Determination of 1,8-dihydroxyanthranoids in senna

Determination of Total Sennosides and Sennosides A, B, and A1 in Senna Leaflets, Pods, and Tablets by Two-Dimensional qNMR

In the present work, a two-dimensional qNMR method for the determination of sennosides was established. Using band-selective HSQC and the cross correlations of the characteristic 10-10' bonds, we quantified the total amount of the value-determining dianthranoids in five minutes, thus, rendering the method not only fast, but also specific and stability indicating. The validation of the method revealed excellent accuracy (recovery rates of 98.5 to 103%), precision (RSD values of 3.1%), and repeatability (2.2%) and demonstrated the potential of 2D qNMR in the quality control of medicinal plants. In a second method, the use of 2D qNMR for the single analysis of sennosides A, B, and A1 was evaluated with acceptable measurement times (31 min), accuracy (93.8%), and repeatability (5.4% and 5.6%) for the two major purgatives sennoside A and B. However, the precision for sennoside B and A1 was not satisfactory, mainly due to the low resolution of the HSQC signals of the two compounds.

Development of an LC-DAD-MS-Based Method for the Analysis of Hydroxyanthracene Derivatives in Food Supplements and Plant Materials

Products based on plants containing hydroxyanthracene derivatives (HADs)—such as Rheum, Cassia, and Aloe species—are widely used in food supplements or nutraceuticals due to their laxative effects. A more restricted control of HAD contents in food supplements has been implemented by EU Regulation 2021/468, in order to increase the safety of these preparations. Due to their toxicity, aloin A, aloin B, aloe emodin, emodin, and the synthetic derivative danthron have been listed as prohibited substances in food supplements, being tolerated in amounts < 1 mg kg−1 in marketed products. In this work, we report the development of a sensitive and fast LC−DAD−MS-based procedure for the determination of these five compounds in food supplements and plant materials or extracts. The entire procedure includes a simple sample preparation step, where target analytes are concentrated by means of solvent extraction and evaporative concentration (solid samples), or by lyophilisation (liquid samples). The average LOQ of 0.10 mg/L, LOD of 0.03 mg/L, accuracy, and precision with CVs below 12.72 were obtained for the studied analytes. This method is suitable for assessing the compliance of commercial products and raw materials with EU Regulation 2021/468. Furthermore, the proposed method can represent a starting point for the development of a unique and standardised analytical approach for the determination of other HADs under the attention of EU authorities.

Integrated comparative metabolite profiling via MS and NMR techniques for Senna drug quality control analysis

Senna alexandrina Mill (Cassia acutifolia and Cassia angustifolia) are used for the laxative medicine Senna. Leaves and pods from two geographically different sources were distinguished from each other via proton nuclear magnetic resonance (1H-NMR) and ultra performance liquid chromatography-mass spectrometry (UPLC-MS) analysis. Under optimized conditions, we were able to simultaneously quantify and identify 107 metabolites including 21 anthraquinones, 24 bianthrones (including sennosides), 5 acetophenones, 25 C/O-flavonoid conjugates, 5 xanthones, 3 naphthalenes, 2 further phenolics, and 9 fatty acids. Principal component analysis (PCA) and hierarchical clustering analysis (HCA) were used to define both similarities and differences among samples. For sample classification based on tissue type (leaf and pod), both UPLC-MS and NMR were found to be more effective in separation than on geographical origin. Results reveal that the amounts of the major classes of bioactives in Senna, i.e., flavonoids and sennosides, varied significantly among organs. Leaves contained more flavonoids and ω-3 fatty acids but fewer benzophenone derivatives than pods. In contrast, pods were more enriched in bianthrones (sennosides). PCA analysis was found to be equally effective in predicting the origin of the commercial Senna preparation using NMR and/or UPLC-MS datasets. Furthermore, a selection of six so far uninvestigated Senna species were analyzed by UPLC-MS. Results revealed that the Senna alata leaf in terms of secondary metabolite composition is the most closely related species to S. alexandrina Mill, showing the highest levels of the anthraquinone "rhein" and flavonoid conjugates. To the best of our knowledge, this study provides the first approach utilizing both UPLC-MS and NMR to reveal secondary metabolite compositional differences among Senna species.

