DAD Detection Research Articles

Development and Validation of Analytical Method for Quantification of Losartan Potassium in Solid Dosage Form

The aim of this study was to develop and validate a simple, robust, reliable and an accurate isocratic reverse phase high-performance liquid chromatography (RP-HPLC) method for quantification of Losartan potassium in solid dosage form using DAD Detector. Elution was carried out with mobile phase comprising of 0.01 M monobasic potassium dihydrogen phosphate buffer (adjusted at pH 3.0 ± 0.05 with ortho-phosphoric acid) and methanol (40: 60), through octadecyl silyl (C18) column (15 cm x 4.6 mm x 5 μl), at flow rate of 1 ml/min. The detection was carried out at 230 nm. The developed method was validated according to International Conference on Harmonization (ICH) guidelines (ICH 2005). The assay was linear in concentration range of 1-3 µgmL-1 with Correlation coefficient of 0.999. The limit of detection was 0.036 µgmL-1 and limit of quantification was 0.110 µg/ml. Similarly, method accuracy was asses by comparing the %RSD of BP method with the %RSD of the method developed which shows RSD for standard method was 1.012% while for developed method it was 1.516% and combined RSD of both two methods was found 1.823% that was as per the precision criteria of accuracy i.e. <2%. The result of intraday study was 0.129% and Intermediate precision among inter day and brand to brand was 0.332%. Moreover, the devised method seems to be linear over broad range of LK concentration (1-3 µgmL-1) with appreciable repeatability and reproducibility (RSD <2.00). The results of present study indicate that the method is efficient, specific, sensitive and suitable to be used for the determination of losartan potassium in solid dosage forms using isocratic mode in comparison to gradient mode used by United States pharmacopoeia (USP 2016).

Phenolic content and in vitro antifungal activity of unripe grape extracts from agro-industrial wastes

The antifungal activity of unripe grape extracts from agro-industrial wastes has been evaluated against several strains of Candida spp. and dermatophytes. All the extracts tested showed antifungal activity. The geometric mean MIC ranged from 53.58 to 214.31 μg/mL for Candida spp. and from 43.54 to 133.02 μg/mL for dermatophytes. The chemical analyses have been carried out using Liquid Chromatograph equipped with a DAD and MS detectors. Flavan-3-ols were the main metabolites within all samples ranged from 3.3 to 6.8 mg/g fresh weight. For Candida spp. highest negative significant correlation has been found between MICs and polymeric flavan-3-ols (r = −0.842; p < 0.001) and for dermatophytes between MICs and caffeoyl derivatives (r = −0.962; p < 0.01). The results indicate that total extracts obtained from unripe grapes, a large source of waste material derived from the wine industry, could be used as a cheap source of value-added products.

The validated and sensitive HPLC-DAD method for determination of patulin in strawberries

This work outlines HPLC coupled with DAD detection for accurate quantification of patulin (mycotoxin) in strawberries. The optimized extraction of fruit samples through the modified QuEChERS technique in acetonitrile acidified with acetic acid (1%, v/v) and citrate-buffered salts followed by dispersive solid phase extraction using a primary secondary amine and graphitized carbon is described. The method presents LOD and LOQ of 1.5 and 5µg/kg, respectively and has been validated in strawberry matrix at three concentration levels (5, 10 and 50µg/kg), according to SANTE/11945/2015 and the 2002/657/EC Decision requirements. All validated patulin levels show high percentage of patulin recovery. The validation procedure also includes the intermediate precision performed within three successive days in samples spiked with patulin. The developed method was applied for analysis of fresh and frozen strawberries purchased at local markets. Patulin level in analyzed samples was below the level of detection.

