Chemical investigation of the organic solvent extract of Cretaceous Ginkgo coriacea Florin leaves by liquid chromatography-mass spectroscopy （LC-MS） and gas chromatography-mass spectrometry （GC-MS）, analogous to those from extant leaves of Ginkgo biloba L., led to the detection of a group of natural flavonoids and other volatiles. The similarity of the chemical constituents in these two species of Ginkgo suggest that the secondary metabolism of extant G. biloba is close to that of the Cretaceous species. The remaining natural products may be one explanation why the leaves of the Cretaceous G. coriacea have been preserved morphologically in fossilization. The detection of flavonoids suggests that the leaves of G. coriacea experienced a mild post-depositional environment during their fossilization. This appears to be the oldest occurrence of flavonoids in plant fossils.
Specimens of fossil wood preserved lignified in Pliocene brown coal and identified as Pinus armandii Francher come from an opencast coalmine at Longling in western Yunnan Province, China. Phytochemical investigation of the fossil wood isolated using liquid column chromatography seven compounds （1-7） including a new fluorene derivative named 11,11-dimethyl-11H-benzo[b]fluorene. A further 28 volatiles were detected by gas chromatography-mass spectrometry （GC-MS）. Spectroscopic investigation methods, including MS and 1D and 2D-NMR techniques elucidated the structure of the seven compounds. Two types of natural products, isopimara and stilbene commonly occuring in extant and Pliocene fossil P. armandii indicate phytochemical fidelity during burial under certain circumstances in sediments. Discovery of stilbenes that can inhibit the activities of wood-destroying fungi in the Pliocene P. armandii prompts the assumption that the chemical preservation of this Pliocene fossil wood of P. armandii in brown coal might contribute to the presence of inner natural inhibitors against wood-destroying fungi.
ZHAO YouxingLI ChengsenYI TiemeiLUO XiaodongZHOU Jun
