Screening Withania somnifera as biostimulant for crop plants and chemical profiling of its active fractions

Abstract

Studies have highlighted that Withania somnifera contain endogenous molecules, with varying biological activities. In light of this, the current experiment aimed the plant growth-promoting potential of Withania somnifera leaf extract (WsLE) through seed priming. Twenty crop plants were tested to assess the bio-stimulatory effects of WsLE. The selected morphological features for evaluation included germination percentage, plant length and fresh biomass while the biochemical parameters assessed were total polyphenolic, protein, and flavonoid content, enzymatic activities: peroxidase, phenylalanine ammonia lyase and antioxidant activities. The results demonstrated that WsLE enhanced the evaluated parameters though the bio-stimulant effects varied across the crop species. Certain crop plants, such as, T. foenum-graceum, V. radiata and S.bicolor showed particularly strong responses, exhibiting marked improvements in plant growth and biochemical traits. To better understand the variability in response, Principal component analysis was conducted to categorize the crop plants according to the influence of different WsLE dilutions. Chromatographic profiling and identification of bioactive compounds in WsLE were performed using HPLC and UHPLC/HRMS. The analytical characterization revealed that the presence of 26 withanolides, 5 phytohormones and 26 other bioactive phytoconstituents. Quantitative analysis demonstrated that 27- hydroxywithanone and withaferin A exhibited the highest abundance among all identified compounds, suggesting potential role as the primary bioactive constituent. The comprehensive chemical characterization indicated that these major bioactive compounds likely serve as key modulators of physiological and biochemical pathways.