Lokesh Ravi

Bio: Lokesh Ravi is an academic researcher from St. Joseph's College, Bangalore. The author has contributed to research in topics: Ligand (biochemistry) & Gas chromatography. The author has an hindex of 2, co-authored 10 publications receiving 8 citations. Previous affiliations of Lokesh Ravi include Saint Joseph's College.

Marine Actinomycetes Derived Pyrrolo Compounds Mediated Green Synthesis of AgO and Ag 2 O 3 Nanoparticles and its Antidermatophytic Activity

Abstract: Antimicrobial potential of silver nanoparticles synthesised by using various biological sources was already been reported by many researchers. The green synthesis of silver nanoparticles using microbial sources has been proved to be more effective. In this study, anti-dermatophytic silver nanoparticles were synthesised by using pyrrolo metabolites producing actinomycetes as a green catalyst. Different characterization methods such as UV-Visible, XRD, and AFM were used to identify the physiochemical characteristics of synthesised nanoparticles. The synthesised nanoparticles showed λ-max at 427 nm and 402 nm, respectively. The XRD analysis based on the JCPDS database identified the two synthesized nanoparticles as silver oxide nanoparticles (AgO NPs) and silver peroxide nanoparticles (Ag2O3 NPs). The size of these nanoparticles was found to be in the range of 40-44 nm (AgO NPs) and 23-25 nm (Ag2O3 NPs), respectively. The synthesized nanoparticles demonstrated significant anti-fungal activity against dermatophytic fungi Trichophyton mentagrophyes with the zone of inhibition of 38 mm by AgO NP and 17 mm by Ag2O3 NPs. Screening of marine actinomycetes LG003 and LG005 revealed the presence of pyrrolo derivatives as the major metabolites, suggesting that these pyrrolo derivatives could be responsible for synthesis and stabilization of AgO and Ag2O3NPs. Among the synthesized NPs, the AgO NPs showed great potential as an anti-dermatophytic agent. This study provides further research opportunities for AgONPs as anti-fungal agents.

Nanoparticle’s Significance as Antibacterial Agents & Other Pharmaceutical Applications and Their Limitations: A Critical Review

Abstract: Nanoparticles (NPs) a potential next generation candidate for human well-being in the world of healthcare, have been observed to be effective anti-bacterial agents. The significance of nanoparticles as anti-bacterial agents has taken spotlight, due to the inability of pathogenic bacteria to develop resistance against NPs. In this review, mode of action of some scientifically important anti-bacterial NPs were discussed, along with summary of recent pre-clinical and clinical studies reported on anti-bacterial NPs are discussed. Some of the current hurdles and barriers that should be addressed to complete marketability and human applications, in regards to NPs as nanomedicines are also critically discussed along with focus on reported toxicity in NPs. Some additional pharmaceutical effects of NPs, reported in the recent years, such as antidiabetic and anticancer are also included for discussion. This review provides significant information on recent discoveries in the field of nanomedicines as antibiotics, that show promising future for drug development and drug delivery. As in every human domain, evidence begins to point to the actual undeniable fact that in conjunction with the existing medicine, nanomedicines could be the future of the healthcare that replace or enhance the potential current pharmaceutical drugs.

Risks for public health related to the presence of tetrodotoxin (TTX) and TTX analogues in marine bivalves and gastropods

Abstract: Tetrodotoxin (TTX) and its analogues are produced by marine bacteria and have been detected in marine bivalves and gastropods from European waters. The European Commission asked EFSA for a scientific opinion on the risks to public health related to the presence of TTX and TTX analogues in marine bivalves and gastropods. The Panel on Contaminants in the Food Chain reviewed the available literature but did not find support for the minimum lethal dose for humans of 2 mg, mentioned in various reviews. Some human case reports describe serious effects at a dose of 0.2 mg, corresponding to 4 μg/kg body weight (bw). However, the uncertainties on the actual exposure in the studies preclude their use for derivation of an acute reference dose (ARfD). Instead, a group ARfD of 0.25 μg/kg bw, applying to TTX and its analogues, was derived based on a TTX dose of 25 μg/kg bw at which no apathy was observed in an acute oral study with mice, applying a standard uncertainty factor of 100. Estimated relative potencies for analogues are lower than that of TTX but are associated with a high degree of uncertainty. Based on the occurrence data submitted to EFSA and reported consumption days only, average and P95 exposures of 0.00–0.09 and 0.00–0.03 μg/kg bw, respectively, were calculated. Using a large portion size of 400 g bivalves and P95 occurrence levels of TTX, with exception of oysters, the exposure was below the group ARfD in all consumer groups. A concentration below 44 μg TTX equivalents/kg shellfish meat, based on a large portion size of 400 g, was considered not to result in adverse effects in humans. Liquid chromatography with tandem mass spectroscopy (LC–MS/MS) methods are the most suitable for identification and quantification of TTX and its analogues, with LOQs between 1 and 25 μg/kg.

