Natural product studies of U.S. endangered plants: volatile components of Lindera melissifolia (Lauraceae) repel mosquitoes and ticks

Acaricidal assessment of the fungal extract of Pleurotus ostreatus against Rhipicephalus microplus: Role of in vitro and in silico analysis

The Pleurotus ostreatus mushroom, commonly referred to as the oyster mushroom, is a widely consumed edible mushroom that grows in clusters on dead or dying trees. In addition to its culinary uses, research has found that the mushroom may also have potential medicinal properties. The current study investigated the potential use of a fungal extract from P. ostreatus as a natural acaricide against Rhipicephalus microplus, a major vector of economically significant infections and one of the most significant bovine ectoparasites. The study used the adult immersion test (AIT) and the larvae packet test (LPT) to evaluate the effectiveness of the extract against ticks. To evaluate the reproductive effect of the fungal extract on the reproduction of R. microplus engorged females, the eggs were tested for weight and egg-laying index. The results of the study showed that P. ostreatus extract had a significant acaricidal effect, with a 40 mg/mL concentration causing 89 ± 2.64% mortality in R. microplus larvae compared to the 91.00 ± 3.60% mortality by the positive control at 48 h interval. Whereas in the AIT, the extract inhibited 39.86 ± 4.13% of oviposition. The study also used in silico approach to further examine the binding mechanisms of the compounds in the fungal extract to the target protein R. microplus Triosephosphate isomerase RmTIM, using molecular docking in AutoDock Vina software. Docking scores of -8.3, -7.7 and -6.9 kcal/mol, respectively, showed that rutin, naringin and myricitin had significant interactions with the active site residues of the target protein. Our results suggest that P. ostreatus extract may be a potential alternative to traditional acaricides for controlling R. microplus in livestock.

Acaricidal Efficacy of Plants from Ecuador, Ambrosia peruviana (Asteraceae) and Lepechinia mutica (Lamiaceae) against Larvae and Engorged Adult Females of the Common Cattle Tick, Rhipicephalus microplus

Control measures against common cattle tick Rhipicephalus microplus are of the upmost importance because of considerable, deleterious impact on a farm's economy. Due to resistance phenomena to synthetic acaricides being a constraint in affected farms, the search for plant derivatives as acaricides has increased dramatically in recent years. In this work, essential oils obtained from two Ecuadorian plants, Ambrosia peruviana and Lepechinia mutica (EOAp, EOLm), traditionally used as insecticides in indigenous communities, were studied on larvae and engorged females at the parasitic stages of R. microplus. Larvae and females were treated with five (0.0625, 0.125, 0.25, 0.50 and 1%) and six concentrations (0.125, 0.25, 0.50, 1, 2 and 4%), respectively, of each EOsAp/Lm. A 98-99% larval mortality was achieved with 0.5% of both EOsAp/Lm. EOAp inhibited oviposition and egg hatching up to 82% and 80%, respectively, and had an overall efficacy of 93.12%. Efficacy of EOLm was 72.84%, due to the low influence of EOLm on reproductive parameters. By steam distillation and GC-MS analysis, γ-Curcumene was identified as the main constituent (52.02%) in the EOAp and Shyobunol (10.80%) in EOLm. The results suggest that major components of both essential oils should be further studied as promissory acaricides against R. microplus.

Ethnoveterinary for food-producing animals and related food safety issues: A comprehensive overview about terpenes

Alternatives to the use of conventional veterinary drugs in food-producing animals have gained attention, such as the use of natural products (NPs), mainly to soften the risks to the animal, the environment, and consumer's health. Although NPs have consistent advantages over conventional drugs, they cannot be considered risk free under food safety matters. In this way, this document presents a comprehensive overview of the importance of considering both the pharmacological and toxicological properties of the constituents of a NP from plants intending the standardization and regulation of its use in food-producing animals. Terpenes are the most diverse class of natural substances present in NP of vegetal origin with a broad range of biological activities that can be explored in veterinary science; however, certain plants and terpenes also have significant toxic effects, a fact that can harm the health of animals and consequently generate economic losses and risks for humans. In this context, this review gathered scientific data of vegetal species of importance to ethnoveterinary for food-producing animals, which produce terpenes, its biological effects, and their implications on food safety issues for consumers. For this, more than 300 documents were selected from different online scientific databases. The present data and discussion may contribute to the rational commercial exploration of this class of NPs in veterinary medicine.

