Samambaia

What Is Samambaia?

Samambaia is a tropical American fern whose standardised extracts are taken by mouth to help protect the skin from sun damage. It is sold under the name Polypodium leucotomos, and is also known as calaguala ^{34Reference 34Taylor · 2005The Healing Power of Rainforest Herbs}.

The fern grows on trees and palms from Florida through Central and South America ^{35Reference 35NaumanNauman, C. E. (n.d.). Phlebodium aureum (Linnaeus) J. Smith — species description, habitat and distribution — flora. In Flora of North America Editorial Committee (eds.), Flora of North America North of Mexico, Vol. 2 (Polypodiaceae). http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=233500905View study →}. Its creeping rhizome is the source of Anapsos, a Spanish pharmaceutical developed for psoriasis and vitiligo, and its fronds are the source of the modern extract Fernblock ^{9,34Reference 9Garcia et al. · 2006In vitroPhenolic components and antioxidant activity of Fernblock, an aqueous extract of the aerial parts of Polypodium leucotomos — in vitroView study →Reference 34Taylor · 2005The Healing Power of Rainforest Herbs}. In Latin American folk medicine a decoction of the rhizome and fronds is used for skin and respiratory complaints ^{34Reference 34Taylor · 2005The Healing Power of Rainforest Herbs}.

The extract is rich in phenolic acids such as caffeic and ferulic acid ^{8,9Reference 8Gombau et al. · 2006In vitroPolypodium leucotomos extract: antioxidant activity and disposition — in vitroView study →Reference 9Garcia et al. · 2006In vitroPhenolic components and antioxidant activity of Fernblock, an aqueous extract of the aerial parts of Polypodium leucotomos — in vitroView study →}. Trials have found that it raises the dose of UV light needed to cause sunburn and reduces UV damage in the skin, and it has been tested alongside standard treatments for melasma, vitiligo and actinic keratosis ^{4,5,17,20,22Reference 4González et al. · 1997RCTTopical or oral administration with an extract of Polypodium leucotomos prevents acute sunburn and psoralen-induced phototoxic reactions — randomisedView study →Reference 5Kohli et al. · 2017Clinical trialThe impact of oral Polypodium leucotomos extract on ultraviolet B response: a human clinical studyView study →Reference 17Goh et al. · 2018RCTDouble-blind, placebo-controlled trial to evaluate the effectiveness of Polypodium leucotomos extract in the treatment of melasma — randomisedView study →Reference 20Pacifico et al. · 2021RCTNB-UVB plus oral Polypodium leucotomos extract display higher efficacy than NB-UVB alone in patients with vitiligo — randomised placebo-controlledView study →Reference 22Pellacani et al. · 2023RCTThe combination of oral and topical photoprotection with a standardized Polypodium leucotomos extract for actinic keratosis — randomised controlledView study →}.

In the supplement trade the fern is also listed as Polypodium aureum ^{34Reference 34Taylor · 2005The Healing Power of Rainforest Herbs}, a name now placed in Phlebodium aureum, the golden polypody ^{35Reference 35NaumanNauman, C. E. (n.d.). Phlebodium aureum (Linnaeus) J. Smith — species description, habitat and distribution — flora. In Flora of North America Editorial Committee (eds.), Flora of North America North of Mexico, Vol. 2 (Polypodiaceae). http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=233500905View study →}.

How Is Samambaia Used?

• Fernblock — a standardised aqueous extract of the fronds, taken as capsules and also used in topical sun-protection products ^{9Reference 9Garcia et al. · 2006In vitroPhenolic components and antioxidant activity of Fernblock, an aqueous extract of the aerial parts of Polypodium leucotomos — in vitroView study →}.
• Anapsos — an older extract of the rhizome, developed in Spain for psoriasis and vitiligo ^{34Reference 34Taylor · 2005The Healing Power of Rainforest Herbs}.
• Decoction — rhizome and fronds, in Latin American folk medicine ^{34Reference 34Taylor · 2005The Healing Power of Rainforest Herbs}.

