Identification of Odontella aurita by rbcL gene sequence - a high antibacterial potential centric marine diatom.

The antibacterial potential of centric marine diatoms has been compared against the clinical pathogens and identified the potential diatom by rbcL gene sequencing. Totally, five diatoms namely Odontella aurita, Thalassiosira subtilis, Chaetoceros curvisetus, Skeletonema costatum and Coscinodiscus centralis were isolated from Cuddalore coastal waters. The diatoms were morphologically identified and isolated using micro capillary-pipette and serial dilution method. The isolated diatoms were cultured in Guillard's f/2 medium to get biomass for the antibacterial study. The dried biomass of the cultured diatoms was individually extracted with methanol, ethanol and hexane. All the obtained extracts were tested against Staphylococcus haemolyticus, Proteus vulgarius and Vibrio alginolyticus. The crude ethanol extract of O. aurita was exhibited highest zone of inhibition against all the test pathogens. The MIC of O. aurita was recorded as 50 µg/ml against both Staphylococcus haemolyticus and Proteus vulgarius whilst 75 µg/ml against Vibrio alginolyticus. This study indicates that O. aurita possesses antibacterial activities but the release of antibiotics depends on physical or chemical rupture of algal cells and extractive solvents. Based on the maximum antibacterial activity, O. aurita was further identified by rbcL gene sequencing. The rbcL gene could be an identical region for the species level identification of diatoms.

Antifouling Activity of Lipidic Metabolites Derived from Padina tetrastromatica.

An attempt has been made to identify the potential seaweed for antifouling property due to the growing need for environmentally safe antifouling systems. The antibacterial, antimicroalgal, and antimussel foot adherence potentials of methanol, dichloromethane, and hexane extracts of the chosen seaweeds such as Padina tetrastromatica, Caulerpa taxifolia, and Amphiroa fragilissima have been compared against copper sulfate. Among the extracts, the maximum antibacterial activities were exhibited by the methanol extract of P. tetrastromatica. The minimum inhibitory concentration (MIC) of the methanolic extract of P. tetrastromatica was found to be 10 and 1 µg/ml against test biofilm bacteria and diatoms, respectively. The antimussel foot adherence assay indicated that the extract had inhibited the foot adherence of the green mussels Perna viridis with the effective concentration (EC50) of 25.51 ± 0.03 µg/ml, and lethal concentration for 50 % mortality (LC50) was recorded at 280.22 ± 0.12 µg/ml. Based on the prolific results, the crude methanolic extract of P. tetrastromatica was subjected to purification using silica gel column and thin-layer chromatography (TLC). Then, the active compounds of the bioassay-guided fraction (F13) were identified using gas chromatography coupled with mass spectroscopy (GC-MS), and it was observed that fatty acids were the major components, which may be responsible for the antifouling properties.

Antibacterial Activity of Red Pigment Produced by Halolactibacillus alkaliphilus MSRD1--an Isolate from Seaweed.

The present study was carried out with the aim to isolate an antibacterial pigment from seaweed-associated bacterium. The bacterium was identified as Halolactibacillus alkaliphilus MSRD1 by 16S rRNA sequencing. The isolated bacterium was cultured in 50% Luria-Bertani seawater broth (LB-SWB) with 1% glycerol. The pigment was extracted with 99% ethanol and analyzed by UV-Vis spectroscopy at 490 nm. The candidate bacterium was optimized with various NaCl concentrations from 5 to 20%. The results inferred that the bacterium produce maximum pigment at 5% NaCl level. The candidate bacterium H. alkaliphilus MSRD1 was found to be producing the maximum pigment during the 120-h incubation. The protein content of the pigment was found to be maximum of 72% at the end of the 120-h incubation. The extracted pigment was stable up to 80 °C, pink at acidic pH (1 to 5) and orange at basic pH (8 to 12). The isolated pigment was fractionated by silica gel column chromatography. Fractionated pigment was characterized by TLC, FT-IR, and SDS-PAGE. In the antibacterial context, the pigment was highly inhibited Staphylococcus aureus and Salmonella typhi with the zone of inhibition 16 and 14 mm, respectively. According to SDS-PAGE, the size of the pigment was approximately 80 kDa. The H. alkaliphilus MSRD1 has high capacity to produce the pigment with antibacterial properties. This could be effectively used in the future.

Antifouling and toxic properties of the bioactive metabolites from the seagrasses Syringodium isoetifolium and Cymodocea serrulata.

