The pest kill rate of thirteen natural enemies as aggregate evaluation criterion of their biological control potential of Tuta absoluta.

Ecologists study how populations are regulated, while scientists studying biological pest control apply population regulation processes to reduce numbers of harmful organisms: an organism (a natural enemy) is used to reduce the population density of another organism (a pest). Finding an effective biological control agent among the tens to hundreds of natural enemies of a pest is a daunting task. Evaluation criteria help in a first selection to remove clearly ineffective or risky species from the list of candidates. Next, we propose to use an aggregate evaluation criterion, the pest kill rate, to compare the pest population reduction capacity of species not eliminated during the first selection. The pest kill rate is the average daily lifetime killing of the pest by the natural enemy under consideration. Pest kill rates of six species of predators and seven species of parasitoids of Tuta absoluta were calculated and compared. Several natural enemies had pest kill rates that were too low to be able to theoretically reduce the pest population below crop damaging densities. Other species showed a high pest reduction capacity and their potential for practical application can now be tested under commercial crop production conditions.

Chemical composition of Schinus areira essential oil and antimicrobial action against Staphylococcus aureus.

The antimicrobial activities of plant extracts have formed the basis of many alternative medicines. In this context, the genus Schinus L. (Anacardiaceae), exhibits many traditional uses in medicine. However, a few studies on the antimicrobial properties of Schinus areira essential oils were conducted. The essential oil from S. areira leaves from Santiago del Estero was obtained by hydrodistillation and twenty-eight compounds were identified using CG-MS-EI spectrometry. The sesquiterpenoid alcohol 1-epi-cadinol was the major compound, followed by δ-cadinene, alloaromadendrene, ß-pinene, ß-caryophyllene, and γ-cadinene. The essential oil obtained exhibited antimicrobial activity against Staphylococcus aureus, showing a bacteriostatic activity at 64 µg/mL and bacteriolytic activity at 256 µg/mL; in contrast, non antibacterial effect was observed in Escherichia coli in the assayed conditions. The antibacterial activity was accompanied by significant changes in Zeta potential on the S. aureus surface. The data obtained suggest that the essential oil of S.areira leaves presents potential use in pharmaceutical industries.

Trypanocidal Activity of Flavokawin B, a Component of Polygonum ferrugineum Wedd.

The trypanocidal potential of the natural chalcone flavokawin B, which was isolated from the hexanic extract of Polygonum ferrugineum Wedd., is reported here. Although flavokawin B is widespread, this is the first report about its trypanocidal properties on both Trypanosoma cruzi (IC50 = 9.5 µM, IC50 = 34.7 µM benznidazol, Y strain) epimastigotes and Trypanosoma brucei (IC50 = 4.8 µM, IC50 = 6.4 µM pentamidine, 29-13 strain) procyclic forms, which was also corroborated on T. brucei strain 427 (IC50 = 6.2 µM). In order to learn more about its properties, unspecific cytotoxicity on Hep G2 cells was investigated as well as the trans-splicing inhibitory potential on T. brucei cells. The results shown here point to flavokawin B as a candidate in the search for new agents. It is also cheaper and less toxic than the available drugs to treat trypanosomiasis with a special focus on sleeping sickness disease.

Ficus carica L. (Moraceae): an ancient source of food and health.

Since early in the man history, common fig was appreciated as food and for its medicinal properties. This review explores some aspects about the importance of Ficus carica L., an amazing and ancient source of medicines and food. Topics regarding chemistry, biological activity, ethno-pharmacological uses, and its nutritional value are discussed, as well as the potential of the species as a source of new and different chemical scaffolds. Very important in the past, appreciated in our time and extremely promising in the future, F. carica represents an interesting example of healthy foods and bioproducts.

Structure elucidation and absolute stereochemistry of isomeric monoterpene chromane esters.

Six novel monoterpene chromane esters were isolated from the aerial parts of Peperomia obtusifolia (Piperaceae) using chiral chromatography. This is the first time that chiral chromane esters of this kind, ones with a tethered chiral terpene, have been isolated in nature. Due to their structural features, it is not currently possible to assess directly their absolute stereochemistry using any of the standard classical approaches, such as X-ray crystallography, NMR, optical rotation, or electronic circular dichroism (ECD). Herein we report the absolute configuration of these molecules, involving four chiral centers, using vibrational circular dichroism (VCD) and density functional theory (DFT) (B3LYP/6-31G*) calculations. This work further reinforces the capability of VCD to determine unambiguously the absolute configuration of structurally complex molecules in solution, without crystallization or derivatization, and demonstrates the sensitivity of VCD to specify the absolute configuration for just one among a number of chiral centers. We also demonstrate the sufficiency of using the so-called inexpensive basis set 6-31G* compared to the triple-ζ basis set TZVP for absolute configuration analysis of larger molecules using VCD. Overall, this work extends our knowledge of secondary metabolites in plants and provides a straightforward way to determine the absolute configuration of complex natural products involving a chiral parent moiety combined with a chiral terpene adduct.

Isolation of antifungal saponins from Phytolacca tetramera, an Argentinean species in critic risk.

The methanolic extract of the berries of Phytolacca tetramera, an Argentinean species submitted to a great anthropic impact, and therefore in critic risk of extinction, not previously studied, showed antifungal activity against opportunistic pathogenic fungi. Through fractionation of the extract followed by agar dilution assays, three monodesmosidic triterpenoid saponins have been isolated from the butanolic extract of P. tetramera. The structures were established as phytolaccosides: B [3-O-beta-D-xylopiranosyl-phytolaccagenin], E [3-O-beta-D-glucopyranosyl-(1-->4)-beta-D-xylopiranosyl-phytolaccagenin]. and F [3-O-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-glucopyranosyl-(1-->2)-beta-D-xylopyranosyl-phytolaccagenic acid]. The three saponins belong to the olean-type triterpenoid saponins, with 28,30 dicarboxylic groups and an olefinic double bond on C-12. Phytolaccosides B and E but not phytolaccoside F, showed antifungal activities against a panel of human pathogenic opportunistic fungi. Phytolaccoside B was the most active compound and showed the broadest spectrum of action. The most sensitive fungus was Trichophyton mentagrophytes.