Harikesh Bahadur Singh

Oxidative DNA damage protective activity, antioxidant and anti-quorum sensing potentials of Moringa oleifera

The aqueous extract of leaf (LE), fruit (FE) and seed (SE) of Moringa oleifera was assessed to examine the ability to inhibit the oxidative DNA damage, antioxidant and anti-quorum sensing (QS) potentials. It was found that these extracts could significantly inhibit the OH-dependent damage of pUC18 plasmid DNA and also inhibit synergistically with trolox, with an activity sequence of LE > FE > SE. HPLC and MS/MS analysis was carried out, which showed the presence of gallic acid, chlorogenic acid, ellagic acid, ferulic acid, kaempferol, quercetin and vanillin. The LE was with comparatively higher total phenolics content (105.04 mg gallic acid equivalents (GAE)/g), total flavonoids content (31.28 mg quercetin equivalents (QE)/g), and ascorbic acid content (106.95 mg/100 g) and showed better antioxidant activity (85.77%), anti-radical power (74.3), reducing power (1.1 ascorbic acid equivalents (ASE)/ml), inhibition of lipid peroxidation, protein oxidation, OH-induced deoxyribose degradation, and scavenging power of superoxide anion and nitric oxide radicals than did the FE, SE and standard alpha-tocopherol. Eventually, LE and FE were found to inhibit violacein production, a QS-regulated behavior in Chromobacterium violaceum 12472.

Antioxidant and anti-quorum sensing activities of green pod of Acacia nilotica L.

The antioxidant and anti-quorum sensing activities of eight extracts were studied in green pods of Acacia nilotica. The specific phenolic compositions and their quantifications were performed by HPLC and MS/MS, which showed that the HEF (pH 4) was higher in gallic acid, ellagic acid, epicatechin, rutin, and GTs. In order to find antioxidant potential of various extracts, their activities were studied for TPC, AOA, FRSA, RP, inhibition of LPO, FIC activity, HO* and O(2)(-) scavenging activities. Among them HEF (pH 4) has shown potent antioxidant activity. HEF (pH 4) was also found effective in protecting plasmid DNA and HAS protein oxidation induced by HO*. Pre-treatment of HEF (pH 4) at 75 and 150 mg/kg body weight for 6 days caused a significant increase in the levels of CAT and SOD and decrease in the level of MDA content in liver, lungs, kidneys and blood when compared to CCl(4)-intoxicated rats. Eventually, the extracts were also screened for anti-QS activity. Of these extracts two showed QS inhibition: HEF (pH 4) and HCE. The results obtained strongly indicate that green pod of A. nilotica are important source of natural antioxidants.

Potential chemoprevention of N-nitrosodiethylamine-induced hepatocarcinogenesis by polyphenolics from Acacia nilotica bark

Chemopreventive potential of Acacia nilotica bark extract (ANBE) against single intraperitoneal injection of N-nitrosodiethylamine (NDEA, 200mg/kg) followed by weekly subcutaneous injections of carbon tetrachloride (CCl(4), 3 ml/kg) for 6 weeks induced hepatocellular carcinoma (HCC) in rats was studied. At 45 day after administration of NDEA, 100 and 200mg/kg of ANBE were administered orally once daily for 10 weeks. The levels of liver injury and liver cancer markers such as alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP), gamma-glutamyl transferase (gamma-GT), total bilirubin level (TBL), alpha-feto protein (AFP) and carcinoembryonic antigen (CEA) were substantially increased following NDEA treatment. However, ANBE treatment reduced liver injury and restored liver cancer markers. ANBE also significantly prevented hepatic malondialdehyde (MDA) formation and reduced glutathione (GSH) in NDEA-treated rats which was dose dependent. Additionally, ANBE also increased the activities of antioxidant enzymes viz., catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione-S-transferase (GST) in the liver of NDEA-administered rats. Eventually, ANBE also significantly improved body weight and prevented increase of relative liver weight due to NDEA treatment. Histological observations of liver tissues too correlated with the biochemical observations. HPLC analysis of ANBE showed the presence of gallic, protocatechuic, caffeic and ellagic acids, and also quercetin in ANBE. The results strongly support that A. nilotica bark prevents lipid peroxidation (LPO) and promote the enzymatic and non-enzymatic antioxidant defense system during NDEA-induced hepatocarcinogenesis which might be due to activities like scavenging of oxy radicals by the phytomolecules in ANBE.