Identification of cis/trans isomers of menaquinone-7 in food as exemplified by dietary supplements

For the first time, the cis/trans isomer content of menaquinone-7 in food products has been identified and marked. A novel method of marking isomers of vitamin K2MK-7 in dietary supplements was developed and validated. Five different isomers of cis/trans vitamin K2MK-7 were identified. Identification of cis/trans isomers was performed by HRMS-QTOF, whereas their quantities were determined by using CAD and DAD detectors. In the majority of cases, the content of biologically active all trans vitamin K2MK-7 was below its declared content. The content of all trans K2MK-7 was in the range between 5.5 and 49 µg in pills. In one of the studied supplements, this vitamin was not found, regardless of the claim on the product label. The content of cis/trans isomers in certain dietary supplements exceeded the content of all trans K2MK-7 by up to 3.7 times.

Online comprehensive two-dimensional hydrophilic interaction chromatography × reversed-phase liquid chromatography coupled with hybrid linear ion trap Orbitrap mass spectrometry for the analysis of phenolic acids in Salvia miltiorrhiza

In the present study, a system was developed for the analysis of phenolic acids in Salvia miltiorrhiza using online comprehensive two-dimensional hydrophilic interaction chromatography and reversed-phase liquid chromatography coupled to a DAD detector and hybrid linear ion trap-Orbitrap mass spectrometry (HILIC×RP-DAD-ESI/HRMS/MSn). The system was configured based on the combination of an XBridge Amide column (150mm×4.6mm, 3.5μm) and Accucore PFP column (50mm×4.6mm, 2.6μm) for the first and second dimensions, respectively. An additional LC pump was used to dilute the eluent from the first dimension to decrease its elution strength in the second dimension. A back-flush trap column was selected as an interface to make up for the loss of efficiency and resolution due to the online dilution. Under the optimized conditions, a total of 196 peaks of polar compounds were successfully separated and detected in Salvia miltiorrhiza using the developed online HILIC×RP system, which exhibited high orthogonality (73%). The online combination of HILIC and RP provides powerful separation capability for the analysis of polar compounds in samples with complex matrices.

Rapid quantification of persulfate in aqueous systems using a modified HPLC unit

Existing analytical techniques used for the quantification of persulfate (PS) in water mostly rely on polarography, reductometry or spectrophotometry. Although acceptable to a certain extent, these methods did not satisfy environmental chemists seeking rapid, reproducible and accurate quantification of PS upon the application of ISCO and AOPs technologies. Accordingly, a novel flow injection/spectroscopy analytical technique is developed via the use of an HPLC coupled to bypass capillary columns and a DAD detector. Special HPLC configuration uses concentrated KI solution as mobile phase to readily reduce PS present in the sample. The reaction takes place inside the capillary columns, under moderate pressure facilitating the production of Iodine suspension (I2), to yield finally the formation of the Triiodide anion (I3−) in the presence of an excess of I−. Triiodide absorbs at 352nm which minimizes interferences from other organic contaminants (OCs). The method was validated by comparison to traditional PS quantification methods and tested on several environmental samples. The new method proved its superiority in terms of time requirement, labor need, material consumption, sample volume and simplicity. It eliminates the inconsistency present in other idiometric methods which is caused by the delay between the PS/I− reaction and I3− measurement. The obtained LDR extends from 0.075 to 300mmolL−1 with a LOD of 6.6 × 10−3mmol L−1 and a LOQ of 2.20 × 10−2mmolL−1. The method is successfully implemented in our laboratory to rapidly and automatically monitor the variation in the concentration of PS used in different projects, which facilitates the rapid determination of the reaction stoichiometric efficiency (RSE) of the oxidation reaction, a key factor toward the optimization of the mineralization process and its sustainability.

Development and validation of a new HPLC-DAD method for quantification of sofosbuvir in human serum and its comparison with LC-MS/MS technique: Application to a bioequivalence study.

