Optimization of conditions to achieve a high content of alizarin and purpurin in the adventitious roots of Rubia cordifolia L.

Rubia cordifolia L. (Indian madder) is a valuable medicinal plant known for its natural dye content, notably alizarin and purpurin, with applications in textiles and cosmetics. This study aims to optimize the concentrations of auxin, salicylic acid, elicitors, and precursors to maximize the production of alizarin and purpurin in adventitious roots. Various concentrations and combinations of auxins were systematically tested to explore their effects on the yield of adventitious root formation and dye compounds. Nodal explants cultivated in MS media supplemented with IAA + IBA + NAA (1.5 + 0.5 + 0.75 mg/L) at a pH of 5.7 exhibited the highest adventitious root production. Post-establishment of root cultures, the impact of salicylic acid, L-phenylalanine, elicitors (yeast extract, pectin, and Xylan), and the precursor α-ketoglutaric acid on the production of anthraquinones (AQ) was evaluated. High-Performance Liquid Chromatography (HPLC) analysis revealed enriched alizarin, purpurin, and total AQ content. The maximum amount of AQ (64.65 mg/g), alizarin (17.59 mg/g), and purpurin (19.61 mg/g) was observed when cultured on 30 mg/L of α-ketoglutaric acid, compared to other elicitors and precursors. This optimized condition provides valuable insights for the sustainable cultivation and utilization of R. cordifolia as a prominent source of natural dyes. It offers practical implications for the dye industry and its production.