Neuroprotective effect of the marine macroalga Gelidiella acerosa: identification of active compounds through bioactivity-guided fractionation

Context Gelidiella acerosa (Forsskal) Feldmann & G. Hamel (Rhodophyta-Gelidiales) is a marine red macroalga. Our previous work found that a benzene extract of G. acerosa possesses noticeable neuroprotective activity, when evaluated through in vitro and in vivo systems. Objective Bioactive-guided fractionation and identification of active compounds by column chromatography using solvents of varying polarity. Materials and methods Fractionation was done by column chromatography, antioxidant and anticholinesterase activity was assessed by DPPH and cholinesterase inhibition assays (50-200 mu g/ml), compound identification was done by LC-MS analysis, the mode of interaction of active compound was analyzed through docking studies and quantification was done by high-performance thin-layer chromatography (HPTLC) analysis. Results The results suggest that fractions F9-F13 exhibited significant (p<0.05) antioxidant and anticholinesterase activities. Hence, these fractions were pooled together and verified for neuroprotective activity. The pooled fraction was subjected to LC-MS analysis and among all the compounds, phytol was previously reported to possess excellent neuroprotective potential. Hence, the neuroprotective potential of phytol was assessed. The results suggest that phytol showed significant (p<0.05) antioxidant activities (25-125 mu g/ml) with an IC50 value of 95.27 +/- 1.65 mu g/ml and cholinesterase inhibitory potential (5-25 mu g/ml) with IC50 values of 2.704 +/- 0.07 and 5.798 +/- 0.72 mu g/ml for AChE and BuChE, respectively. Molecular docking studies suggest that phytol interacts with cholinesterase through the arginine residue of the enzyme. HPTLC quantification showed that about 6.266 mu g of phytol was present per mg of pooled fraction. Conclusion The study suggests that phytol might act as the key compound in contributing to the neuroprotective potential of G. acerosa.