Institute of Chemistry, Food Chemistry, Martin-Luther-University Halle-Wittenberg, Kurt-Mothes-Str. 2, 06120 Halle/Saale, Germany.
J Agric Food Chem. 2024 Oct 9;72(40):22316-22326. doi: 10.1021/acs.jafc.4c07633. Epub 2024 Sep 26.
Singlet oxygen-mediated fragmentation of various dihydrochalcones and chalcones was reported. (Dihydro)cinnamic acids formed in the fragmentation showed a B-ring substitution pattern of the precursor (dihydro)chalcone. For the first time, the intrinsic generation of singlet oxygen by aspalathin and ascorbic acid under mild aqueous conditions (37 °C, pH 7.0) and exclusion of light was verified using HPLC-(+)-APCI-MS experiments. If a 4 molar excess of aspalathin or ascorbic acid was used, fragmentation of dihydrochalcones with monohydroxy and -hydroxymethoxy B-ring substitution was induced up to 2 mol %, respectively. Incubations of the dihydrochalcone phloretin with ascorbic acid not only led to -dihydrocoumaric acid but also to a novel ascorbyl adduct, which was isolated and identified as 2,4,6-trihydroxy-5-[3-(4-hydroxyphenyl)propanoyl]-2-[(1, 2)-1,2,3-trihydroxypropyl]-1-benzofuran-3(2)-one. The impact of different structural elements on adduct formation was evaluated and verified to be a phloroglucinol structure linked to an acyl moiety. Formation of the ascorbyl adduct was shown to occur in apple puree when both ascorbic acid and phloretin were present at the same time.
报道了各种二氢查尔酮和查尔酮的单线态氧介导的断裂反应。在断裂中形成的(二氢)肉桂酸显示出与前体(二氢)查尔酮的 B 环取代模式。首次在温和的水相条件(37°C,pH 7.0)和避光下,使用 HPLC-(+)-APCI-MS 实验验证了 aspalathin 和抗坏血酸内在产生单线态氧。如果使用 4 摩尔过量的 aspalathin 或抗坏血酸,则分别诱导具有单羟基和 -羟甲基 B 环取代的二氢查尔酮的断裂,最高可达 2 摩尔%。抗坏血酸与二氢查尔酮根皮素的孵育不仅导致 -二氢肉桂酸的生成,还导致一种新型的抗坏血酸加合物的生成,该加合物被分离并鉴定为 2,4,6-三羟基-5-[3-(4-羟基苯基)丙酰基]-2-[(1,2)-1,2,3-三羟基丙基]-1-苯并呋喃-3(2)-酮。评估了不同结构元素对加合物形成的影响,并验证了其为与酰基部分相连的间苯三酚结构。当苹果泥中同时存在抗坏血酸和根皮素时,显示出抗坏血酸加合物的形成。