Isothermal microcalorimetric investigation of the toxic action of the effective constituents of Podophyllum emodi Wall on Tetrahymena thermophila BF5

The effects of podophyllotoxin (PPT), etoposide (VP16), and teniposide (VM26) on the growth of Tetrahymena thermophila BF₅ (T.t.BF₅) was investigated by the TAM AIR isothermal microcalorimetric system. The extent and duration of toxic effects on T.t.BF₅ metabolism were evaluated by studying the growth rate constant (k), inhibitory ratio (I), maximum heat-output power (P _max), peak time of maximum heat-output power (t _p), and total heat production (Q _t). Experimental results showed that the value of t _p increased and the value of k and P _max decreased with the increasing compound concentrations. Furthermore, the growth rate constant k was linear with compound concentration. The corresponding I was obtained from different k values. According to the IC₁₀ (the concentration of inhibitor when the inhibitory ratio is 10 %), the relative toxicity of the three compounds was PPT (IC₁₀ = 49.6 μg mL^?1) > VP16 (IC₁₀ = 117.5 μg mL^?1) > VM26 (IC₁₀ = 359.1 μg mL^?1). The preliminary investigation of structure–activity relationships showed that the thienyl group was likely responsible for reducing the toxicity of the compounds.     

Influences of levofloxacin salts on the metabolism of Escherichia coli by microcalorimetry

A microcalorimetric technique was used to evaluate the influence of both Levofloxacin lactate in sodium chloride injection (drug A) and Levofloxacin hydrochloride in sodium chloride injection (drug B) on the metabolism of Escherichia coli. By means of an isothermal calorimeter and ampoule method at 37 °C, the power-time curves of E. coli growth were obtained under different conditions. The parameters such as the growth rate constant k, maximum power output P _m, time t _m corresponding to the maximum power output and inhibitory ratio I of these two drugs were obtained. The results reveal that the inhibitory abilities enhance with increasing concentrations of the two drugs. The critical growth concentration and the half-inhibitory concentration IC₅₀ were 0.15 and 0.079 μg mL^?1 (for drug A), 0.13 and 0.061 μg mL^?1 (for drug B), respectively. These results show the drug A has slightly better inhibitory effect on E. coli than that of drug B.     

A Rapid Method for the Analysis of Ten Compounds in Psoralea corylifolia L. by UPLC

The objective of this study was to develop a simple, efficient and reliable method for routine quantitative analysis for Psoralea corylifolia L. An ultra performance liquid chromatography with DAD detector system was employed for simultaneous quantification of ten compounds. The chromatographic analysis was performed by UPLC with C₁₈ column and gradient elution of 0.05% formic acid aqueous solution and acetonitrile in 16 min. All calibration curves were linear (R ² ≥ 0.9990) over the tested ranges. The LOD and LOQ were lower to 13.07 and 39.22 ng mL^?1 with 2 μL of injection volume, respectively. The intra- and inter-day precisions as determined from sample solutions were below 4.1 and 4.2%. The average recoveries were ranged from 94.2 to 108.8% with RSDs ≤ 4.6%. This validated method was applied for the analysis of ten analytes in P. corylifolia L. from different origins. The variation of the content of ten compounds was remarkable among the tested samples: psoralenoside increased from 7.42 to 17.04 mg g^?1, isopsoralenoside from 6.05 to 14.34 mg g^?1, psoralen from 2.37 to 3.90 mg g^?1, isopsoralen from 2.53 to 3.65 mg g^?1, neobavaisoflavone from 1.59 to 2.96 mg g^?1, bavachin from 1.02 to 2.35 mg g^?1, psoralidin from 0.45 to 1.91 mg g^?1, isobavachalcone from 1.33 to 4.71 mg g^?1, corylifol A from 1.02 to 2.40 mg g^?1 and bakuchiol from 28.10 to 63.89 mg g^?1.     

