Effects of arteannuin B, arteannuic acid and scopoletin on pharmacokinetics of artemisinin in mice

Targeted screening of the synergistic components in Artemisia annua L. leading to enhanced antiplasmodial potency of artemisinin based on a "top down" PD-PK approach

ETHNOPHARMACOLOGICAL RELEVANCE

Artemisinin (ART) showed enhanced antimalarial potency in the herb Artemisia annua L. (A. annua), from which ART is isolated. Increased absorption of ART with inhibited metabolism in the plant matrix is an underlying mechanism. Several synergistic components have been reported based on a "bottom-up" approach, i.e., traditional isolation followed by pharmacokinetic and/or pharmacodynamic evaluation.

AIM OF THE STUDY

In this study, we employed a "top-down" approach based on in vivo antimalarial and pharmacokinetic studies to identify synergistic components in A. annua.

MATERIALS AND METHODS

Two A. annua extracts in different chemical composition were obtained by extraction using ethyl acetate (EA) and petroleum ether (PE). The synergistic antimalarial activity of ART in two extracts was compared both in vitro (Plasmodium falciparum) and in vivo (murine Plasmodium yoelii). For the PD-PK correlation analysis, the pharmacokinetic profiles of ART and its major metabolite (ART-M) were investigated in healthy rats after a single oral administration of pure ART (20 mg/kg) or equivalent ART in each A. annua extract. A liquid chromatography-tandem high-resolution mass spectrometry (LC-HRMS)-based analytical strategy was then applied for efficient component classification and structural characterization of the differential components in the targeted extract with a higher antimalarial potency. Major components isolated from the targeted extract were then evaluated for their synergistic effect in the same proportion.

RESULTS

Compared with pure ART (ED50, 5.6 mg/kg), ART showed enhanced antimalarial potency in two extracts in vivo (ED50 of EA, 2.9 mg/kg; ED50 of PE, 1.6 mg/kg), but not in vitro (IC50, 15.0-20.0 nM). A significant increase (1.7-fold) in ART absorption (AUC0-t) was found in rats after a single oral dose of equivalent ART in PE but not in EA; however, no significant change in the metabolic capability (AUCART-M/AUCART) was found for ART in either extract. The differential component analysis of the two extracts showed a higher composition of sesquiterpene compounds, especially component AB (3.0% in PE vs. 0.9% in EA) and component AA (14.1% in PE vs. 5.1% in EA). Two target sesquiterpenes were isolated and identified as arteannuin B (AB) and artemisinic acid (AA). The synergism between ART and AB/AA in the same proportion with PE extract (20:1.6:7.6, mg/kg) was verified by a pharmacokinetic study in rats.

CONCLUSIONS

A "top-down" strategy based on PD-PK studies was successfully employed to identify synergistic components for ART in A. annua. Two sesquiterpene compounds (arteannuin B and artemisinic acid) could enhance the antimalarial potency of ART by increasing its absorption.

Enhanced Antimalarial Activity of Extracts of Artemisia annua L. Achieved with Aqueous Solutions of Salicylate Salts and Ionic Liquids

Artemisinin, a drug used to treat malaria, can be chemically synthesized or extracted from Artemisia annua L. However, the extraction method for artemisinin from biomass needs to be more sustainable while maintaining or enhancing its bioactivity. This work investigates the use of aqueous solutions of salts and ionic liquids with hydrotropic properties as alternative solvents for artemisinin extraction from Artemisia annua L. Among the investigated solvents, aqueous solutions of cholinium salicylate and sodium salicylate were found to be the most promising. To optimize the extraction process, a response surface method was further applied, in which the extraction time, hydrotrope concentration, and temperature were optimized. The optimized conditions resulted in extraction yields of up to 6.50 and 6.44 mg·g-1, obtained with aqueous solutions of sodium salicylate and cholinium salicylate, respectively. The extracts obtained were tested for their antimalarial activity, showing a higher efficacy against the Plasmodium falciparum strain compared with pure (synthetic) artemisinin or extracts obtained with conventional organic solvents. Characterization of the extracts revealed the presence of artemisinin together with other compounds, such as artemitin, chrysosplenol D, arteannuin B, and arteannuin J. These compounds act synergistically with artemisinin and enhance the antimalarial activity of the obtained extracts. Given the growing concern about artemisinin resistance, the results here obtained pave the way for the development of sustainable and biobased antimalarial drugs.

Site selective synthesis and anti-inflammatory evaluation of Spiro-isoxazoline stitched adducts of arteannuin B

A library of new spiroisoxazoline analogues of arteannuin B was synthesized through 1, 3-dipolar cycloaddition in stereoselective fashion and consequently screened for anti-inflammatory activity in RAW 264.7 macrophage cells. Three potent analogues (8i, 8 m, and 8n) were found to attenuate the LPS induced release of cytokines IL-6 and TNF-α more potently than the parent molecule. Also, the inhibition of LPS induced nitric oxide production in these cells show moderate to high efficacy. None of the three potent molecules have altered the viability of RAW 264.7 cells following 48 h incubation suggesting that the inhibition of cytokines and nitric oxide production exhibited in the cells was not due to toxicity. In addition, these compounds exhibit an IC₅₀ range of 0.17 µM-1.57 µM and 0.09 µM-0.35 µM for the inhibition of IL-6 release and nitric oxide production respectively. The results disclose potent inhibition of pro-inflammatory mediators which are encouraging and warrant further investigations to develop new therapeutic agents for inflammatory diseases.

