Insecticidal and nematicidal essential oils from Argentinean Eupatorium and Baccharis spp

Nematicidal Effects of Volatile Organic Compounds from Microorganisms and Plants on Plant-Parasitic Nematodes

Plant-parasitic nematodes (PPNs) are one of the most destructive plant pathogens worldwide, and controlling them is extremely challenging. Volatile organic compounds (VOCs), which naturally exist in plants and microorganisms, play an important role in the biological control of PPNs and are considered potential substances for the development of commercial nematicides. This paper summarizes the VOCs produced by microorganisms and plants as well as their toxic effects on PPNs. VOCs from 26 microbial strains and 51 plants that are active against nematodes from over the last decade were reviewed. Furthermore, the mechanisms of toxicity of some VOCs against PPNs are also illustrated.

A Review of the Potency of Plant Extracts and Compounds from Key Families as an Alternative to Synthetic Nematicides: History, Efficacy, and Current Developments

The global nematicides market is expected to continue growing. With an increasing demand for synthetic chemical-free organic foods, botanical nematicides are taking the lead as replacements. Consequently, in the recent years, there have been vigorous efforts towards identification of the active secondary metabolites from various plants. These include mostly glucosinolates and their hydrolysis products such as isothiocyanates; flavonoids, alkaloids, limonoids, quassinoids, saponins, and the more recently probed essential oils, among others. And despite their overwhelming potential, variabilities in quality, efficacy, potency and composition continue to persist, and commercialization of new botanical nematicides is still lagging. Herein, we have reviewed the history of botanical nematicides and regional progresses, the potency of the identified phytochemicals from the key important plant families, and deciphered some of the impediments involved in standardization of the active compounds in addition to the concerns over the safety of the purified compounds to non-target microbial communities.

Chemical composition, antioxidant and anti-inflammatory activities of the essential oils from male and female specimens of Baccharis punctulata (Asteraceae)

ETHNOPHARMACOLOGICAL RELEVANCE

Baccharis punctulata (Asteraceae), popularly known as "Chíllka saru saru" in Bolivia, has been used by rural communities in Bustillo Province of the Potosi Department for treatment of asthma, luxations and contusions.

AIM OF THE STUDY

To analyze the chemical composition of the essential oils obtained from leaves of female (BPF) and male (BPM) specimens and evaluate their anti-inflammatory and antioxidant properties.

MATERIAL AND METHODS

Chemical composition analyses of Baccharis punctulata essential oils isolated by hidrodistillation from leaves of male and female specimens were performed by GC-FID-MS. The in vivo anti-inflammatory activity was evaluated using the model of TPA (12-O-tetradecanoylphorbol-13-acetate) induced ear edema, and the polymorphonuclear cell migration was evaluated by mieloperoxidase (MPO) and analyzed histologically. To measure the reactive oxygen species (ROS) in the inflamed tissue, the DCFH-DA fluorescent probe was used. The chemical in vitro antioxidant activity of essential oils was determined using the 2,2-diphenyl-1-picryl-hydrazyl (DPPH) free radical assay.

RESULTS

The chemical analysis showed high proportion of sesquiterpenes in the volatiles samples obtained from BPM, such as δ-elemene (14.29%), germacrene D (11.29%) and bicyclogermacrene (10.90%), and in the sample from BPF, bicyclogermacrene (42.44%), germacrene D (21.18%) and β-caryophyllene (14.06%). A statistical difference (p < 0.05) on chemical composition between both essential oils was observed. Topical administration of both BPM and BPF essential oils was able to inhibit the formation of TPA-induced edema in the treated groups. Isolated administration of TPA promoted an increase in MPO enzyme activity, and inhibition of the increase of MPO activity was observed when animals were treated with BFP at concentrations of 0.1 mg/ear (13.69 ± 0.20%), 0.3 mg/ear (22.35 ± 0.11%), and 1.0 mg/ear (44.98 ± 0.27%). Topical treatment with BPM was able to inhibit MPO activity at 22.40 ± 0.29% (0.1 mg/ear), 36.49 ± 0.07% (0.3 mg/ear) and 52.19 ± 0.28% (1.0 mg/ear). The positive control of dexamethasone (DEXA, 0.1 mg/ear) was able to revert the increase in the enzymatic activity of MPO caused by TPA (65.16%). Histological analysis showed that topical application of TPA promoted intense cellular infiltration. This inflammatory parameter was reduced with the topical application of the BPF and BPM oil samples as well as with DEXA. The results observed in the ROS and DPPH tests suggest that both samples were able to reduce the inflammatory cells influx and have in vitro antioxidant properties, respectively.

