In Vitro and In Vivo Antidiabetic, α-Glucosidase Inhibition and Antibacterial Activities of Three Brown Algae, Polycladia myrica, Padina antillarum, and Sargassum boveanum, and a Red Alga, Palisada perforata 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, Polycladia myrica, Padina antillarum, and Sargassum boveanum, and a red alga, Palisada perforata, 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 Escherichia coli, Klebsiella pneumonia, Pseudomonas aeruginosa; Staphylococcus epidermidis, Staphylococcus aureus, and Bacillus subtilis, 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 S. boveanum on the blood glucose levels in streptozotocin-induced diabetic rats. Results: The MeOH extract of S. boveanum was the best antibacterial extract with MIC = 2.5 mg/mL against all bacterial strains except for E. coli. The MeOH and 80% MeOH extracts of P. myrica and P. antillarum inhibited α-glucosidase at most with IC50 values of 12.70 ± 1.88 µg/mL and 13.06 ± 4.44 µg/mL, respectively. The oral gavage of S. boveanum 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 S. boveanum, we suggest the alga as a new source for the isolation and identification of potential antidiabetic and antibacterial compounds.

Comparison of inhibitory activities of 50 Salvia species against α-Glucosidase.

Objectives: Type 2 diabetes is a common metabolic disease affecting millions of people worldwide. α-Glucosidase inhibitors can be used as one of the therapeutic approaches to decrease the postprandial glucose levels through the inhibition of carbohydrate hydrolysis. Medicinal plants are one of the main sources of α-glucosidase's natural inhibitors. In this study, we report the inhibitory effects of 50 different accessions of 32 Salvia species against α-glucosidase. Methods: To estimate the relative potency of the crude extracts, the inhibitory activities of the 80% methanol of the plants extracts were determined in three different concentrations (1000, 500 and 250 µg/ml) and compared to that of acarbose as the positive control. Results: S. multicaulis, S. santolinifolia, S. dracocephaloides, and S. eremophila were stronger inhibitors than acarbose (p < 0.05) with IC50 values in the range of 26.23- 92.35 µg/mL. According to the LC-PDA-ESIMS and NMR analysis of crude extracts of the studied Salvia species, 8 phytochemicals including luteolin-7-O-glucoside (1) luteolin-7-O-glucuronide (2), apigenin-7-O-glucoside (3), apigenin-7-O-glucuronide (4), Hispidulin-7-O-glucuronide (5), hispidulin-7-O-glucoside (6), rosmarinic acid (7), carnosol (8) and carnosic acid (9) were identified as the most common α-glucosidase inhibitors. The above compounds constituted the major compounds in the active Salvia species in the range of 1.5-95.0%. Among them rosmarinic acid (39-95%) was detected in almost all potent α -glucosidase inhibitor species. Therefore, it can be considered as a biochemical marker in the antidiabetic Salvia species in addition to the other minor compounds. Conclusions: Considering the high α-glucosidase inhibitory potential of the four- out of fifty Salvia species, they are suggested for further in vivo antidiabetic tests as potential medicinal plants.

Antidiabetic and cytotoxic polyhydroxylated oleanane and ursane type triterpenoids from Salvia grossheimii.

Two polyhydroxylated oleanane and seven ursane triterpenoids were isolated from aerial parts of Salvia grossheimii. The chemical structures of the undescribed triterpenoids (1-6) were characterized using 1 and 2 D NMR and ESI-MS spectral data as; 2α, 3ß, 11α -trihydroxy-olean-12- ene (1), 2α, 3ß, 11α-trihydroxy-olean-18-ene (2), 2α- acetoxy-urs-12-ene-3ß, 11α, 20ß-triol (3), 3-keto-urs-12-ene-1ß, 11α, 20ß -triol (4), 2α, 3ß-diacetoxy-urs-12-ene-1ß, 11α, 20ß -triol (5), and 3ß-acetoxy-urs-12-ene-1ß, 11α, 20ß -triol (6). All compounds were evaluated for the in vitro α-glucosidase inhibitory and cytotoxic activities against MCF-7 human cancer cell line. Compounds 1, 2, 4, and 6 showed in vitro α-glucosidase inhibitory activity with IC50 = 43.6-198.4 µM, which were more potent than the antidiabetic medicine, acarbose. The remaining compounds; 3, and 7-9 showed potent cytotoxic activity (IC50 = 6.2-31.9 µM) against the cancerous cell line, while the potent α-glucosidase inhibitors were inactive. Molecular docking analysis and kinetic studies were applied to investigate the structure activity relationships and mechanisms of the human and Saccharomyces cerevisiae α-glucosidase inhibitory of the purified compounds. Comparing the high cytotoxicity and α-glucosidase inhibitory of the oleanane and ursane type triterpenoids suggest them as potential lead compounds for further research in anticancer and antidiabetic research.