Calcitriol modulates epidermal tight junction barrier function in human keratinocytes.

BACKGROUND: The aberrant expression of tight junction (TJ) proteins play an important role in several diseases with impaired skin barriers, including atopic dermatitis, psoriasis, and chronic wounds. The evidence provided thus far suggests an important role of calcitriol in skin homeostasis. However, it is not known whether calcitriol improves the impaired skin barrier. OBJECTIVE: To investigate the effect of calcitriol on TJ barrier function in human primary keratinocytes. METHODS: Normal human primary keratinocytes were stimulated with calcitriol, and the expression of TJ-related proteins was measured by real-time PCR and Western blotting. Immunofluorescence was used to examine the intercellular distribution of TJ-related proteins. TJ barrier function was assessed by the transepithelial electrical resistance (TER) assay. RESULTS: We demonstrated that calcitriol increased the expression levels of TJ-related proteins, including claudin-4, claudin-7, occludin, and zonula occludens (ZO)- 1. Calcitriol enhanced the distribution of TJ-related proteins at cellcell borders and induced the phosphorylation of pathways involved in the regulation of TJ barrier function, such as atypical protein kinase C (aPKC), Ras-related C3 botulinum toxin substrate 1 (Rac1), phosphoinositide 3-kinase (PI3K), and protein kinase B (Akt), as evidenced by the effects of specific inhibitors on the above pathways. Indeed, we confirmed that calcitriol enhanced TER in keratinocyte monolayers. CONCLUSION: These findings showed that calcitriol could modify the expression of keratinocyte TJ proteins, contributing to the maintenance of homeostatic barrier function.

Tailoring hierarchical structures in cellulose carbon aerogels from sugarcane bagasse using different crosslinking agents for enhancing electrochemical desalination capability.

Sugarcane bagasse is one of the most common Vietnamese agricultural waste, which possesses a large percentage of cellulose, making it an abundant and environmentally friendly source for the fabrication of cellulose carbon aerogel. Herein, waste sugarcane bagasse was used to synthesize cellulose aerogel using different crosslinking agents such as urea, polyvinyl alcohol (PVA) and sodium alginate (SA). The 3D porous network of cellulose aerogels was constructed by intermolecular hydrogen bonding, which was confirmed by Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and nitrogen adsorption/desorption. Among the three cellulose aerogel samples, cellulose - SA aerogel (SB-CA-SA) has low density of 0.04 g m-3 and high porosity of 97.38%, leading to high surface area of 497.9 m2 g-1 with 55.67% micropores of activated carbon aerogel (SB-ACCA-SA). The salt adsorption capacity was high (17.87 mg g-1), which can be further enhanced to 31.40 mg g-1 with the addition of CNT. Moreover, the desalination process using the SB-ACCA-SA-CNT electrode was stable even after 50 cycles. The results show the great combination of cellulose from waste sugarcane bagasse with sodium alginate and carbon nanotubes in the fabrication of carbon materials as the CDI-utilized electrodes with high desalination capability and good durability.

Serine protease inhibitor 3 (Serpin3) from Penaeus vannamei selectively interacts with Vibrio parahaemolyticus PirAvp.

Acute Hepatopancreatic Necrosis Disease (AHPND) represents a significant challenge in the field of shrimp aquaculture. This disease is primarily caused by Vibrio parahaemolyticus strains harbouring the pVA1 plasmid encoding the PirAvp and PirBvp toxins. To combat this epidemic and mitigate its devastating consequences, it is crucial to identify and characterize the receptors responsible for the binding of these pathogenic toxins. Our studied discovered that Penaeus vannamei's Serine protease inhibitor 3 (PvSerpin3) derived from shrimp hepatopancreatic tissues could bind to recombinant PirAvp , confirming its role as a novel PirAvp -binding protein (PA BP). Through comprehensive computational methods, we revealed two truncated PirAvp -binding proteins derived from PvSerpin3 called Serpin3(13) and Serpin3(22), which had higher affinity to PirAvp than the full-length PvSerpin3. The PA BP genes were amplified from a cDNA library that was reversed from total RNA extracted from shrimp, cloned and expressed in Escherichia coli. Three PA BP inclusion bodies were refolded to obtain the soluble form, and the recovery efficacy was found to be 100% for Serpin3 and Serpin3(13), while Serpin3(22) had a recovery efficacy of roundly 50%. Co-Immunoprecipitation (co-IP) and dot blot assays substantiated the interaction of these recombinant PA BPs with both recombinant PirAvp and VPAHPND (XN89)-producing natural toxins.

