A number of shikonin (1) [5, 8-dihydroxy-2-(llhydroxy-14-methyl-1 3-pentenyl)-1 ,4-naphthoquinone] and its enantiomer alkannin derivatives have been recently isolated from higher plants belonging to Boraginaceae. These compoundshave drawn considerable interest due to their proven antibacterial and antifungal properties.1 "9) However, polymers of these derivatives are devoid of such activities7>8) and the naphthoquinone moiety of these compounds, appears to be necessary for their activities. The pentenyl side acts as a delivery system for the naphthoquinone, whereas an esterification of the benzylic hydroxyl function at Cn in shikonin and alkannin leads to products with enhanced antimicrobial activities.7'8* Our continued interest in plants belonging to Boraginaceae prompted us to investigate the chemical components of potentially useful Arnebia decumbens,
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