The present study documents the antifouling and toxic properties of seagrasses Syringodium isoetifolium and Cymodocea serrulata. For that, the seagrasses S. isoetifolium and C. serrulata were extracted individually using organic solvents viz. dichloromethane, acetone and methanol. Amongst the extracts, the maximum antimicrofouling and antimacrofouling activities were exhibited by methanol extracts of both the seagrasses. The Minimal Inhibitory Concentration (MIC) of methanolic extracts of seagrasses was ranged from 1.0 to 10µg/ml against test biofilm bacteria and microalgal strains. Similarly, 100% fouling inhibition of limpet Patella vulgata was found at 6.0mg/ml of methanolic extracts of seagrasses. The mussel Perna indica showed 50% of byssal production and attachment inhibition at 21.51±2.03, 17.82±1.07µg/ml and the anticrustaecean activity for 50% mortality of Artemia salina was recorded at 732.14±9.21 and 394.16±5.16µg/ml respectively for methanolic extracts of S. isoetifolium and C. serrulata. The minimal inhibitory and higher lethal concentrations of active methanol extracts shows it׳s less toxic nature. Based on the prolific results, methanol extracts of S. isoetifolium and C. serrulata were subjected to purification using silica gel column and thin layer chromatography. Then the active compounds of the bioassay guided fractions were partially characterized using gas chromatography coupled with mass spectroscopy (GC-MS) and keyed out that fatty acids (C16 to C24) were the major components which responsible for the antifouling properties of the candidate seagrasses.

Pharmaceutical potential of a fucoidan-like sulphated polysaccharide isolated from Halodule pinifolia.

In continuation with the screening of biological properties of seagrasses, we isolated sulphated polysaccharides from Halodule pinifolia. This is the first report that indicates the presence of fucoidan-like H. pinifolia crude sulphated polysaccharide (HPCSP) that are commonly found in brown algae being present in marine angiosperms. Fucoidan-like structures such as ß-mannuronic acid residues and sulphate groups were confirmed by Fourier transform infrared (FTIR) spectral analysis. There was a high content of uronic acid. The isolated HPCSP consisted mainly of total sugar (54.17%), protein (11.06%), carbon (18.25%), nitrogen (1.77%), hydrogen (3.62%), C/N ratio (2.04%) and uronic acid (2.61%). This isolated HPCSP was further investigated to determine anticoagulant and antioxidant activity. The HPCSP had high activity in the total antioxidant assay (125.86 mg ascorbic acid equivalents/g), DPPH radical scavenging rate (IC50 value 2.024 ± 0.12 µg/mL), deoxyribose radical scavenging rate (51.82% at 1000 µg/mL) and H2O2 radical scavenging rate (IC50 value 6.904 ± 0.34 µg/mL). In the anticoagulant assay, prolonged clotting time was observed with application of HPCSP with increasing concentrations. Further purification and characterization process is underway to confirm the structures of HPCSP. From the observed results, this fucoidan-like HPCSP could be developed as a new natural source of potential antioxidants in the functional food industry.

Hydrographic and sediment characteristics of seagrass meadows of the Gulf of Mannar Marine Biosphere Reserve, South India.

The aim of the study was to examine the spatial and temporal variations in the physicochemical parameters of seagrass meadows of the Gulf of Mannar, South India using multivariate statistical techniques, namely, cluster analysis (CA) and principal component analysis (PCA), to explore the relationship. There were clear spatial and temporal variations in physicochemical variables of the seagrass meadow of the Gulf of Mannar, but such changes were subjected to seasonal variations especially during monsoon and post-monsoon seasons. The multivariate statistical techniques, viz., CA and PCA helped in the discrimination of islands according to the physicochemical parameters of the seagrass meadows. It was inferred that electrical conductivity, nitrate, particulate organic carbon, and phosphate strongly determined the discrimination of 19 islands, respectively, upon physicochemical characteristics of their seagrass meadows. These results highlight the important role of seagrasses in the Gulf of Mannar Marine Biosphere Reserve.

In vitro antibacterial, cytotoxicity and haemolytic activities and phytochemical analysis of seagrasses from the Gulf of Mannar, South India.

It is essential to study the phytochemical constituents and toxicological properties of seagrasses when considering their food applications. Aqueous methanolic extracts of six seagrasses were evaluated for their antibacterial, cytotoxic (brine shrimp leathality assay) and haemolytic activity. Thin layer chromatography (TLC) and phytochemical analysis were used to compare the phytochemical profiles of six seagrasses. Among the six seagrasses examined, Halodule pinifolia and Cymodocea rotundata showed predominant growth inhibitory activity against all the tested human pathogens. Cytotoxicity of seagrass extracts against nauplii of Artemia salina revealed that Syringodium isoetifolium exhibited lesser toxicity with LC(50) value of 699.096 µg/ml. Of all the seagrasses tested, H. pinifolia recorded the minimum haemolytic activity of 2.07±0.63% at 1000 µg/ml concentration. Phytochemical analysis showed the presence of common plant chemical constituents which varied with respect to species. The present findings suggest the possible pharmacological applications of selected seagrasses that can be used as food ingredients.

