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 P. 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 IAA and 2.3 .+-. 0.4 ng g-1 indole-3-carboxylic acid (ICA) (Sandberg et al., 1984). Metabolism studies with needles incubated in a culture medium in darkness revealed that both [3-14C]-tryptophan and [2-14C]tryptamine are converted to [14C]IEt. [3-14C]IEt acted as a precursor of [14C]IAA. The observed metabolism apparently is enzymic in nature. The [2-14C]IAA was not catabolized to [14C]ICA in detectable quantities implying that, at best, only a minor portion of the endogenous ICA pool in the Pinus needles originates from IAA.