Pyranocoumarins as chemotaxonomic markers in Eriostemon coccineus and Philotheca citrina

Examination of the aerial parts of Eriostemon coccineus and Philotheca citrina has shown both to contain the unusual pyranocoumarins avicennol, avicennin and cis-avicennol. Three minor coumarins isolated from P. citrina have been identified as avicennol methyl ether, cis-avicennol methyl ether and avicennol ethyl ether. Philotheca citrina also yielded another pyranocoumarin, dipetalolactone, and the common lignan sesamin. Eriostemon coccineus, in addition to coumarins, gave the furoquinoline alkaloids maculosidine and γ-fagarine and two dihydrocinnanic acid derivatives, eriostoic acid and a new compound with a substitution pattern comparable to cis-avicennin and which has been assigned the trivial name cis-avicennic acid. The co-occurrence of these rare pyranocoumarins supports the contention that Philotheca is closely allied to certain taxa currently placed in Eriostemon sect. Nigrostipulae.