Hydrangeamines A and B, novel polyketide-type pseudoalkaloid-coupled secoiridoid glycosides from the flowers of Hydrangea macrophylla var. thunbergii

Two novel secoiridoid glycosides with a pyridine ring named hydrangeamines A and B have been isolated from the flowers of Hydrangea macrophylla SERINGE var. thunbergii MAKINO (Saxifragaceae). The absolute stereostructures of the two hydrangeamines were characterized on the basis of chemical and physiochemical analyses, which included the application of CD for the 4,5-dihydro-[6H]-pyrano chromophore. This is the first isolation of the unique polyketide-type pseudoalkaloid-coupled secoiridoid glycosides.