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Bio-active Compounds in Seaweeds

Macroalgae, better known as ‘seaweed’, represent a sustainable source of nutrients and biologically active compounds for food and feed. The bioactive compounds which are present in seaweed have been extensively studied and have demonstrated interesting functional properties that are beneficial for both human and animal health. These bioactive compounds include structural/storage polysaccharides, amino acids and proteins, pigments, lipids and polyphenols. Studies have demonstrated that these compounds have a number of biological activities including anti-viral, anti-microbial, anti-fungal, ACE-inhibitory, anti-inflammatory, anti-adhesion, anti-oxidant and anti-cancer activity.

Obesity: How seaweed can help reduce it!

Based on 2008 figures, the World Health Organisation estimates that 1 in 10 of the world’s population is obese. This fact is a significant concern given that some cancers as well as a number of musculoskeletal and cardiovascular diseases are associated with being either overweight or obese. There is evidence for a similar trend in pets where one American study found that over 34% of adult dogs were either overweight or obese. Similar to humans, obese dogs are more likely to be diagnosed with hypothyroidism, diabetes mellitus, pancreatitis, ruptured cruciate ligament, or neoplasia (Lund, 2006).

Fucoxanthin and Obesity

There is scientific evidence to suggest that fucoxanthin, a carotenoid pigment that is found in brown seaweed, has anti-obesity activity and thus helps to protect against numerous diseases. A study by Woo et al. (2009) investigated the anti-obesity effects of fucoxanthin on obese mice over a six week period. This study found that inclusion of fucoxanthin at levels lower than 0.2% resulted in a reduced body weight when compared to the group that was not supplemented with fucoxanthin. This anti-obesity activity arises due the fact that fucoxanthin down-regulates the mRNA and protein expression of lipid-regulating enzymes and uncoupling proteins in adipose tissue and also because it decreases fatty acid beta-oxidation activity (Maeda et al., 2005; Woo et al., 2009).

Alginates and Obesity

Alginates are another group of seaweed-derived compounds that can act as an anti-obesity agent. In a 12 week randomised controlled trial 96 obese adults were provided with either an alginate-based supplement or a placebo while on an energy-restricted diet. The authors of this study reported a significantly larger reduction in body fat percentage and a decrease in body weight for the group that received the alginate supplementation. This supports the findings of other studies that have reported anti-obesity, cholesterol-lowering and/or anti-diabetic activity of seaweed alginates (Zee et al. 1991; Kimura et al., 1996; Awang et al 2014).

Anti-cancerous Bio-active Compounds

Cancer is a disease that is characterised by the growth of abnormal cells in any part of the body. According to the World Health Organisation, around 8.2 million people died from cancer in 2012. In domestic pets such as dogs, cancerous tumours are similar to those which occur in humans and thus and will have a similar response to cancer treatments (Paoloni and Khanna, 2008). A number of seaweed-derived compounds have been studied for their anti-cancer activity. These bioactive compounds include polysaccharides (alginic acid, carrageenan, agar, fucoidan, laminarin) various peptides and proteins (particularly lectins and phycobiliproteins), polyphenols and carotenoids such as fucoxanthin and β-carotene (Holdt and Kraan, 2011).

Interesting seaweed-derived compounds for anti-cancer applications include the polysaccharides fucoidan and ascophyllan as well as the carotenoid fucoxanthin. These compounds are found at relatively high levels in brown seaweeds such as Laminaria digitata, Fucus vesiculosus and Fucus serratus. Fucoidan is a sulphated polysaccharide that has been shown in a number of studies to mediate the apoptosis (cell death) of cancer cells via the up-regulation and/or down-regulation of certain signalling pathways. Scientists are currently investigating the in vivo anti-cancer activity of fucoidan to investigate the will be essential for its potential use as a marine drug (Kwak, 2014).

Ascophyllan: Promising Signs

Another sulphated polysaccharide, ascophyllan, extracted from the seaweed Ascophyllum nodosum has shown promising anti-cancer activity both in vitro and in vivo. In a recent study using mice, Jiang et al., (2014) found that oral administration of ascophyllan reduced tumour size by an average of 68.7% when compared to mice which received no seaweed extract.

Fucoxanthin: Anti-Cancerous Activities

Fucoxanthin is a xanthophyll carotenoid that has been studied extensively for its’ anti-cancer activity. As a result, the anti-carcinogenic action of fucoxanthin and its derivative fucoxanthinol has been demonstrated both in vitro and in vivo. So far, scientists have discovered that fucoxanthin acts as an anti-cancer agent by influencing the activity and expression of Bcl-2 proteins, mitogen-activated protein kinases, transcription factors and other enzymes in a specific manner.The net effect of this activity is to reduce the growth rate and number of tumours (Kumar, 2013).

