Sugathan Sujith

Antimicrobial activity of seaweeds extracts against multiresistant pathogens

Fourteen seaweeds collected from the intertidal zone of Southwest coast of India were tested against ten human pathogen bacteria and one human pathogen fungus using the well diffusion test in the casitone agar medium. The species used in the present study include five Chlorophyta (Bryopsis plumosa, Ulva fasciata, Acrosiphonia orientalis, Chaetomorpha antennina, Grateloupia filicina), five Rhodophyta (Hypnea pannosa, Gracilaria corticata, Centroceras clavulatum, Portieria hornemannii, Cheilosporum spectabile) and four Phaeophyta (Padina tetrastromatica, Sargassum wightii, Stocheospermum marginatum, Chnoospora bicanaliculata). Of these, seven species were determined to be highly bioactive and screened on the multiresistant pathogens. We found that drying process has eliminated the active principles in the seaweeds. In the present study, methanol:toluene (3∶1) was found to be the best solvent for extracting the antimicrobial principles from fresh algae. However, the ethanolic extract showed no antibacterial activity.Acrosiphonia orientalis showed activity against 70% of the tested organisms.Stocheospermum marginatum was the only seaweed that showed activity againstKlebsiella pneumoniae. The extract fromGracilaria corticata was highly active againstProteus mirabilis, a Gram negative pathogenic bacterium. The present findings revealed that the tested seaweeds were highly active against Gram negative bacteria than Gram positive bacteria. The antimicrobial principle from seaweed was found to be a lipophilic compound. The compound was stable over a wide range of temperature (30–60 °C). The active principles of highly active seaweedsAcrosiphonia orientalis andStocheospermum marginatum were bactericidal.

Antimicrobial potential and seasonality of red algae collected from the southwest coast of India tested against shrimp, human and phytopathogens

Fifteen seaweeds belong to 13 families and 6 orders of the rhodophyta were sampled for one year from April 2007 to March 2008 along the southwest coast of India (Indian Ocean). The species were examined forin vitro antimicrobial activity against six pathogenicVibrio strains isolated from moribund tiger shrimp (Penaeus monodon), six type cultures (Microbial Type Culture Collection, MTCC) of prominent shrimpVibrio pathogens, 10 multidrug resistant clinical pathogens, four species ofCandida obtained from pulmonary TB patients and four species of plant pathogenic fungi to evaluate their potency to be used as natural antibiotics in pharmaceutical and agriculture field. Bioactivity was analyzed from crude extract of fresh and dried samples prepared from different polar and nonpolar solvents. Of these, four species of red algae (Asparagopsis taxiformis, Laurencia ceylanica, Laurencia brandenii, Hypnea valentiae) were found to be highly active. Broadest and highest activity was observed in the crude extract ofA. Taxiformis. Among the pathogens tested, shrimp pathogenicVibrios were the most susceptible organisms while phytopathogens were found to be little resistant. In the present study, methanol was found to be the best solvent for extracting antimicrobial metabolites from dried samples rather than fresh. Seasonal variation in the antimicrobial activity was observed with higher level of activity recorded fromA. Taxiformis between December and January. The active principle ofA. Taxiformis was purified in column chromatography, TLC and reverse phase HPLC. The individual HPLC peaks were subsequently tested against a panel of pathogenic microorganisms and the active constituent was identified by GC-MS. The antimicrobial profile ofA. Taxiformis suggested that lipophilic compound which was primarily composed of pyrrole-2-carboxylic acid, pentadecanoic acid and octadecanoic acid might have functional role in the chemical defence against microbial invasion and these compounds could be utilized for the development of medically potential products.

Bioactivity of the red algae Asparagopsis taxiformis collected from the Southwestern coast of India

Entre as diversas variedades de algas vermelhas, Asparogopsis taxiformis constitui uma das que apresentam alta biomassa na costa de Kollam (Sudoeste da India). No presente estudo A. taxiformis foi coletada, seca e reduzida a po, apos o que foi realizada sua extracao e feito o fracionamento usando-se cromatografia por coluna. As fracoes individuais foram avaliadas in vitro em ensaios para testar sua capacidade anti-incrustante, anticianobacteria e toxicidade para peixes e crustaceos. A fracao extraida com eter de petroleo e etil acetato (2:8) apresentou o espectro de bioatividade mais forte e amplo. No ensaio anti-incrustacao efetuado com com o molusco pulmonado Limnea truncatula, a fracao algal ativa produziu 80% de repelencia do pe em 150 mg/l, enquanto que no ensaio anticianobacteria a fracao ativa inibiu 100% do crescimento de Trichodesmium sp., em 320 mg/l. A fracao algal mostrou o efeito mais intenso contra peixes no nivel de 60 mg/l. Em relacao aos crustaceos, a toxicidade da fracao ativa foi avaliada tambem visando encontrar compostos nao toxicos para organismos nao alvo, tais como Penaeus monodon e Macrobrachium rosembergii. Foi visto que a fracao ativa da coluna mostrou menor toxicidade para estas especies. Os componentes quimicos da fracao ativa foram identificados por meio dos sistemas cromatograficos, tais como TLC, fase reversa do HPLC e GC-MS. O perfil geral de atividade aponta que a fracao ativa da coluna para A. taxiformis pode conter metabolitos bioativos sinergicos que podem ser utilizados para o controle de organismos incrustantes, explosao algal e peixes herbiboros/predadores em tanques de aquicultura.

