Crocin

Crocin is a carotenoid chemical compound that is found in the flowers crocus and gardenia. Crocin is the chemical primarily responsible for the color of saffron.
Chemically, crocin is the diester formed from the disaccharide gentiobiose and the dicarboxylic acid crocetin. When isolated as a pure chemical compound, it has a deep red color and forms crystals with a melting point of 186 °C. When dissolved in water, it forms an orange solution.
The term "crocins" may also refer to members of a series of related hydrophilic carotenoids that are either monoglycosyl or diglycosyl polyene esters of crocetin. The crocin underlying saffron's aroma is α-crocin (a carotenoid pigment that may compose more than 10% of dry saffron's mass): trans-crocetin di-(β-D-gentiobiosyl) ester; it bears the systematic (IUPAC) name 8,8-diapo-8,8-carotenoic acid. 
The major active component of saffron is the yellow pigment crocin 2 (three other derivatives with different glycosylations are known) containing a gentiobiose (disaccharide) group at each end of the molecule. The five major biologically active components of saffron, namely the four crocins and crocetin, can be measured with HPLC-UV.
Physiological effects on mammalian tissues and organisms.
Crocin has been shown to be an antioxidant, and neural protective agent. The antioxidant behavior of crocin is related to the sugar moiety in crocin molecule which has a vital role in its chemical reactivity. It has also been shown to have an antiproliferative action against cancer cells "in vitro". Limited evidence suggests possible antidepressant properties of crocin in mice and humans. One study reports aphrodisiac properties in male rats at very high doses.