| Summary: | In continuation of studies for α-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 <b>6f</b> and a diacyl derivative <b>13a</b> of CGA showed superior inhibition profiles (IC<sub>50</sub>: 2.5 ± 0.7 μM and 1.1 ± 0.1 μM, respectively) of <i>α</i>-MSH activities than positive controls, kojic acid and arbutin (IC<sub>50</sub>: 54 ± 1.5 μM and 380 ± 9.5 μM, respectively). The SAR studies showed that both –CF<sub>3</sub> and –Cl groups exhibited better inhibition at the <i>meta</i> position on benzylamine than their <i>ortho</i> and <i>para</i> 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.
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