*Author to whom correspondence should be addressed.

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1 Journal of Chromatographic Science, 2016, Vol. 54, No. 3, doi: /chromsci/bmv154 Advance Access Publication Date: 4 November 2015 Article Article Simultaneous Quantification of Syringic Acid and Kaempferol in Extracts of Bergenia Species Using Validated High-Performance Thin-Layer Chromatographic-Densitometric Method Nishi Srivastava 1,2, Amit Srivastava 1, Sharad Srivastava 1, Ajay Kumar Singh Rawat 1, *, and Abdul Rahman Khan 2 1 Pharmacognosy and Ethnopharmacology Division, CSIR-National Botanical Research Institute, Lucknow , India, and 2 Department of Chemistry, Integral University, Lucknow , India *Author to whom correspondence should be addressed. pharmacognosy1@rediffmail.com; nishisri13jan@gmail.com Received 5 December 2014; Revised 24 July 2015 Abstract A rapid, sensitive, selective and robust quantitative densitometric high-performance thin-layer chromatographic method was developed and validated for separation and quantification of syringic acid (SYA) and kaempferol (KML) in the hydrolyzed extracts of Bergenia ciliata and Bergenia stracheyi. The separation was performed on silica gel 60F254 high-performance thin-layer chromatography plates using toluene : ethyl acetate : formic acid (5 : 4: 1, v/v/v) as the mobile phase. The quantification of SYA and KML was carried out using a densitometric reflection/absorption mode at 290 nm. A dense spot of SYA and KML appeared on the developed plate at a retention factor value of 0.61 ± 0.02 and 0.70 ± A precise and accurate quantification was performed using linear regression analysis by plotting the peak area vs concentration ng/band (correlation coefficient: r = 0.997, regression coefficient: R 2 = 0.996) for SYA and ng/band (correlation coefficient: r = 0.995, regression coefficient: R 2 = 0.991) for KML. The developed method was validated in terms of accuracy, recovery and inter- and intraday study as per International Conference on Harmonisation guidelines. The limit of detection and limit of quantification of SYA and KML were determined, respectively, as 91.63, and , ng. The statistical data analysis showed that the method is reproducible and selective for the estimation of SYA and KML in extracts of B. ciliata and B. stracheyi. Introduction Thin-layer chromatography (TLC) is often used to provide first characteristic fingerprints of herbal drugs that seem to be multicomponent mixtures of different types of phytoconstituents. High-performance thin-layer chromatography (HPTLC) is efficient instrumental analysis and can produce results analogous to those obtained with highperformance liquid chromatography (HPLC) and gas chromatography (1, 2). HPTLC is the method generally applied for the identification and stability study of herbal raw materials and formulations. At present, the HPTLC method is emerging as an alternative to HPLC due to less solvent consumption, cost-effectiveness and reduction of analysis time (3). The investigated species from genus Bergenia (Saxifragraceae) are evergreen perennial herbs, widely distributed in Central and East Asia. It is found in the temperate Himalayas from Kashmir to Bhutan at high altitudes in the range of 7,000 10,000 ft and in Khasia hills at about 400 ft (4). The diameter of the rhizome is 1 cm; the surface is brown with a smooth inner skin (5). Bergenia is highly consumed by the The Author Published by Oxford University Press. All rights reserved. For Permissions, please journals.permissions@oup.com 460

2 Simultaneous Quantification of Syringic Acid and Kaempferol 461 pharmaceutical industry for preparation of various Ayruvedic formulations. In India, Bergenia is commonly known as Pashanbheda and one of the important constituents of the herbal formulation Cystone, used in the Indian system of medicine for kidney stone dissolution. Its major chemical constituents indicated the presence of bergenin (C-glycoside of 4-O-methyl gallic acid), gallic acid (3,4,5-trihydroxybenzoic acid), (+)-catechin, leucocyanidin, (+)-catechin-3-gallate, (+)- catechin-7-o-β-d-glucopyranoside, Paashaanolactone, β-sitosterol, β-sitosterol-d-glucoside and (+)-afzelechin (6, 7). These phytochemicals have a variety of biological activities such as antioxidant (8, 9), antidiarrheal, anti-inflammatory and as treatment for excessive hemorrhage (10, 11), antibacterial, antitussive (12, 13), litholytic (14) and in the treatment of pulmonary infections (15). Syringic acid (SYA; O-methylated triydroxybenzoic acid) (Figure 1A), a naturally occurring