Novel approaches towards over-production of andrographolide in in vitro seedling cultures of Andrographis paniculata

Abstract

Andrographis paniculata (Burm. f.) Wall. ex Nees is an important medicinal plant of the family Acanthaceae and andrographolide is its most important secondary metabolite. Commercial demand for andrographolide is sustained through wild collection and limited cultivation of this plant. However, the rate of seed setting in this plant is low and a huge variation in andrographolide content was recorded in wild. The objective of the present study was to over-produce andrographolide in vitro seedling cultures of A. paniculata upon treatment with elicitors like metal salts, amino acids and growth additives. Seedlings were treated with elicitors for 7, 14, 21 and 28 days under controlled in vitro conditions to investigate andrographolide accumulation over time. Significant andrographolide production (3–7 fold higher over untreated control) was observed upon elicitation with silver nitrate, l- aspartic acid and methyl jasmonate. Maximum amount of andrographolide accumulation (25.88 ± 2.72 mg g−1 dry weight, 7.09 fold higher over control) was detected after 14 days of treatment on elicitation with 0.5 mM AgNO3. Biomass increment was prominent in the elicited seedling cultures of A. paniculata, especially upon treatment with aspartic acid and casein acid hydrolysate. However, a negative correlation existed between biomass increase and andrographolide accumulation, indicating the metabolite flux was either directed towards primary metabolism and biomass accumulation, or towards secondary metabolism and andrographolide production. Hence, a protocol for in vitro augmentation in andrographolide accumulation was developed, for rapid and sustained over-production of this commercially important compound.