Green synthesized silver nanoparticle from Allium ampeloprasum aqueous extract: Characterization, antioxidant activities, antibacterial and cytotoxicity effects

Antibacterial carotenoids of three Holothuria species in Hurghada, Egypt

Several echinoderms, including sea urchins, are valuable sources of bioactive compounds but their nutraceutical potential is largely unexplored. In fact, the gonads of some sea urchin species contain antioxidants including carotenoids and polyhydroxylated naphthoquinones (PHNQ’s), such as echinochrome A. Astaxanthin is known to have particular bioactivity for the prevention of neurodegenerative diseases. This carotenoid is produced by microalgae, while several marine invertebrates can bioaccumulate or synthetize it from metabolic precursors. We determined the carotenoid content and analyzed the bioactivity potential of non-harvested Atlantic-Mediterranean sea urchin Arbacia lixula. The comparison of methanol crude extracts obtained from eggs of farmed and wild specimens revealed a higher bioactivity in farmed individuals fed with a customized fodder. HPLC-analysis revealed a high concentration of astaxanthin (27.0 μg/mg), which was the only pigment observed. This study highlights the potential of farmed A. lixula as a new source of the active stereoisomer of astaxanthin.

https://www.mdpi.com/1660-3397/15/6/187/pdf

The Sea Urchin Arbacia lixula: A Novel Natural Source of Astaxanthin.

Background and purpose: Measurement of DPPH free radical scavenging is a valid, accurate, and easy method with high repeatability in evaluating the in vitro antioxidant activity of plant extracts. A positive correlation is reported between antioxidant activity and antimicrobial activity. The aim of this study was to evaluate the correlation between antioxidant and antimicrobial activity of medicinal plant extracts. Materials and methods: The extracts were prepared and DPPH was used to determine free radical-scavenging activity. Antimicrobial effects of hydro-ethanol extract on the bacteria was surveyed using diffusion method in a culture medium Mueller-Hinton agar by paper discs (6 mm) based on Bauer and Kirby instructions. Results: The ability of medicinal plant extracts in scavenging free radicals was found to be higher in the extracts of Myrtus (89.583 μg/mL) and rosemary (80.921 μg/mL). The antioxidant activity of the extracts increased by increase in concentration of the extract. Meanwhile, in low concentrations of the extract (16 and 32 μg/mL) the highest antioxidant activity of the extract was found in Myrtus and then Rosemary, but at high concentrations (64 μg/mL) it was seen in Teucrium polium extract. Rosemary extract was found to be effective against Escherichia coli and Myrtus extract was the most effective on Listeria bacteria, Salmonella typhimurium, and Staphylococcus aureus. Conclusion: The results showed that plants with high antioxidant properties have high antimicrobial activity too, such as the extract of Myrtus and rosemary that were the most effective extracts on bacteria.

Correlation between antioxidant activity and antibacterial activity of nine medicinal plant extracts

Chemical investigation of pharmacologically active compounds from the Echinoidea sea urchin Stomopneustes variolaris resulted in the separation of an unreported cembrane type of diterpenoid, which was characterised as 4-hydroxy-1-(16-methoxyprop-16-en-15-yl)-8-methyl-21,22-dioxatricyclo[11.3.1.15,8]octadecane-3,19-dione by spectroscopic experiments. The compound exhibited greater inhibitory potential against inflammatory agent 5-lipoxygenase (IC50 2.01 mM) than that exhibited by synthetic ibuprofen (IC50 4.50 mM). The selectivity ratio of cyclooxygenase-1 to cyclooxygenase-2 for the studied compound was found to be greater (1.25) than that of ibuprofen (0.43), which could be accounted for the prospective anti-inflammatory property of the cembrane-type diterpenoid against inducible pro-inflammatory cyclooxygenase-2. Potent antioxidant activity of the studied compound was characterised by its greater scavenging effects on 2,2-diphenyl-1-picrylhydrazyl and 2,2′-azino-bis-3-ethylbenzothiozoline-6-sulfonic acid radicals (IC50 1.41 and 1.61 mM, respectively) than the standard antioxidative agent α-tocopherol (IC50 1.51 and 1.70 mM, respectively). The greater electronic parameters (topological polar surface area of 82.06) together with two hydrogen bonded interactions at the active site of cyclooxygenase-2 and lesser binding energy (−8.91 kcal/mol) corroborated its prospective anti-inflammatory activity. Therefore, the presently studied cembrane-type diterpenoid could be utilised in medicinal formulations as an effective anti-inflammatory agent.