derivative of gallic acid and kaempferol (KML; 3,5,7-trihydroxy-2-(4-hydroxyphenyl)-4H-chromen-4-one) (Figure 1B), is a medicinally important compound that has already been reported in several plants. SYA is well known for its pharmacological activity as an antioxidant to scavenge free radicals (16). KML is also reported to have antioxidant, anti-inflammatory, neuroprotective, antianxiety and cognitive-enhancing effects (17 21). To the best of our knowledge and literature survey, there is no report on the simultaneous quantitative determination of SYA and KML in extracts of B. ciliata and B. stracheyi. The major objective of the present communication was the development and validation of a simple, precise, selective and reproducible HPTLC method for simultaneous separation and quantification of SYA and KML in two industrially important Bergenia species namely B. ciliata and B. stracheyi. We have developed a simple, precise and robust HPTLC method for the quantification of SYA and KML in B. ciliata and B. stracheyi. The developed method was validated using International Conference on Harmonisation (ICH) guidelines in terms of precision, repeatability and recovery. Experimental Plant materials and reagents Bergenia ciliata and B. stracheyi were collected from different locations of Uttrakhand, India and the herbarium (voucher no for B. ciliata and for B. stracheyi) is deposited in the repository of CSIR-NBRI. After washing with water, rhizomes were chopped and dried under shade. The dried rhizome (100 g) was crushed into powder and soaked in 100% methanol (250 ml 4 times) at room temperature (27 ± 2 C) for 5 6 days. The suspension was filtered through a paper filter (Whatman no. 4), and the methanol was evaporated using a rotary evaporator (Buchi, USA) at a temperature 30 C. Standard compounds SYA (purity: 98% w/w) and KML (purity: 99% w/w) were procured from MP Biomedicals, LLC, France. All the solvents used were of HPLC grade and purchased from Merck India. Before use, solvents were filtered and sonicated for 15 min. Standard stock solution and sample preparation Standard stock solutions of concentrations 1 mg/ml of pure SYA and KML were prepared in methanol and filtered through a 0.45 µm (Millipore) filter prior to analysis. Samples were prepared from airdried powdered rhizomes (1 g) of sample B. ciliata and B. stracheyi. The extract initially obtained by cold percolation and then the acid hydrolysis method is used to unbound the bounded compounds (22). The organic extracts were combined, filtered and concentrated over vacuum to obtain a crude extract. Known amount of extracts were taken and dissolved in HPLC grade methanol (final concentration 10 mg/ml) and filtered through a 0.45 µm filter for HPTLC analysis. HPTLC method Apparatus A CamagLinomat V automated TLC applicator, Camag twin trough glass chamber, ascending, and a Camag TLC scanner model 3 equipped with CamagWincats IV software were used during the study at a temperature of 27 ± 2 C, and at relative humidity. Chromatographic experiments Sample solution and standards were applied on precoated silica gel 60F 254 HPTLC plates with 6 mm bandwidth using a Camag 100 μl sample syringe (Hamilton, Switzerland) with a Linomat 5 applicator (Camag, Switzerland) under a flow of N 2 gas. The linear ascending development was carried out in the Camag glass twin trough chamber (20 10 cm) after saturation with the mobile phase. The mobile phase was selected using a Vario System wherein varying ratio and polarity were tried. The mobile phase consisting of toluene : ethyl acetate : formic acid (5 : 4 : 1, v/v/v) was optimized for quantitative study. The saturation time of the TLC chamber in the mobile phase was optimized to 20 min for a good resolution of the tested markers and the total run time was 25 min at room temperature (27 ± 2 C), at 50 ± 2% relative humidity. After the run, plates were dried over a hair dryer. Scanning of the TLC plate was performed using the Camag TLC Scanner 3 at λ max 290 nm in the ultraviolet (UV) absorbance mode for all s; TLC plates were developed at a distance of 80 mm from the point of application and slit dimensions were mm. Quantification of SYA and KML in extracts of both species on the TLC plate was performed using the peak area with linear regression of an amount of ng/spot (Table I). Peak profiling was done in the UV region at 290 nm (variable wavelength was used to get the best absorbance range) (Figure 2); to check the identity of the bands, the UV absorption spectrum of each standard was overlaid Figure 1. Chemical structure of SYA and KML.