Determination of element contents in herbal drugs: chemometric approach.

The elemental content of 23 commercial herbal drugs was evaluated and multivariate analysis such as principal component analysis (PCA) and hierarchical cluster analysis (HCA) were performed with aim to know the relationship among the elements in the herbal drugs. Among the 13 elements investigated K (8096.97), Na (581.53), Cu (2.06); Mg (678.4); Fe (476.93), Al (321.5), Co (0.22); Zn (4.46), Ni (0.56); Mn (25.77); Pb (13.33); and Cr (13.18)mg/kg dry weight, respectively, were found at high concentrations in Eclipta prostrata; Adhatoda vasica; Phyllanthus amarus; Hybanthus enneaspermus; Cardiospermum halicacabum; Acacia nilotica; and Denolix elata. Interestingly, the toxic element Cd was below detectable level in all the samples and Cr, Pb and Ni were lower than the permissible limit as prescribed by the World Health Organisation (WHO). This study clearly shows that PCA and HCA procedures appear useful tools for the differentiation and classification of herbal drugs using the profile of elements.

Chemical composition and antibacterial activity of Indian seagrasses against urinary tract pathogens.

Seagrasses have a long history of being used for a variety of remedial purposes, such as the fever, skin diseases, muscle pains, wounds and stomach problems. Hence it is essential to study their bioactive metabolites and medicinal properties when considering their food applications. The chemical composition of six seagrasses were determined and evaluated for their potential to urinary tract infection bacteria (UTI). The chemical composition determined by GC-MS yielded 24 compounds. For the first time 4H-Pyran-4-one-2,3-dihydro-3,5-dihydroxy-6-methyl- (6.68%), d-allose (3.67%) and 5-Caranol, trans,trans-(+)- (2.14%) were identified from Halodule pinifolia. d-Allose is a aldo-hexose (sugar) used as a potential inhibitor of glycosidases and low-calorie carbohydrate sweeteners. Among the six seagrasses tested, H. pinifolia and Cymodocea rotundata exhibited predominant growth inhibitory activity against all the UTI bacteria. This study shows the presence of various biological metabolites in tested seagrasses that can be used effectively in food and pharmacological industries.

In vitro antioxidant activities of selected seaweeds from Southeast coast of India.

OBJECTIVE: In vitro antioxidant activities of three selected Indian seaweeds viz., Halimeda tuna (H. tuna), Turbinaria conoides (T. conoides) and Gracilaria foliifera (G. foliifera) were evaluated. METHODS: Total antioxidant activity, total phenolic content, and reducing power of crude methanol and diethyl ether extracts were determined. RESULTS: Total phenolic content and total antioxidant activity were higher (1.231±0.173 mg GAE/g, 1.675± 0.361 mg GAE/g) in T. conoides respectively. Reducing power of crude methanol extract increased with concentrations of the extract. The Fourier transform-infra red spectrum analysis revealed the presence of polyphenolic signals. The seaweed extracts displayed moderate antioxidant activity compared to gallic acid standard. CONCLUSIONS: The seaweeds could be considered for curing diseases from oxidative deteriorations.

Chemometric studies of multielemental composition of few seagrasses from Gulf of Mannar, India.

This paper discusses the determination of minerals content (cadmium, cobalt, chromium, copper, nickel, lead, manganese, magnesium, iron, zinc, sodium, potassium and calcium) of six seagrass samples, Enhalus acoroides, Thalassia hemprichii, Halodule pinifolia, Syringodium isoetifolium, Cymodocea serrulata and Cymodocea rotundata using inductively coupled plasma optical emission spectrophotometry and flame photometer. Principal component analysis (PCA) and hierarchical cluster analysis revealed different mineral compositions of the seagrass samples. Among the 13 elements investigated, Ni 1.513, Na 690.167 and Ca 220.333; Cr 3.957; Mn 23.427, Zn 17.593 and Fe 156.567; Cd 0.357, Co 0.431, Pb 2.040, Mg 912.733 and K 300.9; Cu 7.8 mg/kg dry weight, respectively, were found at high concentrations in E. acoroides; T. hemprichii; H. pinifolia; S. isoetifolium and C. rotundata. PCA analysis confirmed the presence of three components with 91.28% of the total variance. The toxic elements Pb, Cr and Cd were also found in all six seagrasses, although the concentrations were below the permissible limits proposed by the World Health Organization.