FCC Horiuchi Co., Ltd. based in Kurume City, Fukuoka Prefecture, western Japan, has conducted an experiment in inhibiting binding between ACE2 and virus spike protein using HORIUCHI L-FUCOIDAN, manufactured by the company, in collaboration with a graduate school of Kyushu University (Associate Professor Kuniyoshi Shimizu of Division of Sustainable Bioresources Science, Department of Agro-Environmental Sciences, Faculty of Agriculture).

Angiotensin Converting Enzyme II (ACE2) provides a foothold when COVID-19 and SARS viruses enter human cells. If the binding of viral spike protein to ACE2 can be inhibited, viruses cannot enter human cells, and so the protective effect against COVID-19 can be expected.

Figures courtesy of Kyushu University

Originally, fucoidan is a high-molecular-weight polysaccharide, but HORIUCHI L-FUCOIDAN is a low-molecular-weight fucoidan which is composed of 500 or less molecular weight by the company's original technique. To evaluate whether fucoidan inhibits the binding of ACE2-virus spike protein, a kit containing ACE2 and coronavirus spike protein was used. L-FUCOIDAN or H-FUCOIDAN (high molecular weight) was incubated together with ACE2 and virus spike protein and the binding inhibition activity was measured.

L-FUCOIDAN showed approximately 100% ACE2-virus spike protein binding inhibition activity at 1.15 mg/mL (left side of the figure below). On the other hand, H-FUCOIDAN (high molecular weight) showed about 20 to 30% of binding inhibition activity in all the tested concentrations. It did not show as much inhibition activity as L-FUCOIDAN (right side of the figure below).