Traditional Uses

Latin American Folk Medicine

The rhizome and fronds have long been prepared as a decoction and used for a range of skin conditions and for upper-respiratory complaints ^{34Reference 34Taylor · 2005The Healing Power of Rainforest Herbs}.

The herb carries two principal common names: samambaia, chiefly in Brazil, and calaguala across most of Latin America ^{34Reference 34Taylor · 2005The Healing Power of Rainforest Herbs}.

Indications

• Sunburn prevention [frond extract, oral]
• Polymorphic light eruption and other sun-induced rashes [extract, oral] ⚠Caution: The supporting studies are open-label case series without a placebo group ^12,13,14.
• Melasma [extract, oral; with hydroquinone and sunscreen]
• Vitiligo [extract, oral; with phototherapy] ⚠Caution: In the first trial the main result was borderline (P = 0.06), and benefit has only been seen alongside phototherapy ^19,20.
• Actinic keratosis [extract, oral and topical; with standard care]
• Atopic dermatitis [extract, oral] ⚠Caution: In the one trial it did not reduce the use of steroid creams, though it reduced antihistamine use ²⁹.
• Psoriasis [rhizome extract; Anapsos]
• Skin and upper-respiratory complaints [rhizome and fronds; Latin American folk medicine]
• Mild dementia [rhizome extract; Anapsos] ⚠Caution: One small four-week pilot trial found improvement at 360 mg/day but not at 720 mg/day, and it has not been repeated ³⁰.

Botany

Samambaia is an epiphytic fern of the polypody family (Polypodiaceae). Its creeping rhizome is 8–15 mm thick, sometimes up to 30 mm, and densely covered in long, reddish to golden scales ^{35Reference 35NaumanNauman, C. E. (n.d.). Phlebodium aureum (Linnaeus) J. Smith — species description, habitat and distribution — flora. In Flora of North America Editorial Committee (eds.), Flora of North America North of Mexico, Vol. 2 (Polypodiaceae). http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=233500905View study →}.

The fronds are bright green or bluish-grey, arching to hanging, and 30–130 cm long. The blade is deeply cut into lance-shaped to linear segments, each 6–20 cm long ^{35Reference 35NaumanNauman, C. E. (n.d.). Phlebodium aureum (Linnaeus) J. Smith — species description, habitat and distribution — flora. In Flora of North America Editorial Committee (eds.), Flora of North America North of Mexico, Vol. 2 (Polypodiaceae). http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=233500905View study →}.

The spore clusters (sori) sit in a single line, occasionally two, on each side of the midrib of each segment ^{35Reference 35NaumanNauman, C. E. (n.d.). Phlebodium aureum (Linnaeus) J. Smith — species description, habitat and distribution — flora. In Flora of North America Editorial Committee (eds.), Flora of North America North of Mexico, Vol. 2 (Polypodiaceae). http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=233500905View study →}.

The golden polypody is a tetraploid fern, thought to have arisen from a cross between Phlebodium pseudoaureum and Phlebodium decumanum, a widespread tropical American species ^{35Reference 35NaumanNauman, C. E. (n.d.). Phlebodium aureum (Linnaeus) J. Smith — species description, habitat and distribution — flora. In Flora of North America Editorial Committee (eds.), Flora of North America North of Mexico, Vol. 2 (Polypodiaceae). http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=233500905View study →}. The fern sold as Polypodium leucotomos and the closely related P. decumanum account for almost all of the medicinal and research use ^{34Reference 34Taylor · 2005The Healing Power of Rainforest Herbs}.

Distribution

The golden polypody grows from Florida and Georgia through Mexico, the West Indies, and Central and South America ^{35Reference 35NaumanNauman, C. E. (n.d.). Phlebodium aureum (Linnaeus) J. Smith — species description, habitat and distribution — flora. In Flora of North America Editorial Committee (eds.), Flora of North America North of Mexico, Vol. 2 (Polypodiaceae). http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=233500905View study →}. It grows on trees, on logs and in deep humus, most often among the old leaf bases of cabbage palms (Sabal palmetto), in habitats from hammocks to swamps ^{35Reference 35NaumanNauman, C. E. (n.d.). Phlebodium aureum (Linnaeus) J. Smith — species description, habitat and distribution — flora. In Flora of North America Editorial Committee (eds.), Flora of North America North of Mexico, Vol. 2 (Polypodiaceae). http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=233500905View study →}.