Fabrication and characterization of a NiO-ZnO/PANI-CNTs composite for sensing of methanol in an aqueous environment.

In this study, we fabricated a composite of NiO-ZnO/PANI-CNTs on a fluorine tin oxide (FTO) electrode and examined the electrochemical sensing behavior of the modified electrode to detect methanol in aqueous solution. The structural, morphological, and electrochemical properties of the composite were characterized using various methods such as X-ray diffraction (XRD), EDS, FTIR, X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and electrochemical techniques such as cyclic voltammetry (CV) and chronoamperometry (CA). The composite-based electrode showed excellent electrocatalytic activity and selectivity for methanol oxidation. The calibration equation obtained was ΔI = 0.0003 × CMeOH + 0.02811, with a high correlation coefficient of 0.9993, over a wide detection range of 0 to 500 mM. The material exhibits great potential for the fabrication of sensors to detect methanol in commercial products. Real gasoline samples have been selected to evaluate the practical performance and feasibility of this as-prepared sensor. The experimental data indicated that the recovery of gasoline samples is about 98%, indicating this to be an appropriate detection procedure for effective electrochemical determination of MeOH in real gasoline samples.

A combination of annual and nonannual forces drive respiratory disease in the tropics.

Background: It is well known that influenza and other respiratory viruses are wintertime-seasonal in temperate regions. However, respiratory disease seasonality in the tropics remains elusive. In this study, we aimed to characterize the seasonality of influenza-like illness (ILI) and influenza virus in Ho Chi Minh City (HCMC), Vietnam. Methods: We monitored the daily number of ILI patients in 89 outpatient clinics from January 2010 to December 2019. We collected nasal swabs and tested for influenza from a subset of clinics from May 2012 to December 2019. We used spectral analysis to describe the periodicities in the system. We evaluated the contribution of these periodicities to predicting ILI and influenza patterns through lognormal and gamma hurdle models. Findings: During ten years of community surveillance, 66,799 ILI reports were collected covering 2.9 million patient visits; 2604 nasal swabs were collected 559 of which were PCR-positive for influenza virus. Both annual and nonannual cycles were detected in the ILI time series, with the annual cycle showing 8.9% lower ILI activity (95% CI: 8.8%-9.0%) from February 24 to May 15. Nonannual cycles had substantial explanatory power for ILI trends (ΔAIC = 183) compared to all annual covariates (ΔAIC = 263). Near-annual signals were observed for PCR-confirmed influenza but were not consistent along in time or across influenza (sub)types. Interpretation: Our study reveals a unique pattern of respiratory disease dynamics in a tropical setting influenced by both annual and nonannual drivers. Timing of vaccination campaigns and hospital capacity planning may require a complex forecasting approach.

A Potent Antioxidant Sesquiterpene, Abelsaginol, from Abelmoschus sagittifolius: Experimental and Theoretical Insights.

The sesquiterpenoid compound abelsaginol (AS) was successfully isolated from Abelmoschus sagittifolius for the first time. The compound was identified using NMR and MS data. The antioxidant activity of AS was also evaluated both theoretically and experimentally. AS was found to be a weak HOO• radical scavenger in organic solvents such as pentyl ethanoate and dimethyl sulfoxide (k overall = ∼ 102 M-1 s-1), in a good agreement with the results of the 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) assay. However, AS exhibited good HOO• antiradical activity in water at pH 7.40 (k overall = 9.00 × 106 M-1 s-1) through the single-electron transfer mechanism of the anion state. Further calculations also demonstrated that AS could exert good to moderate activity against CH3O•, CH3OO•, CCl3OO•, NO2, and SO4 •- radicals, with k f values from 4.00 × 103 to 1.52 × 107 M-1 s-1. However, AS exerted much lower activity against HO•, CCl3O•, NO, O2 •-, and N3 • radicals under the studied conditions. In general, the activity of AS in water at pH 7.40 is higher than that of Trolox or butylated hydroxytoluene, which are common reference antioxidants. Thus, in an aqueous physiological milieu, AS is a promising natural antioxidant.

