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Biosynthesis of silver nanoparticles (AgNPs) is emerging as a simple and eco-friendly alternative to conventional chemical synthesis methods. The role of AgNPs is expanding as antimicrobial and anticancer agents, sensors, nanoelectronic devices, and imaging contrast agents. In this study, biogenic AgNPs were synthesized using extracts of different marine algae species, including Ulva rigida (green alga), Cystoseira myrica (brown alga), and Gracilaria foliifera (red alga), as reducing and capping agents. The Physiochemical properties, cytotoxicity, anticancer and antimicrobial activities of the biosynthesized AgNPs were assessed. Surface plasmonic bands of the biosynthesized AgNPs capped with U. rigida , C. myrica , and G. foliifera extracts were visually observed to determine a colour change, and their peaks were observed at 424 nm, 409 nm, and 415 nm, respectively, by UV–Vis spectroscopy; transmission electron microscopy (TEM) indicated an almost spherical shape of AgNPs with nanoscale sizes of 12 nm, 17 nm, and 24 nm, respectively. Fourier transform-infrared (FTIR) spectroscopy analysis suggested that different molecules attached to AgNPs through OH, C=O, and amide groups. The major constituents of the aqueous algal extracts included, terpenoids, polyphenols, sulfonates, polysaccharides, fatty acids, chlorophylls, amide proteins, flavonoids, carotenoids, aliphatic fluoro compounds, volatile compounds, alkalines, pyruvic acid and agar groups. The cytotoxicity and anticancer activities of the biosynthesized AgNPs were assessed using Artemia salina nauplii, normal skin cell lines (HFb-4), and breast cancer cell lines (MCF-7 cell line). The lethality was found to be directly proportional to the AgNP concentration. The IC 50 values of C. myrica and G . foliifera AgNPs against A. saline nauplii were 5 and 10 μg ml −1 after 4 h and 16 h, respectively, whereas U. rigida AgNPs did not exhibit cytotoxic effects. Anticancer activity of the biosynthesized AgNPs was dose dependent. The IC 50 values of the biosynthesized AgNPs were 13, 13, and 43 µg ml −1 for U. rigida, C. myrica, and G. foliifera , respectively. U. rigida AgNPs particularly exhibited potent anticancer activity (92.62%) against a human breast adenocarcinoma cell line (MCF-7) with high selectivity compared the normal cells (IC 50  = 13 µg/ml, SI = 3.2), followed by C. myrica AgNPs (IC 50  = 13 µg/ml, SI = 3.07). Furthermore, the biosynthesized AgNPs exhibited strong antifungal activity against dermatophyte pathogenic moulds and mild antibacterial activity against the food borne pathogen bacteria. The highest antimicrobial activity was recorded for the U. rigida AgNPs, followed by those capped with C. myrica and G. foliifera extracts, respectively. AgNPs capped with the U. rigida extract exhibited the highest antimicrobial activity against Trichophyton mantigrophytes (40 mm), followed by Trichosporon cataneum (30 mm) and E. coli (19 mm), with minimal lethal concentration of 32 and 64 μg ml −1 respectively. The study finally revealed that extracts of marine algal species, particularly U. rigida extracts, could be effectively used as reducing agents for the green synthesis of AgNPs. These AgNPs are considered efficient alternative antidermatophytes for skin infections and anticancer agents against the MCF-7 cell line.

Objective: The purpose of this study was to assess the ethanolic extract of Gracilaria foliifera. Methods: A preliminary phytochemical analysis of Gracilaria foliifera is carried out using a conventional methodology. The presence of functional components in the ethanolic extracts of Gracilaria foliifera was confirmed using UV-Vis and Fourier transform infrared (FTIR) spectroscopy. Results: The initial phytochemical investigation of Gracilaria foliifera found terpenoids, phenol, tannins, steroids, saponin, and flavonoids. Gracilaria foliifera's UV-Visible spectra showed the existence of biologically active substances in the absorbance range of 200 to 800nm. FTIR study of the ethanolic extract of Gracilaria foliifera indicated the presence of functional groups including Alcohols, Alkanes Aliphatic compounds, Aldehydes, Ketone, Carboxylic Acids, Alkenes, Aromatics, Alkene Methylene Group, Phenols, Aliphatic Amines, and Alkanes. Conclusions: According to the results of this study, Gracilaria foliifera may be a source of naturally occurring bioactive chemicals, and further isolation of the plant may result in the identification of a unique biopotential substance with a variety of biological activities.

