Antibacterial Activity of Alkaloids, Flavonoids, Saponins and Tannins Mediated Green Synthesised Silver Nanoparticles Against Pseudomonas aeruginosa and Bacillus subtilis

Green Synthesis of Silver Nanoparticle Using Black Mulberry and Characterization, Phytochemical, and Bioactivity

Synthesis of silver nanoparticles (AgNPs) using plant extracts has been proposed as a more advantageous and environmentally friendly alternative compared to existing physical/chemical methods. In this study, AgNPs were synthesized from silver nitrate using black mulberry (BM) extract. The biosynthesized AgNPs were characterized through an UV-visible spectrometer, X-ray diffraction, and transmission electron microscopy. Additionally, BM-AgNPs were subjected to antioxidant, antibacterial, anti-inflammatory, and anticancer activities. AgNPs biosynthesized from BM extract were dark brown in color and showed a strong peak at 437 nm, confirming that AgNPs were successfully synthesized. The size of AgNPs was 170.17 ± 12.65 nm, the polydispersity index was 0.281 ± 0.07, and the zeta potential value was -56.6 ± 0.56 mV, indicating that the particles were stable. The higher total phenol, flavonoid, and anthocyanin content of BM-AgNPs compared to BM extract indicates that the particles contain multiple active substances due to the formation of AgNPs. The DPPH and ABTS assays showed decreased IC50 values compared to BM extract, demonstrating improved antioxidant activity. AgNPs inhibited the growth of S. aureus and E. coli at 600 μg/mL, with minimum bactericidal concentrations determined to be 1000 and 1200 μg/mL, respectively. The anti-inflammatory activity was 64.28% at a BM-AgNPs concentration of 250 μg/mL. As the concentration increased, the difference from the standard decreased, indicating the inhibitory effect of AgNPs on bovine serum albumin denaturation. The viability of MCF-7 cells treated with BM-AgNPs was found to be significantly lower than that of cells treated with BM extract. The IC50 value of BM-AgNPs was determined to be 96.9 μg/mL. This study showed that BM-AgNPs have the potential to be used in the pharmaceutical industry as antioxidant, antibacterial, anti-inflammatory, and anticancer agents.

Nanoparticles and root traits: mineral nutrition, stress tolerance and interaction with rhizosphere microbiota

MAIN CONCLUSION

This review article highlights a broader perspective of NPs and plant-root interaction by focusing on their beneficial and deleterious impacts on root system architecture (RSA). The root performs a vital function by securing itself in the soil, absorbing and transporting water and nutrients to facilitate plant growth and productivity. In dicots, the architecture of the root system (RSA) is markedly shaped by the development of the primary root and its branches, showcasing considerable adaptability in response to changes in the environment. For promoting agriculture and combating global food hunger, the use of nanoparticles (NPs) may be an exciting option, for which it is essential to understand the behaviour of plants under NPs exposure. The nature of NPs and their physicochemical characteristics play a significant role in the positive/negative response of roots and shoots. Root morphological features, such as root length, root mass and root development features, may regulated positively/negatively by different types of NPs. In addition, application of NPs may also enhance nutrient transport and soil fertility by the promotion of soil microorganisms including plant growth-promoting rhizobacteria (PGPRs) and also soil enzymes. Interestingly the interaction of nanomaterials (NMs) with rhizospheric bacteria can enhance plant development and soil health. However, some studies also suggested that the increased use of several types of engineered nanoparticles (ENPs) may disrupt the equilibrium of the soil-root interface and unsafe morphogenesis by causing the browning of roots and suppressing the growth of root and soil microbes. Thus, this review article has sought to compile a broader perspective of NPs and plant-root interaction by focusing on their beneficial or deleterious impacts on RSA.

