Characterisation of maritime pine (Pinus pinaster) bark tannins extracted under different conditions by spectroscopic methods, FTIR and HPLC

For the first time an extensive characterisation of maritime pine (Pinus pinaster) bark condensed tannins was conducted. Extractives were obtained from the bark of maritime pine from the south west of France using 1% NaOH and 5% NaOH at 70 °C and 80 °C. For each extraction, extraction yield, total polyphenols (Folin-Ciocalteu), condensed tannins and reactivity to formaldehyde (Stiasny number) were quantified. The extracts were characterised by Fourier transformed infrared spectroscopy (FTIR) and reverse phase high pressure liquid chromatography (RP-HPLC). The higher extraction yields originated from an extraction with 5% NaOH at 80 °C. The extracts obtained with 1% NaOH at 70 °C had the highest amounts of total polyphenols, condensed tannins and reactivity to formaldehyde. Absorbance at 1260 cm−1, 1440 cm−1 and 1495 cm−1 were only detected for extracts obtained with 1% NaOH. RP-HPLC revealed that catechin was the main condensed tannin in the extracts, lower quantities of epicatechin and epicatechin gallate were also measured.