“Out of this nettle – danger – we pluck this flower – safety.” — William Shakespeare
When I think of nettles, I remember an observation one of my student classmates at John Bastyr College shared with me that he had learned in an undergraduate botany class. Stinging nettles (Urtica spp.) have fine hairs on the leaves and stems that contain irritating chemicals, which are released when the plant comes in contact with the skin. When a forest is disturbed by fire the first plants that grow in the burnt, broken underbrush are nettles. Nettles are renowned for their stinging ability. In fact Roman soldiers in Northern England used to rub their legs with nettle to cause flushing and ward off the cold northern winds. My friend’s botany teacher saw this as a perfect example of Gaia, the concept of the Earth as a living organism: The fast-germinating nettles act like barbed wire, preventing animals from rooting around in the disturbed area until it could begin to regenerate itself.
Nettle leaves have a long history as a potherb. They can be sautéed, or par-boiled in salted water, and have a taste beween spinach (perhaps with a bit more of an ‘iron’ taste) and arugula (bit more peppery). The leaves have a long history of use in herbal medicine, where it has been used for osteoarthritis and skin inflammations. Nettle capsules can be used to reduce sneezing and itching in people with hay fever, and this likely constitutes its most frequent modern use.
Nettle root also has medicinal usage, predominantly for benign prostatic hypertrophy, where it is thought that elements in the root reduce symptoms such as frequent urination. It may be because it contains chemicals that affect hormones (including testosterone and estrogen) by interacting with sex hormone binding globulin (SHBG).
The root also possesses what I consider one of the most interesting plant lectins, known as Urtica Dioica Agglutinin (UDA). UDA is known in immunology as a superantigen, a lectin that induces cell growth and division (clonal activation). When these lectins induce specific white blood cells to multiply, they are known as mitogens . Many plant lectins are mitogens; Poke Weed (Phytolacca spp.) and Jimson Weed (Datura spp.) come to mind, but UDA is unique. It activates CD8+ T cells (often called cytotoxic T lymphocytes, or CTLs), which are very important for our immune defense against intracellular pathogens, including viruses and bacteria.
Which brings us this blog. For all intents and purposes, UDA lectin has properties that may make it worthy of consideration as an anti-coronavirus agent. It has been studied and shown to possess antiviral activity against HIV, CMV, RSV, H1N1 and SARS-CoV.
Two targets of possible antiviral intervention were identified in the replication cycle of SARS-CoV. The first target is located early in the replication cycle, most probably viral attachment, and the second target is located at the end of the infectious virus cycle. This study also showed that UDA was a potent and selective inhibitor of SARS-CoV strain Frankfurt-1.
Plant lectins like UDA probably target viral attachment and fusion, and its eventual exit (exocytosis or egress) from the cell. In an article entitled ‘Ready, Set, Fuse! The Coronavirus Spike Protein and Acquisition of Fusion Competence’ the authors noted that lectins such as UDA do not affect binding of the S-protein to the ACE2 receptor, but rather seem to inhibit viral entry at some undefined later stage.
In a separate study UDA lectin was tested for efficacy in lethal SARS-CoV-infected mice. All virus-infected mice receiving UDA treatments were also significantly protected against weight loss and had effectively reduced lung pathology scores. At day 6 after virus exposure, all groups of mice receiving UDA had much lower lung weights than did the placebo-treated mice, which indicates that their lungs were not filling up with liquids. The authors concluded that UDA inhibited severe acute respiratory syndrome (ARDS) associated with coronavirus replication. However, when UDA was exposed to the amino sugar N-acetylglucosamine the UDA lectin did not inhibit the virus infection.
UDA was reported to inhibit coronaviruses in vitro with some selectivity in mice. The researchers concluded that UDA was a potent and selective inhibitor of SARS-CoV strain Frankfurt-1. The reduction of IL6 in lungs along with 50% survival of mice in this study was thought to provide evidence to support further investigation of UDA treatment regiments as potential antiviral therapies.
So what’s the take home message for the man (and woman) in the street? I think nettle root may have significant benefit as a potential safe, low cost and readily available traditional medicine for Covid-19. Health authorities should include this traditional medicine in the evaluation panels exploring potentially effective treatments for Covid-19. Nettle root can obviously be found in its native form and simply lightly cooked and used with the greens as a potherb, or can be purchased as a nutritional supplement from any number of vendors. We would need to insure that the formula was from the root. A sure sign that the supplement contains the root would be a claim that the formula was useful for ‘prostate health’.
As with all medicines, natural or otherwise, please consult with experts who are experienced in their actions, interactions, contraindications and potential side effects before starting this or any other supplement program.