Mechanism of antibacterial activity of diallyl sulfide against Bacillus cereus

World health organization (WHO) recognizes antimicrobial resistance as a silent pandemic. It is estimated that 10 million deaths will occur annually due to antimicrobial resistant infections by 2050. Phytochemicals exhibit activity against drug resistant bacteria, offering potential for developing novel antibacterial agents. Garlic organosulphur compounds exhibit potent activity against a variety of drug-resistant bacteria. Identifying their mechanism of action is critical to assess their potential to be developed as novel antibacterial agents. Diallyl sulfide (DAS) is a component of garlic essential oil with antibacterial activity. In this study antibacterial activity of DAS was investigated against Bacillus cereus, a common foodborne pathogen. DAS exhibited activity against B. cereus with a minimum inhibitory concentration (MIC) of 54.75 mM. The presence of DAS significantly reduced the growth of B. cereus. The study also investigated the mechanism of antibacterial activity of DAS against B. cereus. Treating B. cereus with sub-MIC and MIC concentration of DAS resulted in a dose and time-dependent leakage of intracellular proteins. The protein leakage was enhanced at acidic pH. Scanning electron microscopy (SEM) of B. cereus treated with DAS showed deformation in the cell membrane. Thus, the data indicate that DAS exerts its antibacterial activity by compromising the membrane integrity of B. cereus. The study demonstrates DAS could be used to control B. cereus infections. The findings indicate that DAS has a membrane altering activity, suggesting that development of resistance to this mechanism is less likely and the compound could be novel antibacterial or a good adjuvant for antibiotics.

Histone acetyltransferases derived RW20 protects and promotes rapid clearance of Pseudomonas aeruginosa in zebrafish larvae

Pseudomonas is a group of bacteria that can cause a wide range of infections, particularly in people with weakened immune systems, such as those with cystic fibrosis or who are hospitalized. It can also cause infections in the skin and soft tissue, including cellulitis, abscesses and wound infections. Antimicrobial peptides (AMPS) are the alternative strategy due to their broad spectrum of activity and act as effective treatment against multi-drug resistance pathogens. In this study, we have used an AMP, RW20 (1RPVKRKKGWPKGVKRGPPKW20). RW20 peptide is derived from the histone acetyltransferases (HATs) of the freshwater teleost, Channa striatus. The antimicrobial prediction tool has been utilized to identify the RW20 sequence from the HATs sequence. We synthesized the peptide to explore its mechanism of action. In an in vitro assay, RW20 was challenged against P. aeruginosa and we showed that RW20 displayed antibacterial properties and damaged the cell membrane. The mechanism of action of RW20 against P. aeruginosa has been established via field emission scanning electron microscopy (FESEM) as well as fluorescence assisted cell sorter (FACS) analysis. Both these experiments established that RW20 caused bacterial membrane disruption and cell death. Moreover, the impact of RW20, in-vivo, was tested against P. aeruginosa-infected zebrafish larvae. In the infected larvae, RW20 showed protective effect against P. aeruginosa by increasing the larval antioxidant enzymes, reducing the excess oxidative stress and apoptosis. Thus, it is possible that HATs-derived RW20 can be an efficient antimicrobial molecule against P. aeruginosa.

Antibacterial and smear layer removal efficacy of moringa (Moringa oleifera): An in vitro study

Objective

This study evaluated the effectiveness of moringa (Moringa oleifera) leaves decoction for removing a smear layer compared to sodium hypochlorite (NaOCl) and ethylenediaminetetraacetic acid (EDTA), as well as its antimicrobial activities.

Methods

The moringa leaves were extracted using hot water decoction at two different concentrations (2.5% and 5.0% w/v). A total of 30 extracted human single-rooted teeth were prepared to assess the smear layer removal efficacy. The presence of a smear layer in the middle third of the root canal was detected by confocal microscopy. Then the antibacterial effects were assessed against Enterococcus faecalis and Streptococcus mutans bacteria using the agar diffusion method.

Results

The 2.5% and 5.0% decoction were significantly more effective than 0.25% NaOCl in removing the smear layer (p < 0.05); however, no significant difference was observed compared to EDTA (p > 0.05). The in vitro antimicrobial assay showed that 5.0% decoction had higher antimicrobial activity against both of the test pathogens.

Conclusion

The findings of this study suggest that moringa leaves decoction can be considered an effective irrigant in endodontics.

