Enhanced Curculigoside and Phenolic Compounds Elevate Antioxidant Activity in C. orchioides Gaertn In Vitro Under Exogenous Augmentation with Elicitors Salicylic Acid (SA) and Polyethylene Glycol (PEG) 6000

Abstract

Introduction Curculigo orchioides Gaertn, an endangered medicinal plant, possesses a bioactive compound known as curculigoside (phenolic glycoside) in addition to other phenolic compounds. Curculigoside has multifunctional pharmacological properties including antioxidant and anti-inflammatory. Advances in plant tissue culture provide us with tools for the in vitro propagation of medicinal plants in addition to a well-founded system to enhance pharmacologically bioactive compounds through the use of elicitors. Objective The study evaluates the effect of exogenous application of salicylic acid (SA) and polyethylene glycol 6000 (PEG 6000) to in vitro cultures of C. orchioides for enhanced curculigoside, phenolic compounds production followed by an increase in antioxidant activity (AA). Method Eight-week-old subcultured plants grown in one-fourth strength Murashige and Skoog media were subjected to elicitors treatment. SA (10, 100, and 1,000 ppm) and a PEG 6000 (1,000, 5,000, and 10,000 ppm) were used as elicitors for a period of 1, 2, and 4 weeks. Plants without treatment were considered as control. The treated plants were subjected to 80% acetone solvent for efficient phenolic extract preparation. High-performance liquid chromatography was used for the analysis of curculigoside content (CC), and total phenolic content (TPC) was determined using the Folin–Ciocalteu colorimetric method. AA was evaluated by 1,1-diphenyl-2-picrylhydrazyl assay. Results SA treatment increased CC, TPC, and biological activity of AA properties compared to the control, with the maximum value observed at 10 ppm treatment after week 1 elicitation. CC, TPC, and AA gradually decreased after week 2 elicitation, and the lowest values were observed after week 4 elicitation. In the PEG 6000 treatment, 10,000 ppm elicited the highest CC and TPC, with the maximum AA observed after week 2 elicitation. The treatment also elicited higher CC, TPC, and AA in both the 1st and 4th weeks compared to the control. Conclusion SA and PEG 6000 successfully enhanced CC, TPC, and improved AA in C. orchioides in vitro. The study also offers insightful information for the neutraceutical, cosmeceutical, and pharmaceutical industries about how to potentially manipulate medicinal plants in vitro to increase the synthesis of bioactive compounds.