COMPARATIVE ELICITOR-MEDIATED ENHANCEMENT OF PLUMBAGIN ACCUMULATION IN ADVENTITIOUS ROOT CULTURES OF PLUMBAGO INDICA AND PLUMBAGO AURICULATA

Abstract

Plumbagin, a bioactive naphthoquinone produced by Plumbago species, has considerable pharmaceutical importance but its natural availability is limited by overharvesting and habitat degradation. The present study evaluated methyl jasmonate (MeJA) and chitosan as elicitors for enhancing plumbagin accumulation in non-transgenic adventitious root cultures of Plumbago indica and Plumbago auriculata. Adventitious roots were induced from leaf explants on half-strength Murashige and Skoog medium supplemented with indole-3-butyric acid and 1-naphthaleneacetic acid. Maximum root biomass was obtained on medium containing 1.5 mg L⁻¹ IBA and 0.4 mg L⁻¹ NAA. Four-week-old root cultures were treated for 7 days with MeJA (50–150 µM) and chitosan (100–200 mg L⁻¹), individually and in combination. Elicitation significantly increased plumbagin accumulation in both species compared with untreated controls. The combined treatment of 100 µM MeJA and 150 mg L⁻¹ chitosan produced the highest plumbagin content, reaching 12.73 ± 0.20 µg mg⁻¹ dry weight in P. indica and 10.14 ± 0.06 µg mg⁻¹ dry weight in P. auriculata. These values corresponded to approximately 5.7-fold and 5.6-fold increases, respectively, over the controls. Across treatments, P. indica showed greater responsiveness than P. auriculata, indicating species-specific variation in elicitor-mediated metabolite accumulation. The enhanced response may be associated with the activation of jasmonate- and defense-related secondary metabolite pathways reported in Plumbago species. This study provides a simple, reproducible, and non-transgenic in vitro strategy for enhancing plumbagin accumulation and offers a useful framework for further molecular, metabolic, and process-level optimization.