Purification of fucoxanthin from Sargassum wightii Greville and understanding the inhibition of angiotensin 1-converting enzyme: An in vitro and in silico studies.

The isolation and purification of active components from the brown algae Sargassum.wightii is highly limited. In the present study, fucoxanthin was purified from S. wightii using simple methods. Ethyl acetate fraction obtained by Soxhlet extraction contained high concentration of fucoxanthin. Fucoxanthin-rich fraction was further subjected to open silica column chromatography and thin layer chromatography to obtain purified fucoxanthin. Purified fucoxanthin showed in vitro antioxidant activity. Fucoxanthin showed inhibition of angiotensin I-converting enzyme (ACE) with half maximal inhibitory value of 822.64 ± 17.69 μM. Kinetic analysis revealed mixed non-competitive inhibition with inhibitory constant of 600 μM for fucoxanthin against ACE. Molecular docking analysis showed the interaction of fucoxanthin with amino acids and zinc ion present in the active site of the human ACE. Molecular dynamics analysis demonstrated the stability of the fucoxanthin and ACE complex in in silico. These results show that S. wightii may be used as food ingredient to overcome hypertension.