Isolation, Purification, Structural Characterization, and Encapsulation of Sulforaphane From Cabbage Seeds Using the Ionic Gelation Method

Abstract

Sulforaphane (SFN), a phytochemical with anticancer and antibacterial properties, is a secondary metabolite found in cabbage (both in the plants and seeds), a member of the Brassica (crusifer) family. However, pure sulforaphane is volatile, sensitive to pH, temperature, light, and oxygen, and is also only oil-soluble, limiting its stability and bioaccessibility. Therefore, encapsulation is required to enhance stability and control its release. In this study, sulforaphane-rich extracts were first obtained from cabbage seeds using a hybrid ultrasonic-microwave extraction method yielding 24.35%, with a sulforaphane content of 8202.68 mu g/g DM, followed by purification of sulforaphane through chromatography. Structural elucidation was performed using H-1-NMR, C-13-NMR, and QTOF LC/MS. The pure SFN (> 90% purity) was encapsulated using the ionic gelation method to improve its bioaccessibility and stability. Various coating material combinations, sodium alginate/chitosan and sodium alginate/pectin were evaluated for the encapsulation process. Fourier-transform infrared spectroscopy (FTIR) was used to investigate the relationship between the coating materials, and the most efficient combination was selected. Optimization of process variables using central composite rotatable design (CCRD) identified the optimal conditions: 1.41% sulforaphane-oil mixture, 0.18% chitosan, and 6.88 min waiting time. Under these conditions, microcapsules were produced with high encapsulation efficiency (76.02%) and low solubility (4.78%). & Idot;n vitro bioaccessibility studies further confirmed minimal sulforaphane release during the oral and gastric phases, with a low release in the intestinal phase. These results demonstrate the effectiveness of the encapsulation system in protecting sulforaphane under harsh gastrointestinal conditions.