The glyoxylate shunt (GS) is a two-step metabolic pathway (isocitrate lyase, aceA; and malate synthase, glcB) that serves as an alternative to the tricarboxylic acid cycle. The GS bypasses the carbon dioxide-producing steps of the tricarboxylic acid cycle and is essential for acetate and fatty acid metabolism in bacteria. GS can be up-regulated under conditions of oxidative stress, antibiotic stress, and host infection, which implies that it plays important but poorly explored roles in stress defense and pathogenesis. In many bacterial species, including Pseudomonas aeruginosa, aceA and glcB are not in an operon, unlike in Escherichia coli. In P. aeruginosa, we explored relationships between GS genes and growth, transcription profiles, and biofilm formation. Contrary to our expectations, deletion of aceA in P. aeruginosa improved cell growth under conditions of oxidative and antibiotic stress. Transcriptome data suggested that aceA mutants underwent a metabolic shift toward aerobic denitrification; this was supported by additional evidence, including up-regulation of denitrification-related genes, decreased oxygen consumption without lowering ATP yield, increased production of denitrification intermediates (NO and N 2 O), and increased cyanide resistance. The aceA mutants also produced a thicker exopolysaccharide layer; that is, a phenotype consistent with aerobic denitrification. A bioinformatic survey across known bacterial genomes showed that only microorganisms capable of aerobic metabolism possess the glyoxylate shunt. This trend is consistent with the hypothesis that the GS plays a previously unrecognized role in allowing bacteria to tolerate oxidative stress.

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Recently, green metal nanoparticles have received global attention owing to their economical synthesis, biocompatible nature, widespread biomedical and environmental applications. Current study demonstrates a sustainable approach for the green synthesis of silver nanoparticles (P-AgNPs) and gold nanoparticles (P-AuNPs) from P. serrulata fresh fruit extract. The silver and gold nanoparticles were synthesized in a very rapid, efficient and facile manner, within 50 min and 30 s at 80 °C, respectively. The nanoparticles were characterized by using visual observation, UV-Vis, FE-TEM, EDX, elemental mapping, FT-IR, XRD and DLS, which confirmed the formation of monodispersed, crystalline and stable nanoparticles. Further, we explored these nanoparticles for anti-inflammatory activity through inhibition of downstream NF-κB activation in macrophages (RAW264.7). We demonstrated that the nanoparticles reduced expression of inflammatory mediators such as nitric oxide (NO), prostaglandin E2 (PEG), inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) was attenuated in lipopolysaccharide (LPS)-induced RAW264.7 cells. Furthermore, nanoparticles significantly suppressed LPS-induced activation of NF-κB signalling pathway via p38 MAPK in RAW 264.7 cells. To the best of our knowledge, this is the first report on the efficient green synthesis of P-AgNPs and P-AuNPs using P. serrulata fresh fruit extract and its in vitro anti-inflammatory effects. Collectively, our results suggest that P. serrulata fresh fruit extract is a green resource for the eco-friendly synthesis of P-AgNPs and P-AuNPs, which further can be utilized as a novel therapeutic agent for prevention and cure of inflammation due to their biocompatible nature.

A facile synthesis and biological applications of silver (DH-AgNps) and gold nanoparticles (DH-AuNps) mediated by the aqueous extract of Angelicae Pubescentis Radix (Du Huo) are explored. Du Huo is a medicinal root belonging to Angelica pubescens Maxim which possesses anti-inflammatory, analgesic, and antioxidant properties. The absorption spectra of nanoparticles in varying root extract and metal ion concentration, pH, reaction temperatures, and time were recorded by ultraviolet–visible (UV-Vis) spectroscopy. The presence of DH-AgNps and DH-AuNps was confirmed from the surface plasmon resonance intensified at ~414 and ~540 nm, respectively. Field emission transmission electron micrograph (FE-TEM) analysis revealed the formation of quasi-spherical DH-AgNps and spherical icosahedral DH-AuNps. These novel DH-AgNps and DH-AuNps maintained an average crystallite size of 12.48 and 7.44 nm, respectively. The biosynthesized DH-AgNps and DH-AuNps exhibited antioxidant activity against 2,2-diphenyl-1-picrylhydrzyl (DPPH) radicals and the former exhibited antimicrobial activity against clinical pathogens including Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Salmonella enterica. The expected presence of flavonoids, sesquiterpenes, and phenols on the nanoparticle surface were conjectured to grant protection against aggregation and free radical scavenging activity. DH-AgNps and DH-AuNps were further investigated for their cytotoxic properties in RAW264.7 macrophages for their potential application as drug carriers to sites of inflammation. In conclusion, this green synthesis is favorable for the advancement of plant mediated nano-carriers in drug delivery systems, cancer diagnostic, and medical imaging.Graphical abstractSchematic diagram of biosynthesis of DH-AgNps and DH-AuNps and evaluation of their bioactivities.