Trade accounts give the Honduran rainforest as the home of the medicinal fern, from where it has spread through the Central American, South American and Caribbean tropics ^{34Reference 34Taylor · 2005The Healing Power of Rainforest Herbs}.

Growing Conditions

Cultivation snapshot for Samambaia

SunDappled sunlight to deep shadeWaterMoist but not soggySoilLoose, airy, acidic bark/epiphyte mixLifeperennialZoneUSDA 8-13 outdoors (a houseplant elsewhere)

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Pharmacology & Research

About twenty human studies have been published, including eleven randomised trials ^{2Reference 2Zundell et al. · 2025Systematic reviewThe utility of oral Polypodium leucotomos extract for dermatologic diseases: a systematic reviewView study →}. Almost all of them test standardised aqueous extracts: chiefly Fernblock, from the fronds, and the older Anapsos, from the rhizome ^{9,34Reference 9Garcia et al. · 2006In vitroPhenolic components and antioxidant activity of Fernblock, an aqueous extract of the aerial parts of Polypodium leucotomos — in vitroView study →Reference 34Taylor · 2005The Healing Power of Rainforest Herbs}.

The main use is oral photoprotection. Standardised extract raises the UV dose needed to cause sunburn and reduces UV damage in the skin ^{4,5,6Reference 4González et al. · 1997RCTTopical or oral administration with an extract of Polypodium leucotomos prevents acute sunburn and psoralen-induced phototoxic reactions — randomisedView study →Reference 5Kohli et al. · 2017Clinical trialThe impact of oral Polypodium leucotomos extract on ultraviolet B response: a human clinical studyView study →Reference 6Nestor et al. · 2015RCTSafety and efficacy of oral Polypodium leucotomos extract in healthy adult subjects — randomised placebo-controlledView study →}. Randomised trials have also tested it alongside standard treatments for melasma, vitiligo, actinic keratosis and atopic dermatitis ^{17,20,22,29Reference 17Goh et al. · 2018RCTDouble-blind, placebo-controlled trial to evaluate the effectiveness of Polypodium leucotomos extract in the treatment of melasma — randomisedView study →Reference 20Pacifico et al. · 2021RCTNB-UVB plus oral Polypodium leucotomos extract display higher efficacy than NB-UVB alone in patients with vitiligo — randomised placebo-controlledView study →Reference 22Pellacani et al. · 2023RCTThe combination of oral and topical photoprotection with a standardized Polypodium leucotomos extract for actinic keratosis — randomised controlledView study →Reference 29Ramírez-Bosca et al. · 2012RCTPolypodium leucotomos extract in atopic dermatitis: a randomised, double-blind, placebo-controlled trialView study →}.

The dementia and cancer work rests on one small pilot trial and on cell and animal studies ^{15,16,30Reference 15Zattra et al. · 2009AnimalPolypodium leucotomos extract decreases UV-induced Cox-2 expression and inflammation, enhances DNA repair in Xpc+/− mice — animal modelView study →Reference 16Manna et al. · 2003In vitroCalagualine inhibits nuclear transcription factor-κB activated by various inflammatory and tumour-promoting agents — in vitroView study →Reference 30Álvarez et al. · 2000RCTDouble-blind, randomised, placebo-controlled pilot study with anapsos in senile dementia — randomisedView study →}.

1. Photoprotection

In 21 healthy volunteers, oral extract raised the minimal erythema dose 2.8-fold, and also protected against psoralen-induced phototoxic reactions ^{4Reference 4González et al. · 1997RCTTopical or oral administration with an extract of Polypodium leucotomos prevents acute sunburn and psoralen-induced phototoxic reactions — randomisedView study →}.

