α熊果素與β熊果素為化妝品美白成分，其溶於水中會產生對苯二酚，兩者經日光照射後，α熊果素與β熊果素皆會因光解作用而加速產生對苯二酚。由於對苯二酚具細胞毒性，因此為了抑制熊果素之光解作用，本實驗選擇添加防曬劑甲氧基桂皮酸辛酯比較兩者避光與照光後的差異性，結果證實添加後確實能有效降低α熊果素與β熊果素光解作用後所產生的對苯二酚，意外發現副產物甲氧基桂皮酸。

　　α-andβ-arbutin are two whiting components of cosmetic. Hydroquinone(HQ) was detected by GC-MS when theα-and β-arbutin was dissolved in water. The photolysis induced theα-and β-arbutin to form HQ quickly. Because of the cytotoxicity of the HQ, the OCtyl p-methoxycinnamte(OMC) was used to inhibit the potolysis of theα-and β-arbutin and to compare the difference within dark and light. The result was confirmed: the addition of OMC will decrease the formation of HQ fromα- and β-arbutin by photolysis. The by-product methoxycinnamic acid was formed unexpectedly.