a protein kinase C activator; macrocyclic lactone from marine Bryozoan Bugula neritina; RN given refers to (1S*-(1R*,3R*,5Z,7S*,8E,11R*,12R*(2E,4E),13E,15R*,17S*(S*),21S*,23S*,25R*))-isomer; structure given in first source; activates protein kinase c