Isolation of Volatile Compounds with Repellent Properties against Aedes albopictus (Diptera: Culicidae) Using CPC Technology

Larvicidal, Ovicidal, and Repellent Activities of Leucas stachydiformis (Hochst. ex Benth.) Briq Essential Oil against Anopheles arabiensis

Larvicidal, ovicidal, and repellent activities of the essential oil extracted by hydrodistillation from the leaves of the endemic Ethiopian plant Leucas stachydiformis (Hochst. ex Benth.) Briq were investigated against Anopheles arabiensis, the dominant malaria vector species in Ethiopia with the objective of searching for a plant-based malaria vector control strategy from medicinal plants. The larvicidal effect was tested against the fourth instar An. arabiensis wild larvae whilst freshly laid ova of An. arabiensis were used to determine the ovicidal activity of the essential oil at concentrations ranging from 6.25 to 400 ppm. Concentrations of 41.6-366.7 µg/cm2 were used to evaluate the repellent activity of the essential oil on 3-5 days old adult female An. arabiensis. The oil composition of L. stachydiformis was also analyzed using GC-MS. The study revealed that the oil possesses the highest larvicidal activity at 400 ppm and 200 ppm after 24 h and 48 h of treatment. LC50 values for the fourth larval instar after 24 h and 48 h of treatment were 43.4 ppm and 34.2 ppm, respectively. After 72 h of exposure, the oil displayed 100% ovicidal activity at 400 ppm with an IH50 value of 32.2 ppm. In the repellency test, at concentrations of 366.7, 133.3, and 41.6 µg/cm2, the oil gave a total percentage protection of 67.9 ± 4.2%, 37.2 ± 2.8%, and 32 ± 2.2%, respectively, for 4 h. The highest concentration (366.7 µg/cm2) gave 100% protection up to 90 min. GC-MS analysis of the oil revealed the presence of 24 compounds representing 90.34% of the total oil with caryophyllene oxide, germacrene D, and trans-caryophyllene constituting more than 50% of its components. Results of the present study suggest that the essential oil of L. stachydiformis has the potential to be used for the control of An. arabiensis mosquitoes.

Sugar feeding by invasive mosquito species on ornamental and wild plants

Feeding on plant-derived sugars is an essential component of mosquito biology, affecting key aspects of their lives such as survival, metabolism, and reproduction. Among mosquitoes, Aedes aegypti and Aedes albopictus are two invasive mosquito species in the US, and are vectors of diseases such as dengue fever, chikungunya, and Zika. These species live in heavily populated, urban areas, where they have high accessibility to human hosts as well as to plants in backyards and public landscapes. However, the range of plants that are suitable sugar hosts for these species remains to be described, despite the importance of understanding what plants may attract or repel mosquitoes to inform citizens and municipal authorities accordingly. Here, we tested whether Ae. aegypti and Ae. albopictus would sugar-feed on eleven commonly planted ornamental plant species. We confirmed feeding activity using the anthrone method and identified the volatile composition of plant headspace using gas-chromatography mass-spectroscopy. These chemical analyses revealed that a broad range of olfactory cues are associated with plants that mosquitoes feed on. This prompted us to use plant DNA barcoding to identify plants that field-caught mosquitoes feed on. Altogether, results show that native and invasive mosquito species can exploit a broader range of plants than originally suspected, including wild and ornamental plants from different phyla throughout the Spring, Summer and Fall seasons.

The role of centrifugal partition chromatography in the removal of β-asarone from Acorus calamus essential oil

Β-asarone is a phenylpropane derivative present in the rhizomes of Acorus calamus, that was proved to exhibit toxic effects in humans. Because of its presence the whole plant that is commonly used in traditional medicine for its sedative, anti-inflammatory, neuroprotective and other properties has limited application nowadays. In the study, qualitative and quantitative analysis of a collection of nine essential oil (EO) samples of European and Asian origin was performed. The final content of β-asarone in the tested samples ranged between 0.265 and 1.885 mg/mL. Having in mind a possible application of the EO as a biopesticide, this research aimed at the development of CPC-based purification protocol that could help remove β-asarone from EO. It was proved that the biphasic solvent system composed of n-hexane/EtOAc/MeOH/water, 9:1:9:1 (v/v/v/v) was capable of the removal of the toxic constituent in the CPC chromatograph operated in the ascending elution mode with 2200 rpm and a flow rate of 5 mL/min. The chromatographic analysis that lasted only 144 min effectively separated β-asarone (purity of 95.5%) and α-asarone (purity of 93.7%) directly from the crude Acorus calamus rhizome EO.

In Vitro Anti-Influenza Virus Activity of Non-Polar Primula veris subsp. veris Extract

Medicinal plants have long been recognized as a tremendous source of candidate compounds for the development of pharmaceuticals, including anti-viral agents. Herein, we report the identification of anti-influenza virus activity in non-polar Primula veris L. subsp. veris extracts. We show that P. veris subsp. veris flower extracts, obtained using supercritical fluid or ultrasound-based extraction, possess virucidal/virus inactivation properties and confer prophylactic and therapeutic effects against influenza virus-induced cytolysis in vitro. By GC-MS and UPLC-HRMS analysis of non-polar P. veris subsp. veris extracts we identified terpenes, flavones, tocopherols, and other classes of phytochemicals with known or putative anti-influenza properties. In silico prediction of cellular functions and molecular pathways affected by these phytochemicals suggests putative effects on signal transduction, inflammasome, and cell death pathways that are relevant to influenza virus pathogenesis. Combining P. veris subsp. veris with extracts of medicinal plants with proven anti-influenza activity such as Echinacea purpurea (L.) Moench and Cistus creticus L. subsp. creticus achieves an impressive protective effect against infection by influenza virus H1N1 in vitro and reduced progeny virus production by infected cells. Collectively, these findings uncover a previously uncharted biological property of non-polar P. veris flower extracts that warrants further studies to assess clinical efficacy.

A Themed Issue in Honor of Professor K. Hüsnü Can Baser-Outstanding Contributions in the Fields of Pharmacognosy, Phytochemistry, Botany and Ethnopharmacology

Dear Colleagues, [...].