Component changes of mulberry leaf tea processed with honey and its application to in vitro and in vivo models of diabetes

Honey is a traditional food additive that can be used to preserve food, increase the flavour of food, and enhance the effect of some functional foods. Mulberry leaf is a popular tea, and it is also an anti-diabetic medicinal material. In the traditional processing of mulberry leaf tea, honey is a commonly used additive. This study used ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) to measure the changes in the contents of 11 components of mulberry leaves before and after processing using honey as an additive. We analysed the absorption and elimination characteristics of mulberry leaves before and after processing in diabetes in vivo models, and then compared the effect of mulberry leaves before and after processing in resisting hyperglycaemia and hyperlipidaemia damage in in vitro models. The results showed that honey, as an additive, not only improves the dissolution of mulberry leaves, but in diabetes models also increases the utilisation of some components. In an in vitro model, honey mulberry leaves could significantly reduce the apoptosis of vascular endothelial cells. This demonstrated that the traditional processing method using honey as an additive could promote the anti-diabetic effect of mulberry tea. So far, this is the first research report on the quality and role of honey as an additive in mulberry leaf processing.Abbreviations: ML: mulberry leaves; HML: honey mulberry leaves; QC: quality control; HQC: high quality control sample; LLOQ: lower limit of quantification; LQC: low-quality control sample; MQC: medium-quality control sample; MRM: multiple reaction monitoring; STZ: streptozotocin.

Prolongation of allograft survival by artemisinin treatment is associated with blockade of OX40-OX40L

OBJECTIVES

It has been demonstrated that artemisinin (ART) possesses multiple immune modulatory effects. However, its role as immunosuppressant in allogeneic transplantation is undetermined. Here, we investigated the effect of ART on co-stimulatory signaling in OX40⁺ T cells and evaluated ART as a potential immunosuppressant in transplantation.

MATERIALS AND METHODS

Allogeneic skin transplantation was performed in C57BL/6 to BALB/c mice. Recipient mice were administrated with vehicle, ART or cyclosporine A daily from day 0 to day 19 post transplantation. Proportions of splenic CD4⁺OX40⁺ and CD4⁺CD44^hiCD62L^hi cells, and serum IgG was measured by using flow cytometry. An in vitro lymphocyte stimulation with Con A or LPS under various concentrations of ART was performed, expression of CD4⁺OX40⁺ and CD4⁺CD44^hiCD62L^hi cells was evaluated, and interleukin(IL)-6 production was measured by ELISA.

RESULTS

In in vivo allogeneic skin transplant model, ART significantly prolongs allogeneic skin survival. Furthermore, our in vitro studies demonstrate that the immune suppression of ART on T cells is associated with a reduction in OX40⁺ T cells and inhibition of IL-6 secretion.

CONCLUSION

Our data indicate that the OX40-OX40L pathway and IL-6 are possibly involved in ART-induced immunosuppression, and ART is a potential novel immunosuppressant.

Oral Bioavailability Comparison of Artemisinin, Deoxyartemisinin, and 10-Deoxoartemisinin Based on Computer Simulations and Pharmacokinetics in Rats

Deoxyartemisinin, a compound separated from Artemisinin annua L., shows anti-inflammatory and antiulcer activities. 10-Deoxoartemisinin is a novel compound with a strong antimalarial effect derivatized from artemisinin. Compared to the famous antimalarial natural compound artemisinin, deoxyartemisinin lacks the peroxide bridge structure, while 10-deoxoartemisinin remains this special peroxide bridge group but loses the 10-position keto group. To clarify their pharmacological differences, the absorption, distribution, metabolism, excretion (ADME) properties of artemisinin, deoxyartemisinin, and 10-deoxoartemisinin were first predicted using QikProp software. Also, their pharmacokinetic behaviors in rats were further evaluated by a rapid, sensitive, and specific liquid chromatography-tandem mass spectrometry (LC-MS/MS) method after oral and intravenous administration of each compound, in which deoxyartemisinin and 10-deoxoartemisinin were first evaluated for their pharmacokinetics. All parameters about ADME properties calculated by software met the criteria and the ADME performance order was 10-deoxoartemisinin > deoxyartemisinin > artemisinin. The oral bioavailability of artemisinin was calculated to be 12.2 ± 0.832%, which was about 7 times higher than that of deoxyartemisinin (1.60 ± 0.317%). For 10-deoxoartemisinin, its bioavailability (26.1 ± 7.04%) was superior to artemisinin at a degree of more than twice. Considering their chemical structures, losing the peroxide bridge might decrease the absorption rate of deoxyartemisinin in the gastrointestinal tract, while retaining the peroxide bridge but losing the 10-position ketone might improve the bioavailability of 10-deoxoartemisinin.

