Isolation of yeast Ca2+ signal transduction inhibitors from the Early Cretaceous Burmese amber

Abstract Two kinds of biologically active compounds were isolated from the MeOH extract of the Early Cretaceous Burmese amber [99 million years ago (Ma)], which is older than the K-Pg boundary (65 Ma). These compounds had inhibitory activity against the hypersensitive mutant yeast strain ( zds1 ∆ erg3 ∆ pdr1 ∆ pdr3∆ ) with respect to Ca 2+ signal transduction. They were identified as 16,17-bisnordehydroabietic acid ( 1 ) and 16,17-bisnorcallitrisic acid ( 2 ), respectively, on the basis of spectral analyses including HREIMS, 1D, and 2D NMR. Both have faint growth restoring activities around the clear inhibition zone against the mutant yeast on the 0.31–0.16 μg/spot. This is the first report of direct structural elucidation of 1 and 2 and the biologically active compounds derived from Burmese amber.