In 22 volunteers, two doses of extract reduced UVB-induced skin changes: on clinical and colour measurements in 17, and on histology in all 22 ^{5Reference 5Kohli et al. · 2017Clinical trialThe impact of oral Polypodium leucotomos extract on ultraviolet B response: a human clinical studyView study →}.

In a 60-day placebo-controlled trial in healthy adults, 240 mg twice daily made sunburn episodes less likely and raised the minimal erythema dose, with no change in safety tests ^{6Reference 6Nestor et al. · 2015RCTSafety and efficacy of oral Polypodium leucotomos extract in healthy adult subjects — randomised placebo-controlledView study →}.

In an 8-week trial in 54 fair-skinned volunteers, a syrup combining the extract with red orange extract and vitamins A, C, D and E raised the minimal erythema dose by 23.8% and cut UVB redness by 46.2%. The fern’s own share of the effect cannot be separated from the other ingredients ^{7Reference 7Keršmanc et al. · 2025RCTEffects of eight-week supplementation containing red orange and Polypodium leucotomos extracts on UV response — randomised double-blind placebo-controlledView study →}.

A 2025 systematic review of oral supplements for photoprotection placed Polypodium leucotomos among those with the strongest evidence, while noting small samples and short studies ^{3Reference 3Natarelli N et al. · 2025Systematic reviewOral supplements and photoprotection: a systematic reviewView study →}.

Gap: the data are for standardised extracts, and no trial has measured skin-cancer incidence in humans.

2. Antioxidant

HPLC fractionation of Fernblock identified protocatechuic acid, 4-hydroxybenzoic acid, vanillic acid, caffeic acid, p-coumaric acid, 4-hydroxycinnamoyl-quinic acid, ferulic acid and five chlorogenic acid isomers, which account for part of its antioxidant capacity ^{9Reference 9Garcia et al. · 2006In vitroPhenolic components and antioxidant activity of Fernblock, an aqueous extract of the aerial parts of Polypodium leucotomos — in vitroView study →}.

Of these, ferulic and caffeic acids were the strongest antioxidants in a hydrogen-peroxide assay. In a gut-cell model, their permeability corresponded to 70–100% absorption in people ^{8Reference 8Gombau et al. · 2006In vitroPolypodium leucotomos extract: antioxidant activity and disposition — in vitroView study →}.

Fernblock also switched on the NRF2 antioxidant pathway in keratinocytes exposed to fine pollution particles ^{10Reference 10Delgado-Wicke et al. · 2020In vitroFernblock upregulates NRF2 antioxidant pathway and protects keratinocytes from PM2.5-induced damage — in vitroView study →}. It blocked the formation of cyclobutane pyrimidine dimers in melanocytes in the hours after UVA exposure (so-called dark CPDs) ^{11Reference 11Portillo-Esnaola et al. · 2021In vitroFormation of cyclobutane pyrimidine dimers after UVA exposure (dark-CPDs) is inhibited by a hydrophilic extract of Polypodium leucotomos — in vitroView study →}.

Gap: the strongest data are cell-based, and no trial has measured oxidative-stress markers as an outcome in their own right.

3. Photodermatoses

In an open, uncontrolled study at two centres, 35 patients with long-standing polymorphic light eruption took the extract before repeat UV provocation. About 30% no longer reacted to UVA, and in the others more exposures were needed to trigger the rash ^{12Reference 12Tanew et al. · 2012Oral administration of a hydrophilic extract of Polypodium leucotomos for the prevention of polymorphic light eruptionView study →}.

In 57 patients with idiopathic photodermatoses who took 480 mg/day while exposed to the sun, about 74% had fewer skin reactions and symptoms ^{13Reference 13Caccialanza et al. · 2011Oral Polypodium leucotomos extract photoprotective activity in 57 patients with idiopathic photodermatosisView study →}. A series of 25 patients reported similar results ^{14Reference 14Caccialanza et al. · 2007Photoprotective activity of oral Polypodium leucotomos extract in 25 patients with idiopathic photodermatosesView study →}.

