Chresta

Abstract: Chresta martii (Asteraceae) is a plant found in the Xingo region (semi-arid area) in Northeastearn Brazil, and is recognized by the local population as a traditional herb used to treat gastric diseases. This is the first report of the chemical composition, acute toxicity, and gastroprotective effect in mice of the hydroalcoholic extract (HAE) from the aerial parts (leaves and flowers) of Chresta martii. Animals received HAE doses from 10 to 2000 mg/kg, i.p. or 50 to 3000 mg/kg, p.o.) and were observed over 48 h for toxicity signs and mortality; sub-chronic toxicity was evaluated through 14 days treatment with once-daily HAE doses (400 mg/kg, p.o.). The gastroprotective effect of HAE was demonstrated on the indomethacin-induced gastric ulcer model after the administration of extracts. Data comparison of ulcer index averages between saline and HAE (100 or 400 mg/kg, p.o.) groups showed significant (P < 0.01) inhibition (71.73 and 76.72 %, respectively) of indomethacin-induced gastric lesions. Histological analyses showed significant (P < 0.05) inhibition of leukocyte migration in HAE-treated groups. A fingerprint of the HAE obtained by HPLC/UV/MS analysis showed major peaks characteristic of sesquiterpene lactones. Compound 1 was isolated and elucidated as a new natural product. Its capacity to prevent leukocyte chemotaxis was demonstrated in vitro, corroborating the pharmacological effects observed for C. martii HAE.

Abstract: Chresta filicifolia is described and illustrated. It is a perennial herb known only from open vegetation on top of small rock outcrops at the Rio Doce Valley in Eastern Minas Gerais, Southeastern Brazil. This is the first record of a species of Chresta endemic to a phytogeographic domain other than the Cerrado and Caatinga , since those outcrops are included in the Mata Atlântica Domain (Atlantic Forest). The new species is closely related to C. harleyi and C. hatschbachii, but differs from these by its leaves, which are larger and more deeply lobed than those of the other two species, and also by its florets and cypselae, which are both larger in Chresta filicifolia. Moreover, the two other species are allopatric from C. filicifolia , being restricted to the Caatinga Domain . The southernmost distribution of C. harleyi lies more than 500 km away from the locality where the new species is found, making this discovery unexpected, and raising interesting biogeographical questions, which are briefly addressed here.

Abstract: Chresta and Pycnocephalum are syncephalous herbs that are restricted to the Central Plateau of Brazil. Chresta is adapted to the arid conditions of cerrado, grassy campo, and campo rupestre. The plants are characterized by tomentose to glabrate, strongly coriaceous leaves, corymbs of glom- erules or single, terminal glomerules (formed by the concrescence of several subglomerules), 20 to more than 200 heads per glomerule, typically 3 florets per head, and corollas 5-11 mm tall with a tube to lobe length ratio of 1-2. In contrast, Pycnocephalum is adapted to wet areas at high elevations within these arid regions and is distinguished by typically glabrate, membranaceous leaves, solitary glomerules (not formed by concrescence) or compound corymbs of 6-10 glomerules, 5-25 heads per glomerule, 4-12 florets per head, and corollas 8-21 mm tall with a tube to lobe length ratio of 2-4.5. Two new combinations are made: Pycnocephalum angustifolium and P. pinnatifidum. Chresta Vell. and Pycnocephalum DC. (Com- positae: Vernonieae) comprise, respectively, four and three species of syncephalous peren- nial herbs that are restricted to the arid Central Plateau of Brazil. Chresta is adapted to the arid conditions of shrubby cerrado, grassy campo, and campo rupestre (sensu Eiten 1978, 1982, 1983) at elevations of 500-2400 m within the vast mo- saic of savanna covering south-central Brazil. In contrast, Pycnocephalum is restricted to wet grassy campo or the margins of rivers or streams at elevations of 800-1200 m within these arid regions. Although some taxa are often limited to specific habitats, both genera are abundant within their respective ecological preserves. It has been widely accepted that Pleistocene climate fluctuations produced a repeated alter- nation of semi-arid and humid conditions in South America. During semi-arid phases, wide- spread areas of xerophytic caatinga (Eiten and Goodland 1979; Bucher 1982) and "degraded" cerrado (Vanzolini 1973) created more favorable conditions for long-distance dispersal from the Andes (Van der Hammen 1974). Currently, these climatic fluctuations have produced nu- merous well-documented plant and animal re- fugia peripheral to the Amazon Basin (Vuilleu- mier 1971; Vanzolini 1973; Van der Hammen 1974; Prance 1977; Pires and Prance 1977; Simpson and Haffer 1978; Mori et al. 1981; Prance 1982). The Veadeiros refuge in Goias and the Serra do Mar refuge in southeastern Brazil were formed during the Quaternary pe- riod, were repeatedly colonized during the Pleistocene, and are among the oldest refugia in Brazil. Five out of the seven species in Chres- ta and Pycnocephalum are found within the Veadeiros refuge. Of the remaining two taxa, C. pycnocephala appears to be a Minas Gerais variant of C. exsucca, and modern collections of P. pinnatifidum are unknown. Thus, it is possible that Veadeiros has served as the center of dis- persal and diversification for Chresta and Pyc- nocephalum.