# Stability and Bioaccessibility of \(\beta\)-Arbutin in Simulated Digestion Conditions
## 3 Results  
The content of in vitro bioaccessible \(\beta\)-arbutin after the electrolyte treatment or the whole digestion process and the corresponding bioaccessibility percentages are presented in Table 1 and Figure 1, respectively.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Dose of \(\beta\)-Arbutin** & \multicolumn{4}{c}{**In Vitro Bioaccessible \(\beta\)-Arbutin (mg/g PME)**} \\ \cline{2-5}
**(mg/g PME)** & **GE** & **GD** & **IE** & **ID** \\ \hline \(1\) & 0.98 \(\pm\) 0.01 \({}^{\text{a}}\) & 0.97 \(\pm\) 0.01 \({}^{\text{ab}}\) & 0.95 \(\pm\) 0.01 \({}^{\text{b}}\) & 0.81 \(\pm\) 0.01 \({}^{\text{c}}\) \\ \(2.5\) & 2.47 \(\pm\) 0.03 \({}^{\text{a}}\) & 2.45 \(\pm\) 0.03 \({}^{\text{a}}\) & 2.43 \(\pm\) 0.03 \({}^{\text{a}}\) & 2.29 \(\pm\) 0.03 \({}^{\text{b}}\) \\ \(5\) & 4.97 \(\pm\) 0.06 \({}^{\text{a}}\) & 4.91 \(\pm\) 0.05 \({}^{\text{a}}\) & 4.92 \(\pm\) 0.04 \({}^{\text{a}}\) & 4.81 \(\pm\) 0.06 \({}^{\text{b}}\) \\ \hline \hline \end{tabular}
\end{table}
Table 1: In vitro bioaccessible \(\beta\)-arbutin content.  
The three-way ANOVA analysis showed a statistically significant impact (\(p\leq 0.05\)) of the dose of \(\beta\)-arbutin subjected to digestion, the variant of the treatment (electrolyte treatment or the whole digestion process), the stage of digestion, and their effect on its percentage of bioaccessibility. One of the highest \(\beta\)-arbutin bioaccessibility levels was found after the electrolyte treatment at the gastric digestion stage, where, regardless of the dose, it was close to 100% (there was no statistically significant difference, with 100% bioaccessibility at all the applied doses). The application of the biochemical factors (digestion enzymes and bile salts) at the gastric stage of digestion (GD) resulted in a slight decrease in the bioaccessibility, but without statistically significant differences from samples subjected to the electrolyte treatment (GE). In this case, statistically significantly lower bioaccessibility than 100% was observed only at the lowest dose (GD 1 mg--97.18%). In the electrolyte treatment at the intestinal stage of digestion (IE), statistically lower bioaccessibilities (than 100%) were obtained at the 1 and 2.5 mg doses, i.e., 95.24% and 97.32%, respectively;  
Figure 1: Percentage of in vitro bioaccessibility of \(\beta\)-arbutin. Bars represent means (\(n=3\)) \(\pm\) SD. Means followed by different superscript lowercase letters differ significantly (\(p\leq 0.05\)). Asterisks indicate a statistically significant difference with 100% bioaccessibility (\(p\leq 0.05\)). PME—plant material equivalent, GE—gastric electrolyte treatment, GD—gastric digestion, IE—intestinal electrolyte treatment, ID—intestinal digestion.  
however, when comparing the bioaccessibility level with that observed at the other doses, there was no statistically significant difference between the 1 mg dose and the 2.5, 5, and 7.5 mg doses, and no statistically significant difference was observed between the 2.5 mg dose and all the other doses (5-100 mg). The application of the biochemical factors at the intestinal stage of digestion (ID) in most cases (doses 5-100 mg) caused a slight and insignificant decrease in the bioaccessibility of \(\beta\)-arbutin, in comparison with only the electrolyte treatment (IE). After intestinal digestion (ID), significantly lower bioaccessibility than 100% was found at the 1, 2.5, and 5 mg doses, i.e., 80.63, 91.79, and 96.18%, respectively. At doses in the range of 7.5-100 mg both at the gastric and intestinal stages of digestion, all the applied digestion conditions had no significant influence on the bioaccessibility of \(\beta\)-arbutin, which was close to 100%. Despite the most prominent negative changes in bioaccessibility observed in the samples at the lowest doses, the analysis of chromatograms showed no presence of free-state hydroquinone as a potential degradation product of \(\beta\)-arbutin (Figure 2).