ABSTRACT Marine botanicals are enriched with natural bioactive compounds have been utilized in the current study to alleviate the stored grain pests infestation. Four species of red seaweeds Asparagopsis taxiformis, Laurencia karachiana, Gracilaria foliifera, and Jania rubens found abundantly along the Karachi coast, Pakistan were collected in the year 2015-18. Samples were extracted using a Soxhlet extraction method with solvents of varying polarity (hexane, dichloromethane, and methanol). Five different concentrations of the extracts were subjected to the toxic assessment against two species of stored grain pests (Sitophilus oryzae and Callosobruchus maculatus). Results obtained from experimental trail proved that the C. maculatus were susceptible with higher adult mortality than S. oryzae. The highest toxic effect was induced by dichloromethane obtained extract from A. taxiformis (DA) against C. maculatus (LC50 1.15 mg/cm2) after 24 h exposure and S. oryzae although resist for one day showed (LC50 1.44 mg/cm2) after 48 h. Neurotoxic effects were also determined after 12 and 24 h. L. karachiana was the second in toxicity against C. maculatus and S. oryzae population. In addition, all treatments of A. taxiformis and L. karachiana significantly reduced the eggs laying by C. maculatus counted after 96 h of treatment. More than 70% mortality was also obtained after 96 h exposure at a dose of 2.2 mg/cm2 with most of the seaweed extracts against S. oryzae and C. maculatus. While treatment with J. rubens and G. foliifera provided only low to moderate toxicity to both tested species.

In the present study, phycochemical-loaded silver nanocomplexes (GFAgNPs) were fabricated by using Gracilaria foliifera seaweed extracts as capping agents on silver ions. The growth-stimulating properties of the GFAgNPs were evaluated by using in vitro plant regeneration from axillary nodal explants of Alternanthera sesselis. Explants were sterilized and placed on Murashige and Skoog (MS) medium augmented with various concentrations of GFAgNPs (0.5–3.0 mg L −1 ), 6-benzyl amino purine (BAP), and kinetin (KIN) (0.5–5.0 mg L −1 ) for initiation of shoot buds. One hundred percent shoot bud initiation with highest number of shoot buds (112.5 shoots explant −1 ) was observed on MS medium supplemented with 2.0 mg L −1 GFAgNPs, while shoot bud initiation was 85.3 % with 3.0 mg L −1 BAP. To enhance the percentage of multiple shoot bud proliferation, the mini-shoot buds were subcultured onto MS medium fortified with different doses of GFAgNPs (0.5–3.0 mg L −1 ), BAP, and KIN (0.5–4.0 mg L −1 ) in combination with 50 mg L −1 adenine sulfate (AdS). Of the three growth-promoting compounds tested, 100 % of multiple shoot bud regeneration with twofold increased shoots (153.6 shoots culture −1 ) was obtained on MS medium containing 2.5 mg L −1 GEAgNPs and 50 mg L −1 AdS combination, followed by 3.0 mg L −1 BAP and 50 mg L −1 AdS combination. Elongated shoots were excised from shoot clumps and cultured on half-strength MS medium without auxin but fortified with different concentrations of α-naphthalene acetic acid (NAA) and indole-3-butyric acid (IBA) (0.1–0.5 mg L −1 ) for rooting. IBA at 0.5 mg L −1 was found to be the best dose for 100 % rooting with 13.5 roots shoot −1 . Rooted plantlets were successfully transplanted into plastic cups containing sand and soil mixture, and the acclimatized plantlets were subsequently established in field conditions. The genetic fidelity of in vitro regenerated plants was determined by using random amplified polymorphic DNA (RAPD) analysis. In vitro regenerated plantlets were true to type in nature. The use of phycochemical-coated silver nanocomplex as novel growth-regulating substances was identified as an alternate to commercial cytokinins for large-scale production of genetically uniform plantlets in tissue culture for industrial applications.

Two gracilarioid species, Gracilariopsis bailiniae and Hydropuntia edulis, were compared based on their growth under different temperature and salinity levels and nitrogen source and on their photosynthetic responses under different irradiance levels. Results show that growth of Gp. bailiniae was significantly higher than that of H. edulis. Both species were euryhaline and had optimum growth rates at 27°C (16.06 % d-1 ± 0.10 for Gp. bailiniae and 9.53 % d-1 ± 0.62 for H. edulis) under both ammonium and nitrate enrichment. Gracilariopsis bailiniae was able to use both N-forms as a nitrogen source in all temperature and salinity levels tested. Meanwhile, the interactive effect of nitrogen source with temperature was observed for H. edulis with plants grown in nitrate enrichment showing significantly higher growth rates than those in ammonium. Nitrate enrichment also resulted to higher growth rates for H. edulis in all salinity levels tested. Photosynthetic rates of Gp. bailiniae were higher than H. edulis. We also found a two-fold difference between the maximum photosynthetic rate (Pmax) of Gp. bailiniae (12.41 ± 1.81) and that of H. edulis (6.44 ± 0.62). However, photosynthetic efficiency (a) was significantly higher in H. edulis than in Gp. bailiniae while compensation and saturation point irradiance levels were similar in both species.

