Sword bean (Canavalia gladiata) utilization as an alternative forage to source of bioactive compounds

Sword beans (Canavalia gladiata) are legumes which are easily found in Indonesia. Although its origin is uncertain, it is likely that sword beans are introduced plants. This is because these plants are not found in Indonesia's primary forests, but their distribution is concentrated near residential areas. Taxonomic records state that the type of swordnut found in Java is believed to be a type of cultivation.

When viewed stature, sword beans have morphological characters that are quite aesthetic as an ornamental plant. The flowers are white and fragrant, so they can attract butterflies and bees. The large and thick fruit size is very striking among the rounded and thin leaves. On the other hand, the red seeds contrast with the green color of the sword bean leaves. Sword bean seeds are also larger in size than bean seeds in general, reaching 3 x 2 cm with a thickness of 1.3 cm.

Sword beans including plants that are very rarely used. Not only in Indonesia, even in the world. Despite having large seeds with nutritional content equivalent to soy, not many people use swordnut seeds as food. One reason is the content of "toxic" compounds in the seeds that are difficult to remove. It takes at least 5-6 days to process sword bean seeds for safe consumption. With consideration of the long processing duration, the utilization of sword beans began to be abandoned. But who would have thought if sword beans could still be used as alternative animal feed?

Sword bean seeds consist of two main parts, namely the seed coat and cotyledons. Seed coat contains high anti-nutrient compounds, so only cotyledons are used as animal feed. Anti-nutrient compounds are compounds that can inhibit the absorption of nutrients and minerals in the body. These obstacles will cause nutrient deficiency. In contrast to nutrient compounds, which are the main compounds needed for growth and development, such as carbohydrates, proteins, and fats.

The content of nutrient compounds in swordnut seeds is very high, although it is quite varied. These variations are caused by varieties and differences in environmental factors in which they grow. Sword bean seeds contain at least 25.5 - 29.2% protein. The protein content is high and is in the average range of peanut protein content. Most of the protein in swordfish is canavalin, the main protein reserve in the seeds of the genus Canavalia.

The content of fiber, carbohydrates, and fat is also very varied. Fiber in sword bean seeds ranges from 3.47 - 10.2%, carbohydrates as much as 37 - 61.8%, and as much as 1.6 - 9.9% fat. Sword beans also contain high non-nitrogenous (BETN) extract, which is 54.61 - 62%. BETN is a class of carbohydrates with high digestibility and a good source of energy for livestock. This causes the BETN content to be one of the considerations of superior animal feed. And this proves that sword bean seeds are very potential to be developed as superior animal feed.

If the nutrient compounds cause sword nuts have the potential to be developed as animal feed, it is different from the content of anti-nutrient compounds. Basically, anti-nutrient compounds are secondary metabolites produced by plants. The metabolite can be in the form of food reserves, structural components, even as a defense mechanism. This causes sometimes the anti-nutrient compounds cause interference to the human body.

Anti-nurtrient compounds can be found in the skin and seed cotyledons. In red seed coat, there are various antioxidant compounds, especially polyphenols. Some of these polyphenols are even potentially used in the nutraceutical and food industries such as digalloyl hexoside, methyl gallate, gallic acid, trigalloyl hexoside, and digallic acid. So, seed coat which cannot be used as animal feed turns out to be used as a source of bioactive compounds.

In swordfish cotyledons, anti-nutrient compounds are found in the form of lectins, non-protein amino acids, and various antioxidant compounds. Lectins are a group of proteins that interact with specific types of carbohydrates. Lectins are widely used to study specific glycoprotein interactions. Even lectins in sword beans can be used as haematological markers in leukemia.

Lectins in seeds will interact complementary with non-protein amino acids (such as aminobutryric acid) in the defense mechanism against pathogens. Non-protein amino acids are an essential component of legume seeds. The content of non-protein amino acids reaches 10% of the dry weight of the seeds, which physiologically also acts as a store of nitrogen reserves to support seed growth when sprouting.

Seeing the high potential of sword bean seeds, it's time we glance at the use of sword beans in industry and animal husbandry. The seeds can be used as animal feed, while the seed skin is used as a source of bioactive compounds. Leaves from sword beans can also be used as animal feed. Of course, the use of these leaves must be based on research into the content of nutrients and anti-nutrients in the leaves. In other words, almost all organs of this plant can be utilized. Coupled with the aesthetic morphological character of this plant makes it suitable for planting in the yard of the house.

Publication:

Wijaya IMS, Suarna IW. 2020. Karakter morfologis kacang pedang (Canavaliagladiata (Jacq.) DC: Fabaceae) dan potensinya sebagai pakan ternak. PASTURA9(2): 114—119.

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