Gen info
- Epiphytes are more than 10% of the world total plant species and the majority are found in the Magnoliophyta division.
- Drynaria, commonly known as basket ferns, is a genus of ferns in the family Polypodiaceae, containing about 16 species and one natural hybrid (D. rigidula and D. sparsisora).
- It grows on trees in rainforest and tall open forest, where it forms huge colonies high up in the canopy, providing shelter for amethystine pythons (Morelia amesthistina) and scrub phytons (Morelia kinghorni). (8) In Australia, it was observed that 81% of snakes in epiphytes were in large (>1 m) Drynaria rigidula ferns. (•)
- Etymology: The genus name Drynaria derives from Greek 'drys', the oak tree, referring to the oak-shaped fronds. Species epithet rigidula derives from Latin rigidus, meaning stiff, and rigidulus its diminutive, meaning a little stiff. (8)

Botany
Drynaria rigidula is an epiphytic fern that can reach up to 1.5 long, with stout creeping rhizomes covered in dense brown to dark brown hairs. There are two type of foliage; nest fronds (sterile) and foliage fronds (fertile). Nest fronds are oak-like, stalkless, brownish red in colour with denticulate margins. They have a papery texture and tend to overlap one another, measuring between 10 - 30 cm long and 5 - 15 cm wide. Foliage fronds are pinnate, green, sometimes erect. They can reach between 25 - 200 cm long, made up of linear leaflets with crenate to serrate margins. Each frond is held on a brownish red to purple stipe with short fine hairs measuring up to 40 cm long. The sori are arranged in pairs on both sides of the midrib. The round sori (1 - 2 mm wide) are sunken into the foliage, which creates bulges on the upper surface of the foliage. (3)

Rhizome shortly creeping, 1-2 cm in diam.; scales brown to dark brown, with a lighter margin, spreading, peltate, 5-13 × 0.5-1.5 mm, margin ciliate, apex acute to acuminate; fronds dimorphic, rachises persistent; basal fronds 10-30 × 5-15 cm, lobed from 1/3-4/5, margin irregularly and finely denticulate; foliage fronds stalked, stipe up to 40 cm, not winged, with 2 rows of nectaries; lamina pinnate, 25-100(-200) × 12-50 cm, apex aborted; pinnae articulate to rachis, all equally long or smaller toward apex, 8-25(-30) × 0.5-1.5 cm, base narrowly cuneate, margin crenate to serrate, apex obtuse to acuminate, free veinlets simple or absent, hydathodes absent. Sori in 1 row between costa and margin, costal, single between veins, orbicular, sunken. Spores with short, blunt spines and globules. (Flora of China)

Distribution
- Native to the Philippines.
- Also native to Bismarck Archipelago, Cambodia, China, Hainan, Jawa, Laos, Lesser Sunda Is., Malaya, Maluku, Myanmar, New Caledonia, New Guinea, New South Wales, Queensland, Samoa, Solomon Is., Sulawesi, Sumatera, Thailand, Tonga, Vanuatu, Vietnam. (1)
- Epiphytic, occasionally terrestrial. Occurs in various types of primary and secondary forest, savannah and plantations, wayside trees from sea level to altitude 2400m. (3)

Constituents
- Hexane fraction of crude extract of leaves produced 3 major secondary metabolites, namely: campesterol (1), stigmasterol (2), and ß-sitosterol (3). (see study below) (6)
- Phytochemical study of rhizome isolated two new aromatic glycosides along with three known terpenoids, two benzoic acid derivatives and two known flavonoid glycosides. (7)
- The fertile fronds of D. rigidula exhibited superior TPC and FRP compared to rhizomes. On Tyrosinase inhibition, D. rigidula frond exhibited 24.9% inhibition, the rhizome -65.0% tyrosinase enhancement activity. D. rigidula fertile fronds showed highest chelating activity at approximately 45% at 7 mg/mL. Fronds showed TPC of 1031 mgGAE/100g and rhizomes 305.5 mg GAE/100g; free radical scavenging activity IC50 of 0.79 mg/mL frond and 1.02 mg/mL rhizome; ferric reducing power (FRP) of 2.3 mgGAE/g frond and 1.0 mgGAE/g rhizome; and total flavonoid content (TFC) 4.7 mgQE/100g frond and 3.1 mgQE/100g rhizome. (9)