Therapeutic potential of biogenic and optimized silver nanoparticles using Rubia cordifolia L. leaf extract

Abstract: Abstract Rubia cordifolia L. is a widely used traditional medicine in the Indian sub-continent and Eastern Asia. In the present study, the aqueous leaf extract of the R. Cordifolia was used to fabricate silver nanoparticles (RC@AgNPs), following a green synthesis approach. Effect of temperature (60 °C), pH (8), as well the concentration of leaf extract (2 ml) and silver nitrate (2 mM) were optimized for the synthesis of stable RC@AgNPs. The phytofabrication of nanosilver was validated by UV–visible spectral analysis, which displayed a distinctive surface plasmon resonance peak at 432 nm. The effective functional molecules as capping and stabilizing agents, and responsible for the conversion of Ag + to nanosilver (Ag 0 ) were identified using the FTIR spectra. The spherical RC@AgNPs with an average size of ~ 20.98 nm, crystalline nature, and 61% elemental composition were revealed by TEM, SEM, XRD, and. EDX. Biogenic RC@AgNPs displayed a remarkable anticancer activity against B16F10 (melanoma) and A431 (carcinoma) cell lines with respective IC 50 of 36.63 and 54.09 µg/mL, respectively. Besides, RC@AgNPs showed strong antifungal activity against aflatoxigenic Aspergillus flavus , DNA-binding properties, and DPPH and ABTS free radical inhibition. The presented research provides a potential therapeutic agent to be utilized in various biomedical applications.

Bioactive Compounds Produced by the Accompanying Microflora in Bulgarian Yoghurt

Abstract: Bulgarian yoghurt is associated with health benefits and longevity of consumers. The specific microflora producing bioactive metabolites is responsible for this effect. The present study examines the biodiversity in four homemade yoghurts from regions containing endemic microflora. Metagenome sequencing indicated Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus were predominant in all samples. In addition, yoghurts contained accompanying lactic acid bacteria (LAB) including Lacticaseibacillus paracasei, Lb. helveticus, Limosilactobacillus fermentum, Lb. rhamnosus, Lactococcus lactis, Pediococcus acidilactici, Leuconostoc mesenteroides, and Leuc. pseudomesenteroides. A negligible amount of pollutant strains was found. Twenty-four LAB strains were isolated from the yoghurts and identified. Lb. delbrueckii subsp. bulgaricus strains were genotyped by randomly amplified polymorphic DNA–PCR (RAPD), multi-locus sequence typing (MLST), and pulse field gel electrophoresis (PFGE), which demonstrated their uniqueness and non-commercial origin. To estimate the bioactive metabolites produced by the accompanying microflora, yoghurts fermented by single LAB strains were analyzed using liquid chromatography and mass spectrometry (LC-MS). The fermented samples contained large amounts of free essential amino acids (arginine, citrulline, tryptophan, lysine, and histidine), the neuroprotector indole-3-propionic acid (IPA), and significant quantities of the cyclic antimicrobial peptides cyclo(phenylalanyl-prolyl) and cyclo(leucyloprolyl). The disclosure of these special qualities draws attention to the accompanying microflora as a source of potential probiotic strains that can fortify the yoghurts’ content with bioactive compounds.

Diversity and Biotechnological Potential of Marine Actinomycetes from India

Abstract: Actinomycetes are potential antibiotic producers that have been isolated from various terrestrial ecosystems and are exploited for their bioactive compounds. On the contrary, the marine environments were less explored and the research on marine actinomycetes had gained momentum only for the past three decades. Marine actinomycetes are one of the most significant producers of diverse groups of secondary metabolites and provide a huge scope for pharmaceutical and other industries. These organisms are proved to be important, both biotechnologically and economically considering their global presence. The marine ecosystem in India is less explored for the isolation of actinomycetes and several ecological niches are left unattended. Compared to the global scenario, the contribution from Indian researchers towards the isolation and exploitation of marine actinomycetes from the Indian sub-continent is noteworthy. Exploration of actinomycetes from these ecosystems will certainly yield new species and metabolites. Considering the declining rate of drug discovery from terrestrial actinomycetes, the marine counterparts, especially from unexplored regions from the Indian coast will hold a promising way ahead. Apart from drugs, these organisms are reported for the production of different industrially important enzymes like cellulase, amylase, protease, lipase, etc. They are also used in environmental applications, agriculture, and aquacultures sectors. With the rapid advancement in the study of actinomycetes from different marine sources in India, new metabolites are being discovered which have an important role from the economic and industrial point of view. As the world is witnessing newer diseases such as Sars-Cov 2 and the pandemic due to its demands drugs and other metabolites are increasing day by day. Therefore, the necessity for the quest for unique and rare marine actinomycetes is enhancing too. This review highlights the research on marine actinomycetes in India and also the challenges associated with its research.