Bioaccessibility and Biological Activities of Phytochemicals from Wild Plant Infusions and Decoctions Before and After Simulated In Vitro Digestion

The wild plants Borago officinalis L. (Boraginaceae) and Hypericum perforatum L. (Hypericaceae) are known to have both food and medicinal uses. The aim of the work was to evaluate the bioaccessibility of potentially bioactive phytochemicals in organ-specific infusions and decoctions pre- and post- simulated in vitro oro-gastrointestinal human digestion aiming at both oral intake and topical applications. (Poly)phenols, reducing sugars, and proteins were analysed by spectroscopic and spectrometry techniques (NMR and HPLC-DAD) as well as their antioxidant and antimicrobial activities pre- and post-digestion. As expected, in vitro digestion altered the composition of the extracts. Specifically, the total amount of (poly)phenols as well as the largely correlated antioxidant activity decreased post-digestion, while reducing sugars and proteins increased. Catechins and rutin were detected in both plants. Rosmarinic acid was the most abundant compound in B. officinalis (on average 90% in infusions), while rutin and hyperoside in H. perforatum (up to 100% in stem digested extracts). Hypericum extracts exhibited similar activity against both Gram-positive and Gram-negative bacteria, while the Borago extracts showed higher activity against Gram-negative bacteria. Overall, the minimal inhibitory concentrations ranged from 0.47 to 0.94 mg/ml. In conclusion, the studied herbal preparations may provide significant amounts of bioactive compounds both pre- and post-digestion able to potentially mitigate oxidative stress-related disorders after ingestion and/or to treat skin infection diseases when applied topically.