 4-methoxyacetanilide, an acetamide derivative. The structure of the bioactive compound was confirmed by HR-MS, NMR (1H and 13C) and FT-IR spectra, and by comparison with literature data.
Quorum sensing is involved in biofilm formation and modulates virulence factor production in pathogenic bacteria. Quorum sensing inhibitors can be used as novel intervention strategies for ...attenuating bacterial pathogenicity. Berberine is an isoquinoline alkaloid with pharmacological properties. The present study investigated the sub-inhibitory concentrations of berberine for inhibiting biofilm formation and quorum sensing regulated phenotypes in the bacterial pathogens
PA01 and
serovar Typhimurium. Berberine inhibited quorum sensing regulated violacein production in
. It reduced the pigment production in the wild type strain at 1.6 mg mL
by 62.67%. In the opportunistic pathogen,
PA01, at sub-MIC, it showed significant antibiofilm activity in by reducing biomass by 71.70% (
< 0.05). It prevented biofilm formation and inactivated biofilm maturation in bacterial pathogens at the concentration ranging from 0.019 to 1.25 mg mL
.
studies showed that berberine interacted with the quorum sensing signal receptors, LasR and RhlR. Furthermore, its anti-infective properties in
. Typhimurium were studied. At sub-inhibitory concentrations of 0.019 mg mL
, it reduced biofilm formation in
. Typhimurium by 31.20%. It significantly prevented invasion and adhesion of
invasion in the colonic cell, HT 29 by 55.37% and 54.68%, respectively. It was capable of reducing
virulence in
infected with
at 0.038 mg mL
by 65.38%. Our results suggest that berberine, previously recognised for its antimicrobial activity, could find potential application as an anti-biofilm and anti-infective agent based on its quorum sensing inhibitory activity.
Bioactive natural compounds play pivotal roles in drug discovery and the emergence of multi-drug resistance pathogens demands the development of better/new drugs.
Paenibacillus amylolyticus KMCLE06
...endophytic bacterium isolated from the medicinal plant
Coix lachryma-jobi
were analyzed for the potential bioactive secondary metabolite compounds and its gene responsible within polyketide synthases (PKS) clusters. Ethyl acetate extraction of
P. amylolyticus KMCLE06
showed significant antibacterial activity which was further processed to partial purification and characterization for bioactive compound. The foremost bioactive component in extraction was found to be dipicolinic acid (DPA). The antibacterial activity showed remarkable activity compared to the commercial standard DPA against both gram-positive and gram-negative pathogens. The MIC and MBC concentrations for partially purified extracted DPA ranged from 62.5 to 125 µg/ml and MBC from 208 to 250 µg/ml, respectively. Sequence analysis of gene amplified using degenerative primer, amplified 543 bp DNA region, revealing conserved putative open reading frame for dipicolinic acid synthetase (
DpsA
) key gene to produce DPA in most endospore forming bacteria. A search in the structural database for
DpsA
revealed significant homologous match with enoyl reductase one of the PKS type 1 module protein. This emphasizes endophytic
P. amylolyticus KMCLE06
bacteria has presence of
spoVF
operon producing DPA via dipicolinic acid synthetase and lacks the polyketide synthase type 1 module cluster gene in its genome. And the bioactive compound DPA extracted acts as a stable remarkable antibacterial agent which can be potent compound for multi-resistance pathogens.
The quorum quenching (QQ) activity of endophytic bacteria associated with medicinal plants was explored. Extracts of the Gram-negative Enterobacter sp. CS66 possessed potent N-acylhomoserine lactone ...(AHL) hydrolytic activity in vitro. Using degenerate primers, we PCR-amplified an open reading frame (denoted aiiE) from CS66 that was 96% identical to the well-characterised AHL-lactonase AiiA from Bacillus thuringiensis, but only 30% was identical to AHL-lactonases from other Gram-negative species. This confirms that close AiiA homologs can be found in both Gram-positive and Gram-negative bacteria. Purified AiiE exhibited potent AHL-lactonase activity against a broad range of AHLs. Furthermore, aiiE was able to reduce the production of secreted plant cell wall-degrading hydrolytic enzymes when expressed in trans in the economically important plant pathogen, Pectobacterium atrosepticum. Our results indicate the presence of a novel AHL-lactonase in Enterobacter sp. CS66 with significant potential as a biocontrol agent.