Mechanistic and Kinetic Studies of the Radical Scavenging Activity of 5-O-Methylnorbergenin: Theoretical and Experimental Insights.

5-O-Methylnorbergenin (5-OMB), a natural compound isolated from Rourea harmandiana, is a compound with potential antioxidant activity based on its chemical structure; however, this activity has not been investigated thus far. In this study, the antioxidant activity of 5-OMB was evaluated by experimental and computational methods. 5-OMB exhibited high activity in DPPH (IC50 = 7.25 ± 0.94 µM) and ABTS•+ (IC50 = 4.23 ± 0.12 µM) assays, higher than the reference compound Trolox. The computational results consistently show that 5-OMB is an excellent HOO• radical scavenger (koverall = 8.14 × 108 M-1 s-1) in water at physiological pH, however it only exerts weak activity in lipid medium (koverall = 3.02 × 102 M-1 s-1). The reaction follows the formal hydrogen transfer mechanism in nonpolar solvents, whereas both the sequential proton loss electron transfer and the formal hydrogen transfer pathways contribute to the activity in aqueous solution. There is a good agreement between experimental and computational data, suggesting that 5-OMB is a promising natural radical scavenger in aqueous physiological environment.

New Polyesterified Ursane Derivatives from Leaves of Maesa membranacea and Their Cytotoxic Activity.

Maesa membranacea A. DC. (Primulaceae) is a plant species that has been frequently used by practitioners of the traditional ethnobotany knowledge from northern and central Vietnam. However, the chemical constituents of the plant remained unknown until recently. Chromatographic separation of a chloroform-soluble fraction of extract from leaves of M. membranacea led to the isolation of two new polyesterified ursane triterpenes (1-2) and two known apocarotenoids: (+)-dehydrovomifoliol (3) and (+)-vomifoliol (4). The chemical structures of the undescribed triterpenoids were elucidated using 1D and 2D MNR and HRESIMS spectral data as 2α,6ß,22α-triacetoxy-11α-(2-methylbutyryloxy)-urs-12-ene-3α,20ß-diol (1) and 2α,6ß,22α-triacetoxy-urs-12-ene-3α,11α,20ß-triol (2). The newly isolated triterpenoids were tested for their cytotoxic activity in vitro against two melanoma cell lines (HTB140 and A375), normal skin keratinocytes (HaCaT), two colon cancer cell lines (HT29 and Caco-2), two prostate cancer cell lines (DU145 and PC3) and normal prostate epithelial cells (PNT-2). Doxorubicin was used as a reference cytostatic drug. The 2α,6ß,22α-triacetoxy-11α-(2-methylbutyryloxy)-urs-12-ene-3α,20ß-diol demonstrated cytotoxic activity against prostate cancer cell lines (Du145-IC50 = 35.8 µg/mL, PC3-IC50 = 41.6 µg/mL), and at a concentration of 100 µg/mL reduced viability of normal prostate epithelium (PNT-2) cells by 41%.

Neuroprotective Properties of Kempferol Derivatives from Maesa membranacea against Oxidative Stress-Induced Cell Damage: An Association with Cathepsin D Inhibition and PI3K/Akt Activation.

As components of the human diet with potential health benefits, flavonols are the subject of numerous studies, confirming their antioxidant, free radical scavenging and anti-inflammatory activity. Taking into consideration the postulated pathogenesis of certain CNS dysfunctions characterized by neuronal degradation, flavonols may prevent the decay of neurons in multiple pathways. Leaves of Maesa membranacea yielded several flavonol glycosides including α-rhamnoisorobin (kaempferol 7-O-α-rhamnoside) and kaempferitrin (kaempferol 3,7-di-O-α-rhamnoside). The latter compound was a major constituent of the investigated plant material. Neuroprotective effects of kaempferitrin and α-rhamnoisorobin were tested in vitro using H2O2-, 6-OHDA- and doxorubicin-induced models of SH-SY5Y cell damage. Both undifferentiated and differentiated neuroblastoma cells were used in the experiments. α-Rhamnoisorobin at a concentration range of 1-10 µM demonstrated cytoprotective effects against H2O2-induced cell damage. The compound (at 1-10 µM) was also effective in attenuating 6-OHDA-induced neurotoxicity. In both H2O2- and 6-OHDA-induced cell damage, kaempferitrin, similar to isoquercitrin, demonstrated neuroprotective activity at the highest of the tested concentrations (50 µM). The tested flavonols were not effective in counteracting doxorubicin-induced cytotoxicity. Their caspase-3- and cathepsin D-inhibitory activities appeared to be structure dependent. Inhibition of the PI3-K/Akt pathway abolished the neuroprotective effect of the investigated flavonols.

