## 6 Grape and Winery By-Products: Active Ingredients in Cosmeceuticals
### Antimicrobial Properties  
The addition of antimicrobial agents to cosmetic products is important to ensure their microbiological purity and therefore consumer safety. Improper use of cosmetics, as well as inappropriate storage and handling conditions, can lead to microbial contamination, which is associated with serious health consequences such as eye infections, corneal ulcers, dermatitis, phlebitis, and bursitis [91]. Contamination can occur at any stage of production, packaging, or use of products, and their high water, organic, and inorganic content creates an ideal environment for the growth of pathogenic microorganisms [92]. For this reason, the incorporation of effective and natural antimicrobial agents in cosmetic formulations is essential to ensure the quality, safety, and efficacy of the final products. Therefore, grape by-products, thanks to their unique chemical composition and high content of phenolic compounds and bioactive molecules, are a good solution for enhancing antimicrobial protection in cosmetic products as shown in Table 5.  
A study reported on the antioxidant activity of grape seed, seed kernel extracts, and oils also evaluated their antimicrobial activity [85]. In particular, the Kirby-Bauer disc diffusion test method was used to study the antimicrobial activity and to assess the sensitivity or resistance of microbes to the extracts. The assessments were carried out against Gram-negative bacteria (_Escherichia coli_) and Gram-positive bacteria (_Staphylococcus aureus_, _Staphylococcus epidermidis_). Grape pomace and grape seed extracts showed efficacy against Gram-positive bacteria but had no inhibitory activity against Gram-negative bacteria. This is expected, as polyphenolic extracts are generally more effective against Gram-positive bacteria due to their structure. Using the Kirby-Bauer disc diffusion method, no antimicrobial activity was observed for the oils. However, alternative testing methods might reveal inhibitory effects against Gram-positive bacteria, potentially due to the oils' lipid composition [85]. \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Hypothesis-Intervention** & **Study Design-Praameters Examined** & **Main Findings** & **Year of Study** & **Ref.** \\ \hline The aim of the present study was to formulate a motivating face cream containing phenolic extract and oils from grape seeds and grapes seeds, and to evaluate its antimicrobial activity. & The antimicrobial property was determined by the Kirby-Bauer method. & Phenolic extracts exhibit antimicrobial activity, inhibiting the growth of Gram-positive microorganisms. & 2022 & [85] \\ \hline This study aims to evaluate extracts of grape by-products from six different varieties as antimicrobial agents. & The antimicrobial activity of the extracts was evaluated using the disc diffusion assay and the minimum inhibitory concentration (MIC) method & The extracts have shown that they can inhibit the growth of Gram-positive bacteria. & 2020 & [76] \\ \hline \hline \end{tabular} The study examines _Vils fusion_ L extracts for microbiome regulation and antimicrobial action on the skin.  
\end{table} 
Table 5: Antimicrobial Properties. Another study evaluated the antimicrobial activity of grape by-product extracts from six different varieties. Specifically, the extracts were tested against Gram-positive bacteria (_Staphylococcus aureus, Enterococcus faecalis_) and Gram-negative bacteria (_Escherichia coli, Klebsiella pneumoniae_) using the disc diffusion method and the minimum inhibitory activity (MIC) method. The results were significant, as some of the extracts showed higher inhibitory activity against bacteria even compared to specific antibiotics. The inhibition of bacterial growth was due to the phenolic compounds contained in the grape by-products.