Antibacterial and algaecide activity of three natural compounds: Lab-test approaches on their potential use in paint formulations

Abstract

The chemicals added to paints used to prevent biofilms on structural materials, contains chemical products that in general, also have toxic effects on the environment. Plants synthesize secondary metabolites which have antimicrobial properties and that may be a sustainable alternative to traditional biocides . The antimicrobial and algaecide effect of natural compounds of vegetal origin such as isoeugenol, carvacrol and vainillic acid was evaluated in a laboratory test by the agar diffusion method and the microatmosphere technique respectively. As antimicrobials, the compounds exerted a moderate to high activity. Vanillic acid was the least effective, followed by isoeugenol, and being carvacrol the most efficient. In the case of algae, the three compounds produced a decrease in the algal growth with respect to the control. Due to these results, carvacrol and isoeugenol were incorporated separately in an exterior waterborne paint at a concentration of 2 % w/w. Samples painted with these formulations were not colonised by algae indicating that these compounds could be used as biocides in paint formulations. • Algal biofilm was obtained from a deteriorated painted wall surface. • The antimicrobial and algaecide effect of three natural compounds was tested. • Vanillic acid exhibit the lowest antibacterial and alguicide activity. • Isoeugenol and carvacrol inhibited bacterial and algal growth at different degree. • Their incorporation to a paint showed good results for controlling algal biofilm.