Protocyanin

Protocyanin is an anthocyanin pigment that is responsible for the red colouration of roses, but in cornflowers is blue. The pigment was first isolated in 1913 from the blue cornflower,^[1] and the identical pigment was isolated from a red rose in 1915.^[2] The difference in colour was previously explained as a difference in flower-petal pH,^[2] but the pigment in the blue cornflower has been shown to be a supermolecular pigment consisting of a complex of anthocyanin, flavone, one ferric iron, one magnesium and two calcium ions. ^[3]

The molecular formula of protocyanin complex is of the type of C₃₆₆H₃₈₄O₂₂₈FeMg.

References

1. ^ Willstätter R & Everest RW (1913). "Untersuchungen über die Anthocyane. I. Über den Farbstoff der Kornblume". Justus Liebigs Ann Chem 401 (2): 189–232. doi:10.1002/jlac.19134010205. 
2. ^ ^{a b} Willstätter R & Mallison H (1915). "Untersuchungen über die Anthocyane. X. Über Variationen der Blütenfarben". Justus Liebigs Ann Chem 408: 147–162. doi:10.1002/jlac.19154080110. 
3. ^ Shiono M, Matsugaki N, Takeda K (2005). "Structure of the blue cornflower pigment". Nature 436 (7052): 791. doi:10.1038/436791a. PMID 16094358.