Potential Of Seaweeds As A Source To Develop Functional Foods

There has been a combined effort among biochemists, biologists, food technologists, and nutritionists to explore and utilize varying food sources of both terrestrial and marine origin to cater the demand from the consumers who eagerly look forward to have optimum nutrition through their dietary interventions. Further, they quest for health benefits associated with these food sources knowing the current need for molecules with novel modes of action to face emerging diseases, seeking proactive approach than ''firefighting'' with medical interventions. When considering the sustainability of different sources, photosynthetic algae are the most heterogeneous group of organisms and considered the true survivors of the planet as they have been capable of facing the dramatic changes in climatic conditions for centuries and to occupy virtually all niches on earth with a ubiquitous distribution. Seaweeds are taxonomically classified as algae and they belong to four major seaweed classes, the rhodophyceae (red algae), the phaeophyceae (brown algae), the cyanophyceae (blue-green algae), and the chlorophyceae (green algae). A greater diversity in biochemical composition of seaweeds paves the path to explore variety of compounds in their bodily composition with a wide range of physiological and biochemical characteristics, many of which are rare or absent in other taxonomic groups (Holdt and Kraan, 2011).

Knowing the benefits associated with the seaweeds through the experience, seaweed has been used as an important dietary component for centuries in countries like China, Japan, and Korea. However, seaweeds are attracting increasing attention as a valuable food source in other parts of Asia, Africa, and also other western parts of the world, and growing interest is developing to explore all possible seaweed interventions including functional food product development. For this purpose, several countries other than China, Japan, and South Korea have commercially exploited open and closed cultivation systems to grow seaweeds at large scale. These countries are expected to increase culturing of seaweeds dramatically over the years to come. Further advances in science and technology have provided researchers the required know-how and powerful analytical tools to better characterize the physiological roles of bioactive compounds from seaweeds in disease prevention and health promotion. Research currently underway at academic, industry, and government facilities will reveal how a myriad of substances from seaweed sources can be used as functional food products. Moreover, growing consumer interest in functional foods developed using marine sources has been seen as a significant business opportunity for the agri-food sector, and among them, greater potentials exists to promote the utilization of seaweeds in the functional food industry. Recognizing the market potential for functional foods, a number of firms all over the world have begun to capitalize on these emerging markets.

III. BIOCHEMICAL COMPOSITIONAL ANALYSIS OF SEAWEEDS THAT CATER TO THE POTENTIAL OF SEAWEEDS AS A SOURCE TO DEVELOP FUNCTIONAL FOODS

Scientific reports dealing with functional effects of seaweed proteins, peptides, amino acids, polysaccharides, phytochemicals, lipids, and minerals greatly endorse the efforts toward development of ''health foods'' using seaweeds. Table 1.1 provides some seaweed species studied and recognized for their richness in functionally important molecular groups. Evaluation of functional properties requires a clear idea about their biochemical composition, and it provides a platform to have an inspiration to decide on the molecules responsible for different biological activities.

A. Seaweed proteins, peptides, and amino acids

Percentage of proteins in seaweeds varies from about 10% to 40% (w/w) per dry weight, and it varies according to the season and the species (Murata and Nakazoe, 2001). Red algae are rich sources of proteins compared to other divisions of algae. Among the proteins present in

TABLE 1.1 Seaweed species studied for their richness in specific bioactive compounds

Bioactive compound(s)

Total polysaccharides

Carrageenan Agar

Algins/alginic acid Fucoidan

Laminarin Ulvan

Total protein Lectins

Phycobilliproteins Taurine

Kanoids (kainic and domoic acid)

PUFA (o-3 fatty acids)

Phlorotannins

Carotenoids

Iodine

Calcium

Vitamin Bj2

Source: Holdt and Kraan (2011).

Seaweed species

Saccharina latissima, Sargassum pallidum

Chondrus crispus, Eucheuma cottonii Gracilaria cornea, Gracilaria domingensis Laminaria digitata, Laminaria hyperborea Fucus vesiculosus, Ascophyllum nodosum

Fucus vesiculosus, Laminaria hyperborea Ulva lactuca, Ulva rigida Undaria spp., Sargassum spp. Ulva sp., Eucheuma amakusaensis Palmaria palmata, Gracilaria tikvahiae Saccharina latissima, Porphyra tenera Palmaria palmata, Digenea simplex Laminaria digitata, Saccharina latissima Ascophyllum, Fucus spp. Laminaria digitata, Fucus serratus Laminaria japonica, Laminaria digitata Porphyra tenera, Ulva lactuca Ulva lactuca, Porphyra tenera seaweeds, lectins, a group of hemagglutinin proteins that bind with carbohydrates, have captured the interest of researchers due to their ability to take part in host-pathogen interactions, cell-cell communication, recognizing and binding carbohydrates and to exert functional effects to induce apoptosis, metastasis, and cell differentiation in cancer cells, antibiotic, anti-inflammatory, anti-human immunodeficiency virus (anti-HIV) activity, and human platelet aggregation inhibition (Hori et al., 2000; Mori et al, 2005; Smit, 2004).

Other than the lectins, phycobilliproteins (phycocyanins and allphy-cocyanins) are popular for their potency to exert functional effects in the mode of anti-inflammatory, liver protecting, antiviral, antitumor, anti-atherosclerosis, lipase activity inhibitor, serum lipid reducing agent, and antioxidant, and to obstruct absorption of environmental pollutants into the body (Sekar and Chandramohan, 2008). Seaweed peptides obtained through the enzymatic digestion process have shown several biological activities including antioxidant, antimicrobial, antithrombotic, immuno-modulatory, and mineral binding activity (Smit, 2004). These peptides are inactive in the amino-acid sequence of the parental protein and become active upon release through the enzymatic digestion. In vitro and in vivo studies that have been carried out using water extracts of seaweeds have confirmed that dipeptides in extracts are capable of acting against hypertension through inhibition of angiotensin I converting enzyme (Sato et al., 2002).

The free amino-acid fraction of seaweed is a mixture of amino acids and is mainly composed of taurine, alanine, amino butyric acid, omithine, citrulline, and hydroxyproline (Holdt and Kraan, 2011). Taurine is an amino acid present in high concentration in red algae. It also acts as an antioxidant and protects against toxicity of various heavy metals such as lead and cadmium by preventing their absorption in the stomach. Taurine has been shown to be effective in reducing the secretion of serum lipids and apolipoprotein B100, a structural component of low density lipoproteins, thereby reducing the risk of atherosclerosis and coronary heart disease. These finding have been followed and supported by several other research reports that taurine supplementation exerted a hypocho-lesterolemic effect in young overweight adults. Taurine has also shown its capability to relieve complications in people with congestive heart failure by increasing the force and effectiveness of heart-muscle contractions (Lourenco and Camilo, 2002; Mochizuki et al., 1999). The kainoid amino acids, kainic, and domoic acids have also been found in numerous algal species. They act as central nervous system stimulants upon exceeding the safe levels and become neurotoxins. These compounds are currently used in research associated with neurophysiological disorders such as Alzheimer's and Parkinson's disease and epilepsy (Harnedy and FitzGerald, 2011).

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