Isolation and Partial Characterization of Bioactive Fucoxanthin from Himanthalia elongata Brown Seaweed: A TLC-Based Approach

Seaweeds are important sources of carotenoids, and numerous studies have shown the beneficial effects of these pigments on human health. In the present study, Himanthalia elongata brown seaweed was extracted with a mixture of low polarity solvents, and the crude extract was separated using analytical thin-layer chromatography (TLC). The separated compounds were tested for their potential antioxidant capacity and antimicrobial activity against Listeria monocytogenes bacteria using TLC bioautography approach. For bio-autography, the coloured band on TLC chromatogram was visualized after spraying with DPPH and triphenyl-tetrazolium chloride reagents which screen antioxidant and antimicrobial compounds, respectively, and only one active compound was screened on the TLC plate. Preliminary identification of this active compound was done by comparing its colour and (retention factor) value with the authentic fucoxanthin standard. Further, the active compound was purified using preparative TLC. This purified compound showed a strong antioxidant (EC50: ？ g/mL) and antimicrobial (inhibition zone: 10.27？mm, 25？ g？compound/disc) activities, which were examined by DPPH scavenging and agar disc-diffusion bioassay, respectively. The bioactivity shown by the purified compound was almost similar to the fucoxanthin standard. The characteristic UV-visible and FT-IR spectra of the purified active compound completely matched with the standard. Hence, the main active compound in H. elongata was identified as fucoxanthin. 1. Introduction Compared to terrestrial plants, seaweeds are an untapped resource offering substantial potential for the isolation of original natural ingredients of interest for food and health purposes. Of the diverse classes of seaweeds, edible brown seaweed is considered to be the most nutritious and possesses a range of compounds with biological properties [1]. The lipophilic fractions of these seaweeds are a mixture of components including carotenoid pigments especially fucoxanthin, zeaxanthin, violaxanthin, and other minor compounds such as β-carotene and anthocyanins derivatives [1]. Several reports have demonstrated the role of different carotenoids in the prevention of degenerative diseases, and this has been attributed to their antioxidant properties [2, 3]. However, some of these pigments are involved in cell communication and have been explored for their potential antimicrobial behaviour also [1, 4]. Therefore, these pigments play an important role in health maintenance and have traditionally attracted the attention of the pharmaceutical and