Separation and isolation of major polyphenols from maritime pine (Pinus pinaster) knots by two‐step centrifugal partition chromatography monitored by LC‐MS and NMR spectroscopy

Pine knots are a rich source of lignans, flavonoids, and stilbenes. These bioactive compounds are widely known for their roles to combat human disorders but also to protect plants against pathogens. In order to gain knowledge inside their potential activities, a suitable isolation and purification of these high‐added value compounds is required. To this end, centrifugal partition chromatography, as a rapid and useful methodology of separation, was employed and developed. The coefficient partition values (K_D) of six major compounds in nine biphasic solvent systems were determined to evaluate the most appropriate system. Two‐step centrifugal partition chromatography was required to separate lignans using ARIZONA system K (n‐heptane/ethyl acetate/methanol/water 1:2:1:2, v:v) and to isolate stilbenes and flavonoids using ARIZONA system P (n‐heptane/ethyl acetate/methanol/water 6:5:6:5, v:v). Eight one‐compound enriched‐fractions were obtained as follows: nortrachelogenin (70.1%), secoisolariciresinol (53.7%), isolariciresinol (61.1%), taxifolin (48.4%), pinocembrin (91.3%), pinobanksin (91.1%), pinosylvin (91.4%), and pinosylvin monomethyl ether (91.1%). Additionally, the centrifugal partition chromatography allowed to unravel the composition of pine knot owing to the several fractions generated. Twenty‐two compounds were characterized by liquid chromatography‐mass spectrometry and NMR spectroscopy, some of which are described for the first time in literature.