2.1 Chemical and Reagents:
Standards and reagents
Berberine and conessine were purchased from Yucca enterprises Mumbai. The commercially available tablet formulation of biquinol was used for assay. Ethyl acetate, methanol and diethylamine of analytical reagent grade was purchased from M/s SD Fine Chemicals, Mumbai, India. Silica gel GF TLC plates were purchased from merck pvt ltd. All other chemicals and reagents were purchased from loba chemie pvt ltd.
2.2 Instrumentation:
Methanol was used for the prewashing of HPTLC plates and activated by using an oven at 120°C for 10 min, prior to chromatography. The development was carried out in a 20 cm × 10 cm twin-trough glass chamber using Ethyl Acetate: Methanol: diethylamine (6.5:1:0.3 v/v) as the mobile phase, after saturation of the chamber with mobile phase vapor for 10 min; the development distance was 80 mm. After completion of the development, the chromatography plates were dried with the help of an air dryer, and a CAMAG (Muttenz, Switzerland) HPTLC system ‒ containing a CAMAG Linomat sample applicator, a Hamilton syringe (Bonaduz, Switzerland), and a CAMAG TLC Scanner with winCATS software ‒ was used for the current analytical study.
2.2.1 Preparation of Stock Solution:
25 mg standard berberine was weighed and transferred to 50 ml volumetric flask and methanol was added to 50 ml. 100 mg of conessine was weighed and dissolved in 10 ml methanol.1 ml from standard berberine of 500ug/ml and 1 ml from standard conessine of 10000ug/ml was transferred to 10 ml volumetric flask and diluted up to 10 ml with methanol to get 50ug/ml of berberine and 1000ug/ml of conessine which makes it working standard solution for simultaneous estimation of berberine and conessine.
2.2.2 Selection of Analytical Wavelength:
After chromatographic development, the bands were scanned over the range 200–800 nm which was used for detection analytes during method development and validation. The structures of berberine and conessine are presented in Fig. 1.
2.3 Method development as per experimental design:
In the beginning of risk assessment plan, Ishikawa fishbone diagram was constructed using Microsoft Excel to structure the risk operation plan for the critical factor affecting the method critical analytical attributes (CAAs).
Mobile phase is one of the crucial parameter in method development hence various composition of mobile phases were tried to get resolution of berberine and conessine which are presented in Table 1S.
Based on the preliminary results of mobile phase composition, four-factors were used as Critical method parameters namely Mobile phase composition, saturation time, development of plate and derivatizing agents and 27-run regular 4-factorial design was implemented for factor screening studies to know the critical method parameters/critical process parameters which mostly affect the CAAs(area and Rf). The design matrix enrolled considered factors and their i.e., low (-1), intermediate (0) and high (+ 1) levels suggested by the software, as shown in Table 1. A standard concentration 50 µg/mL and 1000 µg/mL of berberine and conessine respectively were used for all experimental runs, which were analyzed for method CAAs, i.e. peak area and retardation factor. The experimental design runs were analyzed for the influence of the study factors on the CAAs. A summarized design matrix consists of 27 experimental runs as per the Box‒Behnken design (Table 1). Translation of coding in actual units for the 27 experimental trials as per box–behnken design matrix is given in Table 2S. All the results were assessed using statistical software Design‒Expert® version 11.
