Chemical Analysis of Polyphenols with Antioxidant Capacity from Pinus durangensis Bark

The most active phenolics in Pinus durangensis residual bark were identified and evaluated following a chromatographic fractionation. Bark powder was defatted with hexane, and a crude extract (CE) was obtained by extraction with aqueous acetone (67%). A liquid partition with ethyl acetate was performed to produce an organic extract (OE), which was subsequently purified by column chromatography (Toyopearl HW-40F, methanol), resulting in ten fractions (MF1 to MF10) and an oligomeric fraction eluted with acetone 67% (OLF). Subfraction MF6-1 was obtained by a second chromatographic purification of MF6. Extraction yields, total phenolics, flavonoids, and flavanols contents were determined in CE and OE. The antioxidant activity of bark extracts was measured by DPPH and ABTS assays at 100 µg/mL, expressed in percentage, median effective concentration (IC₅₀), and TEAC (mM). Also the low density lipoprotein inhibition was evaluated. Identification of major phenolics was carried out by HPLCESI–MS and HPLC–DAD instruments. Bioactive taxifolin (dihydroquercetin), dihydromyricetin, myricetin, quercetin, pinomyricetin (myricetin-methoxy), pinoquercetin (quercetin-methoxy), trimeric, and tetrameric procyanidins were detected and identified in P. durangensis bark extracts. Polyphenols found are similar to those contained in Pycnogenol and other Pinus species.