Aquatic Peptide: The Potential Anti-Cancer and Anti-Microbial Activity of GE18 Derived from Pathogenic Fungus Aphanomyces invadans

Small molecules as well as peptide-based therapeutic approaches have attracted global interest due to their lower or no toxicity in nature, and their potential in addressing several health complications including immune diseases, cardiovascular diseases, metabolic disorders, osteoporosis and cancer. This study proposed a peptide, GE18 of subtilisin-like peptidase from the virulence factor of aquatic pathogenic fungus Aphanomyces invadans, which elicits anti-cancer and anti-microbial activities. To understand the potential GE18 peptide-induced biological effects, an in silico analysis, in vitro (L6 cells) and in vivo toxicity assays (using zebrafish embryo), in vitro anti-cancer assays and anti-microbial assays were performed. The outcomes of the in silico analyses demonstrated that the GE18 peptide has potent anti-cancer and anti-microbial activities. GE18 is non-toxic to in vitro non-cancerous cells and in vivo zebrafish larvae. However, the peptide showed significant anti-cancer properties against MCF-7 cells with an IC50 value of 35.34 µM, at 24 h. Besides the anti-proliferative effect on cancer cells, the peptide exposure does promote the ROS concentration, mitochondrial membrane potential and the subsequent upregulation of anti-cancer genes. On the other hand, GE18 elicits significant anti-microbial activity against P. aeruginosa, wherein GE18 significantly inhibits bacterial biofilm formation. Since the peptide has positively charged amino acid residues, it targets the cell membrane, as is evident in the FESEM analysis. Based on these outcomes, it is possible that the GE18 peptide is a significant anti-cancer and anti-microbial molecule.

Retrospective analysis of the key molecules involved in the green synthesis of nanoparticles

Emerging nanotechnology leads to success in synthesizing and applying nanoparticles (NPs) using the green-chemistry approach. NPs synthesized using naturally derived materials are a potential alternative to chemical and physical methods because they are simple, cost-effective, eco-friendly, and lower the possibility of hazardous residues being released into the environment. Furthermore, NPs synthesized using the green synthesis approach are stable and biocompatible. However, because natural extracts contain a diverse spectrum of bioactive components, it is difficult to pinpoint the specific component involved in NP formation. Furthermore, the bioactive component contained in the extract changes based on a number of environmental factors; therefore, several studies began with the synthesis of NPs using a pure compound isolated from diverse natural sources. Hence, the present review paper makes an effort to retrospectively analyze the key compounds of the extracts which are responsible for the synthesis of the NPs. The analysis was carried out based on the physicochemical characteristics and biological activities of NPs synthesized from either the extract or the pure compounds. These pure-compound-based NPs were studied for their antimicrobial, antibiofilm, anti-inflammatory, anticancer, and antioxidant properties. In addition, the present review also describes progress in the study of pure compound-based numerous biological activities and the underlying mechanisms of action.

Withaferin A targets the membrane of Pseudomonas aeruginosa and mitigates the inflammation in zebrafish larvae; an in vitro and in vivo approach

Infections due to multidrug-resistant Pseudomonas aeruginosa are prevalent among patients with cystic fibrosis. The emergence of antibiotic-resistant pathogens necessitated the development of novel low-risk natural antibacterial compounds. Herbal medicines are used from dates of the origin of mankind and still serve their purpose as therapeutic agents. We demonstrated the antibacterial activity of Withaferin A extracted from the traditional herb, ashwagandha or winter cherry (Withania somnifera). Withaferin A exhibits strong antibacterial activity against P. aeruginosa with a minimum inhibitory concentration of 60 μM and minimum bactericidal concentration of 80 μM. Results obtained from membrane stabilization assay and electron microscopic analysis showed that Withaferin A acts by damaging the cell membrane of P. aeruginosa. Additionally, we investigated oxidative stress and inflammatory response after Withaferin A treatment in P. aeruginosa infected zebrafish larvae model. The results indicate that the level of ROS, and its related lipid peroxidation and apoptosis were significantly reduced after treated with Withaferin A. Consequently, an increment in antioxidant enzymes level such as superoxide dismutase (SOD) and catalase (CAT) was observed. Macrophage localization experiment showed a smaller number of localized macrophages in zebrafish, which indicates the reduction in inflammatory response. In conclusion, Withaferin A could serve as an alternative natural product in the treatment of infections caused by P. aeruginosa.