Gap: there is no large double-blind placebo-controlled trial in polymorphic light eruption, so the size of the benefit is uncertain.

4. Anti-Inflammatory

In hairless Xpc+/− mice fed the extract (300 mg/kg for 10 days) before a single UV exposure, COX-2 levels were four- to fivefold lower at 48–72 hours. Neutrophil infiltration fell by about 60%, p53 activity rose, and more UV-induced DNA damage was repaired ^{15Reference 15Zattra et al. · 2009AnimalPolypodium leucotomos extract decreases UV-induced Cox-2 expression and inflammation, enhances DNA repair in Xpc+/− mice — animal modelView study →}.

In cell studies, calagualine inhibits NF-κB activated by TNF, phorbol ester and bacterial lipopolysaccharide, across a range of cell types ^{16Reference 16Manna et al. · 2003In vitroCalagualine inhibits nuclear transcription factor-κB activated by various inflammatory and tumour-promoting agents — in vitroView study →}.

Gap: human anti-inflammatory read-outs are indirect, measured through skin endpoints rather than inflammatory markers.

5. Melasma

In a double-blind trial in 40 Asian patients already using 4% hydroquinone cream and SPF 50+ sunscreen, adding oral extract for 12 weeks gave lower melasma scores than placebo at weeks 8 and 12. Melanin and redness indices improved slightly in both groups, without a difference between them ^{17Reference 17Goh et al. · 2018RCTDouble-blind, placebo-controlled trial to evaluate the effectiveness of Polypodium leucotomos extract in the treatment of melasma — randomisedView study →}.

A 2025 systematic review of antioxidants in melasma found mixed results for the extract, with most promise when it was combined with other treatments ^{33Reference 33Role of antioxidants in melasma: a syste · 2025Systematic reviewIndian J Dermatol. https://doi.org/10.4103/ijd.ijd_473_24View study →}.

Gap: the only direct trial is small and single-centre, and the extract was an add-on rather than a treatment on its own.

6. Vitiligo

In 50 patients with vitiligo vulgaris, 250 mg of extract three times daily, added to narrow-band UVB twice weekly for 25–26 weeks, gave more repigmentation of the head and neck than placebo (44% vs 27%, P = 0.06). Among patients who attended more than 80% of their UVB sessions, the difference was 50% vs 19% (P < 0.002) ^{19Reference 19Middelkamp-Hup et al. · 2007RCTTreatment of vitiligo vulgaris with narrow-band UVB and oral Polypodium leucotomos extract — randomised double-blind placebo-controlledView study →}.

In 44 patients with generalised vitiligo, narrow-band UVB plus 480 mg twice daily for six months raised the response rate compared with UVB alone (47.8% vs 22%) ^{20Reference 20Pacifico et al. · 2021RCTNB-UVB plus oral Polypodium leucotomos extract display higher efficacy than NB-UVB alone in patients with vitiligo — randomised placebo-controlledView study →}.

A scoping review and meta-analysis listed the extract among antioxidants with potential in vitiligo ^{18Reference 18Speeckaert et al. · 2023Meta-analysisThe impact of antioxidants on vitiligo and melasma: a scoping review and meta-analysisView study →}. A Cochrane review of vitiligo treatments found most trials small, with fewer than 50 participants ^{21Reference 21Whitton et al. · 2010Systematic reviewInterventions for vitiligo — Cochrane systematic reviewView study →}.

Gap: benefit has only been seen alongside phototherapy, the trials are small, and no study supports the extract alone for repigmentation.

7. Actinic Keratosis

In a 12-month open-label trial, 131 older patients with severe sun damage were randomised to topical Fernblock, topical plus oral Fernblock, or their own sun protection. Both treated groups had fewer actinic keratoses and less field cancerisation on confocal microscopy, with the greatest improvement on topical plus oral treatment ^{22Reference 22Pellacani et al. · 2023RCTThe combination of oral and topical photoprotection with a standardized Polypodium leucotomos extract for actinic keratosis — randomised controlledView study →}.

