Work

Green extraction of natural indigoid from Baphicacanthus cusia (Nees) Bremek using hydrophilic and hydrophobic deep eutectic solvent technology

Year: 2024

Type: article

Abstract: This study focused on the development of an alternative and more environmentally friendly extraction solvent, a deep eutectic system (DES), for extracting indigoid pigments, specifically indigo and indirubin, from Baphicacanthus cusia (BC). BC is recognized in the textile industry as a natural vat dye and in traditional Chinese medicine as "Qing-Dai". It is known for treating inflammatory diseases such as psoriasis. In this study, 46 DES systems were compared with conventional methods. The hydrophobic DES, a terpenoid and fatty acid system comprising thymol:decanoic acid (DES40), and the hydrophilic DES, a choline chloride-based system comprising choline chloride: p -toluenesulfonic acid (DES19), showed significant extraction improvements. DES40 and DES19 achieved approximately 26-fold higher indigo content compared to classical ethanol and outperformed the harsh organic solvent dichloromethane. The green extraction process was optimized using a Box–Behnken design, considering parameters such as temperature, time and co-solvent. DES19 maximized indigo and indirubin content to 270.91±14.38 and 5.70±0.11 mg/g, respectively, while DES40 yielded 108.28 ± 3.9 and 0.16 ± 0.00 mg/mg/g, respectively. Safety evaluations using a cell-based MTT model with human skin cells in keratinocytes and fibroblasts showed that both DES19 and DES40 were safe at all concentrations tested. These results indicate that a more environmentally friendly solvent technology for the extraction of indigoids from BC using the DES is an efficient and potential application in the textile and pharmaceutical industries. • Environmentally friendly solvents, 46 deep eutectic systems (DES) have been extensively prepared and investigated for indigoid extraction. • Indigoid pigments yield was significantly improved by DES. • Natural DES, thymol:decanoic acid (DES40) and the semi-natural DES, ChCl: p -toluenesulfonic acid (DES19) showed significant improvements-achieving ∼26-fold higher indigo yield than classical ethanol and were clearly superior to the harsh organic solvent, dichloromethane. • DES19 and DES40 were tested for safety on human skin cells, fibroblasts, and keratinocytes.

Source: Next Sustainability

DOI: 10.1016/j.nxsust.2024.100090