Miriam Pérez

Non-toxic alternative compounds for marine antifouling paints

Abstract In order to search for alternative non-pollutant substances as antifouling compounds, the effects of sodium benzoate and different tannins (from chestnut, mimosa and quebracho) were studied. Balanus amphitrite (Cirripedia, Balanidae) nauplii were used in the laboratory for the bioassays. The results showed that both benzoates and tannins have a narcotic effect on these larvae, this effect was faster as the concentration of these compounds was increased. Larvae rapidly recovered when they were transferred to fresh, non-toxic, artificial sea water. Field trials in Mar del Plata harbor confirmed that soluble matrix paints, formulated with sodium benzoate or tannins as antifouling agents, were successful in preventing barnacle attachment. These results indicate the potential bioactivity of these compounds on fouling organisms.

Tannin and tannate from the quebracho tree: an eco-friendly alternative for controlling marine biofouling.

Abstract Current antifouling coatings are based on toxic compounds that can be harmful to the natural environment. A promising alternative to these compounds is the use of natural products that are non-toxic, but have antifouling properties. Tannins are natural, water-soluble, complex polyphenolic substances, which precipitate proteins and have anticorrosive and antimicrobial properties. In this study, the effect of quebracho tannin as a probable antifouling pigment in both laboratory and field trials is evaluated. As tannins have high solubility in aqueous media and consequently would leach rapidly, they were precipitated as aluminium tannate, which has an adequate solubility for use as a component in marine paints. In vitro exposure of Balanus amphitrite and Polydora ligni larvae to low concentrations of both quebracho tannin and saturated aluminium tannate solutions produced complete appendage immobilisation. In 28-d field trials of test gels, a significant decrease in micro- and macrofouling density and diversity in relation to the control gel was detected (p < 0.05). This study suggests that natural tannins could be employed as bioactive pigment for new antifouling technologies.

Solubility and toxic effect of the cuprous thiocyanate antifouling pigment on barnacle larvae

Cuprous oxide is one of the most commonly employed antifouling pigments. However, its red color limits further pigmentation of the paint. On the other hand, cuprous thiocyanate is a white pigment that can be employed when film pigmentation in other colors is required. The purpose of this paper is to study the chemical and biocidal properties of cuprous thiocyanate, in comparison with those of cuprous oxide, with a view of its utilization in paint elaboration.The solubility, oxidability, particle size distribution, and oil absorption of the pigment were determined along with two methods for its preparation. A solubilization mechanism for cuprous thiocyanate is also outlined.Biological tests were carried out in the laboratory in order to evaluate the biocidal properties of cuprous thiocyanate. Lt50 and Lt100 were determined for Balanus amphitrite nauplii and cyprids.White cuprous thiocyanate has, in many ways, similar properties to those of cuprous oxide, although it is less oxidizable and has a greater lethal action than cuprous oxide.

Evaluation of low copper content antifouling paints containing natural phenolic compounds as bioactive additives

Cuprous oxide is the most commonly used biocide in antifouling paints. However, copper has harmful effects not only on the fouling community but also on non-target species. In the current study, we investigated the use of thymol, eugenol and guaiacol in this role combined with small quantities of copper. Phenolic compounds were tested for anti-settlement activity against cyprid larvae of the barnacle Balanus amphitrite and for their toxicity to nauplius larvae. Thymol, eugenol and guaiacol were active for anti-settlement but guaiacol had the disadvantage of being toxic to nauplius larvae. However, all of them showed therapeutic ratio>1. Antifouling paints with thymol (low copper content/thymol, LCP/T), eugenol (low copper content/eugenol, LCP/E) and guaiacol (low copper content/guaiacol, LCP/G) combined with small copper content were formulated for field trials. After 12 months exposure in the sea, statistical analysis revealed that LCP/T and LCP/E paints were the most effective combinations and had similar performances to control paints with high copper content (traditional cuprous oxide based paints). In contrast, LCP/G paint was only partially effective in preventing and inhibiting biofouling and was colonized by some hard and soft foulers. However, this antifouling paint was effective against calcareous tubeworm Hydroides elegans. In the light of various potential applications, thymol, eugenol and guaiacol have thus to be considered in future antifouling formulations.

Reversible effect of potassium sorbate on Balanus amphitrite larvae. Potential use as antifoulant

Marine biofouling constitutes a major worldwide technical and economic problem. International regulations concerning the protection of both the environment and industrial workers have prompted paint manufacturers and end users to look for suitable replacements for traditional antifouling (AF) pigments. For this reason, the potential AF activity of potassium sorbate (KS) on nauplii and cyprids of Balanus amphitrite was tested in laboratory and field trials. Larval bioassays demonstrated a marked inhibitory and reversible effect. The values obtained for EC50 and LC50 were 9.91 mM and 36.73 mM, respectively, and the therapeutic ratio was 3.71, indicating that KS acts via a non-toxic mechanism. After 60 days in the sea, a varnish coating incorporating KS showed a substantial decrease in micro- and macrofouling density and diversity. This investigation indicated that KS is a promising AF agent for replacing the traditional toxic compounds.

