International Journal of Drug Development and Research

Key words

UV- Visible Spectrophotometer, Curcumin, ICHguidelines

INTRODUCTION

The powdered dry rhizome of the plant Curcumalonga, commonly called turmeric, is widely used as acolouring agent and spice in many food items [1]. Itcontains a wide variety of phytochemicals, including curcumin, demethoxycurcumin,bisdemethoxycurcumin, zingiberene, curcumenol,curcumol, eugenol, tetrahydrocurcumin,triethylcurcumin, turmerin, turmerones, andturmeronols [2, 3]. Curcumin is the phytochemical thatgives a yellow color to turmeric and is nowrecognized as being responsible for most of thetherapeutic effects [4]. Chemically described as (1E,6E)-1.7-bis (4 hydroxy – 3 methoxyphenyl) – 1,6Heptadiene-3,5-dione, the aromatic ring systems,which are polyphenols are connected by two α, β –unsaturated carbonyl groups (Fig. 1), while the α,β –unsaturated carbonyl is a good Michael acceptor andundergoes nucleophilic addition [5, 6]. It ishydrophobic in nature and frequently soluble indimethylsulfoxide, acetone, ethanol, and oils. It hasan absorption maximum around 420 nm [7, 8].

Literature survey revealed that a variety of analyticalmethods viz. HPLC, HPTLC, UV-Visible has beendeveloped for their analysis but in plasma and urine[9, 10]. As the formulations are available withoutcombinations of any drugs, there is a need for comingup with analytical method which is simple, sensitive,rapid and accurate for estimation of Curcumin inpure form and in pharmaceutical preparations [11, 12].Therefore, the aim of the present work is to developand validate a method for the analysis by UV-Visiblespectrophotometer which is easily adaptable as aroutine in quality testing laboratories. This hasenabled us to reduce total time of analysis besidestaking care of the error caused due to

MATERIALS AND METHODS

Materials

Curcumin was obtained from Loba chieme Mumbai,India as gift sample. Methanol used was of analyticalgrade and purchased form Merk Chemicals, India.Three formulations collected from market (A, B & C)with drug equivalent to 500 mg curcumin. All the other chemicals and reagents used were of analyticalgrade.

Method development

Instrumentation

Spectroscopic analysis was carried out using DoublebeamShimadzu recording UV-VisibleSpectrophotometer (Kyoto, Japan) model 1601 with10 mm path length matched quartz cells was used foranalytical purpose.

Standard stock solution

Stock solutions of curcumin containing 10μg/ml wereprepared in methanol and its aliquots weretransferred in a series of 10 ml volumetric flasks invarying fractions and their volumes were made withmethanol to prepare different standard dilutionsvarying in between 1-7mg ml-1.

Method optimization

Selection and Optimization of Solvent

It is well known that the solvent do exerts a profoundinfluence on the quality and shape of the peak [13].The choices of solvents for UV method developmentare: Chloroform, Acetone, Methanol etc. Different ofsolvents were optimized. Out of which methanolsatisfied all the conditions relative to Peak quality &non-interference at the specified wavelength.

Selection of Wavelength

The wavelength at which maximum absorption takesplace in UV detector is selected for further analysisi.e. 421nm.

Method validation

Validation of the method was carried out as per theInternational Conference on Harmonization (ICH)guidelines Q2 (R1) (ICH, 2005) [14]. And accordinglythe parameters evaluated were:

Sensitivity

Sensitivity of the method was determined withrespect to limit of detection (LOD) and limit of quantification (LOQ) [15]. Series of concentrations ofdrug solutions (0.01–7 μg/ml) were used andanalyzed to determine LOD and LOQ.

LOD and LOQ were experimentally verified bydiluting known concentration of Curcumin until theaverage responses were approximately 3 or 10 timesthe standard deviation of the responses for sixreplicate determinations [16].

Specificity and selectivity

Three different marketed tablets of Curcumin ofconcentration 4 mg ml-1 were prepared in methanoland 4 mg ml-1 of standard Curcumin were analyzed bythe proposed method. The estimated amounts ofmarketed formulation were compared with that ofpure Curcumin solution of the same strength.

Linearity and range

Seven different concentrations (1-7mg ml-1) ofCurcumin were prepared in methanol from a freshstock of 10 mg ml-1.Least square regression analysiswas done for the obtained data.

Accuracy

In standard analysis method, three differentconcentrations of the standard Curcumin inmethanol were prepared (2.5 mg ml-1, 4 mg ml-1& 5.5mg ml-1) from independent stock solutions and theirstrengths were estimated by the standard curve.Standard addition method was followed to supportthe accuracy by adding separately three differentstandard concentrations of Curcumin (0.5 mg ml-1, 1mg ml-1 and 1.5 mg ml-1) to a pre-analyzed Curcuminsolution of 4 mg ml-1 and analyzing them again in thesame way. The accuracy was reported as % recovery ±(% confidence interval) with % relative error on thebase of actual and estimated concentrations.

Precision

Repeatability was done by analyzing three differentconcentrations of Curcumin( 2.5mg ml-1, 4 mg ml-1and 5.5 mg ml-1) in methanol in six let on a single day.Intermediate precision was done by analyzing thesame three concentrations on three different days in six let (drug was found stable for three days).Reproducibility was determined by analyzing threedifferent concentrations of Curcumin (2.5 mg ml-1, 4mg ml-1 and 5.5 mg ml-1) in six let on different UVspectrophotometers (One Cintra 5 double beam UVSpectrophotometer and two different Shimadzu 1601double beam Spectrophotometers in different labs).% Relative standard deviation, standard deviationand confidence interval of the estimatedconcentrations based on standard curve werereported for each set of data.

