Abstract
Melanogenesis plays an important role in the protection of skin against UV through production of melanin pigments, but abnormal accumulation of this pigment causes unaesthetic hyperpigmentation. Much effort is being made to develop effective depigmenting agents. Here, we show for the first time that a small library of mimosine dipeptide enantiomers (Mi-l/d-amino acid) inhibit the melanogenesis in B16F10 melanoma cells by down-regulating the cellular tyrosinase with little effect on their growth or viability. Two of them, Mi-d-Trp and Mi-d-Val, turned out to be the most potent inhibitors on melanin content and cellular tyrosinase in B16F10 melanoma cells. In addition, most of the mimosine dipeptides were more potent than mimosine for inhibiting cyclooxygenase 1 (COX-1) with IC50 of 18–26 μM. Among them, Mi-l-Val and Mi-l-Trp inhibited cyclooxygenase 2 (COX-2) more potently than indomethacin, with IC50 values of 22 and 19 μM, respectively. Taken together, our results suggest the possibility that mimosine dipeptides could be better candidates (than mimosine) for anti-melanogenic (skin hyperpigmentation treatment) and cyclooxygenase (COX) inhibition.
Highlights
Melanogenesis is a physiological process that results in the synthesis of melanin pigment and has many functions in living systems [1]
Our general strategy for the design of these compounds was based on the conjugation of mimosine and an amino acid through solid-phase synthesis using Fmoc chemistry
We showed that a small library of mimosine dipeptides had strong tyrosinase inhibition in vitro
Summary
Melanogenesis is a physiological process that results in the synthesis of melanin pigment and has many functions in living systems [1]. Tyrosinase is a key enzyme in melanogenesis in melanocytes [4]. The inhibition of tyrosinase activity is capitalized for inhibition of melanogenesis and the treatment of skin hyperpigmentation and whitening [2]. The major action of NSAIDs is based on inhibition of cyclooxygenase (COX), which is the rate limiting enzyme in the pathway facilitating the conversion of arachidonic acid to inflammatory prostaglandins [7]. Mimosine [β-[N-(3-hydroxy-4-oxypyridyl)]-α-aminopropionic acid] is a non-protein amino acid containing an alanine side chain bound to the nitrogen atom of a pyridine ring. It is found in several tropical and subtropical plants, which possesses a wide range of biological activities [11,12].
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