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Polypodium leucotosum: the tropical plant that protects us from photodamage

When summer arrives we need to do our best to protect our skin to avoid serious damage.

We should all be aware that the sun, even though it gives us such a pleasant feeling, can also be dangerous.

The main type of radiations we should worry about are the UV rays (UVR): with wavelengths between 100nm and 400nm, these radiations can reach our skin causing several issues.

We can’t see them, as we do with visible light, but we can perceive them.


It is true that the sun has some beneficial effects too: it allows us to synthesize vitamin D, induces the release of endorphins, has a bactericidal activity on our skin and ameliorates some disorders such as psoriasis [1].

However, the negative effects caused by UV are multiple and severe: sunburn, erythema, pigmentation, skin aging (such as wrinkles), immune suppression and skin cancer [3].



So, what could we use to protect ourselves?


There are different measures for protecting us from the negative aspects of the UVR, but in this article, we will talk about a traditional herbal remedy that could come in our help.


The plant

Polypodium leucotosum (PL) is a tropical fern from Central and South America of the family of Polypodiaceae. This plant has been used in traditional medicine to treat many inflammatory disorders of the skin, such as atopic dermatitis and psoriasis. However, this fern has recently raised deep interest for its photoprotective capacity, thanks to its antioxidant and anti-inflammatory properties [4].

Thanks to its qualities, it has demonstrated to be useful to counteract the skin photodamage (the harm due to the sunlight) through multiple mechanisms [5].


Chemical composition

The extract is obtained from the aerial parts of the fern. The main active principles are phenolic compounds, such as benzoates and cinnamates, acid molecules like shikimic and malic acids, together with an abundance of ferulic acid, caffeic acid, vanillic and chlorogenic acid.

The richness in polyphenols confers to this plant an incredible antioxidant and antinflammatory activity.

Due to this strong antioxidant power, also antimutagenic and antitumoral properties are under study. Both caffeic and ferulic acid prevent peroxidation, responsible of the chain reaction generating free radicals, though protecting cell membranes [6]. Furthermore, ferulic acid has an intrinsic ability of absorbing UV-photons and in synergism with caffeic acid helps in skin protection from erythema [7].


Mechanism of action

Polypodium leucotomus antioxidant activity is mainly due to ROS (reactive oxygen species) and RNS (Reactive nitrogen species) diminution with the inhibition of lipidic peroxidation. Moreover, it inhibits the photoisomerization of trans-urocanic acid, inhibits the apoptosis UVRs induced, have an immunomodulatory action, and finally has a double action reducing the DNA damage and enhancing the DNA repair [8]. This antioxidant capacity is directly proportional to the concentration of the extract [6].


In vitro and in vivo studies

Many studies showed both the topical and systemic application of Polypodium leucotosum extract, in vitro and in vivo (in animals and humans).

In vitro studies confirmed that PL can stop the death of fibroblasts and keratinocytes induced by UVA (UVR type A), enhance the membrane integrity together and reduce proteases release [9].


A study in mice demonstrated that the oral administration of the extract before and after irradiation with UVR increased the quantity of p53 (the protein guardian of the genome) and strengthened the elastic fibers in the dermis [10].


Furthermore, topical photoprotection was investigated with interesting results. Hamsters with topical application of PL before irradiation showed almost complete photoprotection from UVB (UVR type B). Similar results were obtained in human volunteers irradiated with UVA [8].

In addition, topical application in mice decreased inflammatory infiltrate and the number of vessels induced by UVR [8].


PL was tested in different group of human volunteers in oral and systemic administration to evaluate its possible applications, showing outstanding outcomes in healthy people but also in patients with vitiligo, psoriasis, melasma and photodermatosis. In all these clinical studies, Polypodium leucotomos demonstrated to be a safe and effective treatment to counteract the several damages induced by UVR:

· decreasing the inflammation,

· decreasing sun burn and erythema

· preventing hyperpigmentation

· reducing the lesions

· normalizing the skin

· In vitiligo patients, it ameliorates the repigmentation [8].


Preclinical and clinical studies seem to confirm the beneficial action of Polypodium leucotosum, which for this reason has been introduced in these years in topical sunscreen and nutraceuticals that are mainly recommended in summer to people that already experienced skin cancer or other dermatological diseases, to increase the protection and reduce the possible damage due to the UV light.

No mutagenicity and genotoxicity have been observed, so this plant is up to now considered safe at the dose suggested in oral and topical formulations.


Have you ever heard about this plant? Do you know that it is present in some famous sun care brands? Now you have learnt more about this.


And remember… Use always the sunscreen!







Here an infographic we did about sun protection:



Sitography





Bibliography


1. D'Orazio J, Jarrett S, Amaro-Ortiz A, Scott T. UV radiation and the skin. Int J Mol Sci. 2013 Jun 7;14(6):12222-48. doi: 10.3390/ijms140612222. PMID: 23749111; PMCID: PMC3709783.


2. Kemény L, Varga E, Novak Z. Advances in phototherapy for psoriasis and atopic dermatitis. Expert Rev Clin Immunol. 2019 Nov;15(11):1205-1214. doi: 10.1080/1744666X.2020.1672537. Epub 2019 Oct 1. PMID: 31575297.


3. Gonzaga ER. Role of UV light in photodamage, skin aging, and skin cancer: importance of photoprotection. Am J Clin Dermatol. 2009;10 Suppl 1:19-24. doi: 10.2165/0128071-200910001-00004. PMID: 19209950.


4. Berman B, Ellis C, Elmets C. Polypodium Leucotomos--An Overview of Basic Investigative Findings. J Drugs Dermatol. 2016;15(2):224-228.


5. Pourang, Aunna et al. “The potential effect of Polypodium leucotomos extract on ultraviolet- and visible light-induced photoaging.” Photochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology vol. 20,9 (2021): 1229-1238. doi:10.1007/s43630-021-00087-x


6. Gombau L, Garcı´a F, Lahoz A, Fabre M, Roda-Navarro P, Majano P, Alonso-Lebrero JL, Pivel JP, Castell JV, Go´mez-Lechon MJ, Gonzalez S (2006) Polypodium leucotomos extract: antioxidant activity and disposition. Toxicol In Vitro 20:464–471.


7. Saija A, Tomaino A, Lo Cascio R et al (1999) Ferulic and caffeic acids as potencial protective agents against photooxidative skin damage. J Sci Food Agric 79:476–480


8. Palomino OM. Current knowledge in Polypodium leucotomos effect on skin protection. Arch Dermatol Res. 2015 Apr;307(3):199-209. doi: 10.1007/s00403-014-1535-x. Epub 2014 Dec 25. PMID: 25539991.


9. Philips N, Smith J, Se´ller T, Gonzalez S (2003) Predominant effect of Polypodium leucotomos on membrane integrity, lipid peroxidation expression of elastin and matrixmetalloproteinase-1 in ultraviolet radiation exposed fibroblasts, and keratinocytes. J Dermatol Sci 32:1–9


10. Rodríguez-Yanes E, Juarranz A, Cuevas J, Gonzalez S, Mallo J (2012) Polypodium leucotomos decreases UV-induced epidermal cell proliferation and enhances p53 expression and plasma antioxidant capacity in hairless mice. Exp Dermatol 21:630–642


11. Murbach, Timothy S et al. “A comprehensive toxicological safety assessment of an aqueous extract of Polypodium leucotomos (Fernblock(®)).” Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association vol. 86 (2015): 328-41.


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