Department of Chemistry, University of Otago, P. O. Box 56, Dunedin, New Zealand.
The New Zealand Institute for Plant and Food Research Limited, Private Bag 92169, Auckland, 1142, New Zealand.
Phytochemistry. 2020 May;173:112297. doi: 10.1016/j.phytochem.2020.112297. Epub 2020 Feb 15.
Non-targeted LC-MS metabolomics on fruit of three wild and domesticated apple species (Malus sylvestris, M. sieversii and M. domestica) showed that two crab apple (M. sylvestris) accessions were distinguished by high concentrations of an ascorbic acid glycoside (AAG). This was partly purified, but key NMR signals were masked by inseparable sucrose. Reference samples of 2-O-β-D-glucopyranosyl L-ascorbic acid and 2-O-β-D-galactopyranosyl L-ascorbic acid were synthesised, but both coincided with the crab apple AAG on LC-MS. Peracetylation of the crab apple extract allowed both purification and characterisation, and the AAG was proven to be 2-O-β-D-glucopyranosyl L-ascorbic acid by comparison of H NMR, HRMS and HPLC data with synthesised peracetylated ascorbyl glycoside standards. The stability of the natural AA 2-β-glycoside was similar to synthetic 2-O-α-D-glucopyranosyl L-ascorbic acid, used widely in cosmetic and pharmaceutical products. This discovery in crab apples (Rosaceae) is only the fourth reported occurrence of any ascorbyl glycoside from plants, the others being from Cucurbitaceae, Solanaceae and Brassicaceae. It is hypothesised that AAGs may be more widespread in plants than currently realised.
对三个野生和栽培苹果属物种（Malus sylvestris、M. sieversii 和 M. domestica）果实的非靶向 LC-MS 代谢组学研究表明，两个海棠果（M. sylvestris）品系的特征是含有高浓度的抗坏血酸糖苷（AAG）。虽然该物质被部分纯化，但关键的 NMR 信号被不可分离的蔗糖所掩盖。合成了 2-O-β-D-吡喃葡萄糖基 L-抗坏血酸和 2-O-β-D-半乳糖吡喃基 L-抗坏血酸的参考样品，但它们在 LC-MS 上与海棠果 AAG 完全重合。对海棠果提取物进行乙酰化处理后，既可以实现纯化，又可以进行表征，并且通过比较 H NMR、HRMS 和 HPLC 数据与合成的乙酰化抗坏血酸糖苷标准品，证明 AAG 为 2-O-β-D-吡喃葡萄糖基 L-抗坏血酸。天然 AA 2-β-糖苷的稳定性与广泛用于化妆品和制药产品的合成 2-O-α-D-吡喃葡萄糖基 L-抗坏血酸相似。在蔷薇科植物中发现的这种海棠果（蔷薇科）中的抗坏血酸糖苷是目前从植物中报道的第四个抗坏血酸糖苷，其他三个分别来自葫芦科、茄科和十字花科。据推测，AAG 在植物中的分布可能比目前认识到的更为广泛。
