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This review concerns the definitions and appropriate analytical characterisations of herbal reference standards within the framework of regulatory requirements. It describes currently applicable rules and regulations, as well as future issues relating to the European Pharmacopoeia and United States Pharmacopoeia. It provides an update on the use and availability of pharmacopoeial (EP and USP) herbal reference standards since our last review was published in 2009. The continuing challenges facing manufacturers, suppliers and analysts are discussed on the basis of exemplary reference substances for herbal products in medicinal and food products. The article also reviews the special aspects of Brazilian stipulations (Brazilian Pharmacopoeia, Anvisa) by comparison with European regulations. The term herbal products as used throughout this article refers to herbal drugs, herbal preparations and finished herbal medicinal products unless a different meaning is obvious from the context. More specific terms are used where necessary.
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*The rich ecology of tropical forests is intimately tied to their moisture status. Multi-site syntheses can provide a macro-scale view of these linkages and their susceptibility to changing climates. Here, we report pan-tropical and regional-scale analyses of tree vulnerability to drought. *We assembled available data on tropical forest tree stem mortality before, during, and after recent drought events, from 119 monitoring plots in 10 countries concentrated in Amazonia and Borneo. *In most sites, larger trees are disproportionately at risk. At least within Amazonia, low wood density trees are also at greater risk of drought-associated mortality, independent of size. For comparable drought intensities, trees in Borneo are more vulnerable than trees in the Amazon. There is some evidence for lagged impacts of drought, with mortality rates remaining elevated 2 yr after the meteorological event is over. *These findings indicate that repeated droughts would shift the functional composition of tropical forests toward smaller, denser-wooded trees. At very high drought intensities, the linear relationship between tree mortality and moisture stress apparently breaks down, suggesting the existence of moisture stress thresholds beyond which some tropical forests would suffer catastrophic tree mortality.
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Secas , Árvores/crescimento & desenvolvimento , Clima Tropical , Adaptação Fisiológica , Biomassa , Brasil , Ecossistema , Modelos Biológicos , Caules de Planta/crescimento & desenvolvimento , Chuva , Estresse Fisiológico , Fatores de Tempo , Água , Madeira/crescimento & desenvolvimentoRESUMO
Amazon forests are a key but poorly understood component of the global carbon cycle. If, as anticipated, they dry this century, they might accelerate climate change through carbon losses and changed surface energy balances. We used records from multiple long-term monitoring plots across Amazonia to assess forest responses to the intense 2005 drought, a possible analog of future events. Affected forest lost biomass, reversing a large long-term carbon sink, with the greatest impacts observed where the dry season was unusually intense. Relative to pre-2005 conditions, forest subjected to a 100-millimeter increase in water deficit lost 5.3 megagrams of aboveground biomass of carbon per hectare. The drought had a total biomass carbon impact of 1.2 to 1.6 petagrams (1.2 x 10(15) to 1.6 x 10(15) grams). Amazon forests therefore appear vulnerable to increasing moisture stress, with the potential for large carbon losses to exert feedback on climate change.
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Biomassa , Secas , Ecossistema , Árvores , Atmosfera , Brasil , Carbono , Dióxido de Carbono , Clima , América do Sul , Árvores/crescimento & desenvolvimento , Clima TropicalRESUMO
Vitisin A was prepared from malvidin 3-glucoside and pyruvic acid in model wine medium, isolated by countercurrent chromatography, and purified by preparative high-performance liquid chromatography (HPLC). The synthesized compound was used as a reference standard to quantify vitisin A in Chilean wines from Vitis vinifera cv. Cabernet Sauvignon, including a vertical row of wines from the same vineyard over 16 years. Maximum vitisin A content was reached within the first year of storage. Importantly, up to half of the initial amount of vitisin A in young wines was still present in 15 year old wines. Although vitisin A was found to be much more stable as compared to other monomeric C-4 underivatized anthocyanins, it also slowly degrades after reaching its peak concentration. The "color activity concept" was applied to vitisin A, malvidin 3-glucoside, malvidin 3-(6' '-acetylglucoside), and polymeric pigments isolated by countercurrent chromatography in order to estimate their contribution toward the overall color expression of wines. It was found that vitisin A is only a minor contributor to the visually perceived color of aged red wines (color contribution approximately 5%). The major contributor is the polymeric fraction (color contribution approximately 70-90%).