Antifouling activity of green-synthesized 7-hydroxy-4-methylcoumarin.

In the search for new environmental-friendly antifoulants for replace metallic biocides, 7-hydroxy-4-methylcoumarin was synthesized according to green chemistry procedures. This compound was characterized by current organic analysis and its antifouling properties were firstly evaluated on the bivalve Mytilus edulis platensis in the laboratory. In the second stage, a soluble matrix antifouling coating formulated with this compound was assayed in marine environment. Laboratory experiments showed that 7-hydroxy-4-methylcoumarin was effective in inhibiting both the settlement as well as the byssogenesis of mussels. In addition, after exposure time in the sea, painted panels containing this compound showed strong antifouling effect on conspicuous species of the fouling community of Mar el Plata harbor. In conclusion, green-synthesized coumarin could be a suitable antifoulant candidate for marine protective coatings.

Transitioning to nontoxic antifouling paints

Purpose – The purpose of this paper is to reduce the amount of copper in antifouling paints by using eugenol as an additive. Biofouling leads to deterioration of any submerged material. The most widespread method for control is the application of cuprous oxide antifouling paints which are toxic. First of all, the paper describes the effect of eugenol on larvae of Balanus amphitrite (fouling organism) under laboratory conditions and then the preparation, application and performance of different types of antifouling paints in field trials. Design/methodology/approach – Three types of soluble matrix antifouling paints were prepared with different pigments. The first one containing 16 per cent v/v copper, the second with 1.6 per cent copper and the third with 1.6 per cent copper + 2 per cent eugenol. Findings – After 12 months of immersion in Mar del Plata harbour paints containing 1.6 per cent copper + eugenol and 16 per cent copper were the most effective. Although these formulations showed a similar perfor...

Alkyl 2-furoates obtained by green chemistry procedures as suitable new antifoulants for marine protective coatings

In search of new sustainable alternatives to reduce the use of metallic antifouling pigments in marine paints, three n-alkyl 2-furoates were synthesized by safe procedures framed within the green chemistry concepts. These compounds were characterized by current organic analysis, and their antifouling properties were first evaluated on Artemia salina nauplii in the laboratory. Then, antifouling paints formulated with these compounds were assayed in a marine environment. Both laboratory and field tests indicate that n-alkyl 2-furoates have strong antifouling activity and are safe chemicals for marine paints.

Isolation and Antifouling activity of Azulene Derivatives from the Antarctic Gorgonian Acanthogorgia laxa

Three azulenoid sesquiterpenes (1 – 3) were isolated from the Antarctic gorgonian Acanthogorgia laxa collected by bottom trawls at −343 m. Besides linderazulene (1), and the known ketolactone 2, a new brominated C16 linderazulene derivative (3) was also identified. This compound has an extra carbon atom at C(7) of the linderazulene framework. The antifouling activity of compounds 1 and 2 was assayed in the laboratory with Artemia salina larvae, and also in field tests, by incorporation in soluble‐matrix experimental antifouling paints. The results obtained after a 45 days field trial of the paints, showed that compounds 1 and 2 displayed good antifouling potencies against a wide array of organisms. Compound 3, a benzylic bromide, was unstable and for this reason was not submitted to bioassays. Two known cembranolides: pukalide and epoxypukalide, were also identified as minor components of the extract.

PO-280 Hypoxia-induced pld2 promotes tumorigenesis and stem cell-like properties in tumour cells

Introduction Phospholipase D (PLD) hydrolyzes phosphatidylcholine, the most abundant phospholipid in eukaryotic cell membranes, and it is overexpressed in a wide variety of cancers. In solid tumours, PLD2 has been associated to hypoxic regions and it has been purposed to mediate postranslational regulation of HIF-α, but its contribution to protein stabilisation or degradation is not clear. Moreover, hypoxia has a key role in tumour population heterogeneity and cancer stem cells increase and it has also been associated with increased malignancy, poor prognosis and resistance to radiotherapy and chemotherapy. Material and methods To characterise the implication of PLD2 in tumorigenesis and the increase of stem cell-like properties under hypoxia conditions, we generated two PLD2 knock-down colon cancer cell lines from HCT116 and LS180 commercial cell lines. We also generated PLD2 lipase mutant cell lines. We checked PLD2 protein and mRNA levels under normoxia and hypoxia conditions, as well as tumorigenesis, using different approaches in vitro: growth curves, colony formation assays, percentage of holoclones and capacity to generate tumorspheres. In addition, we analysed several stem cell markers by FACS analysis and RT-qPCR. Results and discussions We first show that the increase of PLD2 under hypoxia conditions depends on its lipase activity. Hypoxia-induced PLD2 increases cell growth and anchorage-independent cell growth. Additionally, we show that hypoxia-induced PLD2 increases the stem cell-like properties of cancer cells, including clonogenicity and the capacity to form tumorspheres. Conclusion Altogether, our results demonstrate that hypoxia-induced PLD2 increases tumorigenesis and stem cell-like properties in colon cancer cells.