Although for many analyses tandem mass spectrometry (LC-MS/MS) systems have significant advantage over the high-performance liquid chromatography with diode array detection (HPLC-DAD) however, the HPLC methods are easier, cheaper and more available to perform. As no published method is available for quantitative HPLC analysis of sofosbuvir (SOF), an orally administered anti-hepatitis drug in human serum, this study was aimed to evaluate applicability of the HPLC technique to quantify sofosbuvir and comparison of the two methods for analytical performance. Following extraction of the drug and an internal standard (Hexobarbital), same chromatographic conditions were used for both the systems. After the chromatographic separation on a reverse phase C18 column using a mobile phase consisting of water (containing formic acid 0.5mL/L) and acetonitrile (57:43; v/v) at a flow rate of 0.8mL/min, the eluate was introduced into a DAD detector set at 261nm, then passed through the mass spectrometry system in single ion monitoring mode (SIM). For UV and mass spectrometry detections the calibration curves were linear over a concentration range of 25-3200 and 10-3200ng/mL, respectively and the linearity was over 0.998 for both the systems. Lower limit of quantification (LLOQ) for mass spectrometry and DAD detections were 10 and 25ng/mL, respectively. In conclusion sensitivity of DAD detection is sufficient enough to determine concentrations down to 0.5% of Cmax which achieved in bioequivalence study of sofosbuvir and meet FDA requirements for these types of studies.

In tube-solid phase microextraction-nano liquid chromatography: Application to the determination of intact and degraded polar triazines in waters and recovered struvite

In-tube solid-phase microextraction (IT-SPME) coupled to miniaturized liquid chromatography (LC) techniques are attractive mainly due to the column efficiency improvement, sensitivity enhancement and reduction of solvent consumption. In addition, the nanomaterials based sorbents can play a key role in the improvement of the extraction efficiency taking into account their interesting physical and chemical properties. Thus, in this work the performance of IT-SPME coupled to nano LC (NanoLC) has been compared with the performance of IT-SPME coupled to capillary LC (CapLC) with similar configurations for the determination of polar triazines including their degradation products. In both cases, a DAD detector was used. Different extractive phases such as TRB-5, TRB-5/c-SWNTs, TRB-5/c-MWNTs capillary columns have been tested. The dimensions of the capillary columns were 0.32mm id×40cm length and 0.1 or 0.075mm i.d.×15cm length for the couplings with CapLC and NanoLC, respectively. The processed volume was 4mL for CapLC and 0.5mL for NanoLC. The elution was carried out with ACN:H2O (30:70, v/v). IT-SPME-NanoLC has shown a higher performance than IT-SPME-CapLC for the target analytes demonstrating the enhancement of the extraction efficiency with the former configuration. A new phase TEOS-MTEOS-SiO2NPs has been also proposed for IT-SPME-NanoLC, which improves the retention of polar compounds. Compared with previously published works, improved LODs were achieved (0.025–0.5μgL−1). The practical application of the proposed procedure has been demonstrated for the analysis of water samples and recovered struvite samples from wastewater treatment plants. Therefore, the proposed procedure can be an alternative method for regulatory purposes.

Investigation of natural dyes in 15th c. documents seal threads from the Romanian Academy Library, by LC-DAD-MS (triple quadrupole)

Abstract Dyes and biological sources in 40 samples from red seal threads in 38 documents issued by the Chancery of Moldavia between 1460 and 1503 were investigated by liquid chromatography with UV-Vis (DAD) and mass spectrometric (MS) detection. Lac dye ( Kerria lacca Kerr), redwood type ( Caesalpinia spp.) and madder ( Rubia sp.), as individual dyes or in combinations, were responsible for the colour in all the dyed yarns while tannins were present in more than half of the total number of samples. The presence of major dyes, such as alizarin, purpurin, laccaic acid A and soluble redwood — a marker compound for Caesalpinia species were observed by both DAD and MS detectors while minor compounds (rubiadin, anthragallol, xanthopurpurin, munjistin, flavokermesic acid etc.) were only detected by mass spectrometry. Single stage MS detection was used in the Full Scan mode followed by data processing through Ion Extraction according to the molecular ions of compounds in the database. Tandem MS detection (MS 2 ) was also achieved, through using the Product Ion Scan operating mode. Identification of dyes was made according to retention time, UV-Vis and MS data, based on information collected on standards — dyes and dyed fibers. The biological sources detected are discussed as compared with those identified in ecclesiastical embroideries from the same period, ordered by the same Prince, Stephan the Great (1457–1504).

