Abstract：
Rosemary is one of the most promising, versatile, and studied natural preservatives. Carnosic acid (CA) and carnosol (CARN), as the primary active ingredients of rosemary extracts, have little difference in structure, but their antioxidant activities vary significantly, depending on the system studied. The underlying molecular mechanisms remain unclear. By means of optical spectroscopies, stopped-flow, laser photolysis, and density functional theory (DFT) calculations, we have compared CA and CARN between their reaction dynamics of radical scavenging, metal ion chelation, and oxidation inhibition in lipid emulsion and beef, as well as between their interactions with β-carotene (β-Car). For reference, 3-isopropyl catechol (IC), which is structurally similar to the active groups of CA and CARN, was studied in parallel. It is found for CA that the intramolecular hydrogen bond can boost the acidity of its phenol hydroxyl and that the synergistic effect with β-Car can substantially enhance its antioxidation activity in the model systems of lipid and meat via the CA-to-β-Car electron transfer reaction. The substitution of A and B rings on the catechol group in both CA and CARN limits browning caused by their formation of oxidative products as antioxidants.
摘要：
迷迭香是最有前途的,多才多艺，并研究了天然防腐剂。鼠尾草酸（CA）和鼠尾草酚（CARN），作为迷迭香提取物的主要活性成分，在结构上几乎没有差异，但是它们的抗氧化活性差异很大，取决于所研究的系统。潜在的分子机制仍不清楚。通过光学光谱学，停止流动,激光光解，和密度泛函理论(DFT)计算，我们比较了CA和CARN的自由基清除反应动力学，金属离子螯合，脂肪乳剂和牛肉中的氧化抑制，以及它们与β-胡萝卜素(β-Car)的相互作用。供参考,3-异丙基邻苯二酚（IC），在结构上类似于CA和CARN的活性基团，是平行研究的。对于CA，发现分子内氢键可以增强其酚羟基的酸度，并且与β-Car的协同作用可以通过CA到β-Car的电子转移反应在脂质和肉的模型系统中大大提高其抗氧化活性。CA和CARN中儿茶酚基团上的A和B环的取代限制了由其作为抗氧化剂的氧化产物的形成引起的褐变。