In 34 bald patients with actinic keratoses of the scalp, alternately assigned, those who took oral extract after photodynamic therapy had higher clearance and fewer recurrences at six months than those treated with photodynamic therapy alone ^{23Reference 23Auriemma et al. · 2015RCTPolypodium leucotomos supplementation in the treatment of scalp actinic keratosis — randomised controlledView study →}.

A comparative trial set oral extract against colchicine cream and ingenol mebutate ^{25Reference 25Miola et al. · 2023RCTEfficacy of oral Polypodium leucotomos, colchicine cream and ingenol mebutate in the treatment of actinic keratosis — randomised controlledView study →}, and a 2025 systematic review of supplements for actinic keratosis includes it among the polyphenols with clinical support ^{24Reference 24Rodríguez-Luna et al. · 2025Systematic reviewSystematic review on dietary supplements in the prevention and/or treatment of actinic keratosisView study →}.

Gap: all human data are add-on and short-term; no study shows the extract alone clears actinic keratosis or prevents progression to squamous cell carcinoma.

8. Photoaging

In fibroblasts and keratinocytes, P. leucotomos improved membrane integrity, inhibited lipid peroxidation, increased elastin and inhibited MMP-1, with or without UV exposure ^{26Reference 26Philips et al. · 2003In vitroPredominant effects of Polypodium leucotomos on membrane integrity, lipid peroxidation, and expression of elastin and matrix metalloproteinase-1 in UV-exposed fibroblasts and keratinocytes — in vitroView study →}. A follow-up study examined its effects on matrix metalloproteinases, their inhibitors, fibrillar collagens and TGF-β ^{27Reference 27Philips et al. · 2009In vitroBeneficial regulation of matrix metalloproteinases and their inhibitors, fibrillar collagens and TGF-β by Polypodium leucotomos — in vitroView study →}.

Fernblock also protected dermal fibroblasts against visible and infrared-A radiation ^{28Reference 28Zamarrón et al. · 2018In vitroFernblock prevents dermal cell damage induced by visible and infrared-A radiation — in vitroView study →}.

Gap: the data are from cell studies; no trial has tested the extract alone against a photoaging outcome.

9. Atopic Dermatitis

In a phase IV double-blind trial, 105 children and adolescents aged 2–17 with moderate atopic dermatitis took the extract or placebo for six months alongside topical corticosteroids. It did not reduce the share of days on steroid creams (11% vs 12%), but it reduced the days on oral antihistamines (median 4.5% vs 13.6%) ^{29Reference 29Ramírez-Bosca et al. · 2012RCTPolypodium leucotomos extract in atopic dermatitis: a randomised, double-blind, placebo-controlled trialView study →}.

Gap: a single trial, in one population, that missed its main endpoint.

10. Anticancer

Calagualine inhibits NF-κB, a transcription factor involved in inflammation and tumour growth, across several cell types in vitro ^{16Reference 16Manna et al. · 2003In vitroCalagualine inhibits nuclear transcription factor-κB activated by various inflammatory and tumour-promoting agents — in vitroView study →}.

In mice, oral extract lowered UV-induced COX-2, activated p53, sped the removal of UV-induced DNA damage, and cut UV-induced mutations by about 25% two weeks after exposure ^{15Reference 15Zattra et al. · 2009AnimalPolypodium leucotomos extract decreases UV-induced Cox-2 expression and inflammation, enhances DNA repair in Xpc+/− mice — animal modelView study →}.

Gap: there are no human oncology trials, and the animal data measure DNA damage and mutations rather than tumours.

11. Neuroprotective

In a 4-week double-blind pilot trial in 45 patients with mild-to-moderate dementia of vascular or Alzheimer type, 360 mg/day of Anapsos improved cognitive scores (ADAS-cog) compared with placebo; 720 mg/day did not ^{30Reference 30Álvarez et al. · 2000RCTDouble-blind, randomised, placebo-controlled pilot study with anapsos in senile dementia — randomisedView study →}.

