Planta Med 2006; 72 - S_033
DOI: 10.1055/s-2006-949766

Thiolysis-HPLC characterization of the phenolic composition of nut shells of Pinus sibirica (Du Tour) Rupr

AN Shikov 1, ON Pozharitskaya 1, I Laakso 3, HJD Dorman 3, VG Makarov 1, VP Tikhonov 2, R Hiltunen 3
  • 1Interregional Center “Adaptogen“, 47/5, Piskarevsky pr, 195067, St-Petersburg, Russia
  • 2Open joint-stock company “Diod“, 11-A, ul. Derbenevskaya, 115114, Moscow, Russia
  • 3Faculty of Pharmacy, Division of Pharmaceutical Biology, University of Helsinki; P.O. Box 56 (Viikinkaari 5E), FIN-00014 Helsinki, Finland

The chemical composition and biological effects of pine nut kernels and the oils obtained from them have been thoroughly investigated; however, the composition of secondary metabolites from their shells, which contain 55–60% of the nut mass, has not been studied. The purpose of the present work was to (i) study the phenolic composition of nut shells of Pinus sibirica (Du Tour) (Pinaceae) by RP-HPLC, (ii) determine their average degree of polymerization (DPn) and (iii) evaluate their monomeric units by thiolysis using benzyl-α-thiol.

Pine nuts were finely ground and defatted twice with n-hexane. After vacuum filtration and air-drying, they were extracted with acetone/water (95:5, v/v). The confirmation of the presence of protocatechuic acid, catechin, epicatechin, vanillic acid, syringic acid, taxifolin, eriodyctiol, trans-cinnamic acid and naringenin, was assessed by the addition of authentic compounds to the extract. HPLC-PDA analyses were consistent with the major presence of flavan-3-ol related compounds (proanthocyanidins). After thiolysis, taxifolin, eriodyctiol and flavan-3-ol were identified. Since only the terminal units of tannins become free after thiolysis (catechin or epicatechin as such), it could be seen from the chromatogram that catechin monomers, as terminal units, were more abundant than those corresponding to epicatechin. The DPn of the pine nut extract was 9, which correspond to highly polymerized procyanidins.

When the acid-hydrolyzed pine nut extract was analyzed by HPLC, a large amount of polar material was eluted during the first 10min, followed by one major peak corresponding to eriodyctiol and several minor peaks. Isolariciresinol, lariciresinol and secoisolariciresinol were tentatively identified in the extract. On the basis of comparison of the UV-spectra and retention time of authentic samples, gallic and ellagic acids (structural units of hydrolyzed tannins) were identified.

P. sibirica pine nut contains considerable quantities of phenolic compounds. This is of great importance to industry, since extracts of these byproducts are finding increasing applications as active substances in pharmaceutical and cosmetic compositions.