Characteristics of a High Maltose-Forming, Acid-Stable, and Ca2+-Independent α-amylase of the Acidophilic Bacillus acidicola

The purified acidic α-amylase of Bacillus acidicola is a monomer of 66.0 kDa, optimally active at pH 4.0 and 60 °C. The enzyme is Ca²⁺ independent with T _1/2 for 18 min at 80 °C. The K _m, V _max, and catalytic efficiency (k _cat/K _m) of the enzyme are 1.6 mg mL^?1, 23.8 μmol mg^?1 min^?1, and 981 μmol s^?1, respectively. Among detergents, Tween 20, 40, and 80 stimulated enzyme activity, whereas sodium dodecyl sulfate and Triton X-100 inhibited even at low concentration. EGTA has not affected the activity, whereas EDTA β-mercaptoethanol, iodoacetic acid, and Dithiothreitol exhibited a slight inhibitory action. Phenylmethanesulfonyl fluoride, N-bromosuccinimide, and Hg²⁺ strongly inhibited enzyme activity. The experimental activation energy and temperature quotient are 50.12 kJ mol^?1 and 1.37. When thermodynamic parameters (ΔH and ΔS) of the enzyme have been determined at different temperatures, ΔG is positive suggesting that the enzyme is thermostable. The enzyme hydrolyzes raw starches, and therefore, the enzyme finds application in raw starch saccharification at sub-gelatinization temperatures that saves energy needed for gelatinization of raw starch at 105 °C.     

RP-HPLC Method for the Quantitation of Glabridin in Yashti-madhu (Glycyrrhiza glabra)

A reverse phase high performance liquid chromatographic method is developed for the quantitation of glabridin in Glycyrrhiza glabra, using C₁₈ column with acetonitrile-water containing 2% AcOH (70:30) as an eluent. Glabridin is detected by UV absorption at 280 nm after separation by the chromatographic system. Good linearity was obtained in the working range of the concentration (0.01–0.1 mg mL^?1), with correlation coefficients 0.999. Limit of detection and limit of quantitation were 0.0195 and 0.065 mg mL^?1. The method was validated under ICH guidelines. The described method can be utilized for routine analysis (assays and stability tests) of G. glabra extracts and Ayurvedic medicine based on Yashti-madhu.     

Microcalorimetric investigation on antibacterial activity of the peptide from Plutella xylostella

The antibacterial activities of a kind of novel peptide from Plutella xylostella (pxCECA1) on methicillin-resistant staphylococcus aureus (MRSA) and Escherichia coli (E. coli) growth were investigated by microcalorimetry. The heat flow power–time curves of MRSA and E. coli growth in the presence of pxCECA1 were recorded using the 3114/3115 Thermal Activity Monitor Air Isothermal Calorimeter based on ampoule mode at 37 °C. Some parameters including growth rate constant k, maximum power output P _max, total heat output Q_t, generation time t _g, growth inhibitory ratio I, and half-inhibitory concentration of the drugs IC₅₀ were obtained to elucidate the antibacterial activity of pxCECA1. The results showed that k, P _max, and Q _t decreased, but I and t _g increased or delayed with the increase in pxCECA1 concentration. The IC₅₀ of pxCECA1 on E. coli was 6.122 μg mL^?1 and MRSA was 7.809 μg mL^?1. It could be concluded that pxCECA1 had stronger inhibitory effect on E. coli than MRSA. In vivo test was simultaneously performed using an E. coli and MRSA infection model to validate the antibacterial activity of pxCECA1. The results revealed that pxCECA1 with broad spectrum antimicrobial activities hopefully represented a class of promising substitute of antimicrobial agents.     

Purification and Characterisation of a β-1,4-Xylanase from Remersonia thermophila CBS 540.69 and Its Application in Bread Making

This work reports the first investigation of Remersonia thermophila hemicellulosic hydrolytic enzyme production, with subsequent purification of an extracellular endo-β-1,4-xylanase (RtXyl) and its application in bread making. The research describes RtXyl purification from sorghum-induced submerged liquid cultures of this moderately thermophilic, aerobic, ascomycete fungus. The purified enzyme is a single subunit protein with a molecular mass of 42 kDa and exhibits glycosyl hydrolase family-10-like activity over a broad pH and temperature range. Optimal activity was measured at pH 6.0 and 65 °C respectively, which is suitable for bread making applications. Substrate specificity studies revealed that RtXyl is purely xylanolytic with no side-activities against other plant polysaccharides. The RtXyl catalytic efficiency (K _cat/K _m) was highest with oats spelt xylan (810.90 mg mL^?1 s^?1), wheat arabinoxylan (809.52 mg mL^?1 s^?1) and beechwood xylan (417.40 mg mL^?1 s^?1) with less efficiency towards insoluble oats spelt xylan (236.40 mg mL^?1 s^?1). Hydrolysis products analysed by thin layer chromatography yielded a range of xylosaccharides, predominantly xylotriose and xylobiose. RtXyl application in a basic wheat bread recipe at low dosages (0.297 XU/g) showed its suitability to increase loaf volume by 8.0 % compared with the control bread. RtXyl increased loaf softness by 19.6 % while reducing bread staling by 20.4 % up to 4 days of storage.     