Biosurfactants as green stabilizers for the biological synthesis of nanoparticles

Taking into consideration the needs of greener bioprocesses and novel enhancers for synthesis using microbial processes, biosurfactants, and/or biosurfactant producing microbes are emerging as an alternate source for the rapid synthesis of nanoparticles. A microemulsion technique using an oil-water-surfactant mixture was shown to be a promising approach for nanoparticle synthesis. Biosurfactants are natural surfactants derived from microbial origin composed mostly of sugar and fatty acid moieties, they have higher biodegradability, lower toxicity, and excellent biological activities. The biosurfactant mediated process and microbial synthesis of nanoparticles are now emerging as clean, nontoxic, and environmentally acceptable “green chemistry’’ procedures. The biosurfactant-mediated synthesis is superior to the methods of bacterial- or fungal-mediated nanoparticle synthesis, since biosurfactants reduce the formation of aggregates due to the electrostatic forces of attraction and facilitate a uniform morphology of the nanoparticles. In this review, we highlight the biosurfactant mediated synthesis of nanoparticles with relevant details including a greener bioprocess, sources of biosurfactants, and biological synthesized nanoparticles based on the available literature and laboratory findings.

Antimicrobial potential of a marine seaweedAsparagopsis taxiformis againstLeptospira javanica isolates of rodent reservoirs

In this present investigation pharmacologically active compounds were isolated from red algae (Asparagopsis taxiformis) and their efficacy was evaluated against theLeptospira javanica isolates of rodent carriers. The GC-MS analysis of the purified compound revealed the presence of 4,5-dimethyl-1H-pyrrole-2-carboxylic acid ethyl ester (56.012%), fattyacids, 14-methyl-pentadecanoic acid methyl ester (26.6%), octadecanoic acid methyl ester (8.46%), octadec-9-enoic acid 2,3-dihydroxy-propyl ester (4.11%), 9-octadecanoic acid, methyl ester (4.535%) and trace amount of chlorobenzene (0.09%). MICs and MBCs of the purified compound against pathogenic leptospiral strains belonging to 14 serovars and 11 isolates belonging to serovarjavanica ofLeptospira borgpetersenii were determined in a range of 100–1600 μg/ml. The antibiotics penicillin and doxycycline were used as the standards for the efficiency determination of the seaweed extract against the leptospiral reference serovars and isolates. The minimal inhibitory concentration of penicillin and doxycyline were in the range of 25–200 μg/ml. The seaweed active fraction exhibited comparable MIC and MBC values with that of the standard antibiotic doxycycline. In the present study the seaweed compound has been developed to apply for the 2nd nodal point of transmission cycle, the environment. Thus the present study draws the development of a novel drug to treat leptospires particularly in environments augmented with rodent carriers.

Biological activity of the red alga Laurencia brandenii

Biological activity of the red alga Laurencia brandenii The marine red alga Laurencia brandenii collected from the southwest coast of India (Indian Ocean) was extracted and fractioned using column chromatography. The individual fractions were evaluated in vitro via antimicrobial activity against six species of Microbial Type Culture Collection and three species of clinical human pathogens, antipest activity on Sitophilus oryzae, maggoticidal activity against 2nd instar larvae of Sarcophaga sp. and termiticidal activity against Microtermes obesi. It was found that the fraction eluted using petroleum ether:chloroform (6:4) exhibited broader biological activities. The phyco-constituents of the active fraction were identified by gas chromatography-mass spectrometry (GC-MS) analysis. The GC-MS profile of the active fraction revealed that the main constituent was octadecadienoic acid (49.75%) followed by n-hexadecanoic acid (14.24%), which might have a functional role in the biological activities. The overall activity profile envisages that these bioactive compounds from L. brandenii could be utilized as a renewable natural resource for the development of novel environmental-compatible formulations for the control of human pathogens, pests, termites and maggots.