The chemical ecology of tropical forest diversity: Environmental variation, chemical similarity, herbivory, and richness.

Species richness in tropical forests is correlated with other dimensions of diversity, including the diversity of plant-herbivore interactions and the phytochemical diversity that influences those interactions. Understanding the complexity of plant chemistry and the importance of phytochemical diversity for plant-insect interactions and overall forest richness has been enhanced significantly by the application of metabolomics to natural systems. The present work used proton nuclear magnetic resonance spectroscopy (1 H-NMR) profiling of crude leaf extracts to study phytochemical similarity and diversity among Piper plants growing naturally in the Atlantic Rainforest of Brazil. Spectral profile similarity and chemical diversity were quantified to examine the relationship between metrics of phytochemical diversity, specialist and generalist herbivory, and understory plant richness. Herbivory increased with understory species richness, while generalist herbivory increased and specialist herbivory decreased with the diversity of Piper leaf material available. Specialist herbivory increased when conspecific host plants were more spectroscopically dissimilar. Spectral similarity was lower among individuals of common species, and they were also more spectrally diverse, indicating phytochemical diversity is beneficial to plants. Canopy openness and soil nutrients also influenced chemistry and herbivory. The complex relationships uncovered in this study add information to our growing understanding of the importance of phytochemical diversity for plant-insect interactions and tropical plant species richness.

Synthesis of new 1,4-disubstituted 1,2,3-triazoles using the CuAAC reaction and determination of their antioxidant activities.

This study describes the synthesis and antioxidant activity of new 1,4-disubstituted 1,2,3-triazoles. These compounds were generated semi-synthetically using the Cu(I)-catalysed azide-alkyne cycloaddition (CuAAC) reaction between ethyl 2-azidoacetate and terminal acetylenes derived from the natural products carvacrol, eugenol, isovanillin, thymol and vanillin. The products were obtained at 50 to 80% yield and characterised through several spectrographic techniques. Antioxidant activity was assayed using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS). The products exhibited moderate antioxidant activity, with ethyl 2-(4-((4-formyl-2-methoxyphenoxy)methyl)-1H-1,2,3-triazol-1-yl) acetate showing the highest antioxidant capacity (EC50 = 75.5 µg/mL) among the generated 1,4-disubstituted 1,2,3-triazoles. In conclusion, the generation of these compounds opens new possibilities for the development of new antioxidant agents.

New sources of botanical acaricides from species of Croton with potential use in the integrated management of Tetranychus urticae / Nuevas fuentes de acaricidas botánicos de especies de Croton con uso potencial en el manejo integrado de Tetranychus urticae

Essential oils from the leaves and stems of Croton adenocalyx, C. grewioides, C. heliotropiifoliusand C. blanchetianus obtained through hydrodistillation were analyzed by GC-MS. We then investigated the lethal and sublethal effects of the Croton oils and 15 major constituents against Tetranychus urticae. ß-Caryophyllene was the major component in the leaf and stem oils from C. heliotropiifolius and C. adenocalyx. Spathulenol and (E)-anethole were the major constituents identified in the leaf and stem oils of C. blanchetianus and C. grewioides, respectively. The oil with the greatest lethal and sublethal effects was those from C. adenocalyx. Among the constituents ß-caryophyllene and spatulenol were the most toxic to the mite, where as eugenol and methyl eugenol were the most repellent. The toxicity and repellency of the Croton oils, particularly the oils from C. adenocalyx, demonstrate that these oils constitute a promising alternative to synthetic acaricides for use in the control of T. urticae.

Los aceites esenciales de las hojas y tallos de Croton adenocalyx, C. growioides, C. heliotropiifolius y C. blanchetianus obtenidos mediante hidrodestilación fueron analizados a través de GC-MS. Se investigaron los efectos letales y subletales de los aceites de Croton y 15 componentes principales contra Tetranychus urticae. El ß-cariofileno fue el componente principal en los aceites de hojas y tallos de C. heliotropiifolius y C. adenocalyx. El espatulenol y el (E)-anetol fueron los principales componentes identificados en los aceites de hojas y tallos de C. blanchetianus y C. growioides, respectivamente. El aceite con los mayores efectos letales y subletales fue el de C. adenocalyx. Entre los componentes, el ß-cariofileno y el espatulenol fueron los más tóxicos para el ácaro, mientras que el eugenol y el metil eugenol fueron los más repelentes. La toxicidad y la repelencia de los aceites de Croton, particularmente los aceites de C. adenocalyx, demuestran que estos aceites constituyen una alternativa prometedora respecto a los acaricidas sintéticos para uso en el control de T. urticae.

Biosynthesis of Pellucidin A in Peperomia pellucida (L.) HBK.

Peperomia pellucida (L.) HBK (Piperaceae) ("jabuti herb") is an herbaceous plant that is widespread in the tropics and has several ethnomedicinal uses. The phytochemical study of leaf extracts resulted in the isolation of 2,4,5-trimethoxycinnamic acid, 5,6,7-trimethoxyflavone, 2,4,5-trimethoxystyrene, 2,4,5-trimethoxybenzaldehyde, dillapiol, and sesamin in addition to pellucidin A. The co-occurrence of styrene and cyclobutane dimers suggested the formation of pellucidin A by a photochemical [2+2] cycloaddition of two molecules of 2,4,5-trimethoxystyrene. To investigate this biogenesis, analysis of plant leaves throughout ontogeny and treatments such as drought, herbivory and, exposure to jasmonic acid and UV365 light were carried out. Significant increases in the content of dillapiol (up to 86.0%) were found when P. pellucida plants were treated with jasmonic acid, whereas treatment under UV365 light increase the pellucidin A content (193.2%). The biosynthetic hypothesis was examined by feeding various 13C-labeled precursors, followed by analysis with GC-MS, which showed incorporation of L-(2-13C)-phenylalanine (0.72%), (8-13C)-cinnamic acid (1.32%), (8-13C)-ferulic acid (0.51%), (8-13C)-2,4,5-trimethoxycinnamic acid (7.5%), and (8-13C)-2,4,5-trimethoxystyrene (12.8%) into pellucidin A. The enzymatic conversion assays indicated decarboxylation of 2,4,5-trimethoxycinnamic acid into 2,4,5-trimethoxystyrene, which was subsequently dimerized into pellucidin A under UV light. Taken together, the biosynthesis of pellucidin A in P. pellucida involves a sequence of reactions starting with L-phenylalanine, cinnamic acid, ferulic acid, 2,4,5-trimethoxycinnamic acid, which then decarboxylates to form 2,4,5-trimethoxystyrene and then is photochemically dimerized to produce pellucidin A.

Stabilization and detection of hydrophylloquinone as di-O-methyl derivative.

Phylloquinone is a redox active naphthoquinone involved in electron transport in plants. The function of this reduced form remains unclear due to its instability, which has precluded detection. Herein, a simple method that permits the stabilization of the reduced form of phylloquinone by di-O-methylation and HPLC detection is described.