Antiproliferative activity, antioxidant capacity and tannin content in plants of semi-arid northeastern Brazil.

The objective of this study was to evaluate antiproliferative activity, antioxidant capacity and tannin content in plants from semi-arid northeastern Brazil (Caatinga). For this study, we selected 14 species and we assayed the methanol extracts for antiproliferative activity against the HEp-2 (laryngeal cancer) and NCI-H292 (lung cancer) cell lines using the (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazole) (MTT) method. In addition, the antioxidant activity was evaluated with the DPPH (2,2-diphenyl-2-picrylhydrazyl) assay, and the tannin content was determined by the radial diffusion method. Plants with better antioxidant activity (expressed in a dose able to decrease the initial DPPH concentration by 50%, or IC50) and with higher levels of tannins were: Poincianella pyramidalis (42.95±1.77 µg/mL IC50 and 8.17±0.64 tannin content), Jatropha mollissima (54.09±4.36µg/mL IC50 and 2.35±0.08 tannin content) and Anadenanthera colubrina (73.24±1.47 µg/mL IC50 and 4.41±0.47 tannin content). Plants with enhanced antiproliferative activity (% living cells) were Annona muricata (24.94±0.74 in NCI-H292), Lantana camara (25.8±0.19 in NCI-H292), Handroanthus impetiginosus (41.8±0.47 in NCI-H292) and Mentzelia aspera (45.61±1.94 in HEp-2). For species with better antioxidant and antiproliferative activities, we suggest future in vitro and in vivo comparative studies with other pharmacological models, and to start a process of purification and identification of the possible molecule(s) responsible for the observed pharmacological activity. We believe that the flora of Brazilian semi-arid areas can be a valuable source of plants rich in tannins, cytotoxic compounds and antioxidant agents.

Medicinal plants of the caatinga (semi-arid) vegetation of NE Brazil: a quantitative approach.

The caatinga (semi-arid vegetation) is a Brazilian biome with a significant but poorly studied biodiversity closely associated with a diverse cultural heritage. The present work focused on analyzing published information available concerning medicinal plants used by traditional communities. We sought to contribute to future phytochemical and pharmacological investigations by documenting the therapeutic uses of native caatinga plants within the aims of modern ethnopharmacological research. Twenty-one published works cited a total of 389 plant species used by indigenous and rural communities in northeastern Brazil for medicinal purposes. The relative importance index (RI) of each species in these inventories was calculated, and information concerning the plant's local status (spontaneous or cultivated), distribution, and habit was recorded. Of the 275 spontaneous (non-cultivated) species cited, 15.3% were endemic to the caatinga. A statistical relationship was verified between the relative importance of the species and their endemic status (p<0.05). Herbaceous plants were more numerous (169) than trees (90) or shrubs and sub-shrubs (130) at a statistically significant level (p<0.05). A survey of published information on the phytochemical and pharmacological status of the plants demonstrating the highest RI supported the veracity of their attributed folk uses.