Extraction and chromatographic purification of purpurin: A scalable approach using modified dry column vacuum...

Purpurin, a trihydroxy anthraquinone derivative, is an important bioactive compound isolated from Rubia cordifolia roots and recognize for its versatile pharmacological activities. The principal objective of the present study was to develop a rapid, reproducible, and scalable method for well organized extraction and purification of purpurin from Rubia cordifolia roots. Extraction was initiated via acid hydrolysis using optimized concentrations of hydrochloric acid as well as ferric chloride, followed by solvent extraction with chloroform. Including numerous experimental trial conditions, the combination of 20% HCl and 20% FeCl₃ under reflux yielded a dry crude extract of crude anthraquinones with a significantly enhanced yield of 1.76%. To attain high-purity isolation of purpurin, an indigenously developed dry column vacuum chromatography (DCVC) system was employed. Crude purpurin (1 g) was subjected to DCVC by utilizing silica gel as the stationary phase and a polarity gradient of hexane and ethyl acetate as the mobile phase. The DCVC method optimization involved variations in column internal diameter and silica bed size/depth. The most operational set up of DCVC includes a 6.5 cm diameter DCVC column with 8 cm silica bed size which achieved a product recovery yield of 58 - 62% and a purity range of 95-98%, as established by TLC and UHPLC analysis. The developed DCVC method proved excellent reproducibility and scalability across experimental trials. This integrated approach proposes a time-efficient and solvent-economical strategy for the preparative-scale isolation of purpurin with high purity.