Table 1
Design matrix as per BBD for optimization of HPTLC method for simultaneous estimation of berberine and conessine
Run | Factor 1 (A:mobile phase v/v) | Factor 2 (B:saturation time mins) | Factor 3 (C:distance travelled mm) | Factor4 (D: anisalehyde concentration ) |
1 | -1 | -1 | -1 | 1 |
2 | -1 | -1 | -1 | -1 |
3 | 0 | 1 | 0 | 0 |
4 | 1 | -1 | 1 | -1 |
5 | 0 | -1 | 0 | 0 |
6 | -1 | 1 | 1 | 1 |
7 | 1 | 1 | 1 | 1 |
8 | -1 | 0 | 0 | 0 |
9 | 0 | 0 | 0 | 1 |
10 | -1 | -1 | 1 | 1 |
11 | 1 | 1 | -1 | -1 |
12 | -1 | 1 | 1 | -1 |
13 | 1 | -1 | -1 | -1 |
14 | 0 | 0 | 1 | 0 |
15 | 1 | 1 | -1 | 1 |
16 | 1 | -1 | -1 | 1 |
17 | 0 | 0 | -1 | 0 |
18 | 1 | 1 | 1 | -1 |
19 | 0 | 0 | 0 | 0 |
20 | -1 | -1 | 1 | -1 |
21 | -1 | 1 | -1 | 1 |
22 | -1 | 1 | -1 | -1 |
23 | 1 | 0 | 0 | 0 |
24 | 0 | 0 | 0 | 0 |
25 | 1 | -1 | 1 | 1 |
26 | 0 | 0 | 0 | 0 |
27 | 0 | 0 | 0 | 2 |
2.4. HPTLC method optimization
The HPTLC chromatographic conditions were optimized on the basis of results of BBD. The reference standards of berberine and conessine were individually weighed and dissolved in methanol to get the standard solutions having concentration 10000ppm. Stock solutions was diluted suitably to obtain the working standard 50 ppm and 1000 ppm of berberine and conessine.
Table 2: Result of BBD study for comparison of Rf Value between the predicted value and observed values By DoE Software
Response
|
Mean
|
Predicted
|
Observed
|
Rf of berberine
|
0.197719
|
0.197719
|
0.28
|
Ref of conessine
|
0.832561
|
0.832561
|
0.80
|
Camag linomat V sample applicator (Switzerland), was used to inject various amounts of working standards for the aforementioned marker compounds in the band form (6 mm wide) using a Hamilton microliter syringe (100µl). The dimension of slit was 5 mm x 0.45 mm. Appropriate volumes of standard solutions were separately loaded on precoated TLC plates of silica gel 60GF254 (Merck) to get graded amounts in the range of 100-800ng/band for berberine and 2000–16000 ng/band for conessine. The mobile phase of ethyl acetate: methanol: diethylamine 6.5:1:0.3 v/v was used as optimized mobile phase based on results of BBD. Horizontal elution of 20min was done followed in the chromatography process. Plate was removed and kept for drying in over 100 ℃ for 15 min and observed in CAMAG TLC Visualizer at 350 nm.
After Post Derivatization the HPTLC plate was derivatized using Anisaldehyde (1%) sulfuric acid for quantification of Conessine. The derivatized plate was then scanned at 620 nm using CAMAG TLC densitometric Scanner 3 incorporated with winCATS 1.4.8 programming. Plate was dried after development and visualization was performed using CAMAG TLC Scanner4 at wavelength 350nm for berberine. The plate was further derivatized using derivatizing agent 1% Anisaldehyde sulfuric acid for detection of conessine at 620nm.
2.5 Validation of the HPTLC Method
The optimized HPTLC method was validated for linearity, accuracy, precision, robustness, specificity and system suitability using ICHQ2R1 guideline [33].
a. Linearity
As per ICH guidelines Q2 (R1), for the establishment of linearity, a minimum of 5 concentrations is recommended. It was determined by plotting a graph of peak area v/s concentration of standards to obtain correlation coefficient (R2) and equation of the line. 50 ppm and 1000 ppm of berberine and conessine were used as working standard solution. The different volumes of standard stock solution, 4, 8, 10, 16,24 and 30µL, were spotted on HPTLC plate (10 × 10 cm) for berberine and Conessine to get concentration of 100-800ng/spot for Berberine and 2000-16000ng/spot for conessine. The peak areas of all concentrations of linearity were measured with CAMAG HPTLC Software vision CATS for both markers Berberine and Conessine and spots were scanned By TLC SCANNER3. The method was used for quantification of biomarkers berberine and conessine from the inhouse formulation containing standardized extract of berberine and conessine.