Albopunctatone, an antiplasmodial anthrone-anthraquinone from the Australian ascidian Didemnum albopunctatum

Chemical investigation of a MeOH extract of the Great Barrier Reef ascidian Didemnum albopunctatum has led to the isolation and identification of a new anthrone-anthraquinone, albopunctatone (1), together with the known 1,8-dihydroxy-9,10-anthraquinone (2). The structure of 1 was established from interpretation of 1D and 2D NMR spectroscopic and mass spectrometric data. The compounds were screened for antiplasmodial activity against chloroquine-resistant and -sensitive strains of the malaria parasite, Plasmodium falciparum. Albopunctatone (1) was moderately active against both strains (IC(50) 5.3 and 4.4 ± 0.5 μM, respectively), while 2 was inactive at doses up to 40 μM. Both compounds were also inactive up to 40 μM when tested against a variety of cancerous and normal human cell lines and the kinetoplastid Trypanosoma brucei brucei, indicating selectivity for the malaria parasite, P. falciparum.

Ultrasonic extraction and separation of anthraquinones from Rheum palmatum L

The ultrasonic nebulization extraction (UNE) was developed and applied to extract anthraquinones (emodin, aloe-emodin and rhein) from Rheum palmatum L. Several parameters of UNE, including type of extraction solvent, concentration of extraction solvent, volume of extraction solvent, extraction time and ultrasonic power, were studied and the optimized parameters were selected. The operation conditions of micellar electrokinetic capillary chromatography (MEKC) were also studied. Under the selected conditions, contents of emodin, aloe-emodin and rhein obtained from different cultivated areas of R. palmatum L. were 1.08-2.04 mg/g, 0.65-1.16 mg/g and 0.70-2.90 mg/g, respectively. The relative standard deviations (RSDs) for emodin, aloe-emodin and rhein were 1.3-2.4%, 1.9-4.7% and 1.3-3.9%, respectively. Compared with maceration extraction (ME), reflux extraction (RE), stirring extraction (SE) and ultrasonic extraction (UE), the proposed method was more efficient, faster and easier to be operated and lower equipment costs and lower extraction temperature were required. The results indicated that UNE was a good alternative method for extracting anthraquinones from R. palmatum L. Compared with traditional extractions, the proposed extraction has a potential in on-line sampling, especially when the gas is used as the carrier of sample.

Simultaneous determination of anthraquinones in rhubarb by high-performance liquid chromatography and capillary electrophoresis

High-performance liquid chromatography (HPLC) and capillary electrophoresis (CE) were compared to simultaneously determine and separate 11 anthraquinones from rhubarb, including emodin, chrysophanol, rhein and their glucosides, aloe-emodin, sennoside A, and sennoside B. A UV-diode array detector (DAD) at 254 nm with a gradient elution of acetonitrile/water (method A: 0 min 6:94, 12 min 12:88, 15 min 20:80, 40 min 25:75, 53 min 55:45, 55 min 100:0; method B: 0 min 5:95, 2 min 15:85, 5 min 20:80, 12 min 25:75, 15 min 50:50, 19 min 98:2) at 28(+/-1) degrees C (method A) and 30-60 degrees C (method B) in HPLC or with 0.03 M borate buffer (pH 10.0) containing 25% (v/v) acetonitrile with 0.002 M 2,6-di-O-methyl-beta-cyclodextrin (CD) and 0.005 M alpha-CD in CE effectively detected this separation in 25 min. The detection limits of anthraquinones from rhubarb were in the 0.02-0.2 microg/mL and 0.1-0.8 microg/mL ranges for HPLC and CE, respectively. The established HPLC and CE methods are suitable for quantitative determination of emodin, chrysophanol, aloe-emodin, emodin-1-beta-d-glucoside, emodin-8-beta-d-glucoside, chrysophanol-1-beta-d-glucoside, chrysophanol-8-beta-d-glucoside, and rhein-8-beta-d-glucoside.