In the present study, marine actinobacteria
sp.S2A was isolated from the Gulf of Mannar, India. Identification was carried out by 16S rRNA analysis. Bioactive metabolites were extracted by solvent ...extraction method. The metabolites were assayed for antagonistic activity against bacterial and fungal pathogens, inhibition of α-glucosidase and α-amylase enzymes, antioxidant activity and cytotoxic activity against various cell lines. The actinobacterial extract showed significant antagonistic activity against four gram-positive and two gram-negative pathogens. Excellent reduction in the growth of fungal pathogens was also observed. The minimum inhibitory concentration of the partially purified extract (PPE) was determined as 31.25 μg/mL against
, 15.62 μg/mL against
,
and
. The lowest MIC was observed against
as 7.8 μg/mL. MIC against fungal pathogens was determined as 62.5 μg/mL against
and 15.62 μg/mL against
. The α-glucosidase and α-amylase inhibitory potential of the fractions were carried out by microtiter plate method. IC
value of active fraction for α-glucosidase and α-amylase inhibition was found to be 21.17 μg/mL and 20.46 μg/mL respectively. The antioxidant activity of partially purified extract (PPE) (DPPH, ABTS, FRAP and Metal chelating activity) were observed and were also found to have significant cytotoxic activity against HT-29, MDA and U-87MG cell lines. The compound analysis was performed using gas chromatography-mass spectrometry (GC-MS) and resulted in three constituents; pyrrolo1⁻apyrazine-1,4-dione,hexahydro-3-(2-methylpropyl)-, being the main component (80%). Overall, the strain possesses a wide spectrum of antimicrobial, enzyme inhibitory, antioxidant and cytotoxic activities which affords the production of significant bioactive metabolites as potential pharmacological agents.
ABSTRACT
Bacterial endophytes are found in the internal tissues of plants and have intimate associations with their host. However, little is known about the diversity of medicinal plant endophytes ...(ME) or their capability to produce specialised metabolites that may contribute to therapeutic properties. We isolated 75 bacterial ME from 24 plant species of the Western Ghats, India. Molecular identification by 16S rRNA gene sequencing grouped MEs into 13 bacterial genera, with members of Gammaproteobacteria and Firmicutes being the most abundant. To improve taxonomic identification, 26 selected MEs were genome sequenced and average nucleotide identity (ANI) used to identify them to the species-level. This identified multiple species in the most common genus as Bacillus. Similarly, identity of the Enterobacterales was also distinguished within Enterobacter and Serratia by ANI and core-gene analysis. AntiSMASH identified non-ribosomal peptide synthase, lantipeptide and bacteriocin biosynthetic gene clusters (BGC) as the most common BGCs found in the ME genomes. A total of five of the ME isolates belonging to Bacillus, Serratia and Enterobacter showed antimicrobial activity against the plant pathogen Pectobacterium carotovorum. Using molecular and genomic approaches we have characterised a unique collection of endophytic bacteria from medicinal plants. Their genomes encode multiple specialised metabolite gene clusters and the collection can now be screened for novel bioactive and medicinal metabolites.
A collection of bacterial endophytes isolated from a number of medicinal plants of the Western Ghats, India were investigated for their capability to produce specialised metabolites that may contribute to therapeutic properties.
In the present study, nanoparticles of gold, iron oxide and zinc oxide (ZnO) were studied for cytotoxicity in the colorectal cancer cell HT 29. The metallic nanoparticles in the range of <50 and <100 ...nm were screened for anticancer activity by MTT assay. The nanoparticles were tested at concentrations ranging from 0.5 to 50 µg/ml. Zinc oxide exhibited significant anti-cancer activity in comparison to other nanoparticles. It had an IC50 value of 17.12 µg/ml. The mechanism of action was studied by fluorescence microscopy with acridine orange, propidium iodide and DAPI staining techniques. The ROS production of ZnO nanoparticles was determined by DCFH-DA. The ZnO nanoparticles were conjugated with novel hydrophobic peptides and evaluated for anticancer activity. It was observed that the nanoparticles peptide complex showed better cytotoxicity than either peptide or nanoparticle alone. Thus, the ZnO nanoparticles tested in our study has anticancer activity against colon cancer cells. It can also be conjugated with peptides and used for targeting cancer cells with higher efficacy.
The search for novel bioactive metabolites continues to be of much importance around the world for pharmaceutical, agricultural, and industrial applications. Actinobacteria constitute one of the ...extremely interesting groups of microorganisms widely used as important biological contributors for a wide range of novel secondary metabolites. This study focused on the assessment of antimicrobial and antioxidant activity of crude extracts of actinobacterial strains. Western Ghats of India represents unique regions of biologically diverse areas called "hot spots". A total of 32 isolates were obtained from soil samples of different forest locations of Bisle Ghat and Virjapet situated in Western Ghats of Karnataka, India. The isolates were identified as species of
,
, and
by cultural, morphological, and molecular studies. Based on preliminary screening, seven isolates were chosen for metabolites extraction and to determine antimicrobial activity qualitatively (disc diffusion method) and quantitatively (micro dilution method) and scavenging activity against DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS(2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radicals. Crude extracts of all seven isolates exhibited fairly strong antibacterial activity towards MRSA strains (MRSA ATCC 33591, MRSA ATCC NR-46071, and MRSA ATCC 46171) with MIC varying from 15.62 to 125 μg/mL, whereas showed less inhibition potential towards Gram-negative bacteria
(ATCC 25241) and
(ATCC 11775) with MIC of 125-500 μg/mL. The isolates namely S1A, SS5, SCA35, and SCA 11 inhibited
(MTCC 6576) to a maximum extent with MIC ranging from 62.5 to 250 μg/mL. Crude extract of SCA 11 and SCA 13 exhibited potent scavenging activities against DPPH and ABTS radicals. The results from this study suggest that actinobacterial strains of Western Ghats are an excellent source of natural antimicrobial and antioxidant compounds. Further research investigations on purification, recovery, and structural characterization of the active compounds are to be carried out.
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