Isuru Wijesekara

Biological activities and potential health benefits of bioactive peptides derived from marine organisms

Marine organisms have been recognized as rich sources of bioactive compounds with valuable nutraceutical and pharmaceutical potentials. Recently, marine bioactive peptides have gained much attention because of their numerous health beneficial effects. Notably, these peptides exhibit various biological activities such as antioxidant, anti-hypertensive, anti-human immunodeficiency virus, anti-proliferative, anticoagulant, calcium-binding, anti-obesity and anti-diabetic activities. This review mainly presents biological activities of peptides from marine organisms and emphasizing their potential applications in foods as well as pharmaceutical areas.

Phlorotannins from Ecklonia cava (Phaeophyceae): Biological activities and potential health benefits

The importance of bioactive derivatives as functional ingredients has been well recognized due to their valuable health beneficial effects. Therefore, isolation and characterization of novel functional ingredients with biological activities from seaweeds have gained much attention. Ecklonia cava Kjellman is an edible seaweed, which has been recognized as a rich source of bioactive derivatives mainly, phlorotannins. These phlorotannins exhibit various beneficial biological activities such as antioxidant, anticancer, antidiabetic, anti‐human immunodeficiency virus, antihypertensive, matrix metalloproteinase enzyme inhibition, hyaluronidase enzyme inhibition, radioprotective, and antiallergic activities. This review focuses on biological activities of phlorotannins with potential health beneficial applications in functional foods, pharmaceuticals, and cosmeceuticals.

Conotoxins Targeting Nicotinic Acetylcholine Receptors: An Overview

Marine snails of the genus Conus are a large family of predatory gastropods with an unparalleled molecular diversity of pharmacologically active compounds in their venom. Cone snail venom comprises of a rich and diverse cocktail of peptide toxins which act on a wide variety of ion channels such as voltage-gated sodium- (NaV), potassium- (KV), and calcium- (CaV) channels as well as nicotinic acetylcholine receptors (nAChRs) which are classified as ligand-gated ion channels. The mode of action of several conotoxins has been the subject of investigation, while for many others this remains unknown. This review aims to give an overview of the knowledge we have today on the molecular pharmacology of conotoxins specifically interacting with nAChRs along with the structure–function relationship data.

Physcion from marine-derived fungus Microsporum sp. induces apoptosis in human cervical carcinoma HeLa cells.

Recently, the relationship between apoptosis and cancer has been emphasized and the induction of apoptosis is recognized as one of the key mechanisms of anti-cancer agents. Marine-derived fungi are valuable sources of structurally diverse bioactive anticancer agents. In the present study, a marine-derived fungus, Microsporum sp. was cultured and an anthraquinone derivative, physcion (11.8 mg) was isolated from the culture broth extract (1710 mg). Physcion has shown cytotoxic effect on human cervical carcinoma HeLa cells and its apoptosis induction in HeLa cells was investigated by the expressions of p53, p21, Bax, Bcl-2, caspase-9, and caspase-3 proteins. The Western blot analysis has revealed that physcion could significantly induce cell apoptosis through down-regulating of Bcl-2 expression, up-regulating of Bax expression, and activating the caspase-3 pathway. Furthermore, physcion induced the formation of reactive oxygen species (ROS) in HeLa cells. Collectively, these results suggest that physcion could be a potential candidate in the field of anticancer drug discovery against human cervical cancer.

Protective effect of chitin oligosaccharides against lipopolysaccharide-induced inflammatory response in BV-2 microglia

Chitin oligosaccharides (NA-COS) of two different molecular weight ranges (below 1 and 1-3 kDa) were examined for their capabilities against lipopolysaccharide-induced inflammatory responses in BV-2 murine microglia. It was found that NA-COS reduced the level of nitric oxide (NO) and prostaglandin E(2) (PGE(2)) production by suppressing the expression of NO synthase (iNOS) and cyclooxygenase (COX)-2 without significant cytotoxicity. Furthermore, the inhibitory effects of NA-COS on generation of interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α were determined. Notably, NA-COS exerted anti-inflammatory activities via blocking degradation of inhibitor of kappaB-alpha (IκB-α), translocation of nuclear factor (NF)-κB, and phosphorylation of mitogen-activated protein kinases (MAPKs) in a dose-dependent manner. These findings provide mechanistic insights into the anti-inflammatory and neuroprotective actions of NA-COS in BV-2 microglia.

In Vitro and Intracellular Antioxidant Activities of Brown Alga Eisenia bicyclis

The antioxidant activities of a methanolic extract of Eisenia bicyclis and its organic solvent fractions, including dichloromethane (CH 2 Cl 2 ), ethyl acetate (EtOAc), n-butanol (n-BuOH), and water (H 2 O) fractions, were investigated. Scavenging activities against DPPH, hydroxyl, superoxide anion, and peroxynitrite radicals were evaluated using electron spin resonance spectrometry; intracellular reactive oxygen species (ROS) were evaluated by a 2′,7′-dichlorofluorescein diacetate assay using RAW264.7 mouse macrophages. The antioxidant activities of the individual fractions were: EtOAc>n-BuOH>CH 2 Cl 2 >H 2 O. The EtOAc fraction exhibited strong radical scavenging activity and a significantly reduced ROS level in RAW264.7 cells. Moreover, the phenolic con tents of the extract and fractions followed the same order as their radical scavenging activities. Our results indicate that E. bicyclis is a valuable natural source of antioxidants that may be applicable to the functional food industry.

Anticoagulant effect of marine algae.

Recently, a great deal of interest has been developed in the nutraceutical and pharmaceutical industries to isolate natural anticoagulant compounds from marine resources. Among marine resources, marine algae are valuable sources of novel bioactive compounds with anticoagulant effect. Phlorotannins and sulfated polysaccharides such as fucoidans in brown algae, carrageenans in red algae, and ulvans in green algae have been recognized as potential anticoagulant agents. Therefore, marine algae-derived phlorotannins and SPs have great potential for developing as anticoagulant drugs in nutraceutical and pharmaceutical areas. This chapter focuses on the potential anticoagulant agents in marine algae and presents an overview of their anticoagulant effect.