本文通过测定抑制酪氨酸酶活性，DPPH (1, 6-双(二苯基膦)己烷)清除自由基能力以及铜离子螯合能力，研究了柠檬精油和其组成中的六种挥发性成分抑制酪氨酸酶的机理。结果表明：柠檬精油和挥发性成分对酪氨酸酶均产生良好的抑制作用，通过空间位阻效应和清除氧自由基等非抑制酪氨酸酶活性部位的机理；其中柠檬醛（含量为2.16%）和乙位蒎烯（含量为14.30%）对酪氨酸酶的抑制率分别为76.64%和61.82%，表现出显著的抑制能力；然而，D-柠檬烯（含量为61.41%）的抑制率仅有33.25%；六种挥发成分的协同效应使得这些物质的混合物对酪氨酸酶的抑制作用强于柠檬精油;随着浓度的增加，柠檬精油抑制能力增加，其中达到50%的抑制能力的浓度为620±15.72 μg/mL；Linewear-Burk曲线说明柠檬精油的抑制类型为非竞争性，并且Km=0.30±0.003mM；基于DPPH实验得知柠檬精油和柠檬醛具有较强的清除自由基能力，两者的50%清除率浓度分别为123.65±20.20 mg/mL和176.54±23.20 mg/mL；铜离子螯合实验证明六种组分虽然表现为良好的抑制酪氨酸酶作用但均不与酪氨酸酶活性部位相结合。以上结果表明柠檬精油在食品和化妆品行业中可作为潜在的生物性和功能性天然原料。

The mechanism of tyrosinase inhibition by lemon essential oil and its six individual components was studied in terms of tyrosinase activity, radical-scavenging activity, and copper-chelating capability. The results indicated that lemon essential oil and some of its volatile components exhibited good inhibitory effect on tyrosinase activity through non-active-site-inhibition mechanisms such as steric effect and oxygen radical-scavenging activity. Among the components of lemon essential oil, inhibitory rate on tyrosinase activity exerted by citral (2.16% m/m) and beta-pinene (14.30% m/m) was 76.64% and 61.82%, respectively, while that of d-limonene (61.41% m/m) was only 33.25%. Additionally, inhibition exerted by the mixture of all six volatile components was higher than that of lemon essential oil due to a synergistic effect and the inhibitory effect was higher with increasing concentration. Moreover, the inhibitor concentration causing 50% loss of activity (IC50 value) was 620 ± 15.72 μg/mL. The Lineweaver-Burk plot showed that inhibitory activity of lemon essential oil (Km = 0.30 ± 0.003 mM) was noncompetitive. The 1,6-bis(diphenylphosphino) hexane (DPPH) assay showed that lemon essential oil and citral had relatively strong radical-scavenging activity, with IC50 values of 123.65 ± 20.20 and 176.54 ± 23.20 mg/mL, respectively. Copper chelating demonstrated that the six components did not bind to the active sites of tyrosinase while exhibiting good inhibitory effect. These results indicate that lemon essential oil is a natural material with potential biological function that can be applied to food and cosmetic industries.