BOUND 3-METHYLIDENE-7,11,15-TRIMETHYLHEXADECAN-1,2-DIOL - A NEW ISOPRENOID MARKER FOR THE PHOTODEGRADATION OF CHLOROPHYLL-A IN SEAWATER

3-Methylidene-7,11,15-trimethylhexadecan- 1,2-diol was detected after saponification of chlorophyll-a in vitro photoproducts. It is postulat ed that this isoprenoid compound, which probably results from an attac k of singlet oxygen on the olefinic carbon 2 of the chlorophyll-a phyt yl chain, could be a marker for the photodegradation of chlorophyll-a in the marine environment. This theory is supported by the detection o f high quantities (0. 1-2 mug g-1 dry wt) of ''bound'' 3-methylidene-7 ,11,15-trimethylhexadecan-1,2-diol in recent sediments from the Gulf o f Fos sur mer (Mediterranean Sea).