A Critical Review of the Antimicrobial and Antibiofilm Activities of Green-Synthesized Plant-Based Metallic Nanoparticles

Metallic nanoparticles (MNPs) produced by green synthesis using plant extracts have attracted huge interest in the scientific community due to their excellent antibacterial, antifungal and antibiofilm activities. To evaluate these pharmacological properties, several methods or protocols have been successfully developed and implemented. Although these protocols were mostly inspired by the guidelines from national and international regulatory bodies, they suffer from a glaring absence of standardization of the experimental conditions. This situation leads to a lack of reproducibility and comparability of data from different study settings. To minimize these problems, guidelines for the antimicrobial and antibiofilm evaluation of MNPs should be developed by specialists in the field. Being aware of the immensity of the workload and the efforts required to achieve this, we set out to undertake a meticulous literature review of different experimental protocols and laboratory conditions used for the antimicrobial and antibiofilm evaluation of MNPs that could be used as a basis for future guidelines. This review also brings together all the discrepancies resulting from the different experimental designs and emphasizes their impact on the biological activities as well as their interpretation. Finally, the paper proposes a general overview that requires extensive experimental investigations to set the stage for the future development of effective antimicrobial MNPs using green synthesis.

Alkaloid profiling and antimicrobial activities of Papaver glaucum and P. decaisnei

OBJECTIVE

Papaver decaisnei Hochst. & Steud. Ex Elkan and Papaver glaucum Boiss. & Hausskn. growing wild in Northern Iraq have been historically used for medicinal purposes. In this study, both species were evaluated for their alkaloid content and antimicrobial activities.

RESULTS

Alkaloids were extracted and isolated by preparative thin-layer chromatography (TLC). Identification was carried out by comparing spectral data (UV and 1H-NMR) and TLC Rf values with those of authentic samples. Two alkaloids, proapaorphine-type mecambrine and aporphine-type roemerine were isolated from P. decaisnei. Two benzylisoquinoline type alkaloids papaverine (major alkaloid) and palaudine as well as aporphine-type N-methylasimilobine have been obtained in P. glaucum. Both P. glaucum and P. decaisnei extracts revealed strong antimicrobial activity on Pseudomonas aeruginosa ATCC 27853 and Enterococcus faecalis ATCC 29212. Collectively these results indicate that P. glaucum and P. decaisnei are promising sources of alkaloids that could further be investigated for medicinal purposes.

Antimicrobial activity of Centella asiatica and Gigantochloa apus

OBJECTIVES

Antibiotic treatments can create multi-drug resistance among several pathogens. There is a need for an antibiotic alternative to overcome this problem. In Indonesia, Centella asiatica (Asiatic pennywort) and Gigantochloa apus (string bamboo) are two common medicinal plants used to treat tuberculosis, diarrhea, and other symptoms. This study was done to compare the antimicrobial activity of C. asiatica and G. apus against five pathogenic bacteria, i.e., Mycobacterium tuberculosis H37Rv strain, Escherichia coli, Staphylococcus aureus, Bacillus subtilis, and Salmonella typhi.

METHODS

The ethanol extracts of C. asiatica, and G. apus shoot were obtained by using speed extractor, pressure, and temperature extraction. The phytochemical contents of each extract were screened. The ethanol extract's antimycobacterial activity was determined using Lowenstein Jensen (LJ) medium and antibacterial activity was determined using Kirby-Bauer methods on Mueller Hinton agar (MHA).

RESULTS

The phytochemical analysis showed that G. apus extract contains alkaloids and tannins, whereas C. asiatica extract contains flavonoids, alkaloids, saponins, and tannins. This study showed that G. apus inhibited the growth of M. tuberculosis H37Rv strain and S. typhi. C. asiatica showed antimicrobial activity against all pathogenic bacteria tested, except B. subtilis.

