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.
Xin Li,Guangyan Yao,Xiaopeng Chen,Jie Huang,Jiezhen Liang,Xiaojie Wei,Biao Huang,Linlin Wang
Quality deterioration due to undesirable discolorations in crude pine oleoresin during storage is a major problem limiting its subsequent processing applications. To reveal the essence of color changes, the browning phenomenon and comprehensive mechanism of crude pine oleoresin during storage were investigated in depth using an approach based on high-resolution mass spectrometry metabolomics . Crude pine oleoresin was stored with sterile, deionized, tap, and pond water for 30, 60, 90, 120, 150, and 180 days, respectively. The changes in browning substrate were detected by tracking analysis protein, reducing sugar, ascorbic acid , and total phenol content, browning was evaluated through colorimeter measurement. The metabolism of crude pine oleoresin in different storage times was uncovered that total color difference (Δ E ) increased with storage time, and the browning of crude pine oleoresin soaked in tap water was greatest while soaked in deionized water exhibited the mildest. The content of reducing sugars, proteins, and total phenols increased with storage time, whereas the ascorbic acid content tended to increase and then decrease. Furthermore, the metabolomics analyses showed that 1,194 and 979 differentially metabolized compounds were found between days 120 and days 150, and days 120 and days 180. The metabolite profiles in the water samples changed as crude pine oleoresin storage time increased. Most carbohydrate content decreased, and the phenols and organic acids content increased. Metabolic network mapping linking differentially metabolized compounds by mapping different biosynthetic pathways proved that caffeoylquinic acid and catechin play a key role in the browning of crude pine oleoresin during storage: caffeoylquinic acid forms black iron complexes with iron, and catechin is oxidized to catechol quinone, which eventually produces a yellow dimer. This study will provide a scientific basis for developing or choosing more effective methods for controlling the discoloration of crude pine oleoresin and other similar products during storage.
危险品化学品经营许可证（带存储）