# Biocompatibility of Membranes Based on a Mixture of Chitosan and _Lythri herba_ Aqueous Extract
## 4 Discussion  
The therapeutic plant extract _L. salicaria_ L. is known in the specialized literature for its high quantity of tannins [37], and the formulation of chitosan membranes is the first attempt to capitalize on these plant metabolites with as diverse applications as possible, such as obtaining mucoadhesive patches [45] or dressings with a fast local effect in a general context for the reduction of synthetic materials and the development of eco-friendly technologies. The use of water as the main solvent for the extraction of active compounds from the plant _L. salicaria_ L. followed by the choice of a natural, biodegradable and non-toxic material as a support in the development of a pharmaceutical or medical application were decisions made in accordance with the \"green technology\" principle to protect the environment by limiting its contamination with aggressive solvents or toxic materials [68]. The accumulation of the extract within the chitosan membranes can be attributed to the chemical interactions that occur between the biopolymer matrix and the components of the extract. These interactions involved the amino groups from chitosan interacting with tannic acids as well as the OH groups of C\({}_{6}\) from the glycosidic ring of chitosan interacting with tannic acids. The formation of a homogeneous film indicates that the ingredients used were properly incorporated into the polymer matrix. The firm and flexible appearance is suitable for formulations with medical applications [69; 70; 71], ensuring better ease of administration [72]. Previous studies in the current collection of literature have focused on the process of functionalizing chitosan with polyphenols, which are derived from plants as secondary metabolites. This particular research direction has been pursued due to the observed enhancement of antioxidant activity associated with these polyphenols [73]. Among the various options available, tannic acids (TA) emerge as the most suitable choice due to their notable antioxidant properties and excellent water solubility [74; 75]. Furthermore, the coalescence of chitosan and TA has been observed to enhance the bioavailability of TA while also providing protection against their degradation [76]. In relation to the hydration level of the membranes, it was observed that the use of the aqueous freeze-dried extract of _Lythri herba_ resulted in membranes that exhibited enhanced stability compared with the 1% and 0.5% chitosan membranes. Furthermore, these _Lythri herba_-treated membranes did not undergo deformation upon exposure to an alkaline solution. Instead, they displayed desirable properties of flexibility and elasticity, making them suitable for applications in mucoadhesive systems. Due to the presence of hydroxyl and amino groups in its chemical structure, CS chitosan is easily hydrated in water, because water molecules interact strongly with these hydrophilic groups, leading to the weakening of intermolecular hydrogen bonds [77]. Several particular investigations have been conducted on membranes and biofilms made from chitosan, and these studies consistently found that these materials have low water resistance [78; 79]. This aspect was observed at the 0.5% CS membrane tested, whose fragility was the highest. [PERSON] et al. (2022) drew attention to a phenomenon analogous to that observed in the present study. Specifically, they found that membranes containing chitosan as a constituent, along with green banana peel extract, exhibited a lower degree of swelling in both water and phosphate-buffered saline (PBS) solutions compared with membranes composed solely of chitosan. This finding suggests that the robust interactions between chitosan and the extract compounds result in a reduced ability to absorb water [80]. The water content has a considerable influence on the bioadhesive behavior of the membranes, which is modified by disrupting the polymer bonds with the active ingredients [81]. The utilization of extracts derived from medicinal plants has experienced a notable rise in recent decades.