Therapeutic knowledge accumulated by rural populations, through centuries of direct contact with the environment, makes possible the gathering of information concerning use of natural resources. The aim of the present study was to carry out an inventory of the medicinal plants cultivated in homegardens of Demerval Lobão Municipality, Piauí State, Brazil, as well as to learn their uses and importance in the community. A total of 21 homegardens in nine communities of the rural area of Demerval Lobão Municipality with Cerrado vegetation were sampled. The study was conducted by means of semi-structured interviews and direct observation, associated with the technique of a tour guided by the keepers of the homegardens. The collected medicinal plants were cataloged, identified and deposited in the Herbarium Graziela Barroso (TEPB) of Federal University of Piauí (UFPI). Of 100 botanical species, predominantly herbaceous and cultivated species distributed in 49 families, were cited, and the most representative families in number of species were Leguminosae, Euphorbiaceae and Lamiaceae. For the preparation of medicines, leaves were most used and decoction was the main form of preparation. The most frequent diseases treated by homemade remedies are associated with the respiratory and digestive systems. There is no rigidity as to dosage and duration of treatment; it depended on the habit of each interviewed person. The plants that presented an index of relative importance and use agreement above 60% were the following: "cansansão" (Cnidosculus urens), "boldo" (Plectranthus barbatus Andrews), black-jurema (Mimosa verrucosa Benth) and "cidreira" (Lippia alba (Mill.) N.E.Br. ex Britton & P.Wilson). P. barbatus was most cited and also the species that presented the highest indices of CUP (100%), FC (1,00) and CUPc (100%) for stomach pains and liver problems. There is the need of rescuing knowledge concerning medicinal plants to contribute to the improvement of the life quality of the inhabitants of the rural area, as a first step for the appreciation and adaptation of resources of folk medicine for the treatment of the most frequent diseases.
etnomedicine; index of relative importance; use agreement; Piauí