3 462 Srivastava et al. Table I. Statistical Analysis of Calibration Curves in the HPTLC Determination of SYA and KML Parameters SYA KML R f value 0.61 ± ± 0.01 Slope Intercept Linearity range ng/ml ng/ml Regression equation y = 10.79x y = 9.974x Regression coefficient (R 2 ) Correlation coefficient (r) {(r)= (R 2 )} % confidence limits of intercept LOD (ng) LOQ (ng) Standard error of intercept Standard deviation of intercept P-value Figure 2. Comparative HPTLC chromatogram of standard SYA and KML. This figure is available in black and white in print and in color at JCS online. with the corresponding band in the sample. TLC images were captured at two wavelengths: 254 and 365 nm (Figure 3). The chromatogram of the standards along with extracts is illustrated in Figure 4. Results Validation of the developed method Validation of the developed quantitative HPTLC method includes the evaluation of parameters such as specificity, linearity, sensitivity, accuracy, recovery, precision and robustness according to ICH guidelines (23). Calibration and quantification Linearity was achieved with a concentration range of ng/spot of each standard SYA and KML with regression coefficients (R 2 ) and 0.991, and correlation coefficients and 0.995, respectively (Table I). The result of quantitative determination of SYA and KML in both species of Bergenia is presented in Table II. The quantities of analyzed compounds in the extract of B. ciliata and B. stracheyi are found as follows: ± 0.5 and ± 0.4 (ng/10 mg) for SYA, and ± 0.33 and ± 0.32 (ng/10 mg) for KML, respectively. Specificity The specificity of the methods was determined by analyzing the bands of standards and samples. The bands for SYA and KML in sample solutions were confirmed by comparing the R f and UV spectra with the reference standards. The peak purity of these compounds was also

4 Simultaneous Quantification of Syringic Acid and Kaempferol 463 Figure 3. HPTLC photograph of samples (B. ciliata and B. stracheyi) and standards SYA and KML at λ max 254 (A) and 365 nm (B). This figure is available in black and white in print and in color at JCS online. assessed by comparing the spectra at three different levels, i.e., peak start, peak apex and peak end positions, respectively (Table III). Accuracy The accuracy of the methods was determined by analyzing the percentage recoveries of SYA and KML in samples. To obtain it, three sets were prepared from each species, i.e., B. ciliata and B. stracheyi. The samples were spiked with three different concentrations: 100, 150 and 200 ng/spot (Table IV). The spiked samples were recovered in triplicate and then analyzed by the proposed HPTLC method. Precision Instrumental precision was checked by repeated scanning of the spot of SYA and KML each six times. The repeatability of the sample application and measurements of peak area was expressed in terms of percent relative standard deviation (% RSD). Intraday precision study was achieved at the different concentration levels of 200, 400 and 600 ng/spot. SYA and KML were spotted three times within 24 h and expressed in terms of % RSD (Table V). For interday precision study, same concentrations of 200, 400 and 600 ng/spot of SYA and KML were used over a period of 5 days and expressed as %RSD. Limit of detection and limit of quantification To estimate the limit of detection (LOD) and the limit of quantification (LOQ), the signal-to-noise ratio was determined. The LOD was considered as 3 : 1 and the LOQ as 10 : 1. In the present study, the LODs for SYA and KML estimation in the samples are and (ng) and the LOQs are and (ng), respectively (Table I). Robustness Robustness is a measure of the method to remain unaltered by small but deliberate variations in the method conditions, and is indicative of the reliability of the method. The robustness of the method was achieved by introducing small variations in chromatographic parameters, such as small variations in the ratio of the mobile phase, the time gaps between spotting to chromatography and from chromatography to scanning, and the time interval between drying and scanning (Table VI). Discussion The HPTLC technique was optimized with a view to developing a precise, sensitive and selective method for simultaneous quantification of SYA and KML in Bergenia species. Initially various solvent systems for the best separation of the analyzed compounds SYA and KML were tried. Of the various solvent systems tried, the one containing toluene : ethyl acetate : formic acid (5 : 4 : 1, v/v/v) gave the best resolution of SYA (R f ± SD: 0.61 ± 0.02) and KML (R f ± SD 0.70 ± 0.01) in the presence of other compounds in the sample extract and enabled the