Profiling of Vitis vinifera L. canes (poly)phenolic compounds using comprehensive two-dimensional liquid chromatography

Grapevine canes, a pruning-derived by-product, possess a great amount of bioactive (poly)phenolic compounds belonging to different chemical classes, thus, having a good potential for further valorization. However, in order to properly design valorization strategies, the precise chemical composition of this material has to be known. Up to now, this chemical characterization has been based on analysis of different groups of components individually, due to difficulties related to their huge chemical variability. In this work, a comprehensive two-dimensional liquid chromatography-based method (LC×LC) is developed to obtain the profiles of (poly)phenolic compounds present in grapevine canes from several varieties. Three different set-ups have been tested and compared; the combination of diol and C18 columns produced the best results, allowing the characterization of the (poly)phenolic profile in around 80min. This way, 81 different components were detected in the samples; most of them could be tentatively assigned using the information provided by the DAD and MS detectors employed. Indeed, it has been possible to detect in a single run components belonging to stilbenoids, procyanidins and prodelphinidins of varying degrees of polymerization, some of them not formerly described in this natural source. The method has shown extremely good separation capabilities, and is characterized by high effective peak capacity (842) and orthogonality (A0=78%). The obtained results demonstrate that Vitis vinifera L. canes may retain a great potential to be used as an underexploited natural source of bioactive compounds, with potential applications in different fields.

An amino-functionalized grooved nanofiber mat for solid-phase extraction of phenolic pollutants

An amino-functionalized grooved polyacrylonitrile nanofiber mat was modified by both functional groups and in terms of surface morphology. The mat is shown to represent a viable adsorbent for solid-phase extraction of six priority phenolic pollutants and three phenolic xenoestrogens (phenol, 3-methoxyphenol, 4-nitrophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, pentachlorophenol, 4-tert-octylphenol, 4-nonylphenol and bisphenol A) from environmental water samples. Under optimized conditions, the analytes were completely extracted from 90 mL of water sample by using only 9 mg of the mat material. Following elution with an ammoniacal methanol-acetone mixture, the eluent was directly submitted to UPLC-MS/MS or HPLC with DAD detection. Satisfied linearity in range of 50 pg·mL−1 to 100 ng·mL−1 was achieved. The detection limits ranged from 4 to 60 pg·mL−1 which revealed the excellent sensitivity of the method in comparison to standardized and other techniques. The recoveries ranged from 82.4% to 111.4%, with the relative standard deviations of 4.0% to 11.4% (for n = 6). The method was applied to the determination of nine phenolic pollutants in water samples collected from sixteen inflow rivers and six Taihu Lake regions.

Simultaneous Determination and Stability Assessment of Metformin and Sitagliptin in Pharmaceutical Form by High Performance Liquid Chromatography = التحديد المتزامن للميتفورمين والسيتاجلبتين في الشكل الصيدلاني باستخدام الكروماتوغرافيا السائلة عالية الأداء

A simple, rapid and highly selective chromatographic procedure is developed for simultaneous quantification of Metformin and Sitagliptinin tablet formulation. The active ingredients are separated using dihydrogen phosphate buffer (pH 6.00)/acetonitrile mobile phase, flow rate 1.0 mL.min-1, and with DAD detection at 218 nm. The stability and assay separation process are accomplished in 9.0 min with high resolution. The method is precise and accurate. A wide dynamic ranges (1.0-15.0) and (2.0-150.0) mg/L for Metformin and Sitagliptin, respectively, is employed. Both drugs are quantified down to 0.1 and 1.0 mg/L for Metformin and Sitagliptin, respectively, which indicates the high sensitivity of the procedure. Finally, the stability-indicating capability of the procedure is accomplished for tablet formulation (50 mg Metformin and 500 Sitagliptin), and the results indicated that Metformin is unstable to UV and H2O2 with degradation higher than 30.0%. Furthermore, Sitagliptin is unstable at acidic, basic, and oxidation environments

