The objective of the study was to determine and compare the effect of several solvents namely hot water, 50 % methanol, ethanol, 50 % ethanol, acetone, 50 % acetone and ethyl acetate on phenolic composition and free radical scavenging activity in black tea and selected herbal infusions from Zimbabwe and Brazil. For the black tea, made from Camellia sinensis, Quickbrew™ was used. Zimbabwean herbal infusions used were Lippia javanica and Ficus sycamore while those from Brazil were Syzygium j a m b o l a n u m , C u p h e a c a r t h a g e n e n s i s a n d I l e x paraguariensis. Total phenolic content and free radical scavenging activity were determined using Folin-Ciocalteu and 2, 2-diphenyl-1-picrylhydrazyl (DPPH) assay, respectively. IC 50 values for each solvent were calculated and used to interpret radical scavenging activity. Aqueous organic solvents extracted higher quantities of phenolic compounds than in their absolute organic nature. Acetone (50 %) extracted a higher total phenolic content (TPC) in C. sinensis, L. javanica and I. paraguariensis. Hot water extracted the highest TPC in F. sycamore and S. jambolanum while 50 % ethanol was highest in C. carthagenensis. Free radical scavenging activity (FRSA) was not necessarily in the same order as TPC, indicating that high TPC does not always mean high FRSA and vice versa. The highest FRSA for S. jambolanum and C. carthagenensis extracts was in 50 % ethanol, F. sycamore in 50 % methanol, and I. paraguariensis, C. sinensis and L. javanica extracts in 50 % acetone. Ethyl acetate recorded the lowest TPC and FRSA in all plant samples analysed. Generally, solvent used affected TPC and free radical scavenging activity. Organic solvents may need to be separated from phenolics after extraction, as some of them namely acetone, methanol and ethyl acetate can be toxic to humans. Water and ethanol are the least toxic solvents which may need no further separation from extracts.

To anticipate potential seedling damage, plants block seed germination under unfavorable conditions. Previous studies investigated how seed germination is controlled in response to abiotic stresses through gibberellic and abscisic acid signaling. However, little is known about whether seeds respond to rhizosphere bacterial pathogens. We found that Arabidopsis seed germination is blocked in the vicinity of the plant pathogen Pseudomonas aeruginosa. We identified L-2-amino-4-methoxy-trans-3-butenoic acid (AMB), released by P. aeruginosa, as a biotic compound triggering germination arrest. We provide genetic evidence that in AMB-treated seeds DELLA factors promote the accumulation of the germination repressor ABI5 in a GA-independent manner. AMB production is controlled by the quorum sensing system IQS. In vitro experiments show that the AMB-dependent germination arrest protects seedlings from damage induced by AMB. We discuss the possibility that this could serve as a protective response to avoid severe seedling damage induced by AMB and exposure to a pathogen.

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International audienceElionurus muticus is a grass from Pampa biome and it is an excellent alternative as natural source of citral in southern Brazil. The essential oil has a high citral level (80%) and presents variability for other important chemical compounds. The present studies indicated its cytotoxic effect against Artemia salina and also suggested its application in the control of pathogenic fungi. E. muticus could become an alternative to synthetic fungicides for using in agro-industries and also to screen and develop novel types of selective and natural fungicides