Biosynthesis and metabolism of indole-3-ethanol and indole-3-acetic acid by Pinus sylvestris L. needles

Combined gas chromatography-mass spectrometry has been used to identify indole-3-ethanol (IEt) in a purified extract from needles of Pinus sylvestris L. Quantitative estimates obtained by high-performance liquid chromatography with fluorescence detection, corrected for samples losses occurring during purification, indicate that Pinus needles contain 46±4 ng g(-1) IEt. This compares with 24.5±6.5 ng g(-1) indole-3-acetic acid (IAA) and 2.3±0.4 ng g(-1) indole-3-carboxylic acid (ICA) (Sandberg et al. 1984, Phytochemistry, 23, 99-102). Metabolism studies with needles incubated in a culture medium in darkness revealed that both [3-(14)C]-tryptophan and [2-(14)C]tryptamine mine are converted to [(14)C]IEt. It was also shown that [3-(14)C]IEt acted as a precursor of [(14)C]IAA. The observed metabolism appears to be enzymic in nature. The [2-(14)C]IAA was not catabolised to [(14)C]ICA in detectable quantities implying that, at best, only a minor portion of the endogenous ICA pool in the Pinus needles originates from IAA.