Synthesis,antifungal and insecticidal activity of novel [1,2,4]triazolo[4,3-<Emphasis Type="Italic">a</Emphasis>]pyridine derivatives containing a sulfide substructure

A series of [1,2,4]triazolo[4,3-a]pyridine derivatives bearing a sulfide substructure was designed, synthesized and characterized via ¹H·NMR, ¹³C·NMR, IR and elemental analyses. Bioassay Results indicated some of the derivatives displayed good fungicidal activity on Rhizoctonia cerealis, moderated insecticidal activity against Plutella xylostella and good insecticidal activity on Helicoverpa armigera. The inhibitory effects of compounds 4g and 4u against Rhizotonia cerealis were 70.9% at 50 μg mL^?1; the IC₅₀ values of compounds 4d and 4s against Plutella xylostella were 43.87 and 50.75 μg mL^?1, respectively. And the IC₅₀ values of compounds 4d, 4q, and 4s on Helicoverpa armigera were 58.3, 77.14 and 65.31 μg mL^?1, respectively, which were better than that of commercial chlorpyrifos (103.77 μg mL^?1).     

Antimicrobial and antiparasitic activities of three algae from the northwest coast of Algeria

The objective of this study was to investigate the biological activities of Algerian algae, Sargassum vulgare, Cladostephus hirsutus and Rissoella verruculosa. Antimicrobial activity of the crude extracts and their fractions was assessed using the disc diffusion assay, the minimum inhibitory concentration and the minimum bactericidal concentration. Antiparasitic activity was studied in vitro against the blood stream forms of Trypanosoma brucei brucei and the intraerythrocytic stages of Plasmodium falciparum. Ethyl acetate (EA) fractions of the three tested algae showed more potent antimicrobial activity against S. aureus (7–14.5 mm) and B. cereus (7–10.75 mm), MIC values ranged from 0.9375 to 7.5 mg mL^?1 and MBC values > 15 mg mL^?1. Concerning the antiparasitic activity, EA factions of S. vulgare (IC₅₀ = 9.3 μg mL^?1) and R. verruculosa (IC₅₀ = 11.0 μg mL^?1) were found to be more effective against T. brucei brucei, whereas the three EA fractions were little active against P. falciparum.     

Comparisons of Isolation Methods,Structural Features,and Bioactivities of the Polysaccharides from Three Common Panax Species: A Review of Recent Progress

Panax spp. (Araliaceae family) are widely used medicinal plants and they mainly include Panax ginseng C.A. Meyer, Panax quinquefolium L. (American ginseng), and Panax notoginseng (notoginseng). Polysaccharides are the main active ingredients in these plants and have demonstrated diverse pharmacological functions, but comparisons of isolation methods, structural features, and bioactivities of these polysaccharides have not yet been reported. This review summarizes recent advances associated with 112 polysaccharides from ginseng, 25 polysaccharides from American ginseng, and 36 polysaccharides from notoginseng and it compares the differences in extraction, purification, structural features, and bioactivities. Most studies focus on ginseng polysaccharides and comparisons are typically made with the polysaccharides from American ginseng and notoginseng. For the extraction, purification, and structural analysis, the processes are similar for the polysaccharides from the three Panax species. Previous studies determined that 55 polysaccharides from ginseng, 18 polysaccharides from American ginseng, and 9 polysaccharides from notoginseng exhibited anti-tumor activity, immunoregulatory effects, anti-oxidant activity, and other pharmacological functions, which are mediated by multiple signaling pathways, including mitogen-activated protein kinase, nuclear factor kappa B, or redox balance pathways. This review can provide new insights into the similarities and differences among the polysaccharides from the three Panax species, which can facilitate and guide further studies to explore the medicinal properties of the Araliaceae family used in traditional Chinese medicine.     

