Poli Alessandra L, Fanchiotti Brenda G, Gabriel Juliana S, Arandas Anderson M, Schmitt Carla C
Instituto de Química de São Carlos, Universidade de São Paulo, Caixa Postal 780, São Carlos, SP 13560-970, Brazil.
Instituto Federal de Educação, Ciência e Tecnologia do Amapá - IFAP, Rodovia BR 210, Km 103, Zona Rural, Porto Grande, AP 68997-000, Brasil.
ACS Omega. 2025 May 23;10(22):23082-23088. doi: 10.1021/acsomega.5c01178. eCollection 2025 Jun 10.
The stability of curcumin (Cur) in different media, such as buffer, modified chitosan, and solvents, was evaluated by using UV-vis and fluorescence. An amphiphilic derivative of chitosan (modified chitosan) was synthesized by substituting diethylamino and dodecyl groups. The critical aggregation concentration of modified chitosan (ChM) was determined by using pyrene as a hydrophobic probe. The ChM aggregates at concentrations above 1.1 × 10 g·L, and hydrophobic environments are formed. For Cur in the presence of ChM (Cur/ChM), it can be seen that the keto form has spectral characteristics, indicating that ChM is stabilizing the Cur molecules in the keto form. These results agree with Cur absorbance spectra obtained in different solvents, in which the tautomeric equilibrium of Cur is shifted to the keto form in nonpolar solvents. The fluorescence intensity of Cur in ChM (at concentrations above the CAC) increased significantly, unlike that of Cur in the buffer. The quantum yield value obtained for Cur was 0.05 g·L of ChM was higher than that of Cur in the other media. At concentrations of ChM above 0.011 g·L, it aggregates and can incorporate the Cur molecule into the hydrophobic portion, promoting stabilization. This behavior can be confirmed by fluorescence micrographs, which reveal the fluorescent domains of curcumin in the hydrophobic environments of ChM. The percentages of Cur degradation were 96% in the buffer and 71% in 0.05 g·L Ch, 93% in 0.005 g·L ChM, 60% in 0.01 g·L ChM, and 30% in 0.05 g·L ChM. It is possible to notice that the Cur degradation percentage is 0.05 g·L ChM (above CAC concentration) was lower compared with the degradation of Cur in the other media. Therefore, these results indicate that the ChM above the CAC, in its aggregated form, can protect the dye molecule from the effects of water.
通过紫外可见光谱和荧光光谱对姜黄素（Cur）在不同介质（如缓冲液、改性壳聚糖和溶剂）中的稳定性进行了评估。通过取代二乙氨基和十二烷基基团合成了壳聚糖的两亲性衍生物（改性壳聚糖）。以芘作为疏水探针测定了改性壳聚糖（ChM）的临界聚集浓度。ChM在浓度高于1.1×10 g·L时聚集，形成疏水环境。对于存在ChM的Cur（Cur/ChM），可以看出酮式具有光谱特征，表明ChM使酮式的Cur分子稳定。这些结果与在不同溶剂中获得的Cur吸收光谱一致，其中Cur的互变异构平衡在非极性溶剂中向酮式移动。与缓冲液中的Cur不同，ChM中Cur的荧光强度（在浓度高于临界聚集浓度时）显著增加。Cur在0.05 g·L ChM中的量子产率值高于在其他介质中的值。当ChM浓度高于0.011 g·L时，它会聚集并能将Cur分子纳入疏水部分，从而促进稳定性。这种行为可以通过荧光显微镜照片得到证实，照片显示了姜黄素在ChM疏水环境中的荧光区域。Cur在缓冲液中的降解率为96%，在0.05 g·L Ch中的降解率为71%，在0.005 g·L ChM中的降解率为93%，在0.01 g·L ChM中的降解率为60%，在0.05 g·L ChM中的降解率为30%。可以注意到，与其他介质中Cur的降解相比，0.05 g·L ChM（高于临界聚集浓度）中Cur的降解率较低。因此，这些结果表明，高于临界聚集浓度的ChM以聚集形式可以保护染料分子免受水的影响。
