In Vitro and In Vivo Antidiabetic, α-Glucosidase Inhibition and Antibacterial Activities of Three Brown Algae, , , and , and a Red Alga, from the Persian Gulf.

Background: In recent decades, algae have attracted worldwide attention for their great biological activities, such as antidiabetic and antibacterial properties.

Objectives: We measured antibacterial and α-glucosidase inhibition potential of methanol and 80% methanol extracts of three brown algae species, , , and , and a red alga, , from the Persian Gulf coasts.

Methods: Antibacterial activity of the algal extracts was assessed by broth dilution method against three gram-negative and -positive bacteria, including , , ; , , and , respectively. Furthermore, the yeast's α-glucosidase inhibition of the algal extracts was measured via colorimetric assay. In addition, we investigated the beneficial effect of 80% MeOH extract of on the blood glucose levels in streptozotocin-induced diabetic rats.

Results: The MeOH extract of was the best antibacterial extract with MIC = 2.5 mg/mL against all bacterial strains except for . The MeOH and 80% MeOH extracts of and inhibited α-glucosidase at most with IC values of 12.70 ± 1.88 µg/mL and 13.06 ± 4.44 µg/mL, respectively. The oral gavage of extract in streptozotocin- (STZ-) induced diabetic rats resulted in decreasing their postprandial blood glucose levels. The algae and acarbose decreased blood glucose levels after sucrose administration in 60 minutes, compared to the non-drug-treated animals, with p values of 0.03 and 0.007, respectively.

Conclusions: Overall, due to the in vitro and in vivo antidiabetic potential of , we suggest the alga as a new source for the isolation and identification of potential antidiabetic and antibacterial compounds.