Antioxidant and anti-inflammatory cembrane-type diterpenoid from Echinoidea sea urchin Stomopneustes variolaris attenuates pro-inflammatory 5-lipoxygenase

The recent appearance of a growing number of bacteria resistant to conventional antibiotics has stimulated the search for novel antimicrobial agents or lead compounds from a variety of sources, including natural sources  crustaceans, molluscs and echinoderms, with particular interest on their secondary metabolites with desirable antimicrobial properties (Haug et al, 2002, Casas et al, 2010). Antimicrobial activity in several species of echinoderms collected from Gulf of California, Mexico, Caribbean and Coast of Norway has been reported (Rinehart et al, 1981; Bryan et al, 1994; Haug et al, 2002). In addition, a variety of antimicrobial factors, including steroidal glycosides (Andersson et al, 1989), polyhydroxylated sterols (Iorizzi et al, 1995), naphthoquinone pigments (Service and Wardlaw, 1984), lysozymes (Canicatti and Roch, 1989; Stabili and Pagliara, 1994), complement like substances (Leonard et al, 1990) and antimicrobial peptides (Beauregard et al, 2001) have also been isolated from echinoderms. These findings suggest that marine echinoderms are a potential source of new types of antibiotics for pharmaceutical development. Tripneustes gratilla (Echinoidea) collected from the Kenyan Coast. Unfortunately, in most of these studies on antimicrobial activity in echinoderms, whole bodies or body walls have been tested for activity. Recently, Haug et al. (2002) observed wide differences in antibacterial activities between different extracts and organs/tissues, as well as between species, of three echinoderms. Whether the same antibacterial factors are responsible for the activity in all organs or tissues remains unclear. The present work focused on screening and comparing antimicrobial and hemolytic activities in different organs/tissues of the sea urchin

Antimicrobial activity of various extracts of the sea urchin Tripneustes gratilla (Echinoidea)

The degradation of seagrasses is becoming prevalent in the Western Indian Ocean (WIO) region due to anchor damage, sea urchin herbivory, extreme events such as cyclones and floods and anthropogenic factors such as pollution and sediment inflows. Consequently, there have been numerous efforts to advance the restoration of degraded seagrass beds in several countries in the region. In Kenya, experimental restoration efforts were started in 2007 in response to seagrass habitat degradation due to sea urchin herbivory. Although the initial efforts experienced challenges, there were lessons learned which provided insights into subsequent restoration work using different techniques. In this paper, insights are provided into three types of restoration techniques; the sod technique, the seagrass mimic technique, and the Hessian bag technique. In the case of the sod technique, Thalassodendron ciliatum showed a decline from 20 ± 1.7 shoots sod-1 in the first three weeks to 7 ± 4.4 shoots sod-1 at the end of the experimental period of the study, while Thalassia hemprichii sods showed an increase from 28 ± 3.4 shoots sod-1 to 32 ± 2.7 shoots sod-1 over the same period. For the Hessian bag method, the expectation was that the pilot site would be filled with the transplanted seagrass species, Thalassia hemprichii, but the findings showed that different species including Halodule uninervis, Syringodium isoetifolium, Halophila stipulacea, Cymodocea rotundata, and Cymodocea serrulata colonized the area. This indicated that it was not possible to restore the area to its original status, but that the area could be rehabilitated. The costs of restoration have also been assessed as well as community participation in such initiatives. These findings provide insights for restoration efforts in Kenya and provide a baseline for future work.