Simultaneous Quantification of Five Sesquiterpene Components after Ultrasound Extraction in Artemisia annua L. by an Accurate and Rapid UPLC⁻PDA Assay

Objective: To develop an accurate and rapid ultra-performance liquid chromatography (UPLC) coupled with a photodiode array (PDA) method for the simultaneous determination of artemisinin (Art), arteannuin B (Art B), arteannuin C (Art C), dihydroartemisinic acid (DHAA) and artemisinic acid (AA) in Artemisia annua L. Methodology: Chromatography separation was performed on an ACQUITY UPLC BEH C18 Column with isocratic elution; the mobile phase was 0.1% formic acid aqueous solution (A) and acetonitrile (B) (A:B = 40:60, v/v). Data were recorded at an ultraviolet (UV) wavelength of 191 nm for Art, Art C, DHAA and AA, and 206 nm for Art B. Results: The calibration curves of the five sesquiterpene components were all linear with correlation coefficients more than 0.9990. The linear ranges were 31.44–1572 μg/mL, 25.48–1274 μg/mL, 40.56–2028 μg/mL, 31.44–1572 μg/mL and 26.88–1396 μg/mL for Art, Art B, Art C, DHAA and AA, respectively. The precision ranged from 0.08% to 2.88%, the stability was from 0.96% to 1.66%, and the repeatability was all within 2.42% and had a mean extraction recovery of 96.5% to 100.6%. Conclusion: The established UPLC–PDA method would be valuable for improving the quantitative analysis of sesquiterpene components in Artemisia annua L.

Monitoring Antifungal Agents of Artemisia annua against Fusarium oxysporum and Fusarium solani, Associated with Panax notoginseng Root-Rot Disease

Root rot of Panax notoginseng has received great attention due to its threat on the plantation and sustainable utilization of P. notoginseng. To suppress the root-rot disease, natural ingredients are of great importance because of their environment friendly properties. In this study, we found that the methanol extract from Artemisia annua leaves has strong antifungal effects on the growth of Fusarium oxysporum and Fusarium solani resulting into root-rot disease. Essential oil (EO) thereof was found to be the most active. GC-MS analysis revealed 58 ingredients and camphor, camphene, β-caryophyllene, and germacrene D were identified as the major ingredients. Further antifungal assays showed that the main compounds exhibit various degrees of inhibition against all the fungi tested. In addition, synergistic effects between A. annua EO and chemical fungicides were examined. Finally, in vivo experiments were conducted and disclosed that P. notoginseng root rot could be largely inhibited by the petroleum ether extract from A. annua, indicating that A. annua could be a good source for controlling P. notoginseng root-rot.

Artemisinin permeability via Caco-2 cells increases after simulated digestion of Artemisia annua leaves

ETHNOPHARMACOLOGICAL RELEVANCE

Artemisia annua has been used for > 2000yrs to treat fever and is more recently known for producing the important antimalarial drug, artemisinin.

AIM OF THE STUDY

Artemisinin combination therapies (ACTs) are effective for treating malaria, but are often unavailable to those in need. Dried leaves of A. annua (DLA) have recently been studied as a cost effective alternative to traditional ACTs. DLA was shown to dramatically increase oral bioavailability compared to pure artemisinin, so more investigation into the mechanisms causing this increased bioavailability is needed.

MATERIALS AND METHODS

In this study, we used a simulated digestion system coupled with Caco-2 cell permeability assays to investigate the intestinal permeability of DLA compared to pure artemisinin. We also determined the effects of different phytochemicals (7 flavonoids, 3 monoterpenes, 2 phenolic acids, scopoletin and inulin) and the cytochrome P450 isoform CYP3A4 on artemisinin intestinal permeability.

RESULTS

Artemisinin permeability, when delivered as digested DLA, significantly increased by 37% (P_app = 8.03 × 10^-5cms^-1) compared to pure artemisinin (P_app = 5.03 × 10^-5cms^-1). However, none of the phytochemicals tested or CYP3A4 had any significant effect on the intestinal permeability of artemisinin. We also showed that essential oil derived from A. annua negatively affected the intestinal permeability of artemisinin, but only after simulated digestion. Finally, we showed that A. annua essential oil reduced the transepithelial electrical resistance of Caco-2 monolayers, but only in the presence of bile. Although also reduced by essential oils, artemisinin P_app subsequently recovered in the presence of plant matrix.

CONCLUSIONS

These results shed light on the mechanisms by which DLA enhances the oral bioavailability of artemisinin.

Artemisinin Story from the Balkans

The isolation is reported of artemisinin (qinghaosu), a drug remarkably effective against malaria, from the aerial parts of Artemisia annua L. (sweet wormwood) at the Department of Chemistry, University of Belgrade (now Faculty of Chemistry), Serbia by the end of 1970, almost two years before the isolation of the same compound in China.