Chemically mediated plant-herbivore interactions contribute to the diversity of terrestrial communities and the diversification of plants and insects. While our understanding of the processes affecting community structure and evolutionary diversification has grown, few studies have investigated how trait variation shapes genetic and species diversity simultaneously in a tropical ecosystem. We investigated secondary metabolite variation among subpopulations of a single plant species, Piper kelleyi (Piperaceae), using high-performance liquid chromatography (HPLC), to understand associations between plant phytochemistry and host-specialized caterpillars in the genus Eois (Geometridae: Larentiinae) and associated parasitoid wasps and flies. In addition, we used a genotyping-by-sequencing approach to examine the genetic structure of one abundant caterpillar species, Eois encina, in relation to host phytochemical variation. We found substantive concentration differences among three major secondary metabolites, and these differences in chemistry predicted caterpillar and parasitoid community structure among host plant populations. Furthermore, E. encina populations located at high elevations were genetically different from other populations. They fed on plants containing high concentrations of prenylated benzoic acid. Thus, phytochemistry potentially shapes caterpillar and wasp community composition and geographic variation in species interactions, both of which can contribute to diversification of plants and insects.

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Infectious diseases caused by parasites are a major threat for the entire mankind, especially in the tropics. More than 1 billion people world-wide are directly exposed to tropical parasites such as the causative agents of trypanosomiasis, leishmaniasis, schistosomiasis, lymphatic filariasis and onchocerciasis, which represent a major health problem, particularly in impecunious areas. Unlike most antibiotics, there is no "general" antiparasitic drug available. Here, the selection of antiparasitic drugs varies between different organisms. Some of the currently available drugs are chemically de novo synthesized, however, the majority of drugs are derived from natural sources such as plants which have subsequently been chemically modified to warrant higher potency against these human pathogens. In this review article we will provide an overview of the current status of plant derived pharmaceuticals and their chemical modifications to target parasite-specific peculiarities in order to interfere with their proliferation in the human host.

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Essential oils extracted from different plants (Anthemis nobilis L., Artemisia dracunculus L., Cannabis sativa L., Cupressus sempervirens L., Cymbopogon citratus (DC.) Stapf., Curcuma longa L., Foeniculum vulgare L., Hypericum perforatum L., Hyssopus officinalis L., Mentha spicata L., Monarda didyma L., Ocimum basilicum L., Ocotea quixos Kosterm., Origanum vulgare L., Pinus nigra J.F. Arnold, Pinus silvestris L., Piper crassinervium Kunth., Rosmarinus officinalis L., Salvia officinalis L., Salvia sclarea L., Santolina chamaecyparissus L., Thymus vulgaris L., Zingiber officinaie L.) were screened in guinea pig and rat plasma in order to assess antiplatelet activity and inhibition of clot retraction. The oils were chemically analysed and a relationship between components and ability to affect hemostasis was evidenced. O. quixos, F. vulgaris, and A. dracunculus showed the highest antiplatelet activity against ADP, Arachidonic Acid and the Thromboxane A2 agonist U46619 (IC50, 4-132 microg ml(-1)), and a good ability to destabilize clot retraction (IC50, 19-180 microg ml(-1)). For these oils a significant correlation between antiplatelet potency and phenylpropanoids content (54-86%) was evidenced thus suggesting a key role for this moiety in the prevention of clot formation. These findings provide the rationale to take in account the antiplatelet activity in the pharmacological screening of natural products containing phenylpropanoids.

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Eleven essential oils, namely, Cananga odorata (Annonaceae), Cupressus sempervirens (Cupressaceae), Curcuma longa (Zingiberaceae), Cymbopogon citratus (Poaceae), Eucalyptus globulus (Myrtaceae), Pinus radiata (Pinaceae), Piper crassinervium (Piperaceae), Psidium guayava (Myrtaceae), Rosmarinus officinalis (Lamiaceae), Thymus x citriodorus (Lamiaceae) and Zingiber officinale (Zingiberaceae), were characterized by means of GC and GC-MS and evaluated for their food functional ingredient related properties. These properties were compared to those of Thymus vulgaris essential oil, used as a reference ingredient. Antioxidant and radical-scavenging properties were tested by means of 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay, beta-carotene bleaching test and luminol-photochemiluminescence (PCL) assay. In the DPPH assay, C. odorata, C. citratus, R. officinalis and C. longa showed major effectiveness, with a radical inhibition ranging from 59.6 +/- 0.42-64.3 +/- 0.45%. In the beta-carotene bleaching test, C. odorata (75.5 +/- 0.53%), R. officinalis (81.1 +/- 0.57%) and C. longa (72.4 +/- 0.51%) gave the best inhibition results. Similar results were obtained for the same essential oils in the PCL assay. Antimicrobial properties were obtained on five food-spoilage yeasts: Candida albicans ATCC 48274, Rhodotorula glutinis ATCC 16740, Schizosaccharomyces pombe ATCC 60232, Saccharomyces cerevisiae ATCC 2365, Yarrowia lypolitica ATCC 16617. C. citratus and T. x citriodorus were the most effective against the tested strains. Suggestions on relationships between chemical composition and biological activities are outlined.

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Piper crassinervium, P. aduncum, P. hostmannianum, and P. gaudichaudianum contain the new benzoic acid derivatives crassinervic acid (1), aduncumene (8), hostmaniane (18), and gaudichaudianic acid (20), respectively, as major secondary metabolites. Additionally, 19 known compounds such as benzoic acids, chromenes, and flavonoids were isolated and identified. The antifungal activity of these compounds was evaluated by bioautographic TLC assay against Cladosporium cladosporioides and C. sphaerospermum.

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