Evaluation of gliadins-diglycosylated cyanidins interaction from litchi pericarp through ultraviolet and fluorescence measurements

Figures & data

Figure 1. High performance liquid chromatography (HPLC) analysis of main litchi pericarp anthocyanins at 520 nm (a) and ESI-MS (b), MS² (c) information of compound 1.

Figure 2. Ultraviolet absorption spectra of litchi pericarp anthocyanins (LPA)-gliadins at different proportions: L, C — LPA concentration of 5 × 10^–6 mol/L; K, C — gliadins concentration of 5 × 10^–6 mol/L; J-A, LPA/gliadins ratio of 2, 4, 6, 8, 10, 12, 14, 16, 18, 20.

Figure 3. Fluorescence emission spectra (λex = 280 nm) obtained in the presence of increasing concentrations of litchi pericarp anthocyanins (LPA) at temperature of 298 K in the presence of gliadins: A, C – gliadins concentration of 5 × 10^–6 mol/L; for B-K the ratio LPA/gliadins was 2, 4, 6, 8, 10, 12, 14, 16, 18, 20.

Table 1. Stern–Volmer quenching constants of litchi pericarp anthocyanins (LPA) —gliadins binding at different temperatures.

T/ºC	KSV/104(L/mol)	R^2	KA/104(L/mol)	n	R^2
15	7.500	0.9545	6.853	1.022	0.9654
25	7.143	0.9627	5.962	1.008	0.9936
35	6.784	0.9673	4.862	1.017	0.9742

Table 2. Thermodynamic parameters for litchi pericarp anthocyanins (LPA)—gliadins binding at different temperatures.

T/ºC	ΔH/(kJ/mol)	ΔS/(J/mol)	ΔG/(kJ/mol)
15		−25.63	−27.02
25	−36.43	−26.57	−26.74
35		−26.25	−26.26

Figure 4. DPPH scavenging rate of litchi pericarp anthocyanins (LPA) and LPA-gliadins (for LPA-gliadins the ratio of LPA/gliadins was 10).