In chambers containing detritus from periphyton, Gracilaria foliifera (red seaweed), or Spartina alterniflora (marsh grass) aged for various periods we compared total microcosm carbon oxidation, microbial biomass (total adenylates), and net incorporation of detritus by Capitella capitata. Oxidation of periphyton and Gracilaria-derived detritus was higher (3%.d super(-1)) and peaked (at 5-30 days) earlier than Spartina-derived detritus (1%.d super(-1) at 190 days). The ratio of worm production to total detrital oxidation in the chamber (P:O)- the efficiency with which the detritus-based system produces macroconsumers-was lower for decay-resistant detritus and increased with aging for all types. Maximum microbial biomass coincided with maximum detrital oxidation. Changes in the ratio of microbial biomass to detrital oxidation (A:O)-a relative measure of the degradability and efficiency of conversion of detritus into microbial biomass-followed those of P:O.

A particulate organic nitrogen supplement was added to two detrital materials (red macroalga Gracilaria foliifera and marsh grass Spartina alterniflora) and its effect on their utilization by the polychaete Capitella capitata was investigated with isotope tracer techniques. With the decay-resistant Spartina, added nitrogen had no effect on the oxidation or the net incorporation of Spartina carbon by the worms. With easily decomposable Gracilaria detritus there was an exponential increase in both oxidation and net incorporation with increasing nitrogen. Added organic nitrogen had no effect on the microbial biomass associated with Spartina detritus but resulted in an increase with Gracilaria detritus. Nitrogen enrichment by microbial activity is not the only regulator of nutritional value of detritus to macroconsumers. The extent to which the substrate can be broken down and utilized by associated microbes and macrodetritivores also influences the nutritional quality of detritus to macroconsumers.

Observations have been made on photosynthesis (oxygen evolution) and seasonal fluctuations in antenna pigments in 2 seaweeds which co-occur in the vicinity of Beaufort, North Carolina, USA. Gracilaria foliifera (Rhodophyceae) and Ulva sp. (Chlorophyceae) were grown in outdoor continuous-flow cultures at ambient incident light (Iₒ) and .13Iₒ. Pigment contents and accessory pigment: chlorophyll a ratios were higher at .13Iₒ than at Iₒ. Total pigment levels were correlated with soluble N in seaweed tissue. During the spring/summer growing season, pigment levels were low and peaks in pigment content followed nutrient pulses in the ambient seawater. Pigment contents in both species were higher in winter. In G. foliifera, the R-phycoerythrin: chl a ratio was highest in fall-winter and lowest in summer. The higher growth rates achieved by Ulva sp. reflected the higher rates of photosynthesis measured in this species. Photosynthesis-light curves showed that Ulva sp. had a higher photosynthetic capacity (Pmax = 430 μmol O₂ evolved g dry wt⁻¹ h⁻¹) and initial slope (in shadeacclimated plants) than G. foliifera (Pmax = 160 μmol O₂ evolved g dry wt⁻¹ h⁻¹). Increased pigment contents in shade plants of both species resulted in enhanced photosynthetic performance at subsaturating light intensities. It appears that the effect of transient pigment increases in the summer was to increase Pmax temporarily while, in winter, the effect was to limit the decrease in integrated net photosynthesis in the face of decreased light and temperature.

Detritus derived from Spartina alterniflora (cordgrass), Gracilaria foliifera (red seaweed), and periphyton (mixed algae) was decomposed aerobically and anaerobically for various lengths of time and then fed to the polychaete Capitella capitata in flow-through microcosms. Rates of detrital mineralization (CO₂ production), microbial respiration (O₂ consumption) and biomass (adenosine triphosphate and total adenylates, At), and net incorporation by C. capitata varied with detrital source and length of pre-aging. Oxygen consumption per unit microbial biomass (μmoles μgAt⁻¹ d⁻¹) increased linearly with age of the detritus: periphytic algal detritus had the highest daily increase of 4 %, followed by G. foliifera and S. alterniflora detritus at 1 % and 0.3 % respectively. Metabolic respiratory quotient (CO₂/O₂), which varied from < 1 to about 50 : 1, was a function of detrital source and age; it indicated that anaerobic bacteria were important decomposers of detritus. Net incorporation rates by C. capitata, microbial biomass, and O₂ consumption rates did not differ among G. foliifera detritus aged under oxic and anoxic conditions. Rates of CO₂ production, however, were up to 6 times higher for G. foliifera detritus aged anaerobically. The results suggest that anaerobic metabolism, which causes a high CO₂ production, could represent a significant loss of carbon from benthic food webs.