Promising Algerian essential oils as natural acaricides against the honey bee mite Varroa destructor (Acari: Varroidae).

Varroosis induced by Varroa destructor Anderson and Trueman represents the most pathogenic and destructive disease affecting the western honey bee, Apis mellifera. In this study, we investigated the acaricidal activity against the Varroa mite using essential oils (EOs) from the aerial parts of four autochthonous Algerian herbal species, namely Artemisia herba alba, Artemisia campestris, Artemisia judaica and Ruta montana. EOs were obtained by means of hydrodistillation and their composition was characterized by gas chromatography-mass spectrometry. The toxicity of the selected EOs toward V. destructor and A. mellifera adult honey bees was evaluated using the complete exposure method. The results indicate the predominance of davanone (66.9%) in A. herba alba, ß-pinene (19.5%) in A. campestris, piperitone (68.7%) in A. judaica and 2-undecanone (70.1%) in R. montana EOs. Interestingly, the LC50 values coupled to bee mortality rates revealed that all tested oils exhibited significant acaricidal efficiency with selectivity ratio (SR) values of 10.77, 8.78, 5.62 and 3.73 for A. campestris, A. judaica, A. herba alba, and R. montana, respectively. These values were better than that of thymol (SR = 3.65), the positive control. These findings suggest that these EOs could be used as plant-derived veterinary acaricides to control varroosis in field conditions.

Assessment of artemisinin and antioxidant activities of three wild Artemisia species of Algeria.

Artemisinin, a natural product, has received considerable attention in the last few years as a potent antimalarial drug.This study reports the presence of Artemisinin in three Algerian wild Artemisia species assessed by HPLC method: A. herba-alba (AH), A. campestris subsp. glutinosa (AC), and A. judaica subsp sahariensis (AJ).The HPLC analysis of the hexane extracts, showed a difference in artemisinin content in studied species with a yield of 0.64%, 0.34% and 0.04% for AC, AH and AJ, respectively. Moreover, the level of artemisinin obtained in A. campestris was better than those found in A. sieberi and A. annua. This rate has been reported for the first time.Furthermore, the antiradical activities of methanolic extracts of plants were also tested. There was a remarkable antioxidant capacity found in all Artemisia methanolic extracts analysed.

Antimalarial-agent artemisinin and derivatives portray more potent binding to Lys353 and Lys31-binding hotspots of SARS-CoV-2 spike protein than hydroxychloroquine: potential repurposing of artenimol for COVID-19.

Medicinal herbs have proved along history to be a source of multiple cures. In this paper, we demonstrate how hydroxychloroquine can act as a good inhibitor of SARS-CoV-2 Spike protein receptor-binding-domain using molecular docking studies. We also unveil how hydroxychloroquine can interfere in the prevention of Lys353 in hACE2 from interacting with the corresponding binding hotspot present on the Spike protein. Further screening of artemisinin & derived compounds produced better Vina docking score than hydroxychloroquine (-7.1 kcal mol-1 for artelinic acid vs. -5.5 kcal mol-1 for hydroxychloroquine). Artesunate, artemisinin and artenimol, showed two mode of interactions with Lys353 and Lys31 binding hotspots of the Spike protein. Molecular dynamics analysis confirmed that the formed complexes are able to interact and remain stable in the active site of their respective targets. Given that these molecules are effective antivirals with excellent safety track records in humans against various ailment, we recommend their potential repurposing for the treatment of SARS-CoV-2 patients after successful clinical studies. In addition, an extraction protocol for artemisinin from Artemisia annua L. is proposed in order to cope with the potential urgent global demand. Communicated by Ramaswamy H. Sarma.

Membrane-Interactive Compounds From Pistacia lentiscus L. Thwart Pseudomonas aeruginosa Virulence.

Pseudomonas aeruginosa is capable to deploy a collection of virulence factors that are not only essential for host infection and persistence, but also to escape from the host immune system and to become more resistant to drug therapies. Thus, developing anti-virulence agents that may directly counteract with specific virulence factors or disturb higher regulatory pathways controlling the production of virulence armories are urgently needed. In this regard, this study reports that Pistacia lentiscus L. fruit cyclohexane extract (PLFE1) thwarts P. aeruginosa virulence by targeting mainly the pyocyanin pigment production by interfering with 4-hydroxy-2-alkylquinolines molecules production. Importantly, the anti-virulence activity of PLFE1 appears to be associated with membrane homeostasis alteration through the modulation of SigX, an extracytoplasmic function sigma factor involved in cell wall stress response. A thorough chemical analysis of PLFE1 allowed us to identify the ginkgolic acid (C17:1) and hydroginkgolic acid (C15:0) as the main bioactive membrane-interactive compounds responsible for the observed increased membrane stiffness and anti-virulence activity against P. aeruginosa. This study delivers a promising perspective for the potential future use of PLFE1 or ginkgolic acid molecules as an adjuvant therapy to fight against P. aeruginosa infections.