CONCLUSIONS

Both medicinal plants extract can inhibit the growth of five pathogenic bacteria tested, thus, have the potential as an alternative treatment, or complementary, to treat the pathogenic bacterial infection.

Aboveground plant-to-plant communication reduces root nodule symbiosis and soil nutrient concentrations

Aboveground communication between plants is well known to change defense traits in leaves, but its effects on belowground plant traits and soil characteristics have not been elucidated. We hypothesized that aboveground plant-to-plant communication reduces root nodule symbiosis via induction of bactericidal chemical defense substances and changes the soil nutrient environment. Soybean plants were exposed to the volatile organic compounds (VOCs) from damaged shoots of Solidago canadensis var. scabra, and leaf defense traits (total phenolics, saponins), root saponins, and root nodule symbiosis traits (number and biomass of root nodules) were measured. Soil C/N ratios and mineral concentrations were also measured to estimate the effects of resource uptake by the plants. We found that total phenolics were not affected. However, plants that received VOCs had higher saponin concentrations in both leaves and roots, and fewer root nodules than untreated plants. Although the concentrations of soil minerals did not differ between treatments, soil C/N ratio was significantly higher in the soil of communicated plants. Thus, the aboveground plant-to-plant communication led to reductions in root nodule symbiosis and soil nutrient concentrations. Our results suggest that there are broader effects of induced chemical defenses in aboveground plant organs upon belowground microbial interactions and soil nutrients, and emphasize that plant response based on plant-to-plant communications are a bridge between above- and below-ground ecosystems.

Bioactive and nutritional characterization of modeled and optimized consumer-ready flakes from pseudocereal (Amaranthus viridis), high-protein soymeal and modified corn starch

Flake is consumed in many parts of the world. Flakes are majorly prepared from cereals. However, most flakes are deficient in protein and some other healthful substances. High-protein soymeal is rich in protein, mineral, amino acids, antioxidants, and other healthful substances. Formulating flakes with high-protein soymeal would improve the health status of consumers. This work investigated consumer-ready flake from amaranth, high-protein soymeal, and modified corn starch produced under the optimized condition and characterized with the aim to develop models that would give a healthful consumer-ready flake. Amaranthus viridis, corn, and soybean grains were sorted, wet-cleaned, and dried. Soybean grains were processed into high-protein soymeal, starch was extracted from corn grains while A. viridis grains were processed into flour. Formulated flour mixtures were developed into flakes using three-level factorial categoric factor design of response surface methodology. The flakes were analyzed using standard procedures. Optimal flour mixtures of high-protein soymeal (34.78 g/100 g), amaranth (56.52 g/100 g), and modified corn starch (8.70 g/100 g) were established. Results showed the optimized flakes contained per 100 g: 29.05 g protein, 6.00 g fat, 4.10 g fibre, 3.84 g ash, 8.96 g moisture, 249.74 mg calcium, 272.35 mg magnesium, 12.08 mg iron, 618.42 mg phosphorus, 6.41 mg niacin, 4.85 mg pyridoxine, 0.21 g tannin, 1.85 mg phytate, 2.96 mg alkaloids, 908.24GAE total phenolics and 12.75mgRE flavonoids with good quality characteristics in amino acids. The study illustrated the feasibility of formulating quality consumer-ready flakes from amaranth, high-protein soymeal, and modified corn starch. The production process is scalable and could be employed for both domestic and industrial purposes.

Graphical abstract

Comparative Antioxidant Analysis of Moringa oleifera Leaf Extracts from South Western States in Nigeria

Background

Moringa oleifera is a medicinal plant that ethnobotanical studies have shown its inclusion in treatment of many ailments such as diarrhea, diabetes, epilepsy, wound healing and arthritis. It is a plant that was believed to originate from India but could now be found in both the tropics and the sub-topics. Earlier reports have not addressed the association between the location of plant collection and its antioxidant contents. In this study, Moringa oleifera leaves were collected from 21 locations within the south western states of Nigeria. Leaves from each of the locations were dried and evaluated for total phenols, tannin, saponin and flavonoid. DPPH scavenging activity, nitric oxide scavenging activity and inhibition of lipid peroxidation were also evaluated.

