Alpha-amylase inhibitory activity and sterol composition of the marine algae, Sargassum glaucescens

BACKGROUND: Sargassum species (phaeophyceae) are economically important brown algae in southern parts of Iran. Sargassum is mainly harvested as a row material in alginate production industries and is a source of plant foods or plant bio-stimulants even a component of animal foods. OBJECTIVE: In this study, Sargassum glaucescens, collected from the seashore of Chabahar, was employed for phytochemical and biological evaluations. MATERIALS AND METHODS: For that purpose, the dried algae was extracted by methanol and subjected to different chromatographic separation methods. RESULTS: Six sterols, fucosterol (1), 24(S)-hydroxy-24-vinylcholesterol (2), 24(R)-hydroxy-24-vinylcholesterol (3), stigmasterol (4), β-sitosterol (5) and cholesterol (6) were identified by spectroscopic methods including (1)H-NMR, (13)C-NMR and mass spectroscopy. In vitro alpha-amylase inhibitory test was performed on the methanolic extract and the results revealed a potent inhibition (IC(50) = 8.9 ± 2.4 mg/mL) of the enzyme compared to acarbose as a positive control. CONCLUSION: Various biological activities and distribution of sterols in Sargassum genus have been critically reviewed here. The results concluded that these algae are a good candidate for further anti-diabetic investigations in animals and human.