Synthesis, structure, chemical and bioactivity behavior of eight chromium(III) picolinate derivatives Cr(R-pic)3

The worldwide use of chromium(III) picolinate Cr(pic) 3 as nutrition additives has aroused more and more controversies. To reevaluate the   safety and validity of Cr(pic) 3 , seven new derivatives Cr(R-pic) 3 (pic   =   picolinic acid, R   =   H ( 1 ), 5-Br ( 2 ), 5-CF 3 ( 3 ), 4-Cl ( 4 ), 5-COOH ( 5 ), 3-CH 3 ( 6 ), 5-OH ( 7 ), 3-OH ( 8 )) were synthesized and characterized by X-ray crystal diffraction, ESI-MS, IR and elemental analysis. It was found that different substituent group affected physicochemical activities of the complex such as the Fenton-like reaction and oxidation reaction. Especially, –OH group derivatives lose their hydroxyl radical-generation and Cr(VI)-generation abilities comparing with halogen group in tube experiment. Even so, these differences in chemistry properties may be ignored in live cells and animal tests: no obvious cellular   damage (MTT assay) and tissue injury (acute toxicity study) were observed for both Cr(pic) 3 and its derivatives. In addition, hypoglycemic activity study indicated that these Cr(III) complexes have no significant influence than CrCl 3 salt on the blood glucose, serum insulin, total cholesterol, triglyceride, high density lipoprotein and low density lipoprotein of diabetic mice through two months’ study. Therefore, these substituent group is unable to improve the biological activities of Cr(pic) 3 obviously and the validity of Cr(pic) 3 used as a nutrition additives is doubted.