## 4 Essential Oils as Active Secondary Compounds in Wound Dressings  
Secondary metabolites like other antibiotic chemical compounds, e.g., such as aminoglycos [111], beta-lactams [112], glycopeptides [113], quinolones [114], sulphonamides [115], and tetracyclines [116; 117], can be used to control wound infections. The influence of natural antimicrobials on the wound-healing process could be explained by their effects on growth factors (epithelial cells, fibroblasts, vascular endothelial cells) as stimulators of wound cells and cellular mechanisms [118]. In other words, the antimicrobial compounds accelerate and promote skin regeneration by influencing cell migration and ECM deposition [119]. In vitro and in vivo evidence indicates antimicrobial and anti-inflammatory effects of secondary active metabolites in the wound-healing process [8; 14]. Natural antimicrobial compounds defuse through bacteria cell walls and break their cell membranes by invading the bacteria's membrane phospholipids and lipids [120]. Active metabolites can also act as antioxidant agents and accelerate the wound-healing process by decreasing intracellular ROS production and controlling the rate of nitric oxide synthase [121; 122]. Bioactive secondary metabolites of plants could be used for wound healing, including alkaloids, essential oils, flavonoids, tannins, terpenids, saponin, fatty acids, and phenols [36]. These active compounds could improve the wound-healing process by influencing one of the healing stages through antibacterial, antifungal, antioxidant, and anti-inflammatory effects [123]. Many studies have been done on the potential application of essential oils and other secondary metabolites in wound-healing applications by incorporating them in dressing materials. Moreover, essential oils demonstrate the capacity to be used as both a solvent and active material, which improves the synthesis process's sustainability and safety. Table 1 gives an overview of the different types of essential oils that have been formulated into polysaccharide-based wound dressing systems using nanotechnologies and their bioassays. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Essential Oils** & **Wound Dressing System** & **Method** & **Bioassay** & **References** \\ \hline Cinnamon, clove, and & & & & \\ lavender oils & Sodium & & & \\ (_Cinnamonum Syzygium_ & alginate/polyvinyl alcohol & Electrospinning & _Staphylococcus aureus_ & [124] \\ aromaticum and Lavendula) & & & & \\ or Lavender oil/ & & & & \\ \hline Clove, Mandarin, and & & & & \\ Niaouli oil & Sodium alginate film+ & & & _E. coli_, _Staphylococcus aureus_, & \\ (_Syzygium aromaticum,_ & & & & \\ Citrus reticulata and & & & & \\ Mdelauca quinquenervia_) & & & & \\ \hline Eucalyptus essential oil (+ & & & & \\ Manuka honey, aloe vera gel) & & & & \\ \hline Silvery wormwood oil & & & & \\ (_Artemisis argv_) & & & & \\  & & & & \\  & & & & \\ Cabreuva essential oil & & & & \\ (_Myrocarpus fastigitatus_) & & & & \\  & & & & \\ \hline Cardamom oil & & & & \\ (_Elettaria Cardamomom_) & Chitosan nanocomposites & Ionic & & \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Essential oil applications for wound healing. Thymol (TH) and its isomer carvacrol (CA) are monoterenoid phenols from the _Origanum_ genus. They are found in thyme oil extracted from _Thymus vulgaris_, a plant from the Lamiaceae family and a native plant of Southern Europe ranging from the Western Mediterranean to Southern Italy [14]. Many studies have shown that carvacrol and thymol have anti-inflammatory, antioxidant, skin fibroblast-stimulating, and antibiotic effects in the wound-healing process [138; 139; 140; 141; 142; 143; 144; 145; 146]. In this regard, [PERSON] et al. loaded a thyme oil nanoemulsion in chitosan alginate films (TM-PEC) at two different polymer ratios of polymers of 0.4 and 1 w/v% through a solvent evaporation technique [103].