Mimosine accumulation in Leucaena leucocephala in response to stress signaling molecules and acute UV exposure.

Mimosine is a non-protein amino acid of Fabaceae, such as Leucaena spp. and Mimosa spp. Several relevant biological activities have been described for this molecule, including cell cycle blocker, anticancer, antifungal, antimicrobial, herbivore deterrent and allelopathic activities, raising increased economic interest in its production. In addition, information on mimosine dynamics in planta remains limited. In order to address this topic and propose strategies to increase mimosine production aiming at economic uses, the effects of several stress-related elicitors of secondary metabolism and UV acute exposure were examined on mimosine accumulation in growth room-cultivated seedlings of Leucaena leucocephala spp. glabrata. Mimosine concentration was not significantly affected by 10 ppm salicylic acid (SA) treatment, but increased in roots and shoots of seedlings treated with 84 ppm jasmonic acid (JA) and 10 ppm Ethephon (an ethylene-releasing compound), and in shoots treated with UV-C radiation. Quantification of mimosine amidohydrolase (mimosinase) gene expression showed that ethephon yielded variable effect over time, whereas JA and UV-C did not show significant impact. Considering the strong induction of mimosine accumulation by acute UV-C exposure, additional in situ ROS localization, as well as in vitro antioxidant assays were performed, suggesting that, akin to several secondary metabolites, mimosine may be involved in general oxidative stress modulation, acting as a hydrogen peroxide and superoxide anion quencher.

Quillaja brasiliensis saponins induce robust humoral and cellular responses in a bovine viral diarrhea virus vaccine in mice.

A saponin fraction extracted from Quillaja brasiliensis leaves (QB-90) and a semi-purified aqueous extract (AE) were evaluated as adjuvants in a bovine viral diarrhea virus (BVDV) vaccine in mice. Animals were immunized on days 0 and 14 with antigen plus either QB-90 or AE or an oil-adjuvanted vaccine. Two-weeks after boosting, antibodies were measured by ELISA; cellular immunity was evaluated by DTH, lymphoproliferation, cytokine release and single cell IFN-γ production. Serum anti-BVDV IgG, IgG1 and IgG2b were significantly increased in QB-90- and AE-adjuvanted vaccines. A robust DTH response, increased splenocyte proliferation, Th1-type cytokines and enhanced production of IFN-γ by CD4(+) and CD8(+) T lymphocytes were detected in mice that received QB-90-adjuvanted vaccine. The AE-adjuvanted preparation stimulated humoral responses but not cellular immune responses. These findings reveal that QB-90 is capable of stimulating both cellular and humoral immune responses when used as adjuvant.

Oxidative stress and production of bioactive monoterpene indole alkaloids: biotechnological implications.

Monoterpene indole alkaloids (MIAs) encompass plant natural products with important pharmacological relevance. They include the anti-tumoral MIAs found in Catharanthus roseus and Camptotheca acuminata. The often low yields of bioactive alkaloids in plants has prompted research to identify the factors regulating MIA production. Oxidative stress is a general response associated with biotic and abiotic stresses leading to several secondary responses, including elicitation of MIA production. These changes in secondary metabolism may take place directly or via second messengers, such as Ca(2+) and reactive oxygen species (ROS). H2O2 is the main ROS that participates in MIA biosynthesis. This review analyzes the links between oxidative stress, elicitation of bioactive MIA production and their potential roles in antioxidant defense, as well as exploring the implications to developing biotechnological strategies relevant for alkaloid supply.

Bioconversion of (+)- and (-)-alpha-pinene to (+)- and (-)-verbenone by plant cell cultures of Psychotria brachyceras and Rauvolfia sellowii

This work describes the bioconversion of (-)- and (+)-alpha-pinene (2,6,6-trimethyl-bicyclo[3.1.1]hept-2-ene), targeted at the production of (-)- and (+)-verbenone (4,6,6-trimethyl-bicyclo (3.1.1) hept-3-en-2-one), respectively, using Psychotria brachyceras and Rauvolfia sellowii cell suspension cultures. P. brachyceras showed selectivity to (-)-alpha-pinene with 80.9 percent conversion (relative integrated area gas chromatography-mass spectrometry (GC-MS)) of (-)-verbenone in 10-day-incubation, whereas R. sellowii was able to convert both pinene enantiomers (37.6% conversion of (-)-verbenone in 7-day-incubation and 32.2% conversion of (+)-verbenone in 10-day-incubation). In both systems trans-verbenol was formed as main product and then slowly biocatalyzed to verbenone. Verbenone were also present among the autoxidation products during control experiments, but in much lower amounts and accompanied by several by-products, highlighting the usefulness of the biotransformation process.

The use of biodiversity as source of new chemical entities against defined molecular targets for treatment of malaria, tuberculosis, and T-cell mediated diseases: a review

The modern approach to the development of new chemical entities against complex diseases, especially the neglected endemic diseases such as tuberculosis and malaria, is based on the use of defined molecular targets. Among the advantages, this approach allows (i) the search and identification of lead compounds with defined molecular mechanisms against a defined target (e.g. enzymes from defined pathways), (ii) the analysis of a great number of compounds with a favorable cost/benefit ratio, (iii) the development even in the initial stages of compounds with selective toxicity (the fundamental principle of chemotherapy), (iv) the evaluation of plant extracts as well as of pure substances. The current use of such technology, unfortunately, is concentrated in developed countries, especially in the big pharma. This fact contributes in a significant way to hamper the development of innovative new compounds to treat neglected diseases. The large biodiversity within the territory of Brazil puts the country in a strategic position to develop the rational and sustained exploration of new metabolites of therapeutic value. The extension of the country covers a wide range of climates, soil types, and altitudes, providing a unique set of selective pressures for the adaptation of plant life in these scenarios. Chemical diversity is also driven by these forces, in an attempt to best fit the plant communities to the particular abiotic stresses, fauna, and microbes that co-exist with them. Certain areas of vegetation (Amazonian Forest, Atlantic Forest, Araucaria Forest, Cerrado-Brazilian Savanna, and Caatinga) are rich in species and types of environments to be used to search for natural compounds active against tuberculosis, malaria, and chronic-degenerative diseases. The present review describes some strategies to search for natural compounds, whose choice can be based on ethnobotanical and chemotaxonomical studies, and screen for their ability to bind to immobilized drug targets and to inhibit their activities. Molecular cloning, gene knockout, protein expression and purification, N-terminal sequencing, and mass spectrometry are the methods of choice to provide homogeneous drug targets for immobilization by optimized chemical reactions...

Iron homeostasis related genes in rice

Iron is essential for plants. However, excess iron is toxic, leading to oxidative stress and decreased productivity. Therefore, plants must use finely tuned mechanisms to keep iron homeostasis in each of their organs, tissues, cells and organelles. A few of the genes involved in iron homeostasis in plants have been identified recently, and we used some of their protein sequences as queries to look for corresponding genes in the rice (Oryza sativa) genome. We have assigned possible functions to thirty-nine new rice genes. Together with four previously reported sequences, we analyzed a total of forty-three genes belonging to five known protein families: eighteen YS (Yellow Stripe), two FRO (Fe3+-chelate reductase oxidase), thirteen ZIP (Zinc regulated transporter / Iron regulated transporter Protein), eight NRAMP (Natural Resistance - Associated Macrophage Protein), and two Ferritin proteins. The possible cellular localization and number of potential transmembrane domains were evaluated, and phylogenetic analysis performed for each gene family. Annotation of genomic sequences was performed. The presence and number of homologues in each gene family in rice and Arabidopsis is discussed in light of the established iron acquisition strategies used by each one of these two plants.