Solid-state cultivation of Trichoderma harzianum NBRI-1055 for modulating natural antioxidants in soybean seed matrix.

Trichoderma harzianum NBRI-1055 was used, as fungal candidate to enhance the antioxidant activities of soybean matrix by modulating polyphenolic substances during solid-state fermentation. Trichoderma-fermented soybean (TFS) and unfermented soybean (UFS) products were extracted with water (W) and methanol (M). Total phenolic content of TFS-W and TFS-M extracts were significantly higher than that of UFS-W and UFS-M extracts. The effectiveness of extracts for total flavonoid content, antioxidant activity, free radical scavenging activity, reducing power, lipid peroxidation, metal ions-chelation, hydroxyl and superoxide radicals scavenging properties in descending order was TSF-W>TSF-M>USF-M>UFS-W. TFS extracts demonstrated significant protection against oxidative DNA and protein damages caused by hydroxyl radicals. For the specific phenolics profile, HPLC analysis was performed, which showed that the TFS extracts were also higher in isoflavones, flavonoids and phenolic acids, suggesting that this strategy may help to enhance TFS as potential antioxidants for use in preparation of soy food products.

The fungicidal effect of neem (Azadirachta indica) extracts on some soil-borne pathogens of gram (Cicer arietinum).

SUMMARYThe effect of aqueous extracts and oil of neem (Azadirachta indica) on four soil-borne pathogens, Fusarium oxysporum f.sp. ciceri, Rhizoctonia solani, Sclerotium rolfsii, and Sclerotinia scl...

Compatible rhizosphere microbes mediated alleviation of biotic stress in chickpea through enhanced antioxidant and phenylpropanoid activities.

The study was conducted to examine efficacy of a rhizospheric microbial consortium comprising of a fluorescent Pseudomonas (PHU094), Trichoderma (THU0816) and Rhizobium (RL091) strain on activation of physiological defense responses in chickpea against biotic stress caused by the collar rot pathogen Sclerotium rolfsii. Results of individual microbes were compared with dual and triple strain mixture treatments with reduced microbial load (1/2 and 1/3rd, respectively, of individual microbial load compared to single microbe application) in the mixtures. Periodical studies revealed maximum activities of phenylalanine ammonia lyase [E.C. 4.1.3.5] and polyphenol oxidase [E.C. 1.14.18.1] and accumulation of total phenol content in chickpea in the triple microbe consortium treated plants challenged with the pathogen compared to the single microbe and dual microbial consortia. Similarly, the expression of the antioxidant enzymes superoxide dismutase [E.C.1.15.1.1] and peroxidase [E.C.1.11.1.7] was also highest in the triple microbial consortium which was correlated with lesser lipid peroxidation in chickpea under the biotic stress. Histochemical staining clearly showed maximum and uniform lignification in vascular bundles of chickpea stem sections treated with the triple microbes. The physiological responses were directly correlated with the mortality rate as least plant mortality was recorded in the triple microbe consortium treated plants. The results thus suggest an augmented elicitation of stress response in chickpea under S. rolfsii stress by the triple microbial consortium in a synergistic manner under reduced microbial load.

Unraveling the efficient applications of secondary metabolites of various Trichoderma spp.

Recent shift in trends of agricultural practices from application of synthetic fertilizers and pesticides to organic farming has brought into focus the use of microorganisms that carryout analogous function. Trichoderma spp. is one of the most popular genera of fungi commercially available as a plant growth promoting fungus (PGPF) and biological control agent. Exploitation of the diverse nature of secondary metabolites produced by different species of Trichoderma augments their extensive utility in agriculture and related industries. As a result, Trichoderma has achieved significant success as a powerful biocontrol agent at global level. The endorsement of Trichoderma spp. by scientific community is based on the understanding of its mechanisms of action against a large set of fungal, bacterial and in certain cases viral infections. However, it is still an agnostic view that there could be any single major mode of operation, although it is argued that all mechanisms operate simultaneously in a synchronized fashion. The central idea behind this review article is to emphasize the potentiality of applications of target specific secondary metabolites of Trichoderma for controlling phytopathogens as a substitute of commercially available whole organism formulations. With the aim to this point, we have compiled an inclusive list of secondary metabolites produced by different species of Trichoderma and their applications in diverse areas with the major emphasis on agriculture. Outlining the importance and diverse activities of secondary metabolites of Trichoderma besides its relevance to agriculture would generate greater understanding of their other important and beneficial applications apart from target specific biopesticides.

