Antidiabetic and antioxidant activity of phlorotannins extracted from the brown seaweed Cystoseira compressa in streptozotocin-induced diabetic rats

Diabetes mellitus is considered a set of diseases that lead to high glucose level due to the absolute or relative absence of insulin. The study investigated the antioxidant activity and antidiabetic effect of phlorotannins extracted from brown seaweed Cystoseira compressa. Phlorotannins were extracted from C. compressa. It was confirmed by 2,4 dimethoxy benzaldehyde assay (DMBA), ultraviolet spectra, Fourier transform infrared spectroscopy, and ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The free radical scavenging activity of phlorotannins was estimated by total antioxidant capacity, 1,1-diphenyl-2-picrylhydrazyl radical-scavenging activity, and 2,2 azino-bis3-ethylbenthiazoline-6-sulfonic acid assays. Four groups of albino rats used in this study include control normal, control phlorotannins extract, diabetic by intraperitoneally administering of streptozotocin, and diabetic treatment with 60 mg/kg of phlorotannin extract after 4 weeks of diabetes induction. The main compound identified by UPLC-MS/MS in C. compressa extract belonged to the fuhalol. C. compressa extract showed high antioxidant properties. Phlorotannins significantly decreased serum glucose, liver malondialdehyde, and α-amylase, glucosidase activities. However, total antioxidant capacity, serum insulin, hepatic glutathione, and AMPKα2 expression in skeletal muscle were improved compared to the diabetic group. The histopathological examination showed that phlorotannins markedly reduced damage in β cells of pancreases. Phlorotannins from C. compressa have efficient antioxidant activity and the antidiabetic effect that may be utilized in human health.

Phytochemical Analysis and Evaluation of the Antioxidant, Anti-Inflammatory, and Antinociceptive Potential of Phlorotannin-Rich Fractions from Three Mediterranean Brown Seaweeds

Phlorotannins, phenolic compounds produced exclusively by seaweeds, have been reported to possess various pharmacological properties. However, there have been few works on these compounds from Mediterranean seaweeds. In this study, we investigated the phytochemical analysis and pharmacological potential of phlorotannin-rich fractions from three brown seaweeds collected along the Tunisia coast: Cystoseira sedoides (PHT-SED), Cladostephus spongeosis (PHT-CLAD), and Padina pavonica (PHT-PAD). Phytochemical determinations showed considerable differences in total phenolic content (TPC) and phlorotannin content (PHT). The highest TPC level (26.45 mg PGE/g dry material (Dm)) and PHT level (873.14 μg PGE/g Dm) were observed in C. sedoides. The antioxidant properties of these three fractions assessed by three different methods indicated that C. sedoides displayed the highest total antioxidant activity among the three species (71.30 mg GAE/g Dm), as well as the free radical scavenging activity with the lowest IC50 value in both DPPH (27.7 μg/mL) and ABTS (19.1 μg/mL) assays. Furthermore, the pharmacological screening of the anti-inflammatory potential of these fractions using in vivo models, in comparison to reference drugs, established a remarkable activity of PHT-SED at the dose of 100 mg/kg; the inhibition percentages of ear edema in mice model and paw edema in rats model were of 82.55 and 81.08%, respectively. The content of malondialdehyde (MDA) in liver tissues has been quantified, and PHT-SED was found to remarkably increase the lipid peroxidation in rat liver tissues. In addition, in two pain mice models, PHT-SED displayed a profound antinociceptive activity at 100 mg/kg and has proved a better analgesic activity when used in combination with the opioid drug, tramadol.