Hydrogenolytic depolymerization of red pine bark procyanidins: Effects on phenolic composition, antioxidant capacity, bioaccessibility, and cellular accumulation

초록

The bark of Pinus densiflora (red pine bark; RPB) has historically been consumed as a traditional food resource in various regions. In this study, hydrogenolytic depolymerization (HD) was investigated as a strategy to modify the phenolic composition of RPB extract (RPBE). HD altered the procyanidin-associated phenolic profile, as indicated by the loss of procyanidin B1 and concurrent increases in monomeric flavan-3-ol content, together with higher total phenolic content, total flavonoid content, and antioxidant capacity. The most pronounced changes were observed under HD5, with reaction temperature being the primary factor influencing phenolic transformation. Simulated gastrointestinal digestion revealed that phenolic compounds in both RPBE and depolymerized RPBE (DRPBE) followed a consistent pattern of slight decrease in the oral phase, transient increase in the gastric phase, and sharp decline in the intestinal phase. Caco-2 cellular accumulation experiments showed that phenolic compounds from both RPBE and DRPBE remained below the detection limit of the analytical system, preventing a direct comparison of cellular accumulation between the two extracts. More sensitive analytical methods and permeability-based approaches are therefore required to determine whether HD influences intestinal uptake of RPB-derived phenolics. Overall, HD modified the phenolic composition of RPB, including increasing selected low-molecular-weight phenolic compounds and altering chemical antioxidant responses. However, the suitability of DRPBE for food applications remains to be established through further assessment of catalyst removal efficiency, residual Ru content, unknown reaction products, and other relevant food safety parameters.

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