Untargeted metabolomics of purple and orange-fleshed sweet potatoes reveals a large structural diversity of anthocyanins and flavonoids

Anthocyanins are economically valuable phytochemicals of significant relevance to human health. Industrially extracted from multiple fruit and vegetable sources, anthocyanin yield and profiles can vary between sources and growing conditions. In this study, we focused on three purple-fleshed and one orange-fleshed cultivars of sweet potato, a warm-weather, nutritious crop of substantial interest to growers in northern, cooler latitudes, to determine the yield and diversity of anthocyanins and flavonoids. Acidified ethanol extraction of lyophilized roots yielded ~ 800 mg average anthocyanins/100 g dry weight from all three cultivars. UHPLC-DAD-Orbitrap analysis of sweet potato extracts identified 18 high-confidence, mostly acylated peonidin and cyanidin derivatives contributing to > 90% of the total anthocyanin signal. Further assessment of the untargeted Liquid Chromatography-Tandem Mass Spectrometry data using deep learning and molecular networking identified over 350 flavonoid peaks with variable distributions in different sweet potato cultivars. These results provide a novel insight into anthocyanin content of purple-fleshed sweet potatoes grown in the northern latitudes, and reveal the large structural diversity of anthocyanins and flavonoids in this popular crop.

花色素苷（Anthocyanins）是一类兼具经济价值与重要健康关联作用的植物化学物质。工业上可从多种果蔬原料中提取该物质，但其得率与组成谱会因原料来源及种植条件的不同而存在差异。本研究选取3个紫肉甘薯品种与1个橙肉甘薯品种作为研究对象——甘薯是一种喜温且富含营养的作物，在纬度较高、气候偏凉爽的北部种植区受到种植者的广泛关注——旨在探究其中花色素苷与类黄酮的得率及多样性。通过酸化乙醇萃取冻干甘薯块根，三个紫肉品种的平均花色素苷得率约为800 mg/100 g干重。经超高效液相色谱-二极管阵列检测器-轨道阱质谱（UHPLC-DAD-Orbitrap）分析甘薯提取物后，共鉴定出18个高置信度的衍生物，其中绝大多数为酰化芍药素与矢车菊素衍生物，这些组分占总花色素苷信号的90%以上。进一步结合深度学习与分子网络技术，对非靶向液相色谱-串联质谱（Liquid Chromatography-Tandem Mass Spectrometry）数据进行分析，共鉴定出超过350个类黄酮峰，且不同甘薯品种间的类黄酮分布存在显著差异。本研究结果为探究高纬度北部种植区紫肉甘薯的花色素苷含量提供了全新视角，并揭示了这一热门作物中花色素苷与类黄酮丰富的结构多样性。