quantification of the focused standard compounds (Figures 3A and B). Purity of the bands in the samples was confirmed by comparing band spectra of samples with the corresponding band spectra of standards at the start, middle and end position of the bands. Quantification of SYA and KML in the extracts was performed at the maximum absorption spectrum λ max = 290 nm. The linear range for SYA and KML was ng/spot, with respective correlation coefficients (r = 0.997) and (r = 0.995), respectively. In the proposed method, the LODs and the LOQs were found to be 91.63, and , ng/spot for the compounds SYA and KML, respectively (Table I). This indicated that the proposed HPTLC method for simultaneous quantification of SYA and KML exhibits a good sensitivity. Accuracy, intraday and interday precision were chosen to determine the precision of the developed HPTLC method. Accuracy of the proposed method was tested by analyzing the percentage recoveries of SYA and KML in samples. To obtain it, three sets were prepared from each species, i.e., B. ciliata and B. stracheyi. The samples were spiked with three different concentrations and spiked samples were

5 464 Srivastava et al. Figure 4. Chromatogram of extract and standards SYA and KML. This figure is available in black and white in print and in color at JCS online. Table II. SYA and KML Contents in B. ciliata and B. stracheyi Compound B. ciliata ng/10 mg extract B. stracheyi ng/10 mg extract SYA (A) ± 0.5 (ng/10 mg) ± 0.4 (ng/10 mg) KML (B) ± 0.33 (ng/10 mg) ± 0.32 (ng/10 mg) Table III. Peak Purity Test for the Standards SYA and KML Compounds r (s, m) x r (s, m) y Standard Sample Standard Sample SYA KML s: refers to start; m: refers to middle; x: correlation of spectrum at the start of peak with spectrum at the center of the peak; y: correlation of spectrum at center of the peak with spectrum at the end of the peak. recovered in triplicate and then analyzed by the proposed HPTLC method (Table V). Comparative quantitative study provides raw data to understand the relative potency of sample extracts with variation of the contents Table IV. Data of Intra- and Interday Precision Study (n =3) Standards Concentration (ng/band) Intraday Interday % RSD Mean RSD % RSD Mean RSD SYA KML RSD, relative standard deviation. of studied standards SYA and KML in different species of the same genus. Our results have shown that the proposed HPTLC method for simultaneous quantification of SYA and KML in two different species of Bergenia is simple, reproducible, specific, precise and accurate. In addition, the developed HPTLC method was validated for linearity, LOD and LOQ, and accuracy, and was applied to the analysis of both SYA and KML in respective samples. The developed HPTLC method can be applied for simultaneous quantification of SYA and KML.

6 Simultaneous Quantification of Syringic Acid and Kaempferol 465 Table V. Recovery Studies of SYA and KML at 100, 150 and 200 Addition by the Proposed TLC Densitometric Method Standard Amount of standard present (ng/10 mg) Amount of standard added (ng) Theoretical value Observed value Recovery (%) Average recovery (%) SYA ± ± ± KML ± ± ± Table VI. Testing of the Robustness of the HPTLC Method Parameters Conclusion TLC is an official tool used in preparation of primary fingerprinting of chemical constituents prescribed in some herbal monographs of many pharmacopeias. Because of cost-effectiveness and advantages in some aspects, it is frequently used in the pharmaceutical industry in standardization of plant materials. In the present work, we developed a simple, precise robust HPTLC method for separation of SYA and KML in two species of Bergenia namely B. ciliata and B. stracheyi. Optimization of extract preparation was based on solvent extraction at room temperature followed by acid hydrolysis at 60 C to recover optimum contents of SYA and KML. Both compounds were successfully determined on normal phase silica gel HPTLC plates. The method was found to be reproducible and specific. Acknowledgments The authors thank the Director Dr C.S. Nautiyal CSIR-NBRI, Lucknow, for his kind support and for making available required resources during this study. N.S. is thankful to CSIR (New Delhi) for the award of Senior Research fellowship. References RSD % of the peak area SYA KML Time interval difference between spotting and plate development Mobile phase ratio Time interval between drying and scanning Wagner, H., Bladt, S.; Plant drug analysis: a thin layer chromatography Atlas. Springer, Berlin, (2001). 2. Medic-Saric, M., Jasprica, I., Mornar, A., Males, Z.; Application of TLC in the isolation and analysis of flavonoids. 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