Results

All the parameters analysed showed significant within- and between-group differences. Some locations had greater DPPH scavenging ability than the standard (quercetin).

Conclusion

Environmental parameters like annual precipitation, minimum temperature and maximum temperature, and soil type of the location of the plants showed influence on the level of antioxidant, while further analysis using metaboanalyst showed a notable effect of soil type on the antioxidant activity.

Extraction, Purification, and Characterization of Polysaccharides of Araucaria heterophylla L and Prosopis chilensis L and Utilization of Polysaccharides in Nanocarrier Synthesis

Background

Plant gums consist of polysaccharides which can be used in the preparation of nanocarriers and provide a wide application in pharmaceutical applications including as drug delivery agents and the matrices for drug release. The objectives of the study were to collect plant gums from Araucaria heterophylla L and Prosopis chilensis L and to extract and characterize their polysaccharides. Then to utilize these plant gum-derived polysaccharides for the formulation of nanocarriers to use for drug loading and to examine their purpose in drug delivery in vitro.

Methods

Plant gum was collected, polysaccharide was extracted, purified, characterized using UV-Vis, FTIR, TGA and GCMS and subjected to various bioactive studies. The purified polysaccharide was used for making curcumin-loaded nanocarriers using STMP (sodium trimetaphosphate). Bioactivities were performed on the crude, purified and drug-loaded nanocarriers. These polysaccharide-based nanocarriers were characterized using UV-Vis spectrophotometer, FTIR, SEM, and AFM. Drug release kinetics were performed for the drug-loaded nanocarriers.

Results

The presence of glucose, xylose and sucrose was studied from the UV-Vis and GCMS analysis. Purified polysaccharides of both the plants showed antioxidant activity and also antibacterial activity against Bacillus sp. Purified polysaccharides were used for nanocarrier synthesis, where the size and shape of the nanocarriers were studied using SEM analysis and AFM analysis. The size of the drug-loaded nanocarriers was found to be around 200 nm. The curcumin-loaded nanocarriers were releasing curcumin slow and steady.

Conclusion

The extracted pure polysaccharide of A. heterophylla and P. chilensis acted as good antioxidants and showed antibacterial activity against Bacillus sp. These polysaccharides were fabricated into curcumin-loaded nanocarriers whose size was below 200 nm. Both the drug-loaded nanocarriers synthesized using A. heterophylla and P. chilensis showed antibacterial activity with a steady drug release profile. Hence, these natural exudates can serve as biodegradable nanocarriers in drug delivery.

Green synthesis of antimicrobial silver nanoparticles using aqueous leaf extracts from three Congolese plant species (Brillantaisia patula, Crossopteryx febrifuga and Senna siamea)

In the present study, silver nanoparticles (AgNPs) were synthesized using aqueous leaf extracts of three Congolese plant species, namely Brillantaisia patula (BR-PA), Crossopteryx febrifuga (CR-FE) and Senna siamea (SE-SI). The obtained AgNPs were studied for their optical, structural, surface morphological and antibacterial properties. The prepared AgNPs were characterized by using UV-Visible spectra, Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), X-ray spectroscopy (EDX) and X-ray diffractometer (XRD). The synthesized nanoparticles were spherical shaped and well-dispersed with average sizes ranging from 45 to 110 nm. The AgNPs derived from BR-PA, CR-FE and SE-SI exhibited higher antibacterial activity against three bacterial pathogens of the human skin compared to their respective crude extracts and AgNO3. This indicated that the biomolecules covering the nanoparticles may enhance the biological activity of metal nanoparticles. Hence, our results support that biogenic synthesis of AgNPs from Congolese plants constitutes a potential area of interest for the therapeutic management of microbial diseases such as infectious skin diseases.