In rats given beta-amyloid injections into the hippocampus, Anapsos injected into the abdomen altered Cu-Zn superoxide dismutase activity in several brain regions ^{31Reference 31Fernández-Novoa et al. · 1997AnimalEffects of anapsos on Cu-Zn-superoxide dismutase activity in an animal model of neuronal degeneration — animalView study →}.

Gap: the human evidence is a single small pilot from 2000 that has not been repeated, and Anapsos differs from the modern dermatological extracts.

12. Antiviral

The antiviral screen cited for samambaia, a survey of British Columbian medicinal plants, found activity against herpes simplex virus type 1 in Polypodium glycyrrhiza, the licorice fern, not in this species ^{32Reference 32McCutcheon et al. · 1995In vitroAntiviral screening of British Columbian medicinal plants — in vitroView study →}.

Gap: that result belongs to a different fern and does not apply to samambaia.

Mechanisms

The extract’s phenolic acids, chiefly caffeic and ferulic acid, scavenge reactive oxygen species. The extract has also been studied for its effects on the NRF2 antioxidant pathway, UV-induced DNA damage and the enzymes that break down collagen ^{8,10,11,26Reference 8Gombau et al. · 2006In vitroPolypodium leucotomos extract: antioxidant activity and disposition — in vitroView study →Reference 10Delgado-Wicke et al. · 2020In vitroFernblock upregulates NRF2 antioxidant pathway and protects keratinocytes from PM2.5-induced damage — in vitroView study →Reference 11Portillo-Esnaola et al. · 2021In vitroFormation of cyclobutane pyrimidine dimers after UVA exposure (dark-CPDs) is inhibited by a hydrophilic extract of Polypodium leucotomos — in vitroView study →Reference 26Philips et al. · 2003In vitroPredominant effects of Polypodium leucotomos on membrane integrity, lipid peroxidation, and expression of elastin and matrix metalloproteinase-1 in UV-exposed fibroblasts and keratinocytes — in vitroView study →}. Calagualine has been studied as an inhibitor of NF-κB ^{16Reference 16Manna et al. · 2003In vitroCalagualine inhibits nuclear transcription factor-κB activated by various inflammatory and tumour-promoting agents — in vitroView study →}.

In mice, the extract lowered UV-induced COX-2, activated p53 and sped DNA repair ^{15Reference 15Zattra et al. · 2009AnimalPolypodium leucotomos extract decreases UV-induced Cox-2 expression and inflammation, enhances DNA repair in Xpc+/− mice — animal modelView study →}.

Clinical Trials

Multiple randomized controlled trials exist — mostly small, short and testing standardized extract as an adjunct — spanning photoprotection, melasma, vitiligo, actinic keratosis and atopic dermatitis; there is also one small dementia pilot RCT, but no large pivotal monotherapy trial and no human cancer-outcome study.

Last checked: July 2026.

Phytochemistry

Fernblock, the aqueous extract of the fronds, contains the phenolic acids caffeic acid, ferulic acid, vanillic acid, protocatechuic acid, 4-hydroxybenzoic acid, p-coumaric acid, 4-hydroxycinnamoyl-quinic acid and five chlorogenic acid isomers ^{9Reference 9Garcia et al. · 2006In vitroPhenolic components and antioxidant activity of Fernblock, an aqueous extract of the aerial parts of Polypodium leucotomos — in vitroView study →}.

Ferulic and caffeic acids are the strongest antioxidants among them. In a gut-cell model they cross readily, and coumaric, ferulic and vanillic acids are metabolised by liver CYP450 enzymes and partly conjugated ^{8Reference 8Gombau et al. · 2006In vitroPolypodium leucotomos extract: antioxidant activity and disposition — in vitroView study →}.

