本研究主要探討不同脂肪酶來源、脂肪酶濃度、脂肪酸碳鏈長度、基質莫耳濃度比、有機溶劑及反應溫度對麴酸酯 (Kojic acid ester) 合成率的影響，並且探討所合成麴酸酯之生物活性包括抗氧化性、抑制酪胺酸酶活性及調控黑色素生合成作用。最適反應條件為42℃及攪拌轉速150 rpm，加入0.8% Candida Antarctica脂肪酶、硫辛酸與麴酸 ( 莫耳濃度比 4:1 ) 於乙腈溶液中反應40小時，新合成一個親脂性高可應用在油性食品及化妝品之麴酸酯，其轉化率為52.9%，經固定化之脂肪酶可於最適反應條件下重覆操作十五次，其轉化率仍保有67%。產物經由 NMR, EIMS 及 UV 的結構鑑定其 IUPAC 的命名為1,2-dithiolane-3-pentanoic acid, (5-hydroxy-4-oxo-4H-pyran-2-yl)methyl ester，新合成麴酸酯的酯化位置是位於麴酸C7上OH基而非C5上OH基 (enolic hydroxyl)，不僅保留清除自由基功能更強化原有麴酸抑制洋菇酪胺酸酶性，其抑制強度為麴酸的15.8倍，更值得注意的是對於黑色素細胞(B16-F0)具有良好的抑制黑色素生成的作用，其抑制機制是麴酸酯經由抑制B16-F0細胞中轉錄因子MITF (Microphthalmia-associated transcription factor) 進而抑制酪胺酸酶 (tyrosinase)、及酪胺酸酶家族相關蛋白Trp1 (tyrosinase relative protein-1) 及Trp2 (tyrosinase relative protein-2 )蛋白質量，而降低黑色素的生成作用。本研究發展的酵素合成法是利用酵素於溫和簡單、副產物少、低毒性，純化步驟簡單，低能源消耗及廢棄物產生，具環保優點的條件下合成多功能麴酸酯，期望可建立合成多功能酚酯的開發平台。 The effect of factors on esterification between kojic acid with lipoic acid using lipase-catalyzed in organic solvents were investigated. The optimal conditions for the enzyme reaction were obtained using 0.8% of Candida Antarctica, the substrate of kojic acid and lipoic acid at 42℃, 150 rpm speed for 40h in acetontrile. Under these conditions, the yield of esterification was 52.9%. Immobilized lipase retained 67% of its initial activity after 15 batch esterification cycles. The structural characteristics of new synthesized kojic acid ester were conformed as by 1H NMR、13C NMR, EIMS and UV analysis. Kojic acid ester not only showed the similar scavenging activity for free radical with kojic acid, but also improved the inhibitory reaction for mushroom tyrosinase and melaninogenesis. The antimelanogenic mechanism of kojic acid ester in B16-F0 cell model was suggested that the ester inhibited MITF(Microphthalmia-associated transcription factor), sequentially suppressed the expression of tyrosinase, and other melanogenic enzyme such as Trp1, and Trp2. The reaction runs smoothly without the use of hazardous reactant, and new compound synthesized kojic acid ester may play an important role in the regulation of melanin formation, making them the potent candidates for skin-whitening agent and food industry.
