Inhibitory Effect of Chlorogenic Acid Analogues Comprising Pyridine and Pyrimidine on α-MSH-Stimulated Melanogenesis and Stability of Acyl Analogues in Methanol

In continuation of studies for alpha-MSH stimulated melanogenesis inhibitors, we have evaluated the design, synthesis, and activity of a new series of chlorogenic acid (CGA) analogues comprising pyridine, pyrimidine, and diacyl derivatives. Among nineteen synthesized compounds, most of them (fifteen) exhibited better inhibitions of melanin formation in B16 melanoma cells. The results illustrated that a pyridine analogue 6f and a diacyl derivative 13a of CGA showed superior inhibition profiles (IC50: 2.5 +/- 0.7 mu M and 1.1 +/- 0.1 mu M, respectively) of alpha-MSH activities than positive controls, kojic acid and arbutin (IC50: 54 +/- 1.5 mu M and 380 +/- 9.5 mu M, respectively). The SAR studies showed that both -CF3 and -Cl groups exhibited better inhibition at the meta position on benzylamine than their ortho and para positions. In addition, the stability of diacyl analogues of CGA in methanol monitored by HPLC for 28 days indicated the steric bulkiness of acyl substituents as a key factor in their stability.

Automated summary

The study evaluated a new series of chlorogenic acid analogues with pyridine and diacyl derivatives for inhibiting α-MSH activities, showing that the pyridine analogue and diacyl derivative exhibited superior inhibition profiles. The research also indicated that -CF3 and -Cl groups performed better at the meta position on benzylamine, and that steric bulkiness of acyl substituents was a key factor in the stability of diacyl analogues of CGA.