The Essential Oil of Thymbra capitata and its Application as A Biocide on Stone and Derived Surfaces

Abstract

Many chemicals used nowadays for the preservation of cultural heritage pose a risk to both human health and the environment. Thus, it is desirable to find new and eco-friendly biocides that can replace the synthetic ones. In this regard, plant essential oils represent effective alternatives to synthetic substances for the preservation of historical monuments. Thymbra capitata (syn. Thymus capitatus) is a medicinal and aromatic plant growing in the Mediterranean area and endowed with important pharmacological properties related to its essential oil. Among them, the antimicrobial ones make the T. capitata essential oil an ideal candidate for industrial applications; for instance, as biocide for the inhibition and elimination of biological patinas of cyanobacteria and green algae on historical monuments. In the present work, we studied the chemical composition of the essential oil from T. capitata growing in Malta by gas chromatography-mass spectrometry (GC/MS). The major volatile component is the phenolic monoterpene carvacrol (73.2%), which is capable of damaging the cytoplasmic membrane and to interfere both in the growth curve and in the invasive capacity, though the contribution of minor components γ-terpinene and p-cymene cannot be disregarded. For the oil application on the stone surface, Pickering emulsions systems were prepared with an essential oil/water 1:3 mass ratio stabilized with kaolinite at 4 mass% in the presence of Laponite®; this allowed to limit the fast volatility of the oil and guaranteed a better application and an easier removal from the artefacts attacked by biodeteriogens both indoor and outdoor. This formulation caused the elimination of biodeteriogens from treated surfaces without residuals or films on artworks surface, and the effect was retained up to four months.

Potential Effects of Essential Oils Extracted from Mediterranean Aromatic Plants on Target Weeds and Soil Microorganisms

“…Due to the presence of polyphenols, T. capitata EO is used in food preservation [ 31 ] and it has been demonstrated that it possesses antioxidant properties [ 32 ]. Moreover, the antimicrobial [ 33 , 34 ] and herbicidal activities [ 15 , 35 , 36 ] of T. capitata EO have been verified. Santolina chamaecyparissus L. (cotton lavender) is an aromatic plant belonging to Asteraceae family.…”

The Application of the Essential Oils of Thymus vulgaris L. and Crithmum maritimum L. as Biocidal on Two Tholu Bommalu Indian Leather Puppets

“…Several studies highlighted how EOs rich in phenolic compounds, such as thymol or carvacrol, have a strong antimicrobial activity. In particular, thymol seems to be bioactive against more than twelve different bacterial colonies [ 21 , 42 ].…”

“…Thymus EO was selected due to its microbial properties, which have previously been reported in several studies [ 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. In particular, the Thymus vulgaris essential oil has been shown to be quite effective against several microorganisms [ 22 , 23 ].…”

The Control of Cultural Heritage Microbial Deterioration

“…Thymbra capitata essential oil was proposed for use against cyanobacteria and green algae on historical monuments [86]. The major components of the essential oil were the phenolic monoterpene carvacrol (73.2%) and its biogenetic precursors γ-terpinene (6.9%) and p-cymene (4.3%).…”