Pedra Hume CaáMyrcia salicifolia

Did you know?

• The name mixes two languages. Pedra-ume is Portuguese for alum, the mineral salt, and caá is a Tupi word for plant or herb, so pedra hume caá means roughly "alum plant"^{[6, 7, 8]}.

• In Brazil, caá on its own can also mean yerba mate, the leaf behind South America's mate tea^{[6, 8]}.

• Pedra hume caá is not one species. In Brazil the name is shared by several Myrcia shrubs, including Myrcia salicifolia and Myrcia multiflora^{[4, 5]}.

• Myrcia is a big genus: a 2015 review counts 753 species, 260 of them in Brazil^[4].

• It belongs to the myrtle family, alongside guava, clove, allspice, eucalyptus and jaboticaba^[9], and the Amazon's own camu camu^[1].

• Like its relatives clove and eucalyptus, it comes from an aromatic group of plants: Myrcia leaves carry fragrant essential oils^{[4, 9]}.

Origins and history

Pedra hume caá grows in the wet tropical forests of the Amazon. Kew's Plants of the World Online records it from southeastern Colombia to Peru and northern Brazil, and most recorded specimens come from Brazil and Colombia^{[1, 2]}. It grows as a shrub or tree^[1], and like most of the myrtle family it has evergreen leaves dotted with tiny oil glands^{[4, 9]}. De Candolle gave it the name Myrcia salicifolia in 1828, and for a time botanists placed it in a separate genus, as Aulomyrcia salicifolia^[1].

The name pedra hume caá is a Brazilian folk name, not a botanical one, and it is not limited to a single plant. A review of the genus lists nine Myrcia species used under this group of names, among them M. salicifolia, M. multiflora, M. uniflora and M. speciosa^[4]. The US herb trade's standard naming guide, Herbs of Commerce, lists "pedra hume" for Myrcia multiflora^[5]. The words themselves tell a small story about Brazil's two languages. Pedra-ume (spelled pedra hume in the plant's name) is the Portuguese name for alum^{[6, 7]}. Caá comes from Tupi, an Indigenous language of Brazil, where it was a general word for plants and herbs and especially for yerba mate^{[6, 8]}.

The leaf is the part people use. In Brazilian folk tradition, the leaves of these Myrcia shrubs, and sometimes the whole plant, are brewed as an infusion^[4].

Traditional uses

Clinical studies in people are still few, but pedra hume caá has a long place in Brazilian folk tradition, where its leaf tea is widely used^[4].

• Leaf tea

  The leaves are traditionally brewed in hot water as an infusion.^[4]

• Healthy blood sugar

  In Brazil, pedra hume caá leaf tea is traditionally taken for healthy glucose metabolism.* It helps maintain healthy blood sugar levels already within the normal range.*^[4]

• One name, several shrubs

  The tea tradition belongs to several Myrcia species sold under the same name^{[4, 5]}. Raintree's pedra hume caá is labeled as Myrcia salicifolia.

Plant compounds

The Myrcia species sold as pedra hume caá have been studied mainly for their flavonoids. Their leaves contain flavonoid glycosides such as myricitrin and mearnsitrin, plant compounds in which a flavonoid is joined to a sugar^[4]. Myrcia multiflora has also yielded quercitrin, guaijaverin and desmanthin-1, and compounds called myrciacitrins and myrciaphenones^[4]. Like the rest of the myrtle family, Myrcia is also an aromatic genus: its leaves carry fragrant essential oils^{[4, 9]}.