/pdf/seagrass-restoration-trials-in-tropical-seagrass-meadows-of-2dt99jc7.pdf

Seagrass restoration trials in tropical seagrass meadows of Kenya

Solar energy is among the cleanest and most sustainable ways to enhance electrical supply's resiliency and reliability for domestic and industrial use. A Photovoltaic (PV) system is the most effective way of capturing solar energy. Long-term warranty, low-cost maintenance, and vast resource availability, solar power generation has an advantage over other approaches. Thin-film technology PV cells are a new kind of solar cell that offers an efficient technique of generating electricity from sunlight. The thin-film PV technology (FFMAT-10, Renovagen, UK) used in this study can supply 0.9 to 1.6 kW of energy to the fast-fold energy hub. The hub’s system status and configuration display battery power input, battery’s state of charge, thin-film PV power and AC power output. Two fast-fold mats (with a surface area of 25.3 m2) were connected to the energy hub. Increasing energy demand coupled with frequent power outages, and inaccessibility of electricity in rural areas necessitates the usage of PV systems at their best performance level. The study objective, therefore, sought to assess the effect of tilt angle on the performance of the thin-film PV system. The study was conducted at Kimicha in Kirinyaga County Kenya, and Juja, Kenya at tilt angles between 0o to 30o. The results indicated that the mean peak PV power for Kimicha was 347.8±231.9 W at 5o and 517.7± 131.3 W at 15ofor Juja. The maximum solar radiation during the study period was 1086.4 ±211.4 W/m2 for Juja and 973.5±219.93 W/m2 for Kimicha. From the study, it was realized that an optimal tilt angle yields optimum solar radiation that translates to maximum power production. Even though the study was conducted in two different regions, it may be applied to any other geographical location. The outcome of the study aids in acquiring self-sustaining power in the most remote locations where electricity is scarce as well as improving energy security.

Effect of tilt angle on the performance of a thin-film photovoltaic system

Fruits are high moisture agricultural produce rendering them highly perishable hence the danger of postharvest losses is also lurking when there are inadequate storage facilities. The losses result from physical, chemical, and physiological changes that are triggered by the loss in moisture content. Preservation of fruits using available and affordable technologies (such as charcoal coolers) can benefit small-scale farmers in minimizing postharvest losses. An evaporative charcoal cooler 4 m long, 4 m wide, and 2.5 m high providing a 40 m3 storage capacity was utilized in the study. The cooler with a 150 mm wide cavity filled with charcoal had a perforated pipe connected to a 1000-litrecistern raised at 2.5 m above the ground and connected to a water pump (Pedrollo PKm 60, Italy) that kept the charcoal wet by a drip system. The pump and the three axial fans (REC-21725 A2 W, USA) rated 180 cubic feet per minute (CFM) and 2600 revolutions per minute (RPM) were powered by fast fold thin-film PV (FFMAT-10, Renovagen, UK) system connected to a 10-kWh rated energy hub (FFENERGYHUB-10, Renovagen, UK). Temperature, relative humidity and product quality parameters (weight loss, total soluble solids, vitamin C content and firmness were evaluated).The evaporative cooler temperatures reduced significantly (P<0.05) with an average 25.0±0.37 oC and 32.1±0.99 ºC outdoors temperatures. The cooler relative humidity increased significantly (P˂0.05) averaging 76.8±1.6% and 43±2.8% for ambient conditions. The average cooling efficiency in the charcoal cooler was 83.0%.The percentage weight loss of the avocado was 3.9% and 7.5% for the cooler and outdoors respectively. The percentage vitamin C loss was 39.0% for the cooler and 49.6% for those kept outside. The total soluble solids in the cooler rose from 0.5 to 1.6 oBrix and 0.5 to 2.6 oBrix in ambient conditions. Firmness decreased from an average 65.0 N to 10.7 N and 65.0 N to 8.0 N after 12 days for samples in the cooler and ambient conditions, respectively. In conclusion, the evaporative charcoal cooler incorporated with thin-film PV system preserved the postharvest quality and extended the shelf life of hass avocado.

/pdf/performance-evaluation-of-an-evaporative-charcoal-cooler-2uw9ndlt.pdf

Samuel N. Ndirangu

Papers

Antimicrobial activity of various extracts of the sea urchin Tripneustes gratilla (Echinoidea)

Seagrass restoration trials in tropical seagrass meadows of Kenya

Effect of tilt angle on the performance of a thin-film photovoltaic system

Performance evaluation of an evaporative charcoal cooler utilizing thin-film photovoltaic system for preservation of avocado