Plant products as biocides for conservation of cultural asset sustainable for human and environmental health

In the last decades plants products are increasingly used also in defining innovative procedures for sustainable conservation of cultural heritage. Particularly, essential oils or hydro-alcoholic extracts have been fruitful applied to contrast microbial colonization on organic and inorganic artworks or insect infestation (Anobidae) having regard to the repellent action. In this paper, extracts from Asteraceae and Lamiaceae plant families are utilized to counteract widespread microbial colonization (bacteria, cyanobacteria, fungi) due to their antimicrobial activity. In order to define the adequate concentration correlating it to microbial species detected, the antimicrobial activity of natural products is preliminary in vitro assayed by Agar Disc and Well Plate Diffusion methods. Moreover, an integrated approach based on morphological analysis (optical, scanning and confocal electron microscopy), in vitro cultures (Nutrient or Sabouraud agar) and molecular investigation (genomic microbial DNA extraction, sequencing and sequence analysis) are routinely performed for the identification of largest number of microbial taxa. Besides, to enhance the antimicrobial activity different protocols have been performed, such as for Thymus vulgaris products directly applied on wooden sculpture surface as hydro-alcoholic extract, followed by exposure, in a dedicated chamber, to the volatile compound of the corresponding Essential Oil. In other case studies, the exposure to volatile compounds of Crithmum maritmum, Inula critmoides, Thymus vulgaris and Origanum vulgare essential oils was performed under controlled vacuum conditions, comparing the effects to environmental condition exposure. These studies confirm the possible use of plant extracts in replacing synthetic chemical biocides, in full respect of human health and environment sustainability.