<unk>  is a compound with formula MgC12H22O14. It is the magnesium salt of gluconic acid.
According to scientific research,<unk>  shows the highest level of bioavailability of any magnesium salt and is recommended as the optimal salt for human supplementation although of the 10 salts studied, all increased Magnesium levels significantly.
It has E number "E580".
Magnesium gluconate
Magnesium levulinate
Potassium bicarbonate
Magnesium chloride
Magnesium sulfate 
Sodium bicarbonate
Magnesium lactate
Calcium bicarbonate