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Archives (2004)

The bright potential of the sea cucumber by Likha C. Cuevas

April-June 2004 Volume 6 No. 2

Sea Cucumber

I never thought that the 'thing' I've stepped on in Matabungkay when I was a kid would be very important to humankind one day. I just know that this bottom-dweller, filter feeder is anything but beautiful.

Little did I know that the ugly sea cucumber I unwittingly killed has a cancer-fighting agent in its long body. Scientists from the University of the Philippines Los Baños (UPLB) found that lectin in the body walls and internal organs of brown, black, and white sea cucumbers (Holothuria sp.) has the potential to kill cancer cells. Aleli Elizabeth E. Gana and Florinia E. Merca purified and characterized the lectin found in the brown sea cucumber since it has the highest agglutination activity. Agglutination is the clumping together of cells due to the binding of agglutinin molecules (like lectin) on each cell's surface, clumping, mitosis-multiplication or division of a cell forming two daughter cells.

What is lectin?
According to Jun Hirabayashi of Teikyo University, lectins are, “proteins which specifically bind (or crosslink) carbohydrates.” Lectins bind to sugar moieties (one of two equal parts) in cell walls or membranes and thereby change the physiology of the membrane to cause agglutination, mitosis, or other biochemical changes in the cell. As of today, lectins found in animals, according to Hirabayashi, are not potential toxins to humans as some plant counterparts are.

Some lectins from plant sources have some therapeutic value to human immunodeficiency virus (HIV). Lectins activate proliferation and enhance the mitogenic (cell division) activity of lymphocytes (group of white blood cells that fight infections or diseases). Lectins are also used as prognostic indicators of the presence of tumors and may also be involved in the neutralization and exclusion of disease-causing agents (like virus or bacterium).

Such is the importance of lectins to the medical world that these glycoproteins already command high prices in the world market. Even if many lectins are already purified and sold commercially in the country, we still have to import it at US$ 25-150 per milligram.

At that price, we have to source out lectin locally.

The beauty of sea cucumber
According to Gana and Merca, organisms from the sea are potential sources of lectins. “The reason for recommending sea cucumber for treatment of some diseases may be attributed to its lectin content,” they said.

We won't have to worry about sea cucumber supply since the Philippines is now the second major producer and exporter of dried sea cucumber in the world. The study done by the State Polytechnic College of Palawan mentioned that harvesting and processing of sea cucumbers into trepang (edible sea cucumbers) has been a source of income for many Filipino families.

Holothurians are collected during low tide, mainly during the night. They are collected by hand while walking along the inter-tidal zone with a lamp. It is mainly the women who collect sea cucumbers from shallow areas, while the men skin dive or use an air-compressor connected to a breathing hose to reach deeper areas,” the study described.

Promising cucumber lectins
Gana and Merca determined the potential of sea cucumber as lectin source. They isolated these glycoproteins and purified them. Later, they determined its chemical and biological properties.

Results showed that sea cucumber lectin has 0.15% total sugars, 11% glucose, 10% galactose, and 74% oligosaccharide mixture that contains sucrose and maltose.

Gana and Merca found that cucumber lectin is non-blood type-specific because it agglutinated all the human blood types (A, B, AB, and O). It also agglutinated with cattle and goat erythrocytes (red blood cells). “It is classified as a complete lectin because it does not require prior treatment or the red blood cells with trypsin (an enzyme that breaks down proteins into smaller polypeptide units) to exhibit lectin activity,” the research team said.

The lectin has mitogenic activity on lymphocytes. “Three-day incubation of the lymphocytes with the lectin resulted in the formation of lymphoblasts (immature lymphocytes),” Gana and Merca observed. The study also revealed that lectin can also kill mouse cancer cells (cytotoxic) and human lung cancer cells.

Given these beneficial things that cucumber lectin can do to the medical world, there's really more to the 'ugly' sea cucumber than meets the eye.

References:
1) Gana, Aleli Elizabeth E. and Merca, Florinia E. Isolation and purification of a cytotoxic lectin from brown sea cucumber by affinity chromatography. The Philippine Agricultural Scientist. Vol. 85, No.3, 236-247;2) Schoppe, Sabine Sea cucumber fishery in the Philippines. State Polytechnic College of Palawan, Aquatic Science and Technology Institute, Santa Monica, Puerto Princesa City, Palawan, Philippines; 3) Hirabayashi, Jun. Introduction to "Lectin". Teikyo University. www.glycoforum.gr.jp
4) Sullivan, Krispin. Lectin Report. www.krispin.com

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