Isolation and structure elucidation of cyclopeptide alkaloids from Ziziphus nummularia and Ziziphus spina-christi by HPLC-DAD-MS and HPLC-PDA-(HRMS)-SPE-NMR

Seven cyclopeptide alkaloids were isolated from the stem bark of Ziziphus nummularia and Ziziphus spina-christi. Three previously undescribed compounds were identified: nummularine-U, spinanine-B and spinanine-C, together with the known compounds mauritine-F, nummularine-D, nummularine-E and amphibine-D. For their purification either semi-preparative HPLC with DAD and ESIMS detection or HPLC-PDA-(HRMS)-SPE-NMR was applied, together with conventional separation methods. Their structures were elucidated by spectroscopic means.

A capillary coated with a metal-organic framework for the capillary electrochromatographic determination of cephalosporins

The authors have developed a rapid and reliable method for the capillary electrochromatographic determination of cephalosporin antibiotics in environmental waters. An open-tubular capillary column was modified with the complex [Cu(mal)(bpy)], a copper(II) complex with malic acid and 4,4′-bipyridyl, by an amide coupling method to act as the stationary phase. The simultaneous determination of the cephalosporins formulations, namely cefapirin (CP), ceftiofur (EFT) and cefixime (CFM) in environmental water samples was accomplished in buffer of pH 5.0 by applying a voltage of 8 kV and with DAD detection. Detection limits typically are 0.1 μg⋅mL−1.The method was applied to the analysis of cephalosporins in spiked water samples from Kunming Lake to give recoveries betwen 88 and 106%.

Simultaneous determination of Dimenhydrinate, Cinnarizine and Cinnarizine impurity by TLC and HPLC chromatographic methods

Two chromatographic methods have been established and validated for simultaneous determination of mixture of Dimenhydrinate (DMH) and Cinnarizine (CIN) in their pharmaceutical formulation and in presence of Cinnarizine impurity (1-(Diphenylmethyl) piperazine); CIN impurity. The first method was TLC-densitometric one, depends on separation and quantitation of DMH, CIN and CIN impurity on TLC silica gel 60 F254 plates, using chloroform:methanol:glacial acetic acid:ammonia solution (9.5:0.5:0.1:0.1, by volume) as a developing system followed by densitometric measurement at 235nm. Linear relationships were obtained in the range of 0.2–2, 0.4–1.6 and 0.1–1μg/band for DMH, CIN and CIN impurity, respectively. The studied components were well resolved from each other with significantly different Rf values of 0.35, 0.52 and 0.04 for DMH, CIN and CIN impurity, respectively. The second method was RP-HPLC, separation on C8 column using 0.05MKH2PO4 (pH=3):methanol (35:65,v/v) as the mobile phase at a flow rate of 1mL/min and DAD detection at 240nm. Linear relationships were obtained in the ranges of 3–30, 2–20 and 1–10μg/mL, with significantly different Rt values of 3.27, 6.95 and 2.87min for DMH, CIN and CIN impurity, respectively. The developed methods were validated according to ICH guidelines demonstrating good accuracy and precision. The results were statistically compared with those obtained by reported HPLC method and no significant difference was obtained.

