In Vitro Study on the Antioxidant Activity of a Polyphenol-Rich Extract from Pinus brutia Bark and Its Fractions

A crude hydromethanolic extract from Pinus brutia bark and its fractions (diethyl ether, ethyl acetate, n-butanol, and aqueous fractions) were studied with regard to their phenolic content and antioxidant activities. The total phenolics and proanthocyanidins in each extract were quantified by spectrophotometric methods; the polyphenolic profile was analyzed by RP-HPLC-DAD-ESI-MS. All extracts were tested with regard to their ability to scavenge free radicals (ABTS radical cation, superoxide and hydroxyl radicals), reduce ferric ions, and inhibit 15-lipoxygenase. P. brutia bark extracts had high phenolic contents (303.79 +/- 7.34-448.90 +/- 1.39mg/g). Except diethyl ether extract, all other extracts contained proanthocyanidins ranging from 225.79 +/- 3.94 to 250.40 +/- 1.44mg/g. Several polyphenols were identified by RP-HPLC-DAD-ESI-MS: taxifolin in diethyl ether extract, a taxifolin-O-hexoside, catechin, procyanidin dimers, and trimers in ethyl acetate extract. Except diethyl ether extract, all other extracts were effective scavengers of superoxide and hydroxyl radicals (EC50=33.5 +/- 1.1-54.93 +/- 2.85 g/mL and 0.47 +/- 0.06-0.6 +/- 0.0mg/mL, respectively). All extracts had noticeable 15-lipoxygenase inhibitory effects (EC50=22.47 +/- 0.75-34.43 +/- 2.25 g/mL). We conclude that P. brutia bark is very promising for the dietary supplements industry due to its high free radical scavenging and 15-lipoxygenase inhibitory effects.