Šola Ivana, Gmižić Daria
Department of Biology, Faculty of Science, University of Zagreb, Horvatovac 102a, 10000 Zagreb, Croatia.
Plants (Basel). 2025 Apr 11;14(8):1186. doi: 10.3390/plants14081186.
Polyphenolics in plants exist in free, soluble-bound, and insoluble-bound structural forms. The concentration of these structural forms depends on the plant's developmental stage, tissue type, soil water availability, and food preparation methods. In this study, for the first time, the effects of growth temperature (RT-room temperature-23 °C day/18 °C night, HT-high temperature-38 °C day/33 °C night, LT-low temperature-12 °C day/7 °C night) on variations of polyphenolic structural forms-free, soluble-bound (esterified and glycosylated), and insoluble-bound-in broccoli ( L. convar. (L.) Alef. var. Duch.) microgreens were investigated. Using spectrophotometric, RP-HPLC, and statistical analyses, it was found that the highest amount of total phenolics (TP) in broccoli microgreens was present in the esterified form, regardless of the temperature at which they were grown (63.21 ± 3.49 mg GAE/g dw in RT, 65.55 ± 8.33 mg GAE/g dw in HT, 77.44 ± 7.82 mg GAE/g dw in LT). LT significantly increased the amount of free (from 13.30 ± 2.22 mg GAE/g dw in RT to 18.33 ± 3.85 mg GAE/g dw) and esterified soluble TP (from 63.21 ± 3.49 mg GAE/g dw in RT to 77.44 ± 7.82 mg GAE/g dw), while HT significantly increased the amount of TP glycosylated forms (from 14.85 ± 1.45 mg GAE/g dw in RT to 17.84 ± 1.20 mg GAE/g dw). LT also enhanced free and esterified forms of total flavonoids, tannins, hydroxycinnamic acids, and flavonols. HT, on the other hand, increased glycosylated forms of TP, flavonoids, tannins, hydroxycinnamic acids, flavonols, and phenolic acids, and decreased insoluble-bound tannins. According to the ABTS method, HT induced antioxidant potential of free and glycosylated forms, while LT increased antioxidant capacity of free forms only. According to the FRAP method, LT increased antioxidant potential of free and esterified polyphenolic forms. Also, based on ABTS and FRAP assays, esterified polyphenolics showed significantly higher antioxidant capacity than any other form. Principal component analysis showed that structural form had a greater impact than temperature. Hierarchical clustering showed that RT-, HT- and LT-broccoli microgreens were most similar in their glycosylated polyphenolics, but differed the most in esterified forms, which were also the most distinct overall. In conclusion, HT and LT induced specific shifts in the structural forms of broccoli polyphenolics and their antioxidant capacity. Based on the results, we recommend applying LT to increase the amount of free and esterified polyphenolics in broccoli microgreens, while HT may be used to enhance glycosylated forms.
植物中的多酚类物质以游离态、可溶性结合态和不溶性结合态的结构形式存在。这些结构形式的浓度取决于植物的发育阶段、组织类型、土壤水分可利用性以及食物制备方法。在本研究中，首次研究了生长温度（RT-室温-23℃白天/18℃夜晚，HT-高温-38℃白天/33℃夜晚，LT-低温-12℃白天/7℃夜晚）对西兰花（L. convar. (L.) Alef. var. Duch.）微型蔬菜中多酚结构形式（游离态、可溶性结合态（酯化和糖基化）和不溶性结合态）变化的影响。通过分光光度法、反相高效液相色谱法和统计分析发现，无论西兰花微型蔬菜生长在何种温度下，其总酚（TP）含量最高的形式为酯化形式（RT中为63.21±3.49mg GAE/g干重，HT中为65.55±8.33mg GAE/g干重，LT中为77.44±7.82mg GAE/g干重）。LT显著增加了游离态（从RT中的13.30±2.22mg GAE/g干重增加到18.33±3.85mg GAE/g干重）和酯化可溶性TP的含量（从RT中的63.21±3.49mg GAE/g干重增加到77.44±7.82mg GAE/g干重），而HT显著增加了TP糖基化形式的含量（从RT中的14.85±1.45mg GAE/g干重增加到17.84±1.20mg GAE/g干重）。LT还增强了总黄酮、单宁、羟基肉桂酸和黄酮醇的游离态和酯化形式。另一方面，HT增加了TP、黄酮类化合物、单宁、羟基肉桂酸、黄酮醇和酚酸的糖基化形式，并减少了不溶性结合态单宁。根据ABTS法，HT诱导了游离态和糖基化形式的抗氧化潜力，而LT仅增加了游离态的抗氧化能力。根据FRAP法，LT增加了游离态和酯化多酚形式的抗氧化潜力。此外，基于ABTS和FRAP分析，酯化多酚表现出比任何其他形式都显著更高的抗氧化能力。主成分分析表明，结构形式比温度的影响更大。层次聚类表明，RT-、HT-和LT-西兰花微型蔬菜在糖基化多酚方面最为相似，但在酯化形式方面差异最大，酯化形式总体上也是最独特的。总之，HT和LT诱导了西兰花多酚结构形式及其抗氧化能力的特定变化。根据结果，我们建议应用LT来增加西兰花微型蔬菜中游离态和酯化多酚的含量，而HT可用于增强糖基化形式。
