A xylan from the fresh leaves of Piper betle: Structural characterization and studies of bioactive properties.

A pure water soluble xylan (PS-I) with an average molecular weight ~1.1 × 105 Da was isolated from the hot water extraction of fresh leaves of Piper betle (paan). The xylan was found to be composed of xylose, galactose and methyl galacturonate in a molar ratio of nearly 3:1:1. The repeating unit was composed of a backbone containing three (1 â†’ 4)-α-D-Xylp residues, one of which was branched at O-2 position with the side chain consisting of (1 â†’ 4)-α-D-GalpA6Me and terminal ß-D-Galp residues. This xylan exhibited macrophage, splenocyte, and thymocyte stimulatory activities. In vitro antioxidant studies demonstrated that the xylan has DPPH radical scavenging potential (EC50 = 148 µg/mL), ABTS radical quenching activity (EC50 = 188 µg/mL) and ferrous ions chelating activity (EC50 = 370 µg/mL). These findings elicit the need for further exploration of the xylan as a natural antioxidant and a potent immunostimulating agent.

A review on antiviral and immunomodulatory polysaccharides from Indian medicinal plants, which may be beneficial to COVID-19 infected patients.

The emergence of the novel coronavirus, SARS-CoV-2 has pushed forward the world to experience the first pandemic of this century. Any specific drug against this RNA virus is yet to be discovered and presently, the COVID-19 infected patients are being treated symptomatically. During the last few decades, a number of polysaccharides with potential biological activities have been invented from Indian medicinal plants. Many polysaccharides, such as sulfated xylomannan, xylan, pectins, fucoidans, glucans, glucoarabinan, and arabinoxylan from Indian medicinal plants, have been shown to exhibit antiviral and immunomodulating activities. Plant polysaccharides exhibit antiviral activities through interference with the viral life cycle and inhibition of attachment of virus to host cell. Intake of certain immune stimulating plant polysaccharides may also protect from the virus to a certain extent. In process of continuous search for most potent drug, Indian plant polysaccharides may emerge as significant biomaterial to combat COVID-19. This review explores a number of polysaccharides from Indian medicinal plants which showed antiviral and immunomodulating activities. It is aimed to provide an overview about the composition, molecular mass, branching configuration and related bioactivities of polysaccharides which is crucial for their classification as possible drug to induce immune response in viral diseases.

Structural studies of immunomodulatory (1 → 3)-, (1 → 4)-α glucan from an edible mushroom Polyporus grammocephalus.

A water soluble polysaccharide (PGPS) with molecular weight ~ 1.4 × 105 Da was isolated by alkali treatment from an edible mushroom Polyporus grammocephalus and purified by gel chromatography using sepharose-6B column. Monosaccharide analysis revealed that PGPS was made up of glucose only. PGPS contained (1 â†’ 3)-α-D-Glcp and (1 â†’ 4)-α-D-Glcp moieties in a molar ratio of nearly 1:2. Through a series of chemical and spectroscopic (1D/2D NMR) investigations, the repeating unit of the glucan was established as: →3)-α-D-Glcp(1 â†’ [4)-α-D-Glcp(1]2→ This α-glucan was observed to stimulate some prime components of immune system, namely, macrophages, splenocytes, and thymocytes.

Flocculating, emulsification and metal sorption properties of a partial characterized novel exopolysaccharide produced by Rhizobium tropici SRA1 isolated from Psophocarpus tetragonolobus (L) D.C.

A novel exopolysaccharide (EPS) was produced by a bacterium which was isolated from Psophocarpus tetragonolobus (L) D.C. and identified as 99% Rhizobium tropici SRA1 by 16S rDNA sequencing. The flocculating performances along with emulsifying activity began simultaneously with the growth and the production of EPS and reached its utmost at 28 h. EPS was purified via chilled ethanol precipitation followed by dialysis and lyophilization. The existence of hydroxyl, methoxyl, and carboxylic functional groups were confirmed by Fourier transform infrared (FT-IR) spectrum. EPS was found to be compose of 82.44% neutral sugar and 15.93% uronic acid. The average molecular weight of the exopolysaccharide was estimated as ~ 1.8 × 105. Gas-liquid chromatography indicated the presence of glucose and galactose at a molar ratio of 3:1 in EPS. In the pH range of 3-5 with EPS dosage of 15 mg/l at 30 °C, cation-independent flocculation greater than 90% was observed. Emulsification indices (E24) of EPS were observed as 86.66%, 83.33%, 76.66%, and 73.33% with olive oil, kerosene, toluene, and n-hexane respectively. Biosorption of Cu K [45.69 wt%], Cu L [05.67 wt%], Co K [15.58 wt%], and Co L [11.72 wt%] by EPS was confirmed by energy-dispersive X-ray spectroscopy (EDS). This report on the flocculating, emulsifying, and metal sorption properties of EPS produced by R. tropici SRA1 is unique in the literature.

Effect of feed supplementation with biosynthesized silver nanoparticles using leaf extract of Morus indica L. V1 on Bombyx mori L. (Lepidoptera: Bombycidae).