The influence of seasonality on the content of goyazensolide and on anti-inflammatory and anti-hyperuricemic effects of the ethanolic extract of Lychnophora passerina (Brazilian arnica)

Ethnopharmacological relevanceLychnophora passerina (Mart ex DC) Gardn (Asteraceae), popularly known as Brazilian arnica, is used in Brazilian folk medicine to treat pain, rheumatism, bruises, inflammatory diseases and insect bites. Aim of the studyInvestigate the influence of the seasons on the anti-inflammatory and anti-hyperuricemic activities of ethanolic extract of L. passerina and the ratio of the goyazensolide content, main chemical constituent of the ethanolic extract, with these activities. Materials and methodsEthanolic extracts of aerial parts of L. passerina were obtained from seasons: summer (ES), autumn (EA), winter (EW) and spring (EP). The sesquiterpene lactone goyazensolide, major metabolite, was quantified in ES, EA, EW and EP by a developed and validated HPLC-DAD method. The in vivo anti-hyperuricemic and anti-inflammatory effects of the ethanolic extracts from L. passerina and goyazensolide were assayed on experimental model of oxonate-induced hyperuricemia in mice, liver xanthine oxidase (XOD) inhibition and on carrageenan-induced paw edema in mice. ResultsHPLC method using aqueous solution of acetic acid 0.01% (v/v) and acetonitrile with acetic acid 0.01% (v/v) as a mobile phase in a gradient system, with coumarin as an internal standard and DAD detection at 270nm was developed. The validation parameters showed linearity in a range within 10.0–150.0µg/ml, with intraday and interday precisions a range of 0.61–3.82. The accuracy values of intraday and interday analysis within 87.58–100.95%. EA showed the highest goyazensolide content. From the third to the sixth hour after injection of carrageenan, treatments with all extracts at the dose of 125mg/kg were able to reduce edema. Goyazensolide (10mg/kg) showed significant reduction of paw swelling from the second hour assay. This sesquiterpene lactone was more active than extracts and presented similar effect to indomethacin. Treatments with ES, EA and EP (125mg/kg) and goyazensolide (10mg/kg) reduced serum urate levels compared to hyperuricemic control group and were able to inhibit liver XOD activity. One of the mechanisms by which ES, EA, EP and goyazensolide exercise their anti-hyperuricemic effect is by the inhibition of liver XOD activity. Goyazensolide was identified as the main compound present in ES, EA, EW and EP and it is shown to be one of the chemical constituents responsible for the anti-inflammatory and anti-hyperuricemic effects of the ethanolic extracts. ConclusionThe anti-inflammatory and anti-hyperuricemic activities of the ethanolic extracts from L. passerina were not proportionally influenced by the variation of goyazensolide content throughout the seasons. The involvement of goyazensolide on in vivo anti-inflammatory and anti-hyperuricemic activities of L.passerina extracts was confirmed, as well as the possibility of participation of other constituents on these effects. This study demonstrated that the aerial parts of L. passerina may be collected in any season for use as anti-inflammatory agent. For use in hyperuricemia, the best seasons for the collection are summer, autumn and spring. The ethanolic extract of L. passerina and goyazensolide can be considered promising agents in the therapeutic of inflammation, hyperuricemia and gout.

Estimation of residual antibiotics in soil and underground water of areas affected by pharmaceutical wastewater in Lahore

Drinking water is most essential thing for life on earth. Due to environmental pollution day by day the quality and quantity of drinking water is lowering. Ground water tables are becoming contaminated due industrial pollution. Contamination level of antibiotics namely ofloxacin (OFL), ciprofloxacin (CIP), levofloxacin (LEV), oxytetracycline (OTC), doxycycline (DOX) were quantified in soil and underground water of surrounding areas of pharmaceutical industry in Lahore. HPLC with DAD detector, C-18 column and solid phase cartridges were used to analyze antibiotic residues. In groundwater DOX has highest mean level of contamination and OFL was determined as highest contaminating pollutant in soil. Highest detected value in groundwater of OFL was 0.50, CIP and LEV 0.20, DOX 0.80, OTC 0.40 ng/L. Ground water have residual level of CIP 0.01–0.20 ng/L, LEV 0.02–0.20 ng/L, OFL 0.01–0.50 ng/L, OTC 0.02–0.40 ng/L, and DOX 0.04–0.80 ng/L. Ground water was contaminated by these residues is very important as it is source of accumulation of antibiotics to human and animal body as well as to plants.

