Carrotta Rita, Librizzi Fabio, Martorana Vincenzo, Raccosta Samuele, Mangione Maria Rosalia
Institute of Biophysics, National Research Council, Palermo, Italy.
Eur Biophys J. 2025 Sep 3. doi: 10.1007/s00249-025-01786-4.
The aqueous extract of Moringa oleifera leaves has been previously characterized for its polyphenolic composition, yet the behavior of its colloidal aggregates under dilution remains largely unexplored. In this study, we investigate the structural and chemical properties of these aggregates at room temperature, focusing on their stability and surface exposure upon dilution. Although the aggregates break up as dilution increases, they never fully dissolve within the conditions explored. Both multi-angle static light scattering and dynamic light scattering highlight aggregates fragmentation and size heterogeneity under dilution. UV-vis absorption spectroscopic data strongly suggest that the aggregates of different sizes present in the extract are homogeneously constituted, as their spectra are similar to those of the main polyphenol components. The Folin-Ciocâlteu assay reveals an increase in gallic acid equivalent values normalized for extract concentration, suggesting that fragmentation prompted by dilution enhances the exposure of reactive sites. A very basic model, considering only one kind of aggregate with uniform density, is employed to support this interpretation. Assuming this model, the Folin-Ciocâlteu assay data allow to grasp the law regulating the change of the aggregate average size under dilution, i.e., a power law. Additionally, in-liquid atomic force microscopy imaging confirms the presence of smaller but still aggregated particles at high dilution, enabling the calculation of a height distribution, that is consistent with the model prediction. These findings provide insights into the dynamic behavior of polyphenol-rich aggregates in aqueous systems and their potential implications for bioavailability and reactivity.
辣木树叶的水提取物先前已对其多酚成分进行了表征,但其胶体聚集体在稀释条件下的行为在很大程度上仍未得到探索。在本研究中,我们在室温下研究了这些聚集体的结构和化学性质,重点关注它们在稀释时的稳定性和表面暴露情况。尽管随着稀释度增加聚集体会分解,但在我们探索的条件下它们从未完全溶解。多角度静态光散射和动态光散射均突出了稀释条件下聚集体的破碎和尺寸异质性。紫外可见吸收光谱数据有力地表明,提取物中存在的不同尺寸的聚集体组成均匀,因为它们的光谱与主要多酚成分的光谱相似。福林-西奥尔特试剂法测定结果显示,以提取物浓度归一化后的没食子酸当量值有所增加,这表明稀释引发的破碎增强了反应位点的暴露。我们采用了一个非常简单的模型,仅考虑一种密度均匀的聚集体来支持这一解释。假设该模型成立,福林-西奥尔特试剂法测定数据可以掌握稀释条件下聚集体平均尺寸变化的规律,即幂律。此外,液内原子力显微镜成像证实了在高稀释度下存在较小但仍聚集的颗粒,从而能够计算出高度分布,这与模型预测结果一致。这些发现为富含多酚的聚集体在水性体系中的动态行为及其对生物利用度和反应性的潜在影响提供了见解。