Performance Evaluation of Charged Aerosol and Evaporative Light Scattering Detection for the Determination of Ginsenosides by LC

A sensitive LC-CAD method was developed for simultaneous determination of seven major triterpenoid saponins, namely ginsenosides Rg₁, Re, Rb₁, Rc, Rb₂, Rb₃ and Rd in Panax ginseng C. A. Meyer, a commonly used traditional Chinese medicine. This CAD method was evaluated in sensitivity, linearity and reproducibility compared to ELSD and UV. It was found the developed method has improved sensitivity, linearity and reproducibility compared to ELSD. This method was successfully applied to analyze the ginsenosides in ten samples of Panax ginseng. The validation results indicated that the improved method can be utilized as another approach for quality control of P. ginseng.     

Determination of mycotoxins,alkaloids, phytochemicals,antioxidants and cytotoxicity in Asiatic ginseng (Ashwagandha,Dong quai, <Emphasis Type="Italic">Panax ginseng</Emphasis>)

Mycotoxins and selected hazardous alkaloids in the medicinal plants (Panax ginseng, Angelica sinensis, and Withania somnifera) and dietary supplements were determined. Purine alkaloids were found in majority of samples; however, isoquinoline alkaloids were less abundant than indole. The predominant alkaloids appear to be caffeine (purine group), harman (indole group) and berberine (isoquinoline). Examined medicinal plants and dietary supplements were contaminated by mycotoxins (especially ochratoxin A 1.72–5.83 µg kg^?1), and many species of mold (e.g. Cladosporium, Eurotium, Aspergillus, Rhizopus, Penicillium). MTT cytotoxicity tests revealed that plant and supplements extracts exhibited medium or high cytotoxicity (only Dong quai—low). Moreover, antioxidant activity, total phenolics content and selected phytochemicals were analyzed by spectrophotometric and chromatographic methods. Quercetin and rutin were predominant flavonols (1.94-9.51 and 2.20–7.28 mg 100 g^?1, respectively). Analysis of phenolic acids revealed—gallic acid, as the most abundant, except Panax ginseng, where ferulic acid was prevailing. The results were analyzed by chemometric methods (cluster analysis, ANOVA).     

Activity of ginsenoside Rh<Subscript>2</Subscript> on the growth of mice splenic lymphocytes investigated by microcalorimetry and factor analysis

The power–time curves of mice splenic lymphocytes growth at 37 °C affected by ginsenoside Rh₂ were determined by microcalorimetry using a 3114/3236 TAM air bioactivity monitor with ampoule mode. Then, the minimal inhibitory concentration (MIC) of Rh₂ on splenic lymphocytes growth was determined by serial dilution method. From factor analysis (FA) on six quantitative thermokinetic parameters from the power–time curves, the activity of Rh₂ on splenic lymphocytes could be quickly evaluated by analyzing the changes in the two main parameters: growth rate constant k, and maximum heat-output power, P _m. The results showed that Rh₂ had strong inhibitory activity on splenic lymphocytes growth, and this inhibitory activity was strengthened with increasing concentration of Rh₂ in the concentration range of 1.0–32.0 μg mL⁻¹. This strong inhibitory also could be confirmed from the MIC of 50.0 μg mL⁻¹ of Rh₂ on splenic lymphocytes growth in RPMI-1640 culture medium. This study illustrated that microcalorimetry could not only offer a useful method for evaluating the activity of drugs, but also serve as a quantitative, sensitive, and simple analytic tool for the evaluation of drugs on cell growth.     

Resolution of Racemic Ofloxacin Based on Co-Technology of Bubble Fractionation and Extraction

A method of bubble fractionation, with the help of solvent extraction, was developed for the resolution of racemic ofloxacin (rac OFLX). In this method, dibenzoyl-L-tartaric (L-DBTA), di-(2-ethylhexyl) phosphoric acid (D2EHPA) and sodium lauryl sulfate (SDS) were used as chiral collector, co-extractant and foamer, respectively. Several important parameters influencing the resolution performances, such as pH in aqueous phase, concentration of OFLX, concentration of L-DBTA, concentration of SDS and volume ratio of D2EHPA to n-octanol in solution, were investigated. The optimal resolution conditions were obtained with the aqueous phase pH 7, volume ratio of D2EHPA to n-octanol 6/14 in organic phase, concentration of SDS 0.42 mg mL^?1, concentration of OFLX 1.67 mg mL^?1, and concentration of L-DBTA 0.11 g mL^?1. Under the optimal extraction conditions, the enantiomeric excess value (e.e.%) was 60.08% and the enantioselectivity (??) was 5.58. It was found that the capacity of enantioselective separation can be greatly improved by the co-technology.     