Rapid separation and determination of structurally related anthraquinones in Rhubarb by pressurized capillary electrochromatography

A pressurized capillary electrochromatography (pCEC) with monolithic column has been developed for the rapid separation and determination of five structurally related anthraquinones in Rhubarb. The possibility of rapid separation resulted from the unique pore structure with high permeability and favorable mass transfer characteristics of the monolithic stationary phase. The effect factors such as organic modifier, acidity and concentration of running buffer, separation voltage were investigated to acquire the optimum condition. In the 220 nm wavelengths, the five anthraquinones could be baseline-separated rapidly within 5 min with the separation voltage of -20 kV in 10 mmol/L phosphate buffer (pH 6.2) containing 65% acetonitrile. The calibration graphs of rhein, aloe-emodin, emodin chrysophanol and physcion were linear by plotting the peak area against the analytes concentration over the range of 0.2-65, 0.1-30, 0.1-55, 0.5-30 and 0.5-55 microg/mL, respectively. The detection limits of five anthraquinones were ranged from 0.06 to 0.2 microg/mL and the recoveries of Rhubarb samples were about 81.3-86.4% (R.S.D.< or = 5.2%). This proposed method was successfully applied to determination of the five analytes in Rhubarb with satisfactory results.

Retention modelling in ternary solvent-strength gradient elution reversed-phase chromatography using 30mm columns

An optimization strategy for ternary solvent-strength gradient elution RP chromatography is described in which a two-dimensional model of gradient time (2 levels) against ternary proportions of organic modifiers (4 levels) was constructed. From the resolution surface the optimum ratio of organic modifiers could be selected. Excellent retention time and acceptable peak width and resolution simulations were obtained. The separation could be further optimized from the same input data by using a standard one-dimensional model in order to optimize for gradient slope, duration and shape. Excellent retention time and acceptable peak width and resolution simulations were obtained (< 1, 2 and 6% error, respectively).

Electrochemical studies of danthron and the DNA–danthron interaction

Danthron is an important natural occurring component in laxative drugs. In this paper, electrochemical investigation of danthron and its interaction with DNA is reported. Via the electrochemical approach assisted by ultraviolet-visible (UV-Vis) spectroscopy, we have proved that danthron intercalates into DNA strands forming some nonelectroactive complexes, which results in the decrease of redox peak currents of danthron. In addition, the decrease of the peak currents is proportional to the concentration of DNA. The difference between the interaction of danthron with double-stranded DNA (dsDNA) and with single-stranded DNA (ssDNA) has also been studied. This character implies the potential of danthron to discriminate dsDNA and ssDNA.

Analysis of anthraquinones in cell cultures of Cinchona 'Robusta' by HPLC with photodiode array and mass spectrometry detection

An HPLC-PAD-ESI/MS method has been developed for the analysis of anthraquinones in cell cultures of Cinchona 'Robusta'. Using a C18 column and gradient elution with a mobile phase system containing acetonitrile, water and trifluoroacetic acid, a satisfactory separation of both anthraquinone glycosides and aglycones in a crude dichloromethane extract could be obtained. Robustaquinone B was identified as a major anthraquinone in the extracts, and another five anthraquinones were tentatively identified from spectroscopic data. A number of minor unknown compounds were detected and were distinguished from the known anthraquinones. An isocratic system for the quantitative determination of robustaquinone B has also been developed.

Estimation of individual sennosides in plant materials and marketed formulations by an HPTLC method

Senna is a well-known drug, used in the Ayurvedic and Allopathic systems of medicine, and is a treatment for constipation. The purgative action of senna and its formulations is due to the presence of sennosides A and B. An HPTLC method has been developed for the determination of individual sennosides (A, B, C, D) without any derivatization in marketed formulations (three tablet formulations, two granule formulations and one liquid formulation) and plant materials (senna leaf and pod). The methanolic solution of a sample was applied on a pre-coated silica gel G60 F254 TLC plate (E. Merck.) and was developed using n-propanol : ethyl acetate : water : glacial acetic acid (3 : 3 : 2 : 0.1 v/v) as the mobile phase. The relative band speeds (Rf values) obtained were 0.35, 0.25, 0.61, 0.46 for sennosides A, B, C and D, respectively. The densitometric response was monitored at 366nm. Calibration curves were found to be linear in the concentration ranges 193-1356, 402-2817, 71-497 and 132-927 ng per spot for sennosides A, B, C, and D, respectively. The correlation coefficients were found to be 0.9978, 0.9987, 0.9939 and 0.9983 respectively for sennosides A, B, C and D. The result obtained with the HPTLC method for total sennoside content was compared with the results using the pharmacopoeial methods (spectrophotometric (British Pharmacopoeia) and spectrofluorimetric (United States Pharmacopeia) using the 'F' test). The results revealed no significant difference in the three different methods for estimation of total sennoside. The proposed HPTLC method was found to be simple, specific, precise, accurate and rapid. It can be used for routine quality control of sennosides or senna-containing formulations for individual sennosides.

