Prevention of Marine Biofouling Using the Natural Allelopathic Compound Batatasin-III and Synthetic Analogues

Abstract

The current study reports the first comprehensive evaluation of a class of allelopathic terrestrial natural products as antifoulants in a marine setting. To investigate the antifouling potential of the natural dihydrostilbene scaffold, a library of 22 synthetic dihydrostilbenes with varying substitution patterns, many of which occur naturally in terrestrial plants, were prepared and assessed for their antifouling capacity. The compounds were evaluated in an extensive screen against 16 fouling marine organisms. The dihydrostilbene scaffold was shown to possess powerful general antifouling effects against both marine microfoulers and macrofoulers with inhibitory activities at low concentrations. The species of microalgae examined displayed a particular sensitivity toward the evaluated compounds at low ng/mL concentrations. It was shown that several of the natural and synthetic compounds exerted their repelling activities via nontoxic and reversible mechanisms. The activities of the most active compounds such as 3,5-dimethoxybibenzyl (5), 3,4-dimethoxybibenzyl (9), and 3-hydroxy-3′,4,5′-trimethoxybibenzyl (20) were comparable to the commercial antifouling booster biocide Sea-nine, which was employed as a positive control. The investigation of terrestrial allelopathic natural products to counter marine fouling represents a novel strategy for the design of “green” antifouling technologies, and these compounds offer a potential alternative to traditional biocidal antifoulants.

Design and Biological Evaluation of Antifouling Dihydrostilbene Oxime Hybrids

“…Intrigued whether the allelopathic activity of terrestrially derived natural products can be used to yield effective antifoulants in a marine setting, we recently investigated the AF activity of the allelopathic dihydrostilbene compound batatasin-III ( 1 ) (Fig. 1 ) (Moodie et al 2017a , b ). Batatasin-III is produced by a number of terrestrial plants, including the crowberry ( Empetrum nigrum ), where it accumulates in high amounts (up to 6% of the dry leaf weight).…”

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Fig. 1 Top: representative antifouling compounds and corresponding IC 50 activities against Balanus improvises larvae settlement; 1 (Moodie et al 2017b ), 2 (Moodie et al 2017b ), 3 (Hanssen et al 2014 ), 4 (minimum significant dose to inhibit settlement) (Ortlepp et al 2007 ), 5 (Ortlepp et al 2007 ), 6 (Moodie et al 2017b ). Lower left panel: Empetrum nigrum (the common crowberry), a very prolific producer of 1 which is used to control competing plant species and recently shown to also be a highly potent marine antifoulant.

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“…Compound 2 was chosen as a lead structure given its ng/mL activity against key strains of microalgae and marine bacteria involved in biofilm formation, and its low μg/mL activity against Balanus improvisus and ascidian Ciona savignyi settlement inhibition (IC 50 , 0.75 and 1.1 μg/mL, respectively). Compound 2 also displayed low toxicity against the latter two fouling species and, in particular, effectively inhibited the settlement of C. savignyi even after 5 days (Moodie et al 2017b ). A library of compounds based on lead compound 2 was rationally designed and synthesized, containing the 3,4-dimethoxy-substitution pattern found in 2 , and variants thereof.…”

Isolation and Antimacrofouling Activity of Indole and Furoquinoline Alkaloids from ‘Guatambú’ Trees (Aspidosperma australe and Balfourodendron riedelianum)

“…Terrestrial plants produce secondary metabolites that exhibit a variety of biological activities, and there are reports of the use of plant extracts as antifoulants . Some plant bioactive compounds have shown antifouling properties in previous studies …”

“…[15,16] Some plant bioactive compounds have shown antifouling properties in previous studies. [17][18][19][20][21][22][23][24][25][26] In this work is studied the antifouling activity of five alkaloids: three indole alkaloids from the bark of A. australe and two furoquinoline alkaloids from the bark of B. riedelianum by laboratory and field assays. These compounds, which have been known for several decades, fulfill the following criteria used for sample selection: previous reports of biological activity for compounds of the same family, high yields of extraction from their biological sources and simple purification protocols.…”