Development and Validation of an LC Method for Simultaneous Determination of Ascorbic Acid and Three Phenolic Acids in Sustained Release Tablets at Single Wavelength

A simple, rapid and sensitive column liquid chromatographic method was developed and validated to measure simultaneously the amount of ascorbic acid and phenolic acids at single wavelength (240 nm) in order to assess drug release profiles and drug-excipients compatibility studies for a new sustained release tablet formulation and its subsequent stability studies. A combined isocratic and linear gradient reversed-phase LC method was carried out at 240 nm. Quantification was achieved with reference to the external standards. The linearity for concentrations between 0.042 and 0.150 mg mL^?1 for ascorbic acid, 0.084–0.250 mg mL^?1 for chlorogenic acid, 0.053–0.360 mg mL^?1 for caffeic acid, and 0.016–0.250 mg mL^?1 for ferulic acid (r > 0.99 for all analytes) were established. The recovery of the active ingredients from the samples was at the range of 92.3–102.9%. Intra- and inter-day precisions were less than 2.5%. The limits of detection and quantification were 8 and 24 μg mL^?1 for ascorbic acid, 18 and 54 μg mL^?1 for chlorogenic acid, 37 and 112 μg mL^?1 for caffeic acid, and 11 and 34 μg mL^?1 for ferulic acid. The determination of the four active ingredients was not interfered by the excipients of the products. Samples were stable in the release mediums (37 °C) at least for 12 h.     

Rapid differentiation of Panax ginseng and Panax quinquefolius by matrix-assisted laser desorption/ionization mass spectrometry

A matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS)-based method has been developed for rapid differentiation between Panax ginseng and Panax quinquefolius, two herbal medicines with similar chemical and physical properties but different therapeutic effects. This method required only a small quantity of samples, and the herbal medicines were analyzed by MALDI-MS either after a brief extraction step, or directly on the powder form or small pieces of raw samples. The acquired MALDI-MS spectra showed different patterns of ginsenosides and small chemical molecules between P. ginseng and P. quinquefolius, thus allowing unambiguous differentiation between the two Panax species based on the specific ions, intensity ratios of characteristic ions or principal component analysis. The approach could also be used to differentiate red ginseng or P. quinquefolius adulterated with P. ginseng from pure P. ginseng and pure Panax quinquefolium. The intensity ratios of characteristic ions in the MALDI-MS spectra showed high reproducibility and enabled quantitative determination of ginsenosides in the herbal samples and percentage of P. quinquefolius in the adulterated binary mixture. The method is simple, rapid, robust, and can be extended for analysis of other herbal medicines.     

Optimised isolation of polysaccharides from Lentinula edodes strain NCBI JX915793 using response surface methodology and their antibacterial activities

Mycelial growth in a defined medium by submerged fermentation is a rapid and alternative method for obtaining fungal biomass of consistent quality. Biomass, exopolysaccharides (EPS) and intracellular polysaccharides (IPS) production were optimised by response surface methodology in Lentinula edodes strain LeS (NCBI JX915793). The optimised conditions were pH 5.0, temperature 26°C, incubation period of 25 days and agitation rate of 52 r/min for L. edodes strain LeS. Under the calculated optimal culture conditions, biomass production (5.88 mg mL^? 1), EPS production (0.40 mg mL^? 1) and IPS production (12.45 mg g^? 1) were in agreement with the predicted values for biomass (5.93 mg mL^? 1), EPS (0.55 mg mL^? 1) and IPS production (12.64 mg g^? 1). Crude lentinan exhibited highest antibacterial effects followed by alcoholic, crude and aqueous extracts. The results obtained may be useful for highly effective yield of biomass and bioactive metabolites.     

