The mystery of the 'resin-of-canuaru': A medicine used by caboclos river-dwellers of the Amazon, Amazonas, Brazil

Abstract

Ethnopharmacological relevance: 'Resin-of-canuaru' is a medicine utilized by caboclos living in the Amazon Region, Brazil. There is a mystery regarding its origin because the caboclos maintain that this substance is derived only from animal secretions (from a frog called canuaru), whereas the historic literature claims that 'resin-of-canuaru' is derived solely from a plant exudate (resin). Based on our ethnographic studies, we hypothesized that this substance is a combination of both. Because the past reports on this resiniferous material in the literature are based solely on observations, we aimed to present ethnographic, zoological and chemical data to try to elucidate the origin of the 'resin-of-canuaru'.Materials and methods: Ethnographic techniques and methods were applied, including participant observation, the use of field diaries and informal and unstructured interviews. the canuaru frog (Trachycephalus resinifictrix Goeldi, 1907) and 'resin-of-canuaru' were collected for taxonomic identification and chemical analysis, respectively. the resiniferous 'resin-of-canuaru' was extracted using MeOH and then analyzed by silica gel TLC and NMR.Results: Canuaru frogs live in tree cavities and secrete a large amount of substances during spawning, resulting in a resiniferous material. NMR analysis of the MeOH extract of this crude material showed peaks assigned to 3,4-secofriedel-4(23)-en-3-oic acid (putranjuvic acid) and its methyl ester derivative (methyl putranjivate) and to biogenetic precursor of these two compounds (a lactone derivative), which is formed by the oxidation of friedelin. Based on evidence that Protium species accumulate primarily tetracyclic/pentacyclic triterpenoids and that the co-occurrence of the compounds listed above is rarely described in plant species, we suggest that these compounds could be products of the biotransformation of friedelin by the frog.Conclusions: According to our data, the 'resin-of-canuaru' seems to have both animal and vegetal origins. (C) 2012 Elsevier Ireland Ltd. All rights reserved.