Repellence of essential oils and selected compounds against ticks-A systematic review

Ticks act as vectors of a wide range of infectious agents, far encompassing any other group of bloodsucking arthropods worldwide. The prevention of tick-borne diseases is strictly linked to the successful management of tick vector populations. The employ of repellents can represent a worth solution to avoid tick bites. It is widely adopted to protect travellers and pets exposed to ticks during limited periods of the year. The use of natural products as active ingredients in eco-friendly repellent formulations is currently a prominent research area, due to the wide diversity and high effectiveness of a number of plant-borne compounds, with special reference to essential oils (EOs) extracted from medicinal and aromatic species. Here, we reviewed current knowledge available on EOs tested as repellents against tick species of veterinary importance. Furthermore, we analysed the effectiveness of pure compounds isolated from EOs as tick repellents and their potential implications for practical use in the öreal world". A quantitative analysis of literature available is this research field was provided, along with its impact (i.e., in terms of citations over time) on the scientific community of researchers in tick control science and natural product chemistry. In the final sections, future outlooks are highlighted. We discussed major challenges to stabilize the most effective EOs and pure molecules, explore the synergistic and antagonistic effects in blends of EOs and/or pure constituents, standardize currently adopted testing methods, and evaluate non-target risks of herbal repellents.

Kazakh Ziziphora Species as Sources of Bioactive Substances

Ziziphora species represent the prototypical example of the Lamiaceae family. The phytochemicals present in Ziziphora include monoterpenic essential oils, triterpenes and phenolic substances belonging to the flavonoids. In Kazakh traditional medicine, Ziziphora species possess several medicinal uses. In particular, Z. bungeana Lam. and Z. clinopodioides Lam. are used for the treatment of illnesses related to the cardiovascular system or to combat different infections. Unfortunately, the majority of the information about the complex Ziziphora species is only available in Russian and Chinese language, therefore, we decided gather all available information on Kazakhstan Ziziphora, namely its content compounds, medicinal uses and published patents, to draw the attention of scientists to this very interesting plant with high medicinal potential.

Tick repellents and acaricides of botanical origin: a green roadmap to control tick-borne diseases?

Arthropods are dangerous vectors of agents of deadly diseases, which may hit as epidemics or pandemics in the increasing world population of humans and animals. Among them, ticks transmit more pathogen species than any other group of blood-feeding arthropods worldwide. Thus, the effective and eco-friendly control of tick vectors in a constantly changing environment is a crucial challenge. A number of novel routes have been attempted to prevent and control tick-borne diseases, including the development of (i) vaccines against viruses vectored by ticks; (ii) pheromone-based control tools, with special reference to the "lure and kill" techniques; (iii) biological control programmes relying on ticks' natural enemies and pathogens; and (iv) the integrated pest management practices aimed at reducing tick interactions with livestock. However, the extensive employment of acaricides and tick repellents still remains the two most effective and ready-to-use strategies. Unfortunately, the first one is limited by the rapid development of resistance in ticks, as well as by serious environmental concerns. On the other hand, the exploitation of plants as sources of effective tick repellents is often promising. Here, we reviewed current knowledge concerning the effectiveness of plant extracts as acaricides or repellents against tick vectors of public health importance, with special reference to Ixodes ricinus, Ixodes persulcatus, Amblyomma cajennense, Haemaphysalis bispinosa, Haemaphysalis longicornis, Hyalomma anatolicum, Hyalomma marginatum rufipes, Rhipicephalus appendiculatus, Rhipicephalus (Boophilus) microplus, Rhipicephalus pulchellus, Rhipicephalus sanguineus and Rhipicephalus turanicus. Eighty-three plant species from 35 botanical families were selected. The most frequent botanical families exploited as sources of acaricides and repellents against ticks were Asteraceae (15 % of the selected studies), Fabaceae (9 %), Lamiaceae (10 %), Meliaceae (5 %), Solanaceae (6 %) and Verbenaceae (5 %). Regression equation analyses showed that the literature grew by approximately 20 % per year (period: 2005-2015). Lastly, in the final section, insights for future research are discussed. We focused on some caveats for future data collection and analysis. Current critical points mainly deal with (a) not uniform methods used, which prevent proper comparison of the results; (b) inaccurate tested concentrations, frequently 100 % concentration corresponded to the gross extract, where the exact amounts of extracted substances are unknown; and (c) not homogeneous size of tested tick instars and species. Overall, the knowledge summarized in this review may be helpful for comparative screening among extensive numbers of plant-borne preparations, in order to develop newer and safer tick control tools.

