Antifungal activity evaluation of three traditional Chinese herbs against biodeterioration of cultural heritage

Abstract

Natural biocides are increasingly used in the conservation of cultural heritage against biodeterioration. Traditional Chinese medicine has identified many plants with antimicrobial properties, such as Scutellaria baicalensis, Coptis chinensis and Lonicerae japonicae flos, which provides a rich resource as natural biocides. In this study, the antifungal and antibiofilm activity of these herbs was evaluated against the dominant fungi that always cause deterioration of the cultural heritage. The relationship between the addition of the screened biocide and the color change of the mural and limestone was also analyzed, then the identified maximum acceptable dose was added to the mural and limestone samples to assess the in situ antimicrobial performance. The results showed that S. baicalensis and C. chinensis had the antifungal activity and the active components in the two herbs were baicalin and berberine. Furthermore, a synergistic antifungal activity of the two components was observed and the MICs of the mixture were similar to those of Cinnamomum verum essential oil. In addition, the mixture of baicalin and berberine was also able to inhibit biofilm formation. Because of the yellow color of baicalin and berberine, when they were added, the color of the samples began to turn yellow. However, the maximum addition, with no significant effect on the aesthetic appearance, was still able to inhibit fungal growth in the in situ tests. In conclusion, the mixture of baicalin and berberine could be an alternative natural biocide of C. verum essential oil for the conservation of cultural heritage against biodeterioration.