ABSTRACT Psychotria is the largest genus in Rubiaceae. South American species of the genus are promising sources of natural products, mostly due to bioactive monoterpene indole alkaloids they accumulate. These alkaloids can have analgesic, antimutagenic, and antioxidant activities in different experimental models, among other pharmacological properties of interest. Propagation of genotypes with relevant pharmaceutical interest is important for obtaining natural products in a sustainable and standardized fashion. Besides the clonal propagation of elite individuals, the alkaloid content of Psychotria spp. can also be increased by applying moderate stressors or stress-signaling molecules. This review explores advances in research on methods for plant propagation and elicitation techniques for obtaining bioactive alkaloids from Psychotria spp. of the South Region of Brazil.

Oleoresin is a key defense strategy of advanced gymnosperms, based on the combination of a complex anatomical structure of resin ducts and elaborate terpene biochemistry. Given the vast array of oleoresin economic applications in the chemical, pharmaceutical, agrochemical, and biofuel industries, translating factors that regulate terpene biosynthesis into higher oleoresin yield is a challenge for the forestry industry. Field tests with approximately 3,500 28-year-old slash pine (Pinus elliottii Engelm. var. elliottii) trees were carried out from 2005 to 2008, under the subtropical climate of Southern Brazil, in order to examine the seasonal profile of oleoresin production stimulation in response to different chemical adjuvants, after mechanical injury. Yields of trees treated with oleoresin-inducing pastes containing alternative adjuvants were compared to the standard commercial one used on an industrial scale (based on the ethylene-releasing compound - 2-chloroethylphosphonic acid - CEPA). Significant increases in pine oleoresin yield were observed by modulating its biosynthesis and using chemical stimulants affecting defense responses (benzoic acid, used in addition to CEPA) and biosynthetic enzymes (metal cofactors of terpene synthases, iron or potassium, used as replacements for CEPA). Oleoresin stimulation was consistent over at least four consecutive years. Overall effectiveness of oleoresin yield adjuvant stimulation was higher in the faster growth seasons, although potassium was effective in all of them. Combining metal cofactors did not show synergistic or additive interactions. The results suggest that higher oleoresin yields can be obtained by using individual adjuvants of the same signaling pathway in a season-specific fashion.

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% 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 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. Plant extract preparations, fractionation of promising plant extracts, propagation protocols and definition of in planta studies to maximize product yield of plant species producing active compounds have to be performed to provide a continuing supply of bioactive materials. Chemical characterization of natural compounds, determination of mode of action by kinetics and other spectroscopic methods (MS, X-ray, NMR), as well as in vitro and in vivo biological assays, chemical derivatization, and structure-activity relationships have to be carried out to provide a thorough knowledge on which to base the search for natural compounds or their derivatives with biological activity.

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.