Phytochemical modulation of P-Glycoprotein and its gene expression in an ivermectin-resistant Haemonchus contortus isolate in vitro.

Haemonchus contortus is the most important gastrointestinal nematode in small ruminant systems worldwide and has developed resistance to several drugs, including ivermectin (IVM). IVM is not only a veterinary drug but also a safe, broad-spectrum, antiparasitic drug used in humans. One of the main IVM-resistance mechanisms in H. contortus involves P-glycoprotein (PgP), a trans-membrane transport protein that rids worm cells from toxic molecules. This study aimed to evaluate the anthelmintic activity of IVM, alone or combined with main terpenes of essential oils (alpha-terpinene, beta-citronellol, beta-pinene, citronellal, limonene, menthol, and terpinolene) and with phenolic compounds (epicatechin, epigallocatechin, gallocatechin, pentagalloylglucose, procyanidin, and quercetin). All compounds were tested, alone or combined with IVM, against susceptible (HcS) and resistant (HcR) isolates of H. contortus through the larval development test (LDT) and the adult motility assay (AMT) using verapamil (VP), a known PgP modulator, as a control. Results for the LDT determined that the lethal concentration required to kill 50% of nematodes (LC50) with IVM was 10 times greater (0.01 µg/mL) for HcR than for HcS (0.001 µg/mL). The combination IVM + VP inhibited the activity of PgP in HcR resulting in a LC50 = 0.002 ug.mL-1. Although limonene was the least effective and alpha-terpinene the most effective terpene when tested alone against HcR, the best combinations were IVM + limonene and IVM + quercetin both produced LC50 = 0.002 µg/mL (similar to IVM+VP) which were chosen for subsequent tests. Because adult parasites are the final target for anthelmintics, IVM was evaluated in HcS (LC50 = 0.067 µg/mL) and HcR (LC50 =164.94 µg/mL) through the AMT. Results obtained with IVM + VP (LC50 = 0.020 µg/mL) in HcR were similar to IVM + limonene (LC50 = 0.028 µg/mL) and outperformed IVM + quercetin (LC50 = 1.39 µg/mL). RNA extracts from HcR adult worms exposed to IVM, IVM+VP, and IVM + limonene were evaluated for PgP expression by RT-PCR. For most concentrations, PgP-9 was significantly more expressed in worms treated with IVM alone than in worms treated with IVM + VP or IVM + limonene. Our results suggest that limonene is involved in the modulation of the PgP-9 gene and that it can restore the activity of IVM in the HcR isolate down to levels seen in HcS. Limonene is one of the main compounds found in citrus peel and has the potential to be both safe and affordable if used in combination with IVM to restore its anthelmintic effects against multi-drug-resistant H. contortus isolates. Our results also suggest that we may be more successful by combining natural products with failing commercial anthelmintics than trying to find natural substitutes for them.

Development and Application of a Fast Gas Chromatographic Method Offer New Insights into l-theanine Production Regulation in Camellia sinensis L.

Tea is the most consumed beverage worldwide, and l-theanine in tea leaves significantly affects their flavor and market quality. We have developed and validated a fast and reliable gas chromatographic method with flame ionization detection (GC-FID) to quantify l-theanine after its extraction from Camellia sinensis (tea plant) and derivatization. The procedure was completed in 40 min, from extraction to chromatographic analysis, with a recovery rate of more than 93% and allowing a high sample throughput. The GC-FID intraday precision was within 0.57-2.28%, while the interday precision ranged from 1.57 to 13.48%. The intraday accuracy ranged from -6.84 to 5.26%, while the interday accuracy ranged from -1.08 to 3.12%. The limit of detection was 2.28 µg/mL, and the limit of quantification was 6.47 µg/mL. The GC-FID method was validated by high-performance liquid chromatography with UV detection (HPLC-UV) and was used to investigate the biosynthesis and regulation of l-theanine in tea plants. We found that plants fed with ethylamine significantly increased l-theanine concentrations in roots, while exogenous supplementation of glutamic acid, carbamide, and glutamine did not significantly affect the l-theanine level in roots. Our results also indicated that roots were not indispensable for the biosynthesis of l-theanine, which was detected in undifferentiated embryonic calluses in concentrations (g/100 g dry weight) as high as in leaves of whole plants (1.67 and 1.57%, respectively) and without any exogenous theanine precursor supplementation.

Preparative Separation of High-Purity Dihydroartemisinic Acid from Artemisinin Production Waste by Combined Chromatography.

In order to make full use of artemisinin production waste and thus to reduce the production cost of artemisinin, we developed an efficient and scalable method to isolate high-purity dihydroartemisinic acid from artemisinin production waste by combining anion-exchange resin with silica-gel column chromatography. The adsorption and desorption characteristics of dihydroartemisinic acid on 10 types of anion-exchange resin were investigated, and the results showed that the 717 anion-exchange resin exhibited the highest capacity of adsorption and desorption to dihydroartemisinic acid. Adsorption isotherms were established for the 717 anion-exchange resin and they fitted well with both Langmuir and Freundlich model. Dynamic adsorption and desorption properties of 717 anion-exchange resin were characterized to optimize the chromatographic conditions. Subsequently, the silica-gel column chromatography was performed and dihydroartemisinic acid with a purity of up to 98% (w/w) was obtained. Finally, the scale-up experiments validated the preparative separation of high-purity dihydroartemisinic acid from industrial waste developed in the present work. This work presented for the first time an isolation of dihydroartemisinic acid with a purity of 98% from Artemisia annua (A. annua) by-product, which adds more value to this crop and has the potential to lower the prices of anti-malarial drugs.

Isolation of Dihydroartemisinic Acid from Artemisia annua L. By-Product by Combining Ultrasound-Assisted Extraction with Response Surface Methodology.

Malaria is the most devastating parasitic disease worldwide. Artemisinin is the only drug that can cure malaria that is resistant to quinine-derived drugs. After the commercial extraction of artemisinin from Artemisia annua, the recovery of dihydroartemisinic acid (DHAA) from artemisinin extraction by-product has the potential to increase artemisinin commercial yield. Here we describe the development and optimization of an ultrasound-assisted alkaline procedure for the extraction of DHAA from artemisinin production waste using response surface methodology. Our results using this methodology established that NaOH at 0.36%, extraction time of 67.96 min, liquid-solid ratio of 5.89, and ultrasonic power of 83.9 W were the optimal conditions to extract DHAA from artemisinin production waste. Under these optimal conditions, we achieved a DHAA yield of 2.7%. Finally, we conducted a validation experiment, and the results confirmed the prediction generated by the regression model developed in this study. This work provides a novel way to increase the production of artemisinin per cultivated area and to reduce artemisinin production costs by recycling its commercial waste to obtain DHAA, an immediate precursor of artemisinin. The use of this technology may reduce the costs of artemisinin-based antimalarial medicines.