Herein, we report the synthesis of silver nanoparticles (AgNPs) by a green route using the aqueous leaf extract of Morus indica L. V1. The synthesized AgNPs exhibited maximum UV-Vis absorbance at 460 nm due to surface plasmon resonance. The average diameter (~54 nm) of AgNPs was measured from HR-TEM analysis. EDX spectra also supported the formation of AgNPs, and negative zeta potential value (-14 mV) suggested its stability. Moreover, a shift in the carbonyl stretching (from 1639 cm-1 to 1630 cm-1) was noted in the FT-IR spectra of leaf extract after AgNPs synthesis which confirm the role of natural products present in leaves for the conversion of silver ions to AgNPs. The four bright circular rings (111), (200), (220) and (311) observed in the selected area electron diffraction pattern are the characteristic reflections of face centered cubic crystalline silver. LC-MS/MS study revealed the presence of phytochemicals in the leaf extract which is responsible for the reduction of silver ions. MTT assay was performed to investigate the cytotoxicity of AgNPs against two human cell lines, namely HepG2 and WRL-68. The antibacterial study revealed that MIC value of the synthesized AgNPs was 80 µg/ml against Escherichia coli K12 and Staphylococcus aureus (MTCC 96). Finally, the synthesized AgNPs at 10 µg/ml dosages showed beneficial effects on the survivability, body weights of the Bombyx mori L. larvae, pupae, cocoons and shells weights via enhancing the feed efficacy.

Structural and immunological studies of an exopolysaccharide from Acinetobacter junii BB1A.

A water-soluble heteropolysaccharide (PS) was isolated from extracellular polymeric substances (EPS) produced by a novel metal tolerant bacterium, Acinetobacter junii BB1A. Sugar analysis showed that the PS was composed of mannose, galactose and arabinose in a molar ratio of nearly 3:1:1. Structural characterization of the PS was carried out using methylation analysis, periodate oxidation, Smith degradation and 1D/2D NMR experiments. Methylation analysis revealed that the PS was consisted of 2,4-linked-mannopyranosyl, 3,4-linked-mannopyranosyl, 2-linked-galactopyranosyl, terminal mannopyranosyl and arabinopyranosyl residues in a relative proportion of nearly 1:1:1:1:1. Smith degradation of the PS showed the presence of hydrated glyceraldehyde containing disaccharide unit consisting of α-d-Manp-(1→and→4)-α-d-Manp-(1→residues where the later was directly attached to a hydrated glyceraldehyde moiety. This polysaccharide showed significant in vitro splenocyte, thymocyte, and macrophage activations with optimum dose of 100 µg/mL for macrophage and 25 µg/mL both for the splenocyte and thymocyte.

Green synthesis of silver nanoparticles using glucan from mushroom and study of antibacterial activity.

This work demonstrates synthesis of silver nanoparticles (AgNPs) using glucan isolated from a mushroom Pleurotus florida blue variant. UV-vis spectroscopy showed maximum absorbance at 425 nm due to surface plasmon resonance of AgNPs. Average diameter of the synthesized AgNPs was 2.445 ± 1.08 nm as revealed from TEM analysis. XRD analysis confirmed the face-centered cubic (fcc) crystalline structure of metallic silver. The synthesized AgNPs-glucan conjugates exhibited antibacterial activity against multiple antibiotic resistant (MAR) bacterium Klebsiella pneumoniae YSI6A and the activity was possibly due to damage of cellular macromolecules by the generation of reactive oxygen species (ROS) which was supported by observed degradation of bacterial DNA. Decrease of bactericidal effect of AgNPs-glucan conjugates in dose-dependent manner in presence of a ROS scavenger histidine further ascertained the involvement of ROS in antibacterial activity. AgNPs-glucan conjugates at LD50 dose caused least damage (0.68% hemolysis) to human RBCs. This particular dose of AgNPs-glucan conjugates in combination with each of the four antibiotics (ampicillin, azithromycin, cefepime and tetracycline) to which K. pneumoniae YSI6A was resistant, showed synergistic effect to inhibit almost 100% bacterial growth. It thus opens an avenue to use antibiotics in combination with minimum dosages of AgNPs-glucan conjugates to control MAR bacteria.

Partial characterization and flocculating behavior of an exopolysaccharide produced in nutrient-poor medium by a facultative oligotroph Klebsiella sp. PB12.

A facultative oligotrophic strain from the water sample of River Mahananda, Siliguri India was selected for its property to produce exopolysaccharide (EPS) in nutrient-poor (oligotrophic) medium. Viability assay of the strain was performed in sterile liquid LB, R2A, river water and diluted (10(-3)) LB at 30°C and pH 7 to understand oligotrophy. The selected strain was identified by 16S rRNA gene sequencing and designated as Klebsiella sp. PB12. Phylogenetic analysis showed its closest relationship with Klebsiella variicola ATCC BAA-830(T). Purification of EPS was performed by ethanol precipitation, dialysis and freeze-drying. Chemical analysis revealed that purified EPS was mainly composed of 72.32% (w/w) neutral sugar and 14.12% (w/w) uronic acids. Fourier transform infrared (FT-IR) spectroscopy indicated the presence of hydroxyl, carboxylic and methoxyl functional groups. The optimal dosages for flocculation of activated carbon suspension were 17 mg/l EPS and 4 mM CaCl(2). EPS showed flocculating rate of above 80% over a wide range of pH (pH 3-10) whereas, more than 90% rate was noted in the temperature range (10-50°C) tested in presence of CaCl(2). Moreover, EPS showed characteristic emulsifying activity with toluene (66.6%), n-hexadecane (65%), olive oil (63.3%) and kerosene (50%). The apparent molecular weight of the EPS was ~2 × 10(5) Da.