Department of Food Science and Technology, Science Drive 2, Faculty of Science, National University of Singapore, Singapore 117542, Singapore.
Food Quality and Design Group, Department of Agrotechnology and Food Sciences, Wageningen University, P.O. Box 17, 6700 AA Wageningen, the Netherlands.
Food Chem. 2021 Dec 1;364:130424. doi: 10.1016/j.foodchem.2021.130424. Epub 2021 Jun 19.
In this work, we investigated the degradation of moringin (4-[(α-l-rhamnosyloxy)benzyl]-isothiocyanate), a major bioactive isothiocyanate (ITC) found in moringa seeds (Moringa oleifera Lam), at various food processing conditions. Moringin degrades rapidly to several water-soluble products via a pseudo-first-order kinetics. By analyzing the reaction products, the degradation mechanism was found to be through hydrolyzing to (A) 1-O-(4-hydroxymethylphenyl) α-l-rhamnopyranoside (rhamnobenzyl alcohol RBA) or (B) rhamnobenzylamine. The formed amine further reacts with moringin to form N,N'-bis{4-[(α-l-rhamnosyloxy)benzyl]}thiourea (di-rhamnobenzyl thiourea, DRBTU). In addition, moringin isomerizes to 4-[(α-l-rhamnosyloxy)benzyl]thiocyanate (RBTC), which further reacts with moringin to form S,N-bis{4-[(α-l-rhamnosyloxy)benzyl]}-dithiocarbamate (DRBDTC). Furthermore, pH was found to have an effect on the degradation of moringin. RBA and RBTC were major degraded products in neutral and acidic conditions while thiourea (DRBTU) was in alkaline condition. Although moringin showed higher cytotoxicity to cancer cells, its degraded products showed very weak or no activities, suggesting that the isothiocyanate group of ITCs is essential for their cancer chemoprevention activities.
在这项工作中，我们研究了辣木叶（Moringa oleifera Lam）种子中主要生物活性异硫氰酸酯（ITC）之一的萝卜硫素（4-[(α-l-鼠李糖氧基）苄基]-异硫氰酸酯）在各种食品加工条件下的降解情况。萝卜硫素通过伪一级动力学迅速降解为几种水溶性产物。通过分析反应产物，发现其降解机制是通过水解生成（A）1-O-（4-羟甲基苯基）α-l-鼠李吡喃糖苷（鼠李苄醇 RBA）或（B）鼠李苄胺。形成的胺进一步与萝卜硫素反应，形成 N，N'-双{4-[(α-l-鼠李糖氧基）苄基]}硫脲（二鼠李苄基硫脲，DRBTU）。此外，萝卜硫素异构化为 4-[(α-l-鼠李糖氧基）苄基]异硫氰酸酯（RBTC），它进一步与萝卜硫素反应，形成 S，N-双{4-[(α-l-鼠李糖氧基）苄基]}-二硫代氨基甲酸酯（DRBDTC）。此外，pH 值对萝卜硫素的降解有影响。RBA 和 RBTC 是中性和酸性条件下的主要降解产物，而在碱性条件下则是硫脲（DRBTU）。尽管萝卜硫素对癌细胞的细胞毒性更高，但它的降解产物活性非常弱或没有，这表明 ITCs 的异硫氰酸酯基团对于其癌症化学预防活性是必不可少的。
