Carbohydrate found in the Ecklonia kurome seaweed was found to block an enzyme's activity that's vital for the duplication of severe SARS-CoV-2, the agent that causes COVID-19. This has been found by researchers in China who have recently conducted a study.
Also named "Kun Bu" in this country, the seaweed has long been used as a medicinal or herbal plant in traditional Chinese medicine or TCM.
According to News Medical Life Sciences, the Beijing-based University of Chinese Academy of Sciences' Kan Ding and colleagues discovered that a "crude polysaccharide extracted from the seaweed completely blocked the activity of an enzyme" also known as 3C-like protease or 3CLpro.
Also identified as the central protease, 3CLpro is a type of enzyme found in coronaviruses responsible for splitting viral polyproteins that are vital for viral transcription and duplication.
The study investigators said, their research proposes that such a polysaccharide could function as a possible drug candidate to shield from COVID-19 infection. While it is currently undergoing peer review, a pre-print version of this research can be found on bioRxiv.
Infective SARS-CoV-2 Mechanisms
Since the onset of the pandemic in Wuhan, China on 2019, the study authors have been trying to understand this particular coronavirus type's infective mechanisms to help them create effective antiviral treatments.
Specifically, the researchers have established that the first step in SARS-Cov-2 infection needs a "surface viral structure" also known as the spike protein.
This particular structure is binding the host cell receptor angiotensin-converting enzyme 2 or ACE2, as well as its co-receptor heparan sulfate.
In this research, the researchers specified that the TCM Ecklonia kurome has a polysaccharide content with a sulfate group at its molecular chain's end, which may eventually confer substantial bio-activity.
In addition, the study authors suggested that if the co-receptor mentioned can bind to the spike protein, polysaccharides taking place in nature might bind too, to this protein and possibly block the infection of SARS-CoV-2.
Ecklonia Kurome Investigated
To examine if Ecklonia kurome can target 3CLpro too, the research team extracted from a seaweed, a biomacromolecule polysaccharide which they called 375, and investigated its activity against the latest coronavirus type.
They used infrared spectroscopy and nuclear magnetic resonance or NMR imaging to describe the 375 structure, including three others, the homogeneous polysaccharides which they called 37501, 37502, and 37503, "purified from the native 375" through the use of ion-exchange chromatography.
As a result, the study investigators found that 375 completely blocked the 3CLpro's enzyme activity. More so, in their paper, the researchers indicated that "the homogeneous polysaccharide 37502 bound to 3CLpro and potently disrupted spike - ACE2 binding."
Essentially, polysaccharide 375 showed strong activity against SARS-CoV-2, with a 99.9-percent viral inhibition rate, at a 20-µg/ mL concentration.
Further analysis found that 37501 and 37503 in habited SARS-CoV-2 activity as well, although, to a "much lesser degree" compared to the native polysaccharide 375. Surprisingly though, polysaccharide 37502 did not present any inhibitory effects on SARS-CoV-2.
Study Implications
According to the study authors, their findings suggest that the "heterogeneous polysaccharide 375 within Ecklonia kurome" works more efficiently at inhibiting SARS-CoV-2 compared to the "individual polysaccharides 37501, 37502, and 37503."
The research team suspected that the stronger effect observed for 375 may be because of the "cocktail-like polysaccharide exerting synergetic function" by means of targeting several key molecules linked to both virus infection and duplication.
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