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. Objectives: 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 1H‑NMR, 13C‑NMR and mass spectroscopy. In vitro alpha‑amylase inhibitory test was performed on the methanolic extract and the results revealed a potent inhibition (IC₅₀ = 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.