New dihydrochromene and xanthone derivatives from Lisotrigona furva propolis.

A new dihydrochromene derivative, named lisofurvin (1) and a xanthone, named dihydrobrasixanthone B (2) together with twenty one known compounds (3-23) were isolated from propolis of the stingless bee Lisotrigona furva. Their chemical structures were determined by means of spectroscopic methods including 1D and 2D NMR, and MS. The chemical constituents are predominantly geranyl(oxy) xanthones and Cratoxylum cochinchinense was suggested as a resin source, besides two other plants Mangifera indica and dammar trees (Dipterocarpaceae). Compound 1 showed significant cytotoxic activity against KB, HepG-2, and Lu-1 cancer cell lines with IC50 values range from 12.63 to 15.17 µg/mL. Several isolated compounds were active against one to four tested cancer cell lines. In addition, among the isolated compounds, α-mangostin (15) displayed the strongest antimicrobial activity against three Gram (+) strains, P. aeruginosa, and C. albicans with MIC values ranging between 1 and 2 µg/mL. Compound 22 showed good activity against three Gram (+) strains and C. albicans.

Chemical constituents and biological activities of the fruits of Knema pachycarpa de Wilde.

The n-hexane extract of Knema pachycarpa fruits (Myristicaceae family), exhibiting strong anti-acetylcholinesterase activity, was investigated by gas chromatography/mass spectrometry and then purified by column chromatography. Guided by GC/MS profiling and bioassay, chromatographic separations led to the isolation of five new compounds: two anacardic acid derivatives 1-2, two cardanol derivatives 3-4 and a cardol derivative 5, along with mixtures of known phenolic lipids 6-9. The chemical structures were determined by various spectroscopic methods. New isolated compounds 1-5 were evaluated for their cytotoxicity and anti-acetylcholinesterase activity. Cardanol 3 and cardol 5 were the most active compounds in the acetylcholinesterase inhibitory assay with IC50 values of 2.60 ± 0.24 µM and 2.46 ± 0.23 µM, respectively. Cardanol 4 and cardol 5 showed moderate cytotoxicity against Hela and MCF-7 cancer cell lines with IC50 values ranging from 31.36 ± 0.41 µM to 41.30 ± 2.49 µM.

Efficient nickel or copper oxides decorated graphene-polyaniline interface for application in selective methanol sensing.

Graphene sheets decorated with nickel or copper oxides that were anchored on polyaniline (denoted as PANI-graphene/NiO and PANI-graphene/CuO) were prepared by a simple, easy to-control electrochemical method and applied as novel materials for sensitive and selective methanol sensing. The fabricated sensors exhibited good electrocatalytic activity, appropriate dynamic linear range (20-1300 mM), sensitivity (0.2-1.5 µA mM-1 cm-2) and excellent selectivity towards methanol. It should be highlighted from the selectivity tests that no significant interference was observed from ethanol and other alcohols. To our best knowledge, using inexpensive but efficient transition metals like Ni, Cu instead of Pt, Pd and their composites with PANI, graphene would be scientifically novel and practically feasible approach for sensor fabrication that could be potentially used to identify methanol adulteration in counterfeit alcoholic beverages.

Selection, purification, and evaluation of acarbose-an α-glucosidase inhibitor from Actinoplanes sp.

Actinoplanes sp. A1094 strain had been selected for its high production of acarbose from 20 different strains of Actinoplanes sp. can be found in wild. The content for glucosidase inhibitor of acarbose concentration was recorded at 1.12 g/L. The conducted analysis of 16S rRNA sequence of Actinoplanes sp. A1094 showed 99% similar identity to the corresponding sequence of Actinoplanes hulinensis. Acarbose was purified from Actinoplanes hulinensis 1094 with a yield of 8.48%, purity of 98% and further identified by LC/MS and NMR methods (C25H43NO18; m/z: 645.6 g/mol). The purified acarbose was used to evaluate the hypoglycemia in streptozotocin (STZ)-induced diabetic mice model. The purified acarbose reduced postprandial blood glucose level in comparison with Glucobay® as medication for control type 2 diabetes in a combination therapy. Notably, the outcomes of native acarbose on fasting blood glucose levels in mice resemble akin to the commercial product and the acarbose accumulating fermentation and metabolic engineering from the cell gene in which would reduce in production cost. Therefore, acarbose from Actinoplanes hulinensis 1094 could be potentially used to make products for the treatment of type II diabetes.