ROS-dependent anticandidal activity of zinc oxide nanoparticles synthesized by using egg albumen as a biotemplate

Zinc oxide nanoparticles (ZnO NPs) have attracted great attention because of their superior optical properties and wide application in biomedical science. However, little is known about the anticandidal activity of ZnO NPs against Candida albicans (C. albicans). This study was designed to develop the green approach to synthesize ZnO NPs using egg white (denoted as EtZnO NPs) and investigated its possible mechanism of antimicrobial activity against C. albicans 077. It was also notable that anticandidal activity of EtZnO NPs is correlated with reactive oxygen species (ROS) production in a dose dependent manner. Protection of histidine against ROS clearly suggests the implication of ROS in anticandidal activity of EtZnO NPs. This green approach based on egg white-mediated synthesis of ZnO NPs paves the way for developing cost effective, eco-friendly and promising antimicrobial nanomaterial for applications in medicine.

Biofabricated Silver Nanoparticles Act as a Strong Fungicide against Bipolaris sorokiniana Causing Spot Blotch Disease in Wheat

The present study is focused on the extracellular synthesis of silver nanoparticles (AgNPs) using culture supernatant of an agriculturally important bacterium, Serratia sp. BHU-S4 and demonstrates its effective application for the management of spot blotch disease in wheat. The biosynthesis of AgNPs by Serratia sp. BHU-S4 (denoted as bsAgNPs) was monitored by UV–visible spectrum that showed the surface plasmon resonance (SPR) peak at 410 nm, an important characteristic of AgNPs. Furthermore, the structural, morphological, elemental, functional and thermal characterization of bsAgNPs was carried out using the X-ray diffraction (XRD), electron and atomic microscopies, energy dispersive X-ray (EDAX) spectrometer, FTIR spectroscopy and thermogravimetric analyzer (TGA), respectively. The bsAgNPs were spherical in shape with size range of ∼10 to 20 nm. The XRD and EDAX analysis confirmed successful biosynthesis and crystalline nature of AgNPs. The bsAgNPs exhibited strong antifungal activity against Bipolaris sorokiniana, the spot blotch pathogen of wheat. Interestingly, 2, 4 and 10 µg/ml concentrations of bsAgNPs accounted for complete inhibition of conidial germination, whereas in the absence of bsAgNPs, conidial germination was 100%. A detached leaf bioassay revealed prominent conidial germination on wheat leaves infected with B. sorokiniana conidial suspension alone, while the germination of conidia was totally inhibited when the leaves were treated with bsAgNPs. The results were further authenticated under green house conditions, where application of bsAgNPs significantly reduced B. sorokiniana infection in wheat plants. Histochemical staining revealed a significant role of bsAgNPs treatment in inducing lignin deposition in vascular bundles. In summary, our findings represent the efficient application of bsAgNPs in plant disease management, indicating the exciting possibilities of nanofungicide employing agriculturally important bacteria.

Friends or foes? Emerging insights from fungal interactions with plants

Fungi interact with plants in various ways, with each interaction giving rise to different alterations in both partners. While fungal pathogens have detrimental effects on plant physiology, mutualistic fungi augment host defence responses to pathogens and/or improve plant nutrient uptake. Tropic growth towards plant roots or stomata, mediated by chemical and topographical signals, has been described for several fungi, with evidence of species-specific signals and sensing mechanisms. Fungal partners secrete bioactive molecules such as small peptide effectors, enzymes and secondary metabolites which facilitate colonization and contribute to both symbiotic and pathogenic relationships. There has been tremendous advancement in fungal molecular biology, omics sciences and microscopy in recent years, opening up new possibilities for the identification of key molecular mechanisms in plant–fungal interactions, the power of which is often borne out in their combination. Our fragmentary knowledge on the interactions between plants and fungi must be made whole to understand the potential of fungi in preventing plant diseases, improving plant productivity and understanding ecosystem stability. Here, we review innovative methods and the associated new insights into plant–fungal interactions.