What are the skin benefits of Spirodela polyrhiza?

Redness, itching, minor skin irritations... The signs of skin inflammation are numerous. There are reasons to believe that duckweed might alleviate them. Several studies have shown that this active ingredient is capable oflowering the levels of inflammatory cytokines, such as tumor necrosis factor alpha, interleukin-6, and interferon-γ. The Spirodela polyrhiza also inhibits the infiltration and degranulation of mast cells, thus reducing the skin's allergic and inflammatory responses. Finally, this extract from the water lentil helps to restore certain skin barrier proteins, like filaggrin, sirtuin-1, and claudin-1, which are essential for maintaining healthy and resilient skin.

There are a few studies that have shown that spirodela can reduce the symptoms of atopic dermatitis, an inflammatory skin condition characterized by redness, skin dryness, and varying degrees of itching. Although these studies were conducted on mice and not humans, which limits their applicability, they provide an interesting initial insight. One study, in particular, involved 100 mice in which eczema was induced using 2,4-dinitrochlorobenzene (DNCB). The application of solutions with varying concentrations of Spirodela polyrhiza (1 to 100 mg/mL) allowed for a dose-dependent decrease in serum levels of immunoglobulin E, antibodies associated with eczema. A decrease in mast cell infiltration, as well as the expression of pro-inflammatory cytokines (IL-4, IL-6, TNF-α), was also recorded.

By modulating the release of pro-inflammatory mediators, the Spirodela polyrhiza can help to alleviate skin irritations.

Spirodela appears to be a relevant active ingredient for protecting the skin against free radicals. As a reminder, these are unstable compounds naturally generated during metabolism but also following exposure to UV rays or pollution. Their number is normally regulated through antioxidant enzymes present in the skin, but sometimes these can be overwhelmed. Free radicals then have free rein to oxidize lipids, proteins, and DNA in cells, thus promoting the occurrence of certain chronic diseases, as well as premature skin aging.

Studies highlighting the antioxidant properties of Spirodela polyrhiza are still scarce. However, we can mention the work carried out by JANG and his team in 2009 on human HaCaT keratinocytes. The addition of a methanol extract of Spirodela polyrhiza at 50 and 400 µg/mL in the culture medium showed a significant protective effect against 500 µM of hydrogen peroxide (H2O2). The spirodela not only allowed the cells to survive but also significantly inhibited the release of the enzyme lactate dehydrogenase and DNA fragmentation by H2O2. It also demonstrated free radical scavenging activities, notably of DPPH and superoxide radicals. It would be interesting for more work to be done to better understand the antioxidant effects of spirodela, but this study is encouraging.

It is known that sun exposure can be harmful to the skin, ranging from simple redness to melanomas and carcinomas, including varying degrees of sunburn. However, the sun's impact on the skin doesn't stop there and can also result in premature skin sagging accompanied by brown spots. This is referred to as photoaging. There are reasons to believe that duckweed could help prevent this phenomenon. Indeed, in addition to its antioxidant effects, which are already useful for delaying the appearance of wrinkles, this active ingredient could have tightening and depigmenting effects.

Researchers aimed to evaluate in vitro several biological parameters related to skin sagging and hyperpigmentation. They measured the ability of the spirodela to stimulate pro-collagen synthesis, inhibit the activity of the proteolytic enzyme MMP-1, involved in the degradation of dermal collagen, reduce melanin synthesis, and lower the activity of tyrosinase, a key enzyme in melanogenesis. The scientists focused on two 25 µg/mL solutions of spirodela, called SE and SEE. SE is an extract obtained with a hydroalcoholic solution (70% ethanol). It contains compounds soluble in water and alcohol. SEE corresponds to a fraction of SE, specifically extracted using ethyl acetate, an organic solvent. This fractionation step allows for the isolation of only semi-polar compounds, often more biologically active. The results obtained by the researchers are presented in the table below and show interesting tightening and depigmenting effects of the Spirodela polyrhiza.