Eckol - a new plant growth stimulant from the brown seaweed Ecklonia maxima

The seaweed concentrate Kelpak® made from the brown kelp Ecklonia maxima is used worldwide as a biostimulant for a number of agricultural crops. Plant growth regulators such as auxins, cytokinins, polyamines, gibberellins, abscisic acid, and brassinosteroids were identified from E. maxima and Kelpak®. In this study, we investigated the plant growth stimulating effects of two phlorotannins, i.e., phloroglucinol and eckol that were recently isolated from E. maxima. The activity of isolated eckol was compared with Kelpak® and commercially available phloroglucinol and the auxin indole-3-butyric acid (IBA). The isolated eckol from E. maxima stimulated maize growth in terms of shoot and root elongation and number of seminal roots and exhibited improvement in the biochemical activities of α-amylase compared to Kelpak®, phloroglucinol, and IBA. Furthermore, eckol showed auxin-like activity in the mung bean root assay at 10⁻⁵ M with an increased number of roots, shoot elongation, and seedling weight. Eckol can potentially play a significant role in increasing agricultural productivity.