## 2 Results and Discussion
### Recovery of Polyphenols from mPEG-Grafted Silica Particles
\begin{table}
\begin{tabular}{l c c c c c c c c c} \hline \hline
**Elution** & & & & & & & & & \\
**Solvent** & & & & & & & & & \\ \hline
**60\% (r/o)** & & & & & & & & & \\
**PEG-400** & & & & & & & & & \\
**in Ethanol** & & & & & & & & & \\ \hline
**50\% (r/o)** & & & & & & & & & \\
**PEG-400** & & & & & & & & & \\
**in Ethanol** & & & & & & & & & \\ \hline
**50\% (r/o)** & & & & & & & & & \\
**PEG-400** & & & & & & & & & \\
**in Water** & & & & & & & & & \\ \hline \hline \end{tabular}  
* (Peak area in the elution/Peak area in the grape pomace extract) \(\times\) 100, ND: Not detected, \({}^{1}\) GA: Gallic acid, \({}^{2}\) CA: (+)-Catechin, \({}^{3}\) PB2: Procyanidin-B2, \({}^{4}\) DC: Delphinidin chloride, \({}^{5}\) PCA: p-coumaric acid, \({}^{6}\) IC: Isoquercetin, \({}^{7}\) MC: Malvidin chloride, \({}^{8}\) MY: Myricetin, \({}^{9}\) QU: Quercetin, \({}^{10}\) KA: Kaempfer. Data are represented in mean \(\pm\) standard deviation of duplicates.  
\end{table} 
Table 2: Relative peak areas of eluted polyphenols with various solvent systems as determined by high-performance liquid chromatography (HPLC). solvent used (Figure 5). It is generally believed that the antioxidant activity of polyphenols is facilitated through hydroxyl groups available in the structure [44]. Since the hydroxyl groups are likely involved in the hydrogen bonding of polyphenols to mPEG-grafted silica particles, it is attributed that the recovery of polyphenols via hydrogen bonding mechanism would yield better antioxidant activity compared to grape pomace extract. In support of this statement, polyphenols recovered with 50% PEG-200-water showed the highest potency in comparison to polyphenols recovered using three other solvents used in this study (Figure 5). The high potency observed in PEG-200 can be explained by the higher content of both myricetin and procyanidin-B2 in comparison to PEG-400 cosolvent systems (Table 2). Previous antioxidant assays showed that myricetin and procyanidin-B2 have the highest potencies among 20 well-known polyphenols including gallic acid, resveratrol, kaempfer, quercetin, and (+)-catechin [52]. In addition to its antioxidant activity, myricetin shows significant health promoting activities such as anticarcinogenic, antiviral, and antidiabetic activities. An extensive review of the biological effects of myricetin is provided elsewhere [53] and this highlights the importance of the preferable recovery of myricetin using 50% PEG-200-water cosolvent systems. PEG-400-water showed 1.2-fold higher potency in comparison to PEG-400-ethanol (Figure 5). The high potency observed in PEG-400-water is attributed to \(\sim\)3.5-fold higher gallic acid content in comparison to PEG-400-ethanol (Table 2). Gallic acid was listed as one of the highest potent polyphenols [52] after myricetin and procyanidin-B2. Since PEG-400 cosolvent systems do not contain these polyphenols, it is likely that higher gallic acid content would result in better antioxidant activity seen in the PEG-400-water cosolvent system. Overall, it is likely that enrichment of gallic acid, procyanidin-B2, and myricetin by the use of mPEG-grafted silica particles and PEG cosolvent elution resulted in better antioxidant activity in comparison to grape pomace extract. Figure 5: Normalized antioxidant activity of grape pomace extract and polyphenols recovered from mPEG-5000-grafted silica particles using various cosolvent systems. Ethanol is abbreviated as EtOH. A statistical difference was observed for all measurements (\(p<0.05\)) Error bars indicate a standard deviation observed for duplicates.