COVID-19 News: Taiwanese Study Shows That The Natural Tannins Oligomeric Proanthocyanidins And Punicalagin Inhibit SARS-CoV-2!
Phytochemicals from Grape Seeds and Pomegranates can prevent SARS-CoV-2!
: The COVID-19 pandemic, which emerged in late 2019, has had an enduring impact on societies worldwide. While vaccines have been developed and administered on a global scale, breakthrough infections in vaccinated individuals continue to pose challenges. The emergence of new SARS-CoV-2 variants, notably the omicron variant, has raised concerns about the effectiveness of current vaccines. As such, exploring alternative strategies for preventing SARS-CoV-2 infections has become increasingly crucial.
Serum from the human subjects who intake grape seed extractants had better potency to block the entry of wild-type and different variant Vpps. (A). The schematic illustrates the timeline of blood collection. First, the baseline blood sample was collected before taking control or grape seed extract (GSE) capsules. After baseline blood sample collection, the human subjects were randomized to one of three groups to take the GSE capsule (200 mg or 400 mg), or the placebo and collected the blood at the indicated time. (B–F) Each serum sample from the human subjects was diluted 1/200 and premixed with wild-type or different variants of SARS-CoV-2 spike Vpps for 1 hr before incubation with 293T-ACE2 cells. After 24 hr of infection, the infection efficiency rate was measured according to luciferase activities. All data are shown as mean ± SD (n = 5). The p-values are indicated by asterisks, *p<0.05; **p≤0.01; ***p≤0.001; ****p≤0.0001; n.s., no statistical significance.
Previous studies made a significant breakthrough by discovering that tannic acid, a natural compound belonging to the tannin family, exhibited the ability to block key proteins necessary for SARS-CoV-2 entry and replication within human cells. Numerous COVID-19 News
reports had covered these studies concerning the use of tannins or tannic acid to inhibit SARS-CoV-2 and to treat COVID-19.
These revelations prompted further investigations into whether other tannin derivatives, specifically oligomeric proanthocyanidins (OPCs) and punicalagin, might also possess inhibitory properties against SARS-CoV-2.
The study team from the China Medical University-Taiwan conducted experiments to assess the inhibitory effects of tannic acid, OPCs, and punicalagin on SARS-CoV-2 infection in cultured human cells. Their findings unveiled that all three tannin compounds exhibited the capacity to suppress the critical proteins required for viral entry and replication, albeit to varying degrees. Furthermore, these compounds demonstrated the ability to inhibit various SARS-CoV-2 variants, including the highly transmissible omicron variant, in laboratory cell cultures.
One particularly interesting discovery was that water extracted from grape seeds, rich in OPCs, could effectively block SARS-CoV-2 entry in cell cultures. To substantiate these findings, the study team conducted a supplementary experiment involving 18 healthy individuals who were given capsules containing grape seed extract. The results showed that serum samples collected from these individuals after taking the extract had a notable suppressive effect on the entry of various SARS-CoV-2 variants in cell cultures. These collective findings strongly suggest that natural tannins, particularly OPCs, punicalagin, and grape seed extract, have the potential to act as potent inhibitors of SARS-CoV-2 infection, offering a promising avenue for infection prevention.
Tannins: Nature's Defense Against SARS-CoV-2
The SARS-CoV-2 virus initiates infection by binding to host cells through the interaction between its Spike (S) protein and the cell surface receptor ACE2 (angiotensin-converting enzyme 2). Additionally, the cellular protease TMPRSS2 (transmembrane serine protease 2) primes the S protein, facilitating viral fusion with the host cell membrane. Inhibition of these key processes can effectively thwart viral infection.
Previous research had already demonstrated that tannic acid, a member of the tannin family, could inhibit the activity of TMPRSS2 and Mpro, two critical proteins involved in the SARS-CoV-2 infection process. Tannic acid belongs to the broader family of tannins, which includes hydrolysable tannins, condensed tannins, phlorotannins, and complex tannins. Hydrolysable and condensed tannins are commonly found in terrestrial plants, including fruits and vegetables.
In this study, the study team sought to investigate whether other tannin derivatives, such as OPCs and punicalagin, also possessed anti-SARS-CoV-2 properties.
The results of their experiments indicated that tannic acid, OPCs, and punicalagin exhibited inhibitory effects on SARS-CoV-2 infection. These compounds, while sharing common inhibitory mechanisms, demonstrated variations in their potency, suggesting diverse modes of action. Additionally, all three tannin compounds displayed the ability to block various SARS-CoV-2 variants from infecting cultured cells, including the omicron variant, which has raised concerns due to its immune evasion capabilities.
Grape Seed Extract: A Natural Source of Inhibitory Tannins
A particularly intriguing discovery in this study was the inhibitory potential of water extracted from grape seeds. Grape seeds are known to contain high levels of OPCs, which are a type of condensed tannin. The experiments revealed that this grape seed extract effectively hindered SARS-CoV-2 entry into cells in laboratory settings. To explore this further, the study team conducted an additional experiment involving human subjects who were given grape seed extract capsules. The results demonstrated that the serum samples from these individuals exhibited a dose-dependent suppressive effect on the entry of various SARS-CoV-2 variants in cell cultures.
These findings suggest that grape seed extract, as a natural source of OPCs, could serve as a valuable dietary supplement for preventing SARS-CoV-2 infections. This potential prophylactic option presents a promising alternative to vaccination, particularly as vaccine effectiveness against certain SARS-CoV-2 variants, like omicron, wanes over time.
Safety and Feasibility of Grape Seed Extract Supplementation
Crucially, the safety and feasibility of grape seed extract supplementation were also addressed in the study. Previous research has established that grape seed extract is generally safe for consumption and well-tolerated by humans, with no reported side effects at commonly used doses. Moreover, grape seed extract has been investigated for its beneficial effects on various health conditions, including inflammation, cardiovascular disease, hypertension, diabetes, cancer, peptic ulcers, and microbial infections.
The study findings, along with previous safety assessments, underscore the potential of daily grape seed extract supplementation as a means of enhancing protection against SARS-CoV-2 infection. While frequent vaccination may not be a sustainable or affordable option in the long term, incorporating grape seed extract into one's daily dietary regimen appears to offer a safe and practical approach to bolstering immunity against the virus.
Conclusion: Harnessing Natural Tannins for SARS-CoV-2 Prevention
The study has shed light on the inhibitory properties of natural tannins, specifically OPCs and punicalagin, against SARS-CoV-2 infection. Building upon previous research that highlighted the potential of tannic acid, this study extends our understanding of how tannin derivatives can serve as potent inhibitors of the virus.
Notably, grape seed extract, rich in OPCs, emerges as a compelling dietary supplement with the capacity to reduce the risk of SARS-CoV-2 infections. Given the ongoing challenges posed by emerging SARS-CoV-2 variants and the waning efficacy of existing vaccines, the findings from this study offer a valuable contribution to the development of dietary strategies and supplements for infection prevention.
In a world where SARS-CoV-2 is unlikely to vanish completely, harnessing the protective potential of natural tannins, readily available in common fruits and supplements like grape seed extract, could play a pivotal role in safeguarding public health. Further research and clinical trials are warranted to fully explore and validate the effectiveness of tannin-based interventions in the fight against COVID-19.
The study findings were published in the peer reviewed journal: Medicine, Microbiology and Infectious Disease (eLife).
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