Evaluating the impact of Acanthophora spicifera and Gracilaria edulis extracts on the enhanced growth of selected microgreens and their bioactive metabolite profiles
Abstract
Seaweed-derived bio-stimulants are increasingly explored as a sustainable strategy to enhance the nutraceutical quality of functional foods such as microgreens. This study evaluated the effect of foliar-applied Acanthophora spicifera and Gracilaria edulis extracts (0.5% w/v) on the growth and bioactive metabolite profiles of broccoli, beetroot and red amaranth microgreens, relative to a water control. Total phenolic content, total flavonoid content, ascorbic acid, anthocyanin (pH-differential), glucosinolate (spectrophotometric) and antioxidant activity (DPPH, ABTS) were quantified and analysed by one-way ANOVA with Tukey's Honestly Significant Difference test, followed by crop-wise Pearson correlation and principal component analysis. Seaweed treatment significantly increased all measured bioactive parameters across the three crops (P < 0.05 in all cases), with phenolic content reaching a maximum of 333.75 mg GAE/100 g FW in Acanthophora-treated broccoli, without any corresponding change in fresh biomass or moisture content. Crop identity, rather than treatment, was found to be the dominant source of multivariate variation, and anthocyanin- and glucosinolate-related compounds were positively correlated within each crop once species-level confounding was removed. Because beetroot and red amaranth do not biosynthesise true glucosinolates or anthocyanins, readings for these two crops are interpreted as reflecting related compound classes rather than the named target analytes. This crop-disaggregated statistical approach corrects an ecological-fallacy artefact present when data are pooled across species and clarifies assay-specificity limitations in non-Brassica, non-anthocyanin-producing crops. Within the limitations of the absence of an ethanol-vehicle control and the low ambient light intensity used, the findings support marine red seaweed extracts as promising natural elicitors for nutraceutical enrichment of microgreens, meriting further mechanistic and vehicle-controlled validation.