Microcalorimetric study of the opposing effects of ginsenosides Rg<Subscript>1</Subscript> and Rb<Subscript>1</Subscript> on the growth of mice splenic lymphocytes

Splenic lymphocytes play an important role in host acute or chronic diseases. The abnormality of these cells in the spleens of humans might lead to some riskful diseases for human. Hence, in this study, the effects of two ginsenosides Rg₁ and Rb₁ on splenic lymphocytes growth were studied by microcalorimetry. Some qualitative and quantitative information, such as the metabolic power-time curves, growth rate constant k, maximum heat-output power of the exponential phase P _max, total heat output Q _t of splenic lymphocytes were obtained to present the effects of Rg₁ and Rb₁ on these cells. The values of k, P _max, and Q _t from the thermogenic growth curves of splenic lymphocytes were found to increase in the presence of Rg₁, while the change was adverse for Rb₁, illustrating that Rg₁ had promotion effect and Rb₁ had inhibitory effect on splenic lymphocytes growth and these promotion or inhibitory effects were enhanced with increasing the concentration of the two compounds, respectively. The microcalorimetric results were confirmed by MTT assay for determining the MTT optical density (OD) value and [³H] Thymidine incorporation assay ([³H]-TdR) for determining the count per minute (cpm) value: Rg₁ could increase the MTT OD value and the cpm value of [³H]-TdR incorporation into splenic lymphocytes, and these values were increased with increasing the concentration of this compound, while Rb₁ had the adverse results. The structure–activity relationships showed that the glucopyranoside and hydroxyl groups at the dammarane-type mother nucleus skeleton might play a crucial role for the opposing effects of the two ginsenosides on splenic lymphocytes. Compared with the other two assay methods, the microcalorimetric method provided more useful and reliable information for quickly and objectively evaluating the effects of drugs or compounds on the living cells, which would be a highly promising analytical tool for the characterization of the biological process and the estimation of the drugs’ efficiency.     

HPLC Analysis and Pharmacokinetic Study of Paeoniflorin after Intravenous Administration of a New Frozen Dry Powder Formulation in Rats

A simple and specific high performance liquid chromatographic (HPLC) method with UV detection using picroside II as the internal standard was developed and validated to determine the concentration of paeoniflorin in rat plasma and study its pharmacokinetics after an single intravenous administration of 40 mg kg^?1 paeoniflorin to Wistar rats. The analytes of interest were extracted from rat plasma samples by ethyl acetate after acidification with 0.05 mol L^?1 NaH₂PO₄ solution (pH 5.0). Chromatographic separation was achieved on an Agilent XDB C₁₈ column (250 × 4.6 mm I.D., 5 μm) with a Shim-pack GVP-ODS C₁₈ guard column (10 × 4.6 mm I.D., 5 μm) using a mobile phase consisting of acetonitrile–water–acetic acid (18:82:0.4, v/v/v) at a flow rate of 1.0 mL min^?1. The UV detection was performed at a wavelength of 230 nm. The linear calibration curves were obtained in the concentration range of 0.05–200.0 μg mL^?1 in rat plasma with the lower limit of quantification (LLOQ) of 0.05 μg mL^?1. The intra- and inter-day precisions in terms of % relative standard deviation (RSD) were lower than 5.7 and 8.2% in rat plasma, respectively. The accuracy in terms of % relative error (RE) ranged from ?1.9 to 2.6% in rat plasma. The extraction recoveries of paeoniflorin and picroside II were calculated to be 69.7 and 56.9%, respectively. This validated method was successfully applied to the pharmacokinetic study of a new paeoniflorin frozen dry power formulation. After single intravenous administration, the main pharmacokinetic parameters t _1/2, AUC_0-∞, CL_TOT, V _Z, MRT_0-∞ and V _ss were 0.739 ± 0.232 h, 43.75 ± 6.90 μg h mL^?1, 15.50 ± 2.46 L kg^?1 h^?1, 1.003 ± 0.401 L kg^?1, 0.480 ± 0.055 h and 0.444 ± 0.060 L kg^?1, respectively.     

LC Method for Quantification of Lutein in Rat Plasma: Validation, and Application to a Pharmacokinetic Study

A reversed-phase LC method has been developed for quantitative analysis of lutein in rat plasma and applied to a study of the pharmacokinetics of lutein in rats. From a variety of compounds and solvents tested, astaxanthin was selected as the internal standard. n-Hexane was found to be the best solvent for extracting lutein from plasma. LC analysis of the extracts was performed on a C₁₈ column equipped with a guard pre-column. Linearity was good (r > 0.99) over the range 10–100 ng mL^?1. Recovery from plasma was 82.7–92.9% the intra-day and inter-day precision were always better than 3%. The limits of detection (LOD) and quantification (LOQ) were 2.5 and 8.3 ng mL^?1, respectively. The LC method was used to quantify lutein and zeaxanthin in rat plasma in a 36-h pharmacokinetic study in which experimental rats received a single oral dose of lutein (20 mg kg^?1). The results are presented.