Atopic dermatitis (AD) is a chronic skin disease that affects millions of people worldwide. Keratinocytes and macrophages are two cells types that play a pivotal role in the development of AD. These cells produced different chemokines and cytokines, especially thymus and activation-regulated chemokine (TARC/CCL17) and macrophage-derived chemokine (MDC/CCL22), as well as nitric oxide (NO) through inducible nitric oxide synthase (iNOS) and COX2 in response to stimulation by TNF-α/IFN-γ and lipopolysaccharide (LPS) respectively. These mediators are thought to be crucial regulators of the pathogenesis of AD. Although several natural compounds to treat AD have been studied, the effect of Rg5:Rk1 from Panax ginseng (P. ginseng) on AD has not yet been investigated. In this study, we evaluated the inhibitory effect of Rg5:Rk1 on TNF-α/IFN-γ stimulated keratinocytes (HaCaT cells) and LPS-stimulated macrophages (RAW 264.7 cells). Enzyme-linked immunosorbent assay (ELISA) data showed that pretreatment of HaCaT cells with Rg5:Rk1 significantly reduced the TNF-α/IFN-γ-induced increase in TARC/CCL17 expression in a dose-dependent manner. In addition, Rg5:Rk1 decreased LPS-mediated nitric oxide (NO) and reactive oxygen species (ROS) production in RAW 264.7 cells. A considerable reduction in messenger RNA (mRNA) expression of the aforementioned AD mediators was also observed. Pretreatment with Rg5:Rk1 attenuated the TNF-α/IFN-γ-induced phosphorylation of p38 MAPK, STAT1, and NF-κB/IKKβ in HaCaT cells. Together, these findings suggest that ginsenoside Rg5:Rk1 may have a potential anti-AD effect by suppressing NF-κB/p38 MAPK/STAT1 signaling.

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Gold (FA-AuNps) and silver (FA-AgNps) nanoparticles were synthesized at room temperature by aqueous extract of dried fruits of Amomum villosum, also known as Fructus Amomi (cardamom), in order to confer antioxidant, catalytic, antimicrobial activities and treatment effect against breast cancer cells. Fruit extracts served as both reducing agents and stabilizers in lieu of chemical agents. Ultra-violet visible (UV-Vis) spectroscopy, field emission transmission electron microscopy (FE-TEM), energy-dispersive X-ray (EDX) spectroscopy, elemental mapping, X-ray powder diffraction (XRD), selected area electron diffraction (SAED), dynamic light scattering (DLS) and Fourier transform infrared (FTIR) spectroscopy were employed to characterize the biosynthesized nanoparticles. Both FA-AuNps and FA-AgNps exhibited free radical scavenging activity against 2,2-diphenyl-1-picrylhydrzyl (DPPH). Additionally, biosynthesized nanoparticles successfully reduced methylene blue, a well-known redox indicator. FA-AgNps showed zones of inhibition against pathogenic Staphylococcus aureus and Escherichia coli. Finally, the biological activities and cytotoxicity of nanoparticles were subsequently investigated in vitro. FA-AuNps demonstrated a potential cytotoxic agent against breast cancer cells as evaluated by MTT assay. The study highlights a rapid synthesis of FA-AuNps and FA-AgNps by dried Fructus Amomi aqueous extract and evaluates their potential biological applications on medical platforms.

Panax ginseng C.A. Meyer (P. ginseng), hereafter referred to as P. ginseng, is known to exert a wide range of pharmacological effects both in vitro and in vivo; however, few studies have investigated the effects of ginseng on bone metabolism. We therefore investigated the potential antiosteoporotic properties of ginseng on the growth and differentiation of murine MC3T3-E1 cells. Rg5:Rk1 is a mixture of protopanaxadiol-type ginsenosides, isolated from fresh P. ginseng root, via a repetitive steaming and drying process. In this study, we examined the stimulatory effects of Rg5:Rk1 on the differentiation and mineralization of MC3T3-E1 cells. Undifferentiated cells were treated with a range of concentrations of Rg5:Rk1 (1-50 µg/mL), and cell viability was measured with the 3-(4,5-dimethyl-thiazol-2yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Treatment with Rg5:Rk1 significantly increased cell viability in a dose-dependent manner. To investigate the possible mechanisms by which Rg5:Rk1 affects the early differentiation phase of MC3T3-E1 cells, the cells were treated with Rg5:Rk1 for 14-24 days before assessing the levels of multiple osteoblastic markers. The markers examined included alkaline phosphatase (ALP) activity type I collagen content (Coll-I), calcium deposition (by Alizarin Red S staining), extracellular mRNA expression of bone morphogenetic protein-2 (BMP-2), and the level of Runt-related transcription factor 2 (Runx2). Rg5:Rk1 treatment also increased the activities of proteins associated with osteoblast growth and differentiation in a dose-dependent manner. Overall, we found that the Rg5:Rk1 mixture of ginsenosides improved the osteoblastic function of MC3T3-E1 cells by increasing their proliferative capacity. This improvement is due to the action of Rg5:Rk1 on BMP-2, which is mediated by Runx2-dependent pathways.