Juan Carlos Hernández

Flavans of dragon’s blood from Dracaena draco and Dracaena tamaranae

Abstract Flavans of D. draco subsp. draco and subsp. ajgal and of D. tamaranae were isolated and identified for a chemotaxonomic survey. A major constituent of all taxa was (2 S )-4,7′-dihydroxy-8-methylflavan.

Chemotaxonomy of Gonospermum and related genera

Aerial parts of Gonospermum fruticosum collected at several locations in the Canary Islands afforded, in addition to known compounds, four sesquiterpene alcohols related to costol and a sesquiterpene lactone, whose structures were established on the basis of their spectroscopic data and chemical transformations. Except for Gonospermum species collected on the island of Tenerife, those collected on the island of El Hierro and, in a previous study those from La Gomera, contain sesquiterpene lactones that can be used as chemotaxonomic markers confirming the inclusion of Gonospermum, Lugoa, and species of Tanacetum endemic to the Canary Islands in a genus that does not support the monophyly of Gonosperminae.

Secondary Metabolites from Two Species of Pulicaria and Their Cytotoxic Activity

Two new compounds, the sesquiterpene (1E,5E)‐8β‐acetoxy‐4α‐hydroxy‐7βH‐germacra‐1(10),5‐dien‐14‐oic acid (2), and a nor‐sesquiterpene, (5E)‐8β‐acetoxy‐4α‐hydroxy‐7βH‐germacr‐5‐en‐10‐one (3), were isolated from Pulicaria canariensis ssp. lanata, along with ten known compounds, including the flavonoid 5,3′‐dihydroxy‐3,7,4′‐trimethoxyflavone (4). From Pulicaria burchardii, we isolated seven known compounds; the physical and spectroscopic data of the triterpenoid 3β‐hydroxytaraxaster‐20‐en‐30‐al (1) are reported. The structures of compounds 1–3 were determined on the basis of HR‐MS, and 1D‐ and 2D‐NMR studies. The structure of 2 was corroborated by X‐ray crystal diffraction. Cell viability experiments revealed that the semisynthetic flavonoid 4b was the most cytotoxic compound against human leukemia cells, and the cytotoxicity was caused by induction of apoptosis, as determined by microscopy of nuclear changes.