Study of the degradation in aqueous solution of a refractory organic compound: avermectin type used as pesticide in agriculture.

We examined the removal of abamectin by the electro-Fenton (EF) process and the feasibility of biological treatment after degradation. The effect of the operating parameters showed that abamectin (Aba) degradation was enhanced with increasing temperature. Response surface analysis of the central composite design led to the following optimal conditions for the abatement of chemical oxygen demand: 45.5 °C, 5 mg L-1, 150 mA, and 0.15 mmol L-1 for the temperature, initial Aba concentration, current intensity, and catalyst concentration, respectively. Under these conditions, 68.01% of the organic matter was removed and 94% of Aba was degraded after 5 h and 20 min of electrolysis, respectively. A biodegradability test, which was performed on a solution electrolyzed at 47 °C, 9 mg L-1, 150 mA, and 0.15 mmol L-1, confirms that the ratio of biological oxygen demand/chemical oxygen demand increased appreciably from 0.0584 to 0.64 after 5 h of electrolysis. This increased ratio is slightly above the limit of biodegradability (0.4). These results show the relevance of the EF process and its effectiveness for abamectin degradation. We conclude that biological treatment can be combined with the EF process for total mineralization.

Extraction mechanism of ultrasound assisted extraction and its effect on higher yielding and purity of artemisinin crystals from Artemisia annua L. leaves.

This study proposes an ultrasound-horn system for the extraction of a natural active compound "artemisinin" from Artemisia annua L. leaves as an alternative to hot maceration technique. Ultrasound leaching improves artemisinin recovery at all temperatures where only ten minutes is required to recover 70% (4.42mgg-1) compared to 60min of conventional hot leaching for the same yield. For instance, ultrasound treatment at 30°C produced a higher yield than the one obtained by conventional maceration at 40°C. Kinetic study suggests that the extraction pattern can be assimilated, during the first ten minutes, to a first order steady state, from which activation energy calculations revealed that each gram of artemisinin required 7.38kJ in ultrasound versus 10.3kJ in the conventional system. Modeling results indicate the presence of two extraction stages, a faster stage with a diffusion coefficient of 19×10-5cm2min-1 for ultrasound technique at 40°C, seven times higher than the conventional one; and a second deceleration stage similar for both techniques with diffusion coefficient ranging from 1.7 to 3.1×10-5cm2min-1. It is noted that the efficient ultrasound extraction potential implies extraction of higher amount of co-metabolites so low artemisinin crystal purity is engendered but a combination with a purification step using activated charcoal and celite adsorbents produced crystals with comparable purity for conventional and ultrasound samples.

The effect of O-methylated flavonoids and other co-metabolites on the crystallization and purification of artemisinin.

Methoxylated flavonoids casticin, artemetin and retusin were identified as putative causative factors for low crystallization yields of artemisinin from extracts. Comparative profiling of biomass grown in different countries found elevated levels (∼60% higher) of artemetin in the East African biomass, which also demonstrates poor crystallization yields. The single compound and the combined doping experiments at 0, 25 and 50 µg mL⁻¹ doping levels showed that artemetin (50 µg mL⁻¹) caused a reduction in the amount of artemisinin crystallized by ca. 60%. A combination of the three flavonoids at 50 µg mL⁻¹ almost completely inhibited crystallization, reducing the yield by 98%. Treatment of extracts by adsorbents efficiently resolves the problem of low crystallization yield.

Development of HPLC analytical protocols for quantification of artemisinin in biomass and extracts.

Quantification of artemisinin purity and amount in plant material and extracts to date has been characterized by a considerable inconsistency in values. This is likely to be due to the adoption of varied analytical procedures and use of inappropriate to the specific applications analytical techniques. In this paper we are attempting to further develop artemisinin analysis to the point where a universally acceptable reference method is available to the research and end-users communities. Thus, we have developed and validated an HPLC-RI method and optimized an HPLC-ELSD method. We used the gradient HPLC-UV method recommended by the current artemisinin monograph as a comparison for the method improvements presented herein, and show the limitations for its application scope. The data reported should help to allow more reliable laboratory analysis of artemisinin in both pure samples and in Artemisia annua extracts.

Ultrasound assisted microwave digestion.

Simultaneous microwave and ultrasound irradiation is shown as a new technique for digestion of solid and liquid samples suitable for chemical and food analysis. Its application in analytical chemistry has been shown by decreases in digestion time: determination of copper in edible oils and total Kjeldahl nitrogen.