Traditional knowledge and uses of medicinal plants by the inhabitants of the islands of the São Francisco river, Brazil and preliminary analysis of Rhaphiodon echinus (Lamiaceae)

Abstract This study aimed to carry out an ethnobotanical survey of medicinal plants used by inhabitants of the Rodeadouro Island, Jatoba Island and Massangano Island, located in The Submedium São Francisco River Valley. Also phytochemicals and preliminary pharmacological tests were performed to species most cited by the community. Ethnobotanical data were collected through observation visits and semi-structured interviews with 12 key informants. We calculated the relative importance (RI), the percentage of agreement related to the main uses (cAMU) and use value (UV). The aerial parts of Rhaphiodon echinus (Ness & Mart.) Schauer were used to obtain the lyophilizate (LYO-Re), crude ethanol extract (CEE-Re) and their hexanic (HEX-Re), chloroform (CLO-Re) and ethyl acetate (EA-Re) fractions. The microdilution technique was used for determining Minimum inhibitory concentration (MIC) for selected microorganisms. Already the spasmolytic effect was evaluated in isolated uterus fragments of Wistar rats, pre contracted with KCl 60 mM. We found 34 species cited, belonging to 22 families. The most plants were grown by locals. There were 51 different diseases, but the main indication was infectious and parasitic diseases. The species R. echinus was the most reported and it was indicated for urinary tract infection and dysmenorrhea. The screening revealed a higher prevalence of flavonoids, tannins, lignans and saponins in LYO-Re and AE-Re. Already terpene compounds were more present in HEX-Re and CLO-Re. The RE-Re fraction stood out with strong effect against E. coli and S. aureus while CEE-Re has moderate effect against gram-negative bacteria. The evaluation of the spasmolytic activity showed that LYO-Re, CEE-Re and HEX-Re fractions have similar activity, with partial effect and concentration-dependent response. This work brought about knowledge and use of medicinal plants by the riparian of the São Francisco River. It also revealed the importance of other methodologies for scientific evidence for the popular use of R. echinus.