Kojic Acid Derivatives, Have Tyrosinase Inhibitory Activity to Suppress the Production of Melanin in the Biosynthetic Pathway

생체 내 경로에서 멜라닌 생성을 억제하는 타이로신 억제제로서의 코직산 유도체

Abstract

Kojic acid (KA) is produced by Aspergillus oryzae-sort of like mushrooms, which is commonly called as koji in Japan. KA is used as a chelation agent and a preservative preventing oxidative browning of fruits. KA also shows antibacterial and antifungal properties. Because KA stops the production of melanin by inhibiting tyrosinase in the biosynthetic pathway from tyrosine to melanin in skin, it has been applied as a skin lightening ingredient in cosmetics. Since some animal studies have shown that high amounts of KA had side effects such as in liver, kidney, reproductive, cardiovascular, gastrointestinal, respiratory, brain, and nervous system, more efficient KA derivatives are needed to be developed in order to safely apply as a skin lightening ingredient. A series of KA derivatives via conjugated with triazole by click reaction were synthesized and their in vitro tyrosinase inhibitory activities were evaluated. Most of all KA derivatives have shown in moderate tyrosinase inhibitory activities. In case of KA-hybrid compound, 1~3 have shown tyrosinase inhibitory activities about 50~10,000 times more effective tyrosinase inhibitor compared to KA itself. Specifically, the $IC_{50}$ value of KA-hybrid compound, 2 was $0.0044{\pm}0.74{\mu}M$ against tyrosinase. It is about 10,000 times more effective tyrosinase inhibitor compared to KA itself ($IC_{50}=45.2{\pm}4.6{\mu}M$).

코직산(Kojic acid)은 생리활성물질로서 많이 알려져 있으며 antibacterial, antifungal과 같은 효능을 나타낸다. 또한 티로시나아제(tyrosinase) 억제제로서 작용하여 멜라닌 생성을 저해시키기 때문에 화장품 산업에 있어서도 미백효과를 가지는 중요한 소재로서 각광받고 있다. 본 연구에서는 독립적으로 항산화 효과를 나타내는 유도체와 코직산(Kojic acid)을 연결하여 새로운 기능성을 가지는 신규 화합물을 발굴하고자 하였으며, 클릭 반응(Click reaction)을 통해 트리아졸(triazle)로 연결하여 신규 코직산 컨쥬게이트(conjugated) 화합물을 합성하였다. 먼저 신규 코직산 컨쥬게이트(conjugated) 화합물의 티로시나아제(tyrosinase) 억제 효과에 대해서 연구한 결과 대부분의 화합물이 코직산(Kojic acid)보다 우수한 티로시나아제(tyrosinase) 억제 효과를 나타냈다. 이와 같은 결과로 미루어 보아 신규 코직산 컨쥬게이트(conjugated) 화합물은 항산화용 건강보조식품 조성물 및 항산화 소재, 노화방지 및 미백 기능을 가진 피부외용제 조성물의 유효성분으로 개발될 가능성이 매우 높다고 사료된다.

Fig. 1. General Click reaction.

Fig. 2. Kojic acid (KA) conjugated compounds.

Fig. 3. Synthesis of Kojic acid (KA)-Azide. a) K₂CO₃, PMB-Cl, DMF, reflux, b) MsCl, DIPEA, DCM, rt, then NaN₃, MeCN, c) TFA, DMF, rt.

Fig. 4. A schematic diagram illustrating the proposed action mechanisms of KA-hybrid compounds. KA-hybrid compounds specifically targets the ERK/CREB signaling, thereby inhibiting MITF and MITF-regulated target genes including those encoding tyrosinase, TRP1, and TRP2. AC, adenylate cyclase; α-MSH, alpha-melanocyte stimulating hormone; ATP, adenosine triphosphate; cAMP, cyclic adenosine monophosphate; CREB, cAMP response element-binding protein; ERK, extracellular signal-regulated kinase; MAP kinase, mitogen-activated protein kinase; MC1R, melanocortin receptor type 1; MITF, microphthalmiaassociated transcription factor; PKA, protein kinase A; ROS, reactive oxygen species; TRP, tyrosinase-related protein; TYR, tyrosinase.

Table 1. Cell cytotoxicity in MRC5 cell

Table 2. Inhibitory effect of the Kojic acid (KA)-hybrid compounds on melanin production