Late Quaternary hydroclimate and vegetation changes in an upland lake in southeastern Amazonia.

An integrated approach considering facies, isotopic, and palynological analyses of lake sediments from the Serra Norte de Carajás, southeastern Amazonia, is presented in this work to refine paleoclimate and paleohydrological changes based on upland lake sediments during the late Quaternary. The sediments have a fining-upward deposition cycle typical of upland swamps/lakes. The origin of organic matter is autochthonous mainly related to C3 terrestrial plants, macrophytes and algae. The pollen records of Hedyosmum during the Early Pleistocene suggest lower temperatures than those observed along Holocene. In the transitional period between the Pleistocene and the Holocene, rainfall decreased, causing the retraction of the flooded area, favoring the development of marshy conditions. The Late and Middle Holocene were marked by higher temperatures and lower humidity. Afterward, the increased pollen concentration from canga and forest vegetation, macrophytes, palms, and algae suggested increased humidity in the Early Holocene. The relative contribution of forest pollen along the records indicated that drier conditions were not strong enough for an extensive expansion of canga over forested areas.

Essential oils composition of croton species from the Amazon.

The essential oils of leaves and twigs from the Euphorbiaceous Croton draconoides, C. urucurana and Julocroton triqueter were obtained and analyzed by GC and GC-MS. In total, 101 volatile constituents were identified, comprising an average of 90% of the oil, mostly made up of mono- and sesquiterpenes. The monoterpene hydrocarbons varied from 1.2 to 40.2%, the sesquiterpene hydrocarbons from 34.0 to 49.6% and the oxygenated sesquiterpenes from 11.5 to 51.3%. The main compounds found in the oil of C. draconoides were beta-pinene (16.9%), alpha-pinene (16.5%), curzerene (12.8%), germacrene D (9.0%), gamma-elemene (4.7%), and elemol (4.4%). The oil of C. urucurana showed sesquicineole (23.0%), dehydro-sesquicineole (13.8%), beta-caryophyllene (7.9%), beta-bisabolol (5.0%), germacrene D (4.2%) and beta-elemene (4.1%) as the chief compounds. The oil of J. triqueter was dominated by beta-caryophyllene (16.3%), beta-phellandrene (10.2%), spathulenol (5.1%), caryophyllene oxide (5.0%), delta-cadinene (4.3%), (E)-nerolidol (4.3%), and alpha-copaene (4.1%).

Antioxidant capacity and larvicidal and antifungal activities of essential oils and extracts from Piper krukoffii.

The leaves and twigs of Piper krukoffii, collected in the Carajás National Forest, north Brazil, yielded essential oils (2.0% and 0.8%), the main constituents of which were myristicin (40.3% and 26.7%), apiole (25.4% and 34.1%) and elemicin (2.8% and 3.0%). The antioxidant activities of the oils, methanol extract and its sub-fractions were evaluated. The DPPH EC50 values varied from the ethyl acetate sub-fraction (73.4 +/- 3.7 microg/mL) to the methanol extract (24.9 +/- 0.8 microg/mL), and the ABTS TEAC values ranged in the same order from 265.7 to 349.2 microMol TE/g. These results indicated a significant antioxidant activity for the plant. The lignans (-)-kusunokin, yatein, (-)-hinokin and cubebin were identified in the methanol extract. The hydro-methanolic sub-fraction showed a high value for total phenol content (106.5 +/- 0.7 mg GAE/g), as well as 1H NMR signals for sugar moieties. Crude extracts and sub-fractions were also able to inhibit beta-carotene bleaching, varying from 22.4 to 47.1%. The oils from the leaves and twigs showed strong larvicidal (21.4 and 3.6 microg/mL) and fungicide (0.5 and 0.1 microg/mL) activities.

Essential oil composition and antioxidant capacity of Lippia schomburgkiana.

The leaves and fine stems of Lippia schomburgkiana recorded an essential yield of 1.8%, the main constituents of which were 1,8-cineole (64.1%) and alpha-terpineol (12.0%). The methanol extract of L. schomburgkiana inhibited the DPPH radical, resulting in an EC50 value of 16.1 +/- 0.7 microg x mL(-1), which is only three times lower than that of trolox (4.7 +/- 0.4 microg x mL(-1)), signifying a high antioxidant activity for the species. The amount of total phenolics (376.7 +/- 35.5 mg GAE/g) and the trolox equivalent antioxidant capacity (327.0 +/- 24.8 mg TE/g) of the methanol extract confirmed the significant antioxidative capacity of this plant. The brine shrimp bioassay carried out on the oil (49.6 +/- 0.4 microg x mL(-1)) showed high toxicity, providing important evidence of its biological activity. The sensory evaluation of the leaves of L. schomburgkiana showed a percentage acceptance value very close to commercial oregano, indicating that the plant can be used in spice and condiment products.

Variability in essential-oil composition of Piper marginatum sensu lato.

This paper contains data on the chemical composition of the essential oils of 22 leaf samples of Piper marginatum Jacq. collected in different areas and ecosystems of the brazilian Amazon, as well as an overview of the available literature. The species presents a large synonymy based on their different leaf characteristics and distinct scents where some of them smell like anise or very close compounds. By GC, GC/MS, and cluster analysis, we identified seven chemotypes for the leaf oils. The main components found in chemotype I were safrole (1) and 3,4-(methylenedioxy)propiophenone (2). The chemotype II was dominated by 3,4-(methylenedioxy)propiophenone (2) and p-mentha-1(7),8-diene (10). The major compounds identified in chemotype III were 3,4-(methylenedioxy)propiophenone (2), myristicin (3), (E)-beta-ocimene (11), and gamma-terpinene (12). In the chemotype IV, the principal constituents were beta-caryophyllene (13), alpha-copaene (14), and 3,4-(methylenedioxy)propiophenone (2). The chemotype V was dominated by (E)-isoosmorhizole (6), (E)-anethole (8), and isoosmorhizole (7). The main compounds found in the chemotype VI were 2-methoxy-4,5-(methylenedioxy)propiophenone (4), methoxy-4,5-(methylenedioxy)propiophenone isomer 5, and (E)-isoosmorhizole (6). The major constituents in chemotype VII were beta-caryophyllene (13), bicyclogermacrene (15), and (E)-asarone (9).