Assessment of the repellent effect of Lippia alba essential oil and major monoterpenes on the cattle tick Rhipicephalus microplus

The control of Rhipicephalus microplus (Ixodida: Ixodidae) is achieved using synthetic acaricides. However, resistant tick populations are widespread around the world. Plant essential oils can act as repellents, keeping ticks away from hosts and decreasing the selection pressure on synthetic acaricides. The aim of this study was to evaluate the in vitro repellent effect of Lippia alba essential oil on R. microplus larvae. Leaves from two L. alba genotypes maintained under the same agronomic and environmental conditions were collected. Essential oil was extracted by hydrodistillation and analysed by gas chromatography-mass spectrometry (GC-MS). The major monoterpenes detected in the chemical analysis were commercially acquired and tested. For the repellency test, a glass rod was vertically fixed to measure active climbing of approximately 30 R. microplus larvae aged 14-21 days in response to essential oils and monoterpenes. Repellency was evaluated at 1 h, 3 h and 5 h after treatment. Variation in repellent action was detected between the genotypes. The major monoterpenes identified in the essential oils (limonene and carvone) showed low repellent effects in comparison with intact essential oils. Thus, the present results showed that L. alba essential oil contains bioactive compounds with great repellent activity against ticks that varies according to the plant genotype.

Chemical composition, larvicidal, and biting deterrent activity of essential oils of two subspecies of Tanacetum argenteum (Asterales: Asteraceae) and individual constituents against Aedes aegypti (Diptera: Culicidae)

Water-distilled essential oils from dried aerial parts of Tanacetum argenteum (Lam.) Willd. subsp. argenteum (Lam.) and T. argenteum (Lam.) Willd. subsp. canum (C. Koch) Grierson were analyzed by gas chromatography and gas chromatography-mass spectrometry. In total, 27 and 32 components were identified representing 97.2 and 98.7% of essential oils of subsp. argenteum and canum, respectively. Main compounds of T. argenteum subsp. argenteum were alpha-pinene (67.9%) and beta-pinene (4.8%), whereas alpha-pinene (53.6%), 1, 8-cineole (14.8%), and camphor (4.7%) were the major constituents of subsp. canum. Essential oil of T. argenteum subsp. canum at 10 microg/cm2 with Biting Deterrent Index (BDI) value of 0.73 showed activity similar to N,N-Diethyl-meta-toluamide (DEET) at 25 mol/cm2, whereas the activity of essential oil of subsp. argenteum was lower (BDI = 0.47) than subsp. canum and DEET. Based on 95% CIs, activity of beta-caryophyllene (BDI value = 0.54) and caryophyllene oxide (BDI = 0.66) were significantly lower than DEET. In larval bioassays, essential oil of T. argenteum subsp. argenteum showed LC50 value of 93.34 ppm, whereas T. argenteum subsp. canum killed only 40% of the larvae at the highest dose of 125 ppm. Among the pure compounds, beta-caryophyllene (LC50 = 26 ppm) was the most potent compound followed by caryophyllene oxide (LC50 = 29 ppm), which was also similar to (-)-beta-pinene (LC50 = 35.9 ppm) against 1-d-old Ae. aegypti larvae at 24-h post treatment. Compounds (-)-alpha-pinene and (+)-beta-pinene showed similar larvicidal activity. Activity of (+)-alpha-pinene with LC50 value of was similar to the essential oil of T. argenteum subsp. argenteum.

Configurational assignments of conformationally restricted bis-monoterpene hydroquinones: utility in exploration of endangered plants

BACKGROUND

Endangered plant species are an important resource for new chemistry. Lindera melissifolia is native to the Southeastern U.S. and scarcely populates the edges of lakes and ponds. Quantum mechanics (QM) used in combination with NMR/ECD is a powerful tool for the assignment of absolute configuration in lieu of X-ray crystallography.

METHODS

The EtOAc extract of L. melissifolia was subject to chromatographic analysis by VLC and HPLC. Spin-spin coupling constant (SSCC) were calculated using DFT at the MPW1PW91/6-31G(d,p) level for all staggered rotamers. ECD calculations employed Amber* force fields followed by PM6 semi-empirical optimizations. Hetero- and homo-nuclear coupling constants were extracted from 1D (1)H, E.COSY and HETLOC experiments.

RESULTS

Two meroterpenoids, melissifolianes A (1) and B (2) were purified and their 2-D structures elucidated using NMR and HRESIMS. The relative configuration of 1 was established using the combination of NOE-based distance restraints and the comparisons of experimental and calculated SSCCs. The comparison of calculated and experimental ECD assigned the absolute configuration of 1. The relative configuration of a racemic mixture, melissifoliane B (2) was established utilizing J-based analysis combined with QM and NMR techniques.Conclusion Our study of the Lindera melissifolia metabolome exemplifies how new chemistry remains undiscovered among the numerous endangered plant species and demonstrates how analysis by ECD and NMR combined with various QM calculations is a sensible approach to support the stereochemical assignment of molecules with conformationally restricted conformations.

GENERAL SIGNIFICANCE

QM-NMR/ECD combined approaches are of utility for unambiguous assignment of 3-D structures, especially with limited plant material and when a molecule is conformationally restricted. Conservation of an endangered plant species can be supported through identification of its new chemistry and utilization of that chemistry for commercial purposes.