CONCLUSIONS

This study presents, for the first time, the chemical composition of the essential oils obtained from leaves of male and female specimens of Baccharis punctulata, and their anti-inflammatory and antioxidant activities. The results presented by the volatile samples in our biotests support traditional uses of this plant species.

Assessment of the Insecticidal Potential of the Eupatorium buniifolium Essential Oil Against Triatoma infestans (Hemiptera: Reduviidae). A Chiral Recognition Approach

In this research, bioactivities toward the Chagas' disease vector Triatoma infestans (Klug) (Hemiptera: Reduviidae) by the essential oil (EO) of Eupatorium buniifolium H. et A. (Asteraceae) are reported. The tests were designed in order to determine ovicidal activity as well as the response to vapor exposure (fumigant) and to topical application (contact toxicity) and as repellent. In the last three bioassays, nymphs from the 3rd and 4th instar were used. The assayed materials were obtained from aerial parts of plants collected during the months of March and December, throughout 4 years, in two locations. The EO samples were subjected to a qualitative analysis by GC-MS and the relative area of each component was reported by GC-FID. The main monoterpene detected was α-pinene and by using a chiral column through GC-MS experiments and having both stereoisomers as standards, we were able to determine that the enantiomer present was S,S-(-)-α-pinene. Although usually in studies of EOs changes in chemical composition are often observed due to the time of collection and the environment where the plant develops, in our case the differences were, with some exception, only at the level of the minor components. The best results were obtained in the experiments to determine ovicidal activity, fumigant action, and repellency. No worthy response was found as insecticide in the trials designed for contact toxicity. The results of the studied bioactivities were independent of the location, month, and year of collection of the plant material. This behavior provides an interesting scope in relation to the potential use of this natural blend for the control of this insect at the nymph stage as repellent as well as for decreasing the population by ovicidal effect. Notably, in the course of the two-choice repellency test, it was possible to demonstrate recognition of one of the enantiomers of the α-pinene, giving rise to a non-common chirality/response effect. In this assay, the levorotatory isomer was the most active as repellent. Considering the abundance of the wild plant under study and the fact that its EO is easy to obtain, it is suggested that it could be an adequate natural resource to control this vector in a sustainable way as a complementary approach to conventional methods.

Rapid Discovery and Functional Characterization of Terpene Synthases from Four Endophytic Xylariaceae

Endophytic fungi are ubiquitous plant endosymbionts that establish complex and poorly understood relationships with their host organisms. Many endophytic fungi are known to produce a wide spectrum of volatile organic compounds (VOCs) with potential energy applications, which have been described as "mycodiesel". Many of these mycodiesel hydrocarbons are terpenes, a chemically diverse class of compounds produced by many plants, fungi, and bacteria. Due to their high energy densities, terpenes, such as pinene and bisabolene, are actively being investigated as potential "drop-in" biofuels for replacing diesel and aviation fuel. In this study, we rapidly discovered and characterized 26 terpene synthases (TPSs) derived from four endophytic fungi known to produce mycodiesel hydrocarbons. The TPS genes were expressed in an E. coli strain harboring a heterologous mevalonate pathway designed to enhance terpene production, and their product profiles were determined using Solid Phase Micro-Extraction (SPME) and GC-MS. Out of the 26 TPS's profiled, 12 TPS's were functional, with the majority of them exhibiting both monoterpene and sesquiterpene synthase activity.

Influence of polysaccharides on the rheology and stabilization of α-pinene emulsions

This work focuses on the need to include polysaccharides in a slightly concentrated O(α-pinene)/W emulsion, formulated with amphiphilic copolymers as emulsifiers. Rheology, laser diffraction and multiple light scattering were the main techniques used to assess the performance of gellan gum, xanthan gum and a mixture of both hydrocolloids as stabilizers. Small amplitude oscillatory shear results were consistent with the existence of three distinct microstructures and relaxation mechanisms, which depended on the hydrocolloid system used. The mechanical spectrum of the emulsion containing both polysaccharides signalled the occurrence of thermodynamic incompatibility between the two. Flow curves fitted to the Carreau-Yasuda model demonstrated a negative synergistic effect between gellan and xanthan gums. The droplet size distribution was similar for these systems, which highlighted the importance of the continuous phase for emulsion stability. Multiple light scattering illustrated that creaming was practically eliminated by the incorporation of polysaccharides, coalescence being the main destabilization mechanism.