Rare, seven-membered cyclic ether labdane diterpenoid from Dodonaea polyandra

As part of ongoing research of Dodonaea polyandra, an individual plant displaying male flowers was investigated. This yielded four labdane diterpenoids, of which one contains a rare seven membered cyclic ether ring, the first isolated from a terrestrial source. [Display omitted] ► First phytochemical investigation of a male individual of Dodonaea polyandra. ► Labdane diterpenoids are now shown to exist in this species. ► A rare seven-membered cyclic ether labdane diterpenoid, is reported. Previous phytochemical studies on the leaf resin of dioecious plant species Dodonaea polyandra have identified the presence of furanoclerodane diterpenoids. As part of ongoing research on this species the chemical profile of an individual plant displaying male flowers was investigated. Repeated chromatographic separation of a resinous extract from the leaves of the plant yielded three labdane diterpenoids, 13,17-epoxy-13-methyl-15-oxo-labda-7-ene (1), 17-hydroxy-13-methyl-labda-7,13Z-diene-15-oic acid (2) and 13-methyl-17-oxo-labda-7,13Z-diene-15-oic acid (3) and a fourth known labdane diterpenoid (4) reported as being isolated from a natural source for the first time. Structural elucidation was carried out using conventional 1D and 2D NMR and mass spectrometry together with other complementary techniques (UV and IR). The leaf extract from this individual of D. polyandra with male flowers present displays a marked difference in the chemical composition of diterpenoids compared to previously studied extracts from the leaves of this species.