Cyanidins are a sub-category of the dark pigments found in blue-black fruits and berries as well as some purple vegetables known as Anthocyanins. Cyanidins can be seen as the most pharmaceutically effective anthocyanin subcomponent as they seem to have the greatest uptake rate, the least decay, and the most clinical significance out of all anthocyanins.
It has various effects in cells, most of which can be described as being anti-diabetic and possibly slightly benefit other parameters associated with 'metabolic syndrome' (anti-inflammatory, anti-oxidant, etc.)
It does have some problems with absorption though, so the results you see in in vitro (in laboratory) studies may not apply to when it is consumed. Its bioavailability (percent absorbed) is a concern, and human intervention studies important for this reason.