Polyphenols

Seaweed-derived polyphenols, such as phlorotannins, have also been investigated by scientists as a potential anti-cancer agent. For example, Corona et al. (2014) reported that digested and fermented phlorotannins that were obtained from the brown seaweed Ascophyllum nodosum reduce DNA damage and inhibit growth of colon cancer cells in vitro. Polyphenols are interesting bioactive compounds which can help to prevent cardiovascular diseases, cancers, arthritis and autoimmune disorders by helping to protect tissues against oxidative stress as discussed below.

Anti-oxidants: Eliminate those troublesome free radicals!

Oxidative stress occurs in the body when there is an excess of reactive oxygen species (ROS) and is highly toxic to cells. Excess ROS is associated with a number of diseases including cancer, atherosclerosis, malaria, rheumatoid arthritis and neurodegenerative diseases (Aruoma, 1998). Consequently, the anti-oxidant activity of seaweed has received much attention in recent years and research has shown that some seaweed extracts have superior anti-oxidant activity when compared to synthetic anti-oxidants (Baboa et al., 2013).

Anti-Oxidant Compounds

Seaweed represents an excellent source of anti-oxidant compounds including but not limited to pigments (chlorophylls and carotenoids), vitamins, phenolic compounds, phospholipids, terpenoids and peptides (Holdt and Kraan, 2011). The anti-oxidant activity has been investigated mainly by in vitro experiments focusing on seaweed-derived phenolic compounds, carotenoids, sulphated polysaccharides and proteinaceous compounds such as phycobiliproteins.

Sargassum muticum as an Anti-Oxidant

For example, seaweed extract from the genus Sargassum has recently been shown to prevent the proliferation of cancer cells and this activity was directly related to the polyphenol content of the extract (Namvar, 2013). The authors of this study concluded that the polyphenol-rich seaweed has great potential in cancer research due to its ability to induce apoptosis and its anti-oxidant activity. A protein pigment found in red seaweeds, phycocyanin, has also demonstrated anti-oxidant activity and has been shown to inhibit lipid oxidation by cupric chloride in plasma samples (Sekar and Chandramohan, 2008).

The anti-oxidant activity of sulphated polysaccharides from the brown seaweed Fucus vesiculosus has also been demonstrated (Ruperez, 2002) and such activity may help in the prevention of conditions associated with oxidative stress such as Alzheimer’s disease and the ageing process (Holdt and Kraan, 2011).

Reinforce and Stimulate the immune system!

A number of seaweed species have demonstrated anti-bacterial and/or anti-viral activity. Seaweed extracts derived from Laminaria digitata, Chondrus chrispus, Ulva lactuca, Sargassum spp., Fucus serratus, and Ascophyllum nodosum have demonstrated biological activity against a number of bacteria including Proteus vulgaris, Streptococcus pyogenes, Pasteurella piscicida, Escherichia coli and methicillin resistant Staphylococcus aureus (MRSA) (Kim et al., 2007; Holdt and Kraan, 2011).

Laminarian, Fucoidan and Carrageenan

In brown seaweeds, the polysaccharides laminarin and fucoidan have been reported to stimulate the immune system and protect against infection. For instance, in vivo studies have shown that laminarin, a seaweed-derived polysaccharide, promotes the primary antibody response in sheep (Yang et al. 1995). Studies have also shown that fucoidan and carrageenan, sulphated polysaccharides found in some brown and red seaweed, respectively, may inhibit viral replication and stimulate the immune system via a number of mechanisms (Wu et al. 2003). For instance, in a 2008 in vivo study, Hayashi et al. demonstrated that fucoidan protected mice from infection with the herpes simplex virus when administered orally over a three week period. The study revealed that fucoidan promoted the production of antibodies and increase survival rate in the animals. Recent research has also shown that carrageenan obtained from the red seaweed C. chrispus has great potential as an anti-viral agent, including blocking the transmission of the HIV virus and the herpes simplex virus (Holdt and Kraan, 2011).

Other Compounds

Seaweed also contains other compounds that are known to have important immune-stimulating roles including lectins, phycobiliproteins, vitamins, minerals (including iodine) and the anti-inflammatory omega-3 fatty acids which are considered to have a protective role against cardiovascular disease (Harnedy and FitzGerald, 2011; Mozaffarian and Wu, 2011).

The bioactive properties, combined with the significant levels of vitamins and minerals present in seaweed make it an excellent choice for inclusion in the diet of your pet.