W.A.J.P. Wijesinghe

In vitro and in vivo antioxidant activities of polysaccharide purified from aloe vera (Aloe barbadensis) gel

The in vitro and in vivo antioxidant potentials of a polysaccharide isolated from aloe vera gel were investigated. Enzymatic extracts were prepared from aloe vera gel by using ten digestive enzymes including five carbohydrases and five proteases. Among them, the highest yield was obtained with the Viscozyme extract and the same extract showed the best radical scavenging activity. An active polysaccharide was purified from the Viscozyme extract using ethanol-added separation and anion exchange chromatography. Purified aloe vera polysaccharide (APS) strongly scavenged radicals including DPPH, hydroxyl and alkyl radicals. In addition, APS showed a protective effect against AAPH-induced oxidative stress and cell death in Vero cells as well as in the in vivo zebrafish model. In this study, it is proved that both the in vitro and in vivo antioxidant potentials of APS could be further utilized in relevant industrial applications.

Dieckol isolated from brown seaweed Ecklonia cava attenuates type ІІ diabetes in db/db mouse model.

In the present study, the attenuation of type ІІ diabetes by dieckol, a phlorotannin derivative isolated from brown seaweed, Ecklonia cava was investigated in C57BL/KsJ-db/db, a type ІІ diabetes mouse model. Dieckol was administered intraperitoneal injection at doses of 10 and 20 mg/kg body weight diabetes mice for 14 days. The blood glucose level, serum insulin level and body weight were significantly reduced in the dieckol administered group, compared to that of the saline administered group. Furthermore, reduced thiobarbituric acid reactive substraces (TBARS), as well as increased activities of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-px) in liver tissues were observed in the dieckol administered group. In addition, increased levels of the phosphorylation of AMPK and Akt were observed in the muscle tissues of the dieckol administered group in a Western blotting analysis. According to the findings of this study, it could be suggested that, dieckol can be developed as a therapeutic agent for type ІІ diabetes.

Protective effect of marine algae phlorotannins against AAPH-induced oxidative stress in zebrafish embryo

In this study the protective effect of phlorotannins, including phloroglucinol, eckol, dieckol, eckstolonol and triphloroethol A, isolated from brown algae Ecklonia cava was investigated against AAPH-induced oxidative stress toxicity in zebrafish embryos. Zebrafish embryos were exposed to AAPH and compared with other groups that were co-exposed with phlorotannins until 2-days post-fertilisation. All phlorotannins scavenged intracellular ROS and prevented lipid peroxidation and reduced AAPH-induced cell death in zebrafish embryos. Negative changes in morphological phenomena, such as pericardial oedema, yolk sac oedema, and growth retardation in zebrafish embryos exposed to AAPH were not observed in groups exposed to phlorotannins. These results clearly indicate that phlorotannins possess prominent antioxidant activity against AAPH-mediated toxicity and might be potential therapeutic agents for treating or preventing several diseases implicated with oxidative stress. This study provides a useful tool for examining the protective effect of antioxidants against AAPH-induced oxidative stress in an alternative in vivo model.

Anticancer activity and mediation of apoptosis in human HL-60 leukaemia cells by edible sea cucumber (Holothuria edulis) extract

Sea cucumbers have been a dietary delicacy and important ingredient in Asian traditional medicinal over many centuries. In this study, edible sea cucumber Holothuria edulis was evaluated for its in vitro anticancer potential. An aqueous fraction of the edible sea cucumber (ESC-AQ) has been shown to deliver a strong cytotoxic effect against the human HL-60 leukaemia cell line. An induction effect of apoptotic body formation in response to ESC-AQ treatment was confirmed in HL-60 cells stained with Hoechst 33342 and confirmed via flow cytometry analysis. The up regulation of Bax and caspase-3 protein expression was observed while the expression of Bcl-xL protein was down regulated in ESC-AQ treated HL-60 cells. Due to the profound anticancer activity, ESC-AQ appears to be an economically important biomass fraction that can be exploited in numerous industrial applications as a source of functional ingredients.

Assessment of anti-inflammatory effect of 5β-hydroxypalisadin B isolated from red seaweed Laurencia snackeyi in zebrafish embryo in vivo model

5β-Hydroxypalisadin B, a halogenated secondary metabolite isolated from red seaweed Laurencia snackeyi was evaluated for its anti-inflammatory activity in lipopolysaccharide (LPS)-induced zebrafish embryo. Preliminary studies suggested the effective concentrations of the compound as 0.25, 0.5, 1 μg/mL for further in vivo experiments. 5β-Hydroxypalisadin B, exhibited profound protective effect in the zebrafish embryo as confirmed by survival rate, heart beat rate, and yolk sac edema size. The compound acts as an effective agent against reactive oxygen species (ROS) formation induced by LPS and tail cut. Moreover, 5β-hydroxypalisadin B effectively inhibited the LPS-induced nitric oxide (NO) production in zebrafish embryo. All the tested protective effects of 5β-hydroxypalisadin B were comparable to the well-known anti-inflammatory agent dexamethasone. According to the results obtained, 5β-hydroxypalisadin B isolated from red seaweed L. snackeyi could be considered as an effective anti-inflammatory agent which might be further developed as a functional ingredient.

Investigation of the component of Lycopodium serratum extract that inhibits proliferation and mediates apoptosis of human HL-60 leukemia cells.

In this study, we investigate a plant commonly used in herbal medicines, Lycopodium serratum, which is believed to have anti-cancer properties. An alcoholic extract of L. serratum (LSE) was investigated for its ability to induce apoptosis in cultured human promyelocytic leukemia HL-60 cells. Treatment of HL-60 cells with various concentrations of LSE (6-100 μg/mL) resulted in a sequence of events characteristic of apoptosis, including loss of cell viability, morphological changes, and increased sub-G(1) DNA content. Serratenediol (SE), a known biologically active agent, was isolated from MC fraction of LSE and was able to demonstrate significant and dose-dependent growth inhibitory effects on HL-60 cells. Similar to the effects observed with the crude LSE, the SE-related effects included the formation of apoptotic bodies and fragmented DNA, as well as the accumulation of DNA in the sub-G(1) phase of the cell cycle. Analysis of the mechanism of these events indicated that SE treated cells had an increased ratio of Bax/Bcl-xL, released the cytochrome c, activated caspase-9, -3, and cleaved poly-ADP-ribose polymerase (PARP); these observations are hallmarks of apoptotic events. Thus, the results suggest that SE can induce apoptosis via regulating the ratio of Bax/Bcl-xL in HL-60 cell lines.

Octaphlorethol A isolated from Ishige foliacea prevents and protects against high glucose-induced oxidative damage in vitro and in vivo.

We investigated the protective effect of octaphlorethol A (OPA) isolated from Ishige foliacea against high-glucose-induced oxidative damage, as indicated by reactive oxygen species (ROS) generation, lipid peroxidation, and cell death, in human umbilical vein endothelial cells (HUVECs) and in a zebrafish model. OPA treatment significantly and dose-dependently decreased ROS generation, lipid peroxidation, and cell death in HUVECs and in a zebrafish model. Our results show that OPA can protect HUVECs and zebrafish against high glucose by suppressing intracellular ROS generation, lipid peroxidation, and cell death.