High-performance liquid chromatographic determination of some anthraquinone and naphthoquinone dyes occurring in historical textiles

A reversed-phase HPLC method has been developed for identification and quantitation of nine natural quinone dyes and applied to historical textile fibres. A Purospher RP18e column was used with a convex gradient of methanol in a mobile phase of 0.1 M aqueous citrate buffer (pH 2.5) and spectrophotometric diode-array detection at 270 nm. For identification of alizarin, purpurin and xanthopurpurin, occurring together in the madder plant, an isocratic method was used with a methanol-0.2 M acetate buffer (pH 4.3) (75:25) as the mobile phase. After an acid extraction of textile fibres and the analysis of the extracts, alizarin and purpurin were identified and quantitated in three fibres.

Computer-aided development of a high-performance liquid chromatographic method for the determination of hydroxyanthraquinone derivatives in Chinese herb medicine rhubarb

With computer simulation predicting separation in reversed-phase gradient elution, a method to separate and determine five hydroxyanthraquinone derivatives having a wide range of polarity in extract of Chinese herbal medicine rhubarb has been developed. The software DryLab was used to model the retention behavior of the compounds as a function of gradient conditions, based on data from two scouting gradient runs. Under the optimized conditions, i.e. column, Zorbax RX-C18, 5 microm, 15x0.46 cm; solvent A, 36 mM triethylamine phosphate (TEAP), pH=2.5; solvent B, ACN; gradient, 36/36/80/80% B at 0/5.5/20.5/25.5 min; flow-rate, 1.00 ml/min; temperature, ambient, the method was successfully applied to monitor the quality of rhubarb from different sources. The effect of sample preparation procedures on extraction efficiency was also examined.

Occurrence of emodin, chrysophanol and physcion in vegetables, herbs and liquors. Genotoxicity and anti-genotoxicity of the anthraquinones and of the whole plants

1,8-Dihydroxyanthraquinones, present in laxatives, fungi imperfecti, Chinese herbs and possibly vegetables, are in debate as human carcinogens. We screened a variety of vegetables (cabbage lettuce, beans, peas), some herbs and herbal-flavoured liquors for their content of the 'free' anthraquinones emodin, chrysophanol and physcion. For qualitative and quantitative analysis, reversed-phase HPLC (RP-LC), gas chromatography-mass spectrometry (GC-MS) and RP-LC-MS were used. The vegetables showed a large batch-to-batch variability, from 0.04 to 3.6, 5.9 and 36 mg total anthraquinone per kg fresh weight in peas, cabbage lettuce, and beans, respectively. Physcion predominated in all vegetables. In the herbs grape vine leaves, couch grass root and plantain herb, anthraquinones were above the limit of detection. Contents ranged below 1 mg/kg (dry weight). All three anthraquinones were also found in seven of 11 herbal-flavoured liquors, in a range of 0.05 mg/kg to 7.6 mg/kg. The genotoxicity of the analysed anthraquinones was investigated in the comet assay, the micronucleus test and the mutation assay in mouse lymphoma L5178Y tk+/- cells. Emodin was genotoxic, whereas chrysophanol and physcion showed no effects. Complete vegetable extract on its own did not show any effect in the micronucleus test. A lettuce extract completely abolished the induction of micronuclei by the genotoxic anthraquinone danthron. Taking into consideration the measured concentrations of anthraquinones, estimated daily intakes, the genotoxic potency, as well as protective effects of the food matrix, the analysed constituents do not represent a high priority genotoxic risk in a balanced human diet.