Effect of the Type of Herbal Preparations (Powdered Plant Material vs. Dry Ethanolic Extracts) on the Bioaccessibility of Bearberry (Arctostaphylos uva-ursi (L.) Spreng.) Phytochemicals in Simulated Digestion Conditions

Abstract

The main aim of this study was to determine the potential bioaccessibility of bearberry phytochemicals influenced by the type of herbal preparations. Herbal preparations-powdered plant materials and dry extracts obtained using various ethanol concentrations (0%, 20%, 40%, 60%, 80%, and 100%) were subjected to simulated gastric or gastrointestinal digestion for the evaluation of the bioaccessibility of the phytochemicals. The phytochemical characterization of the plant material, dry extracts, and potentially bioaccessible fractions was performed using high-performance liquid chromatography (HPLC) and spectrophotometric assays. The content of the main compounds, i.e., arbutin, hydroquinone, hyperoside, pentagalloylglucose, and picein, as well as the total phenolic content and in vitro antioxidant activity through the ABTS^•+-scavenging activity and Fe³⁺-reducing power were determined. The bioaccessibility of arbutin, i.e., the main compound in bearberry, was high, in most cases exceeding 95%, and was generally unaffected by the experimental factors; however, the changes in the content of the other compounds, the total phenolic content, and the antioxidant activity were more prominent and influenced by the type of the herbal preparation and the stage of digestion. Given the compromise between the abundance of the bearberry phytochemicals, the antioxidant activity, and the resulting potential bioaccessibility of these phytochemicals, the dry extracts prepared with 40% ethanol seem to be the most promising for phytopharmaceutical purposes and functional food applications.

Keywords: antioxidant activity; arbutin; artificial digestion; dry extract; ethanol extraction; herbal preparations; in vitro bioaccessibility.

Figure 1

Effect of simulated digestion on the potentially bioaccessible content and the bioaccessibility percentage of arbutin (A), hydroquinone (B), hyperoside (C), pentagalloylglucose (D), methylarbutin (E), and picein (F). Bars represent means (n = 3) ± SD. Means followed by different superscript lowercase letters for quantitative results and superscript uppercase letters for the bioaccessibility percentage differ significantly. PPM—powdered plant material, W—water extract, 20E—20% ethanol extract, 40E—40% ethanol extract, 60E—60% ethanol extract, 80E—80% ethanol extract, and E—100% ethanol extract; BD—sample before digestion, GAS—sample after gastric digestion, INT—sample after gastrointestinal digestion, and BA—bioaccessibility percentage.

Figure 2

Effect of simulated digestion on the potentially bioaccessible total phenolic content (A), ABTS^•+ scavenging activity (B), and Fe³⁺-reducing power (C). Bars represent means (n = 3) ± SD. Means followed by different superscript lowercase letters differ significantly for quantitative results. For the bioaccessibility percentage, means followed by different superscript lowercase letters within the same type of digested material indicate a statistically significant difference between the stage of digestion and the means, followed by different superscript lowercase letters and uppercase letters within the same stage of digestion, which indicate a statistically significant difference between the types of digested material. PPM—powdered plant material, W—water extract, 20E—20% ethanol extract, 40E—40% ethanol extract, 60E—60% ethanol extract, 80E—80% ethanol extract, and E—100% ethanol extract; BD—sample before digestion, GAS—sample after gastric digestion, INT—sample after gastrointestinal digestion, and BA—bioaccessibility percentage.