Antiproliferative Effects of Fractionated Crude Lectins From Boiled Japanese Taro Tubers (Colocasia esculenta (L.) Schott)

ABSTRACT

Lectins are carbohydrate-binding proteins with diverse biological functions, including antitumor and immunomodulatory activities. Taro (Colocasia esculenta) tubers, commonly consumed in cooked form, are a potential bioactive lectin source; however, the effects of thermal processing on their functionality remain insufficiently understood.

This study investigated the biological profiles of lectins fractionated from both raw and boiled Japanese taro tubers (JTT). Lectins were fractionated using carboxymethyl-Sepharose and diethylaminoethyl-Sepharose chromatography, depending on their solubility following thermal treatment. To simulate dietary conditions, crude (unpurified) lectin fractions were analyzed directly without further purification. Hemagglutination assays revealed that lectins from both raw and boiled JTT recognized thyroglobulin and fetuin, while those from boiled JTT also exhibited specificity toward N-acetylneuraminic acid. Boiled JTT lectins demonstrated reduced protease resistance and mitogenic activity compared to raw fraction, though mitogenicity remained lower than that of concanavalin A in mouse splenocyte cultures. Lectins from both sources demonstrated notable antiproliferative activity against multiple cancer cell lines, including HepG2, HeLa, B16, LM8, and Ehrlich ascites cells. Boiled taro lectins showed better activity in some cases, which suggests that they still have some bioactivity after being heated. Even after undergoing some structural changes from boiling, their ability to cause clumping of red blood cells and their specific interaction with carbohydrates remained unchanged. This means that certain useful properties of taro lectins are still there. These results help us understand how we can use heated taro lectins as beneficial ingredients in medicine and functional foods.

Practical Application: Colocasia esculenta (L.) Schott is a tuberous monocotyledonous plant that grows in tropical and subtropical climates. Lectins from raw and boiled Japanese tubers showed specificity for thyroglobulin and fetuin. Moreover, lectins fractionated from boiled samples showed specificity for N-acetylneuraminic acid using mouse erythrocytes. They were resistant to proteases and exhibited antiproliferative activity against HepG2, HeLa, B16, LM8, and Ehrlich ascites cells. The crude fractions from raw and boiled tubers could stimulate splenocyte proliferation and inhibit TNF-α, IL-6, IL-1β, and COX-2 expressions. Thus, lectins from boiled tubers have the potential to be used as bioactive proteins in medical research.