Deoxynivalenol occurrence in Serbian maize under different weather conditions

The aim of this paper was to investigate deoxynivalenol (DON) occurrence in maize samples originating from two harvest seasons in Serbia. The key differences between harvest seasons were weather conditions, specifically the humidity. The samples were analyzed using high performance liquid chromatography with DAD detection, after clean-up on SPE columns. In samples from 2014, DON was found in 82 (100.0%) samples with the average content of 2.517 mg/kg (ranged from 0.368 to 11.343 mg/kg). Two samples exceeded maximum level permitted by EU regulations. However, analyzing larger number of samples (163) from 2015 harvest season, DON was present in 51 (31.3%) samples in significantly lower concentrations (average of 0.662 mg/kg, ranged from 0.106 to 2.628 mg/kg). None of the samples from 2015 exceeded maximum level permitted by EU regulations. The data on DON presence in Serbian maize were in relation to the different weather conditions that prevailed during the two harvest seasons.

Development of an HPLC-DAD Method for the Determination of Five Sulfonamides in Shrimps and Validation According to the European Decision 657/2002/EC

A method for the determination of five sulfonamide drugs: sulfadiazine (SDZ), sulfamethazine (SMTH), sulfisoxazole (SIX), sulfadimethoxine (SDMX), sulfaquinoxaline (SQX) in shrimps was developed using a high-pressure liquid chromatography–diode array detection (HPLC–DAD) instrumentation. The drugs were extracted from the samples using a solid-liquid extraction, with a mixture of acetonitrile-methanol and aqueous solution of acetic acid. The separation was achieved with LiChroCART-LiChrospher® 100 RP-18 (5 μm, 250 × 4 mm), and the mobile phase consisted of (A) aqueous solution of acetic acid 0.1% (65%) and (B) mixture of ACN-MeOH 50:50 v/v (35%), delivered at a flow rate of 0.8 mL/min isocratically. A DAD detector was used for the detection of the sulfonamides at 265 nm. The method was validated according to the 657/2002/EC decision of the European Union. The recoveries for within-day repeatability were 90.2–109.0% and for between-day precision 88.6–108.4%. The limit of quantitation for all five suflonamides was 50 μg/kg, and the limit of detection was 15 μg/kg.

Isolation and Structure Elucidation by LC-DAD-MS and LC-DAD-SPE-NMR of Cyclopeptide Alkaloids from the Roots of Ziziphus oxyphylla and Evaluation of Their Antiplasmodial Activity.

Nine cyclopeptide alkaloids (1-9), of which five (compounds 2, 3, 5, 8, and 9) are described herein for the first time, were isolated from roots of Ziziphus oxyphylla by means of conventional separation methods as well as semipreparative HPLC with DAD and ESIMS detection and LC-DAD-SPE-NMR. Structure elucidation was done by spectroscopic means. Nummularine-R (1), a previously known constituent from this species, was isolated along with its new derivatives O-desmethylnummularine-R (2) and O-desmethylnummularine-R N-oxide (3). In addition, the known compounds hemsine-A (4) and ramosine-A (6), as well as hemsine-A N-oxide (5), were isolated. Moreover, oxyphylline-C (7), a known constituent of Z.oxyphylla stems, was obtained, and two new compounds were identified, oxyphyllines-E (8) and -F (9). Just like oxyphylline-C, oxyphyllines-E and -F belong to the relatively rare class of neutral cyclopeptide alkaloids. The antiplasmodial activity and cytotoxicity of compounds 1, 2, 4, 6, and 9 were evaluated, and the most promising activity was found for O-desmethylnummularine-R (2), which exhibited an IC50 value of 3.2 ± 2.6 μM against Plasmodium falciparum K1, whereas an IC50 value of >64.0 μM was evident for its cytotoxicity against MRC-5 cells.