New flavonoid and stilbene derivatives from the fruits of Macaranga balansae.

Two new prenylated flavonoids, 4´-methyl-8-prenyltaxifolin (1) and 6,8-diprenyl-4´-methyl-naringenin (2) and a new geranylated stilbene, 4'-deprenyl-4-methoxymappain (3) together with eight known flavonoids (4-11) were isolated from the fruits of Macaranga balansae Gagnep. Their chemical structures were determined by means of spectroscopic methods including 1D, 2D NMR, and MS data. Compound 2 showed the highest cytotoxic activity against PanC1, A549, KB and LU-1 cell lines with IC50 values range from 7.89 to 22.81 µM.

Plans for Nationwide Serosurveillance Network in Vietnam.

In recent years, serosurveillance has gained momentum as a way of determining disease transmission and immunity in populations, particularly with respect to vaccine-preventable diseases. At the end of 2017, the Oxford University Clinical Research Unit and the National Institute of Hygiene and Epidemiology held a meeting in Vietnam with national policy makers, researchers, and international experts to discuss current seroepidemiologic projects in Vietnam and future needs and plans for nationwide serosurveillance. This report summarizes the meeting and the plans that were discussed to set up nationwide serosurveillance in Vietnam.

Serological inference of past primary and secondary dengue infection: implications for vaccination.

Owing to the finding that Dengvaxia® (the only licensed dengue vaccine to date) increases the risk of severe illness among seronegative recipients, the World Health Organization has recommended screening individuals for their serostatus prior to vaccination. To decide whether and how to carry out screening, it is necessary to estimate the transmission intensity of dengue and to understand the performance of the screening method. In this study, we inferred the annual force of infection (FOI; a measurement of transmission intensity) of dengue virus in three locations in Vietnam: An Giang (FOI = 0.04 for the below 10 years age group and FOI = 0.20 for the above 10 years age group), Ho Chi Minh City (FOI = 0.12) and Quang Ngai (FOI = 0.05). In addition, we show that using a quantitative approach to immunoglobulin G (IgG) levels (measured by indirect enzyme-linked immunosorbent assays) can help to distinguish individuals with primary exposures (primary seropositive) from those with secondary exposures (secondary seropositive). We found that primary-seropositive individuals-the main targets of the vaccine-tend to have a lower IgG level, and, thus, they have a higher chance of being misclassified as seronegative than secondary-seropositive cases. However, screening performance can be improved by incorporating patient age and transmission intensity into the interpretation of IgG levels.

Intravenous Infusion of Human Adipose Tissue-Derived Mesenchymal Stem Cells to Treat Type 1 Diabetic Mellitus in Mice: An Evaluation of Grafted Cell Doses.

Mesenchymal stem cell (MSC) transplantation is a novel treatment for diabetes mellitus, especially type 1 diabetes. Many recent publications have demonstrated the efficacy of MSC transplantation on reducing blood glucose and increasing insulin production in both preclinical and clinical trials. However, the investigation of grafted cell doses has been lacking. Therefore, this study aimed to evaluate the different doses of MSCs on treatment of type 1 diabetes in mouse models. MSCs were isolated and expanded from human adipose tissue. Streptozotocin (STZ)-induced diabetic mice were divided into two groups that were intravenously transfused with two different doses of human MSCs: 106 or 2.106 cells/mouse. After transplantation, both grafted and placebo mice were monitored weekly for their blood glucose levels, glucose and insulin tolerance, pancreatic structural changes, and insulin production for 56 days after transplantation. The results showed that the higher dose of MSCs (2.106 cells/mouse) remarkably reduced death rate. The death rates were 50%, 66%, and 0% in placebo group, low-dose (1.106 MSCs) group, and high-dose (2.106 MSCs) group, respectively, after 56 days of treatment. Moreover, blood glucose levels were lower for the high-dose group compared to other groups. Glucose and insulin tolerance, as well as insulin production, were significantly improved in mice transplanted with 2.106 cells. The histochemical analyses also support these results. Thus, a higher (e.g., 2.106) dose of MSCs may be an effective dose for treatment of type 1 diabetes mellitus.