b. Precision
Interday and intraday precision of the analytical method was determined at three concentrations of quality control. The three quality control concentrations at LQC, MQC, and HQC for 200, 400, and 600 ng/band for berberine and 4000, 8000 and 12000 ng/band for conessine, respectively. The precision was expressed as % RSD at each concentration of quality control samples. The intra-day precision of the marker compounds was assessed using six replicates of quality control samples on the same day. The inter-day or reproducibility parameter was evaluated by analysing QC sample for three consecutive days under the same set of experimental conditions. The results of precision are expressed in terms of the % RSD. (Table 3)
Table 3
Intraday and interday precision of berberine and conesssine
| Intraday Precision | Intraday Precision |
QC samples | Berberine Concentration ng/band | Conessine Concentration ng/band | Berberine Concentration ng/band | Conessine Concentration ng/band |
LQC | 204.06 | 3997.51 | 199.88 | 4108.46 |
199.84 | 4040.08 | 187.21 | 3995.59 |
204.56 | 4153.75 | 190.79 | 4132.22 |
Mean concentration | 202.82 | 4063.78 | 192.63 | 4078.76 |
RSD | 1.64% | 1.98% | 1.31% | 1.78% |
MQC | 383.73 | 7845.64 | 398.13 | 8024.11 |
389.76 | 8127.25 | 394.79 | 7913.07 |
381.76 | 8038.60 | 404.13 | 8018.98 |
| 385.09 | 8003.83 | 399.2 | 7985.39 |
RSD | 1.08% | 1.79% | 1.65% | 0.78% |
HQC | 582.82 | 12120.02 | 602.16 | 11811.61 |
587.19 | 11906.53 | 591.30 | 11750.64 |
595.91 | 11741.93 | 603.53 | 12126.53 |
Mean concentration | 588.64 | 11922.83 | 598.99 | 11897.26 |
RSD | 1.13% | 1.58% | 1.44% | 1.68% |
c. Accuracy
Accuracy study was performed for markers berberine and conessine by % recovery method. The stock solution was spiked in the formulation having known concentration of berberine and conessine at different levels viz. 50, 100 and 150% considering all biomarker. The analysis of all samples by HPTLC method was carried out and percent recovery of each biomarker was calculated to confirm accuracy of the analytical method. Berberine solution having concentration 500 µg/ml standard solution spiked with 50% (250 µg/ml), 100% (500 µg/ml) and 150% (750 µg/ml) of additional amount of standard berberine. 8 µl volume of each solution was loaded on HPTLC plate to get amount of berberine as 600, 800 and 1000 ng/spot. Conessine having concentration 5000 µg/ml was used as standard solution which is spiked with 50% (2500 µg/ml), 100% (5000 µg/ml) and 150% (7500 µg/ml) of additional amount of standard conessine. Further, SD, %RSD and SEM were calculated to check the accuracy of data within the specified limit.
d. Robustness
Robustness parameter was assessed by slight modification in the chromatographic conditions viz mobile phase composition, mobile phase saturation time and wavelength of analysis. The change in area and Rf value of marker compounds was monitored. The final results were examined by calculation of % RSD of concentration.
e. Limit of detection and limit of quantitation
The LOD and LOQ were determined from the slope (S) of the linearity plot and standard deviation of the response to the blank sample (σ) as per the formulae enlisted in Eq. (1).
LOD = 3.3σ/S LOQ = 10 σ/S (Eq. 1)
f. Specificity
Inhouse formulation was formulated containing phytoconstituents berberine, conessine, piperine and quercetin. Specificity of berberine and conessine in presence of other phytoconstituents piperine and quercetin was evaluated. The specificity parameter was evaluated by comparing the chromatograms of the solvent (blank chromatogram) and marketed formulation with the marker compounds. A methanolic solution of standard Berberine and conessine was developed with diluent methanol and compared against blank solution.
2.6 Assay of inhouse Formulation:
Inhouse formulation was prepared by pharmacognosy department which was analysed using validated HPTLC method. Formulation containing B. aristata extract (500 mg), H. antidysenterica extract (70 mg), Piperine (2.5 mg) and Quercetin (2.5 mg) was used for the assay and amount of berberine and conessine was determined. 5 capsules were weighed accurately and granules were crushed using mortar and pestle. This powder was transferred to 50 ml volumetric flask and diluted with methanol 30ml and sonicated for 15 mins or till dissolution of both the extracts as both the markers are soluble in methanol and the volume was made up to the mark using methanol, solution was then filtered through Whatmann filter paper. (Solution I.) Solution I (1ml) was transferred to 10 ml volumetric flask and made up the volume to the mark with methanol (Solution II). Solution II was then analysed by HPTLC using the analytical method as described in section 2.5 to get content of berberine and conessine. The results are expressed as Mean mg/capsule ± SD.