OCCURRENCE OF TIGHTLY BOUND ISOPRENOID ACIDS IN AN ALGAL, RESISTANT BIOMACROMOLECULE - POSSIBLE GEOCHEMICAL IMPLICATIONS

The tightly bound acids, i.e. only released on pyrolysis, of the resistant biomacromolecule PRB L isolated from the outer walls of the microalga Botryococcus braunii L race were analysed. They are dominated by linear fatty monocarboxylic acids but also comprise a linear dicarboxylic acid and a "pseudo" isoprenoid acid and exhibit a substantial contribution of isoprenoid acids. Such tightly bound acids in a resistant biomacromolecule will be selectively preserved on fossilization and their occurrence suggests that isoprenoid acids tightly bound to kerogens, or occurring in the bitumen of mature rock samples, can be directly inherited. Accordingly, such acids do not necessarily derive from the degradation of isoprenoid biolipids like the phytyl chain of chlorophyll.