Stereoisomers of 42-hydroxy palytoxin from Hawaiian Palythoa toxica and P. tuberculosa: stereostructure elucidation, detection, and biological activities

Palytoxin ranks among the most potent marine biotoxins.  Its lethality was well known to native Hawaiians that used to smear a "moss" contg. the toxin on their spears to cause instant death to their victims.  Human intoxications due to exposure to palytoxin and to its many congeners have been reported worldwide.  Currently, palytoxins constitute the main threat to public health across the Mediterranean Sea.  In the present work the authors report on the isolation and stereostructural detn. of a new palytoxin analog from a Hawaiian Palythoa tuberculosa sample.  This new toxin is a stereoisomer of 42-hydroxypalytoxin isolated from Palythoa toxica.  The whole abs. configuration of this latter toxin is also reported in the paper.  Interestingly, the two 42-hydroxypalytoxins do not share the same biol. activity.  The stereoisomer from P. tuberculosa showed cytotoxicity toward skin HaCaT keratinocytes approx. 1 order of magnitude lower than that of 42-hydroxypalytoxin from P. toxica and about 2 orders of magnitude lower than that of palytoxin itself.  This finding holds the prospect of interesting structure-activity relationship evaluations in the future.