Properties
- D. rigidula is the only species in the genus with 1-pinnate foliage fronds.
- Rhizome considered astringent.
- Fronds that develop near the base of the plant are shorter, sterile, and rust-colored, which form a basket-like shape that trap moisture and organic components that nourish it. In cold weather, the basket becomes a prime habitat for animals such as the Amesthystine phyton.
- Studies have suggest antioxidant, tyrosinase inhibitory, anticancer properties.

Parts used
Fronds, rhizomes.

Uses
Edibility
- In Sulawesi, young fronds eaten as vegetable.
Folkloric
- In the Philippines, decoction of rhizome used for treatment of gonorrhea and dysentery. (2)
- In Sulawesi, Indonesia, juicy rhizomes used medicinally only when growing on coconut tree. (2) Indigenous people use the plant to treat eye infection.
Others

Studies
• Cytotoxicity / Anticancer Against MCF-7) Breast Cancer Cell Line / Leaves: Study of dichloromethane (DCM) fraction of D. rigidula showed cytotoxicity against breast cancer cell MCF-7, possibly due to the presence of kaemferitrin 4, which was previously reported to have activity against the cell line with IC50 of 0.062 mM. (see constituent above) (6)
• Antioxidant / Tyrosinase % Inhibition / Fronds and Rhizomes: Study evaluated the antioxidant and tyrosinase inhibition properties of methanolic extracts of fertile fronds and rhizomes of three species in the genus: Drynaria rigidula, D. quercifolia, and D. sparsisora. (see constituents above) (9)

Availability
Wild-crafted.

OTHER IMAGE SOURCE: Photo: Scadoxus multiflorus / image modified /  © World of Succulents / click on image to go to source page / World of Succulents

Additional Sources and Suggested Readings
(1)
Drynaria rigidula / KEW: Plants of the World Online
(2)
Drynaria (PROSEA) / Pl@ntUse
(3)
Drynaria rigidula / National Parks: FLORA & FAUNA WEB
(4)
Biology: Drynaria / HandWiki
(5)
Antioxidant and tyrosinase inhibition activity of the fertile fronds and rhizomes of three different Drynaria species / Tan Joash, Yau Yan Lim / BMC Research Notes, 2015; 8(1) / DOI: 10.1186/s13104-015-1414-3
(6)
Phytochemical and Pharmacological Studies on Four Indonesian Epiphytic Medicinal Plants: Drynaria rigidula, Hydnophytum formicarum, Usnea misaminensis, and Calymperes schmidtii / Ari S Nugraha, Tashi Wangchuk, Anthony C Willis, Rachada Haritakun, Heri Sujadmiko, Paul A Keller / Natural Products Communication, 2019 / DOI: 10.1177/1934578X19856792
(7)
Constituents of the Indonesian Epiphytic Medicinal Plant Drynaria rigidula / Ari S Nugraha, Rachada Haritakun, Paul A Keller / Natural Product Communications, 2013; 8(6): pp 703-705
(8)
Drynaria rigidula / Some Magnetic Island Plants
(9)
Antioxidant and tyrosinase inhibition activity of the fertile fronds and rhizomes of three different Drynaria species / Joseph Ban Lee Tan, Yau Yan Lim / BMC Res Notes, 2015 / DOI: 10.1186/s13104-015-1414-3 /
PMID: 26395256

DOI: It is not uncommon for links on studies/sources to change. Copying and pasting the information on the search window or using the DOI (if available) will often redirect to the new link page. (Citing and Using a (DOI) Digital Object Identifier)