The fern also contains calagualine, studied as an NF-κB inhibitor ^{16Reference 16Manna et al. · 2003In vitroCalagualine inhibits nuclear transcription factor-κB activated by various inflammatory and tumour-promoting agents — in vitroView study →}, and a lipid fraction that includes the sulfoquinovosyldiacylglycerols, a class covered by several patents ^{34Reference 34Taylor · 2005The Healing Power of Rainforest Herbs}.

Other reported constituents include 20-hydroxyecdysone, ecdysone, adenosine, rutin, kaempferols, juglanin, melilotoside, polypodaureine and selligueain, and fatty acids including linoleic, linolenic, oleic, arachidonic and eicosapentaenoic acid ^{34Reference 34Taylor · 2005The Healing Power of Rainforest Herbs}.

The phenolic acid profile and absorption data come from the standardised extracts rather than the raw fern ^{8,9Reference 8Gombau et al. · 2006In vitroPolypodium leucotomos extract: antioxidant activity and disposition — in vitroView study →Reference 9Garcia et al. · 2006In vitroPhenolic components and antioxidant activity of Fernblock, an aqueous extract of the aerial parts of Polypodium leucotomos — in vitroView study →}.

Constituent Summary

Amounts have not been published for the individual compounds.

Dosage

Trials used proprietary standardised extracts, dosed in milligrams of extract.

Traditional Dosage

Safety & Pregnancy

Standardised samambaia extract is well tolerated in trials. Side effects are uncommon and mild, and the safety record covers the extracts rather than raw fern tea or powder ^{1Reference 1Winkelmann et al. · 2015ReviewPolypodium leucotomos extract: a status report on clinical efficacy and safety — reviewView study →}.

Full Safety Detail

Trial record. A review of 19 human and 6 laboratory studies spanning over 40 years, at daily oral doses of 120–1,080 mg, found no adverse effects in laboratory studies. In people, side effects were mild to moderate stomach complaints and itching, in 16 of 1,016 participants (2%) ^{1Reference 1Winkelmann et al. · 2015ReviewPolypodium leucotomos extract: a status report on clinical efficacy and safety — reviewView study →}.

Healthy adults. In a 60-day study, 240 mg twice daily produced no clinically meaningful change in physical examination, vital signs or laboratory tests ^{6Reference 6Nestor et al. · 2015RCTSafety and efficacy of oral Polypodium leucotomos extract in healthy adult subjects — randomised placebo-controlledView study →}.

Interactions. Older secondary sources caution that the fern may strengthen cardiac glycosides (digitalis, digoxin) and that antacids may reduce its absorption. Primary pharmacokinetic studies have not confirmed these, so they remain theoretical.

Raw fern. Almost all safety data concern proprietary standardised extracts. Tea or powder of the raw fern has not been studied.

References

1. Winkelmann, R. R., et al. (2015). Polypodium leucotomos extract: a status report on clinical efficacy and safety — review. J Drugs Dermatol. https://pubmed.ncbi.nlm.nih.gov/25738847/
2. Zundell, M. P., et al. (2025). The utility of oral Polypodium leucotomos extract for dermatologic diseases: a systematic review. J Drugs Dermatol. https://doi.org/10.36849/JDD.8410
3. Natarelli N, et al. (2025). Oral supplements and photoprotection: a systematic review. J Med Food. https://pubmed.ncbi.nlm.nih.gov/39804624/
4. González, S., et al. (1997). Topical or oral administration with an extract of Polypodium leucotomos prevents acute sunburn and psoralen-induced phototoxic reactions — randomised. Photodermatol Photoimmunol Photomed. https://pubmed.ncbi.nlm.nih.gov/9361129/
5. Kohli, I., et al. (2017). The impact of oral Polypodium leucotomos extract on ultraviolet B response: a human clinical study. J Am Acad Dermatol. https://doi.org/10.1016/j.jaad.2017.01.044
6. Nestor, M. S., et al. (2015). Safety and efficacy of oral Polypodium leucotomos extract in healthy adult subjects — randomised placebo-controlled. J Clin Aesthet Dermatol. https://pubmed.ncbi.nlm.nih.gov/25741399/
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