## 3 Discussion  
Plants represent an extraordinary resource for the isolation of compounds with antimicrobial activity. Cinnamaldehyde used in this study derived from _Cinnamomomom cassia_ (CC) Essential Oil (EO). Table 1 shows the chemical volatile composition of CC EO and CIN-MPs obtained by SPME-GC-MS analysis. The content of CIN in CC EO resulted equal to 70.4% as the main component, while the only CIN phytocompound encapsulated in microparticles, reaches 100%. The MFC values obtained with EO are comparable to those obtained with CIN alone. This demonstrates, as known by previous works, that the main component of this phytocomplex is responsible for antifungal properties [18; 19; 20]. EOs and their active components are generally characterized by some drawbacks such as high volatility, chemical instability, and low solubility in water, hence their limited use in medical therapy [21; 22]. To overcome these limitations, microparticles are extensively applied as carriers for drug delivery, because they can prevent the degradation of the drug, can target the active compounds to the specific tissue, can reduce the side effects, etc. [23]. A lot of polymers are used as vectors for drug delivery, among these, PLGA, characterized by good biocompatibility, is widely applied for this purpose. In this study, the single emulsion technique, was used to encapsulate CIN inside PLGA microparticles. In fact, this technique, is particularly used to encapsulate hydrophobic compounds. The encapsulation of CIN, within micro or nano vectors, has been performed in other works and with different aims [24; 25; 26]: antimicrobial activity in the oral cavity, in bone, and in food conservation. On the base of the literature data, we decided to extend our studies also on antibiotic-resistant Candida strains. For this purpose, we characterized the microparticles produced evaluating load, encapsulation efficiency, and release of the active ingredient in different media. In terms of encapsulation efficiency, the obtained results are consistent with the literature considering the ratios between the different compounds used in the single emulsion reaction [27]. Regarding the release curves of the CIN from the microparticles, it is interesting to observe how, in ethanol, the release has the usual initial burst of the particles in PLGA [27], in these conditions, in fact, the medium used is a solvent for CIN. When the test is repeated in a _Candida_ culture medium, i.e., in a non-solvent medium, the release becomes much more gradual and reaches, after 24 h, an amount equal to \(\frac{1}{4}\) of the total encapsulated CIN. The most interesting results are observed when the CIN release is carried out in the culture medium in the presence of _Candida_, in this case, in 24 h the release is practically complete, indicating that the active principle penetrates inside the microorganism favouring the \"emptying\" of the microparticles gradually. This particular effect can be deduced from the higher antifungal efficacy observed when CIN is administered within the microparticle compared to the free form: it is conceivable that the vehiculation maintains the concentration of CIN at fungicidal concentration longer than the non-vehicle form, with a consequent increase \begin{table}
\begin{tabular}{l c c c c} \hline \hline  & \multicolumn{3}{c}{**Nucleic Acid Absorbance \(\pm\) St. Dev.**} \\ \hline  & **C. albicans** R & _C. albicans_ S & _C. glabrata_ R & _C. glabrata_ S \\ \hline CIN-MPs & 0.54 \(\pm\) 0.07 & 0.56 \(\pm\) 0.05 & 0.69 \(\pm\) 0.08 & 0.82 \(\pm\) 0.03 \\ CIN & 0.75 \(\pm\) 0.04 & 0.94 \(\pm\) 0.05 & 0.65 \(\pm\) 0.03 & 0.68 \(\pm\) 0.07 \\ Untreated & 0.20 \(\pm\) 0.01 & 0.25 \(\pm\) 0.05 & 0.26 \(\pm\) 0.02 & 0.34 \(\pm\) 0.04 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Nucleic acid (OD260 nm) released from Candida strains untreated and treated with CIN and CIN-MPs at MFC90 concentrations. Analyses were performed in triplicate (\(p\) value \(<\) 0.0001). in the antimicrobial effect. This is particularly evident with _C.