francisco r.s. mendesa, francisca g.e. silvaa, erl^anio o. sousabc, fab'iola f.g. rodriguesbc, jos'e g.m. costabc*, francisco j.q. monted, telma l.g. lemosd & jo~ao c.c. assunc~aoaa department of chemistry and environment, federal institute for education, science and technology of cear'a, campus of quixad'a, ce, brazilb molecular bioprospection post-graduation program, laboratory of natural products research, regional university of cariri, crato, ce, brazilc northeast network on biotechnology, state university of cear'a, fortaleza ce, brazild department of organic and inorganic chemistry, federal university of cear'a, fortaleza, ce, brazil