Substituted 2-arylquinazolinones: Design, synthesis, and evaluation of cytotoxicity and inhibition of topoisomerases.

A series of 2-arylquinazolinones with structural homology to known 3-arylisoquinolines were designed and synthesized in order to develop safe, effective, and selective cytotoxic agents targeting topoisomerases (topos). 2-Arylquinzolinones with various substitutions on the aromatic rings were obtained by thermal cyclodehydration/dehydrogenation on reacting anthranilamides and benzaldehydes. The compounds had superior topo I-inhibitory activities but were generally inactive against topo IIα. Among the 6-methyl-, 6-amino-, and 7-methylquinazolinones, 6-amino-substituted derivatives displayed potent cytotoxicity at submicromolar to nanomolar concentrations against human colorectal adenocarcinoma cells (HCT-15), human ductal breast epithelial tumor cells (T47D), and cervical cancer cells (HeLa). There was a good correlation between topo I inhibition and the cytotoxic effects of 6-aminoquinazolinones. Docking models demonstrated that topo I inhibition by these compounds is owing to intercalation and H-bond interactions with the DNA bases and amino acid residues at the enzymatic site.

Modification of 3-arylisoquinolines into 3,4-diarylisoquinolines and assessment of their cytotoxicity and topoisomerase inhibition.

Inspired by the initial success of the monoarylisoquinolines and the quest to identify more potent and selective anticancer agents with topoisomerase (topo) inhibitory activity, series of diarylisoquinolines (3,4-diarylisoquinolones and 3,4-diarylisoquinolinamines) were designed and synthesized. Synthesis of these compounds primarily involved lithiated toluamide-benzonitrile cycloaddition, Suzuki coupling, and nucleophilic aromatic substitution reactions. Eight of the derivatives were selectively toxic against human ductal breast epithelial tumor cells (T47D), human prostate cancer cells (DU145), and human colorectal adenocarcinoma cells (HCT-15), but had no effect on normal human breast epithelial cells (MCF10A). The topo inhibitory activities of the diarylisoquinoline compounds were relatively dependent upon their chemical structure. 3,4-Diarylisoquinolones generally did not inhibit topo I and only showed moderate inhibition of topo II. In contrast, several 3,4-diarylisoquinolinamines showed superior topo I inhibitory activity. Isoquinolinamine derivatives had greater affinity for topo I than for topo II. Topo inhibition by 3,4-diarylisoquinolines was further supported by docking models showing intercalative and/or H-bond interactions between these compounds and the DNA/topo(s). An analysis of the correlation between the cytotoxicity and topo inhibition of these compounds indicated that the primary biological target of derivatives with potent cytotoxicity was topo, which in turn establishes diaryl-substituted isoquinolines as a novel class of potential anticancer drugs.

Artemisinin analogues as potent inhibitors of in vitro hepatitis C virus replication.

We reported previously that Artemisinin (ART), a widely used anti-malarial drug, is an inhibitor of in vitro HCV subgenomic replicon replication. We here demonstrate that ART exerts its antiviral activity also in hepatoma cells infected with full length infectious HCV JFH-1. We identified a number of ART analogues that are up to 10-fold more potent and selective as in vitro inhibitors of HCV replication than ART. The iron donor Hemin only marginally potentiates the anti-HCV activity of ART in HCV-infected cultures. Carbon-centered radicals have been shown to be critical for the anti-malarial activity of ART. We demonstrate that carbon-centered radicals-trapping (the so-called TEMPO) compounds only marginally affect the anti-HCV activity of ART. This provides evidence that carbon-centered radicals are not the main effectors of the anti-HCV activity of the Artemisinin. ART and analogues may possibly exert their anti-HCV activity by the induction of reactive oxygen species (ROS). The combined anti-HCV activity of ART or its analogues with L-N-Acetylcysteine (L-NAC) [a molecule that inhibits ROS generation] was studied. L-NAC significantly reduced the in vitro anti-HCV activity of ART and derivatives. Taken together, the in vitro anti-HCV activity of ART and analogues can, at least in part, be explained by the induction of ROS; carbon-centered radicals may not be important in the anti-HCV effect of these molecules.