Shikonin: Extraction, properties and applications in active and intelligent packaging
Shikonin, a red?coloured pigment extracted from Gromwell plant roots, is a natural multifunctional material possessing antimicrobial, antioxidant, and halochromic properties. These attributes make it suitable as an additive with natural or synthetic polymers for developing multifunctional smart food packaging materials. The figure illustrates the fabrication of CNF?based films added with shikonin, which shows colour change and improved physicochemical (mechanical and colour) and functional (antioxidant, antimicrobial and UV?barrier) properties, which are important from a food packaging perspective.Shikonin is a naphthoquinone compound, generally extracted from the roots of the Oriental medicinal herb Lithospermum erythrorhizon or the Indian medicinal herb Arnebia euchroma. It has a rich history of being utilized as a pharmacological compound to treat various diseases such as inflammation, wounds and microbial infections. Besides, it also possesses anticancer, antiviral and antioxidant properties, which interest current medical researchers. Food packaging researchers have recently utilized shikonin's antimicrobial and antioxidant properties for active food packaging. Its halochromic properties and ability to change colour with pH variation have attracted tremendous attention for intelligent packaging applications. This review article covers the important extraction processes for shikonin. Further, the important properties of these functional compounds have been discussed. Finally, the advancements in applying shikonin as a multifunctional material in biopolymer?based films for smart packaging applications have been reviewed for the first time.