Robustness

Robustness of the proposed method was alsodetermined by changing the λ max of the analysis (λ max420 nm) by ± 1.0 nm. % Mean recovery (± %confidence interval) as well as % relative error wasreported.

Use of above method for marketedformulations

The content of Curcumin in tablets (labelled claim:500 mg per tablet) were determined by powderingtwenty tablets and powder equivalent to 10 mg ofCurcumin was weighed. The drug from the powderwas extracted with methanol (Hanif et al., 1997). Forcomplete extraction of the drug, it was sonicated for30 min and volume was made up to 100 ml. Theresulting solution was centrifuged at 2500 rpm for10 min and supernatant was analyzed for drugcontent.

Three different marketed tablets of Curcumin wereused to prepare three independent stocks ofCurcumin in methanol of 500 mg ml-1 concentration.These three stocks were used individually to preparethree different concentrations of Curcumin (2.5 mgml-1, 4 mg ml-1 and 5.5 mg ml-1). The preparedsolutions were assayed by the proposed method. The% assay values with % confidence intervals arereported.

RESULTS AND DISCUSSION

The proposed method was found to be simple,sensitive, accurate, precise, economical and rapid forthe routine estimation of Curcumin in bulk drug andpharmaceutical dosage forms.

Analysis of the Drug

Melting point of curcumin was found to be 183°C.Drug was freely soluble in methanol, chloroform,ethanol, acetone and practically insoluble in water.Spectral scan – λmax of curcumin was found to be at421 nm.

Analytical Method ValidationParameters

The method was validated as per ICH guidelines (Q2(R1).

Linearity and Range

Linearity of an analytical method is its ability, withina given range, to obtain test results that are directly,or through a mathematical transformation,proportional to concentration of analyte [17]. Goodlinear correlations were obtained betweenabsorbance and concentration in the selected rangeof 1 – 7 μg/ml. Characteristic parameters are Slope ±S.D. 0.1265 ± 0.15, Intercept ± S.D. 0.0174 ± 0.27,regression coefficient of 0.9991 and correlationcoefficient of 0.9995 between the standard drugconcentration and corresponding mean absorbanceshow a good linearity of standard curve (Table 1).

Precision

The precision of an analytical method expresses thedegree of scatter between a series of measurementsobtained from multiple sampling of the samehomogeneous sample under prescribed conditions[18]. Intraday precision refers to the use of analyticalprocedure within a laboratory over a short period oftime using the same operator with the sameequipment whereas Interday precision involvesestimation of variations in analysis when a method isused within a laboratory on different days, by different analysts [19, 20]. Repeatability (intraday) wasassessed by analyzing these three differentConcentrations (2.5, 4.0, 5.5 μg/ml), three times aday. Intermediate precision (Interday) wasestablished by analyzing these three differentconcentrations(2.5, 4.0, 5.5 μg/ml), three times a dayfor at least three different days (Table 2).

The Standard Deviation, % RSD and ConfidenceInterval for the intra-assay precision, intermediateprecision and reproducibility for all the threeconcentration levels were found below 0.018, 0.495,± 0.014 & 0.016, 0.570, ± 0.013 and 0.09, 100.006, ±0.072 respectively. The data indicated above showedan excellent intraday precision, intermediateprecision and reproducibility of the proposedmethod.

Accuracy

Accuracy of an analytical method is the closeness oftest results to true value. It was determined by theapplication of analytical procedure to recoverystudies, where known amount of standard is spikedin preanalyzed samples solutions [21, 22].

The % recovery for the standard analysis andreference analysis method for all the threeconcentration levels ranged from 99.1% to 101.4%with confidence interval ranging from ± 0.090 to ±0.190 showing that any small change in the drugconcentration can be accurately determined withhigh accuracy. The results obtained form thestandard addition and reference analysis methodware also found supporting the accuracy of theproposed method.

Specificity

The presence of excipients in formulation does notinterfere with the drug peak. Therefore, the proposedmethod was found specific and selective for the drug.

LOD/LOQ

LOD and LOQ were calculated according to theformulae:

LOD=3.3 σ / S =0.05mg/ml

LOQ=10 σ / S = 0.1724mg/ml

Robustness

The variation in the λ max within limits ± 1.0 nmbrought % recovery lying in between 99.0 to 99.7with a maximum % confidence interval of ± 0.009,indicating it to be a sufficiently robust method.

Application of the Validated UVVisibleSpectrophotometer Method on theMarketed Formulation

The marketed tablet formulations were analyzed bythe proposed method. In accordance with ICHguidelines the assay values for all these formulationswere found to be ranging in between 99.89 to 100.19with a maximum % confidence interval of ± 0.11(Table 3).

CONCLUSION

The analytical method developed on UV- VisibleSpectrophotometer was simple, reliable, accurate andreproducible. The method eliminates extraction stepsthus reduce analytical time, cost and minimize theextraction errors. Low cost, faster speed, satisfactoryprecision and good specificity, to assessunequivocally the analyte in the presence ofcomponents, which may be expected to be present,are the main features of this method. Method wassuccessfully validated as per ICH guidelines and canbe conveniently employed for routine quality controlanalysis of Curcumin in bulk drug, marketed tabletsand other formulations without any interferencefrom excipients. The method was comparable to theexisting methods in all respects, which analyze thedrugs but in plasma.

Conflict of Interest

NIL

Source of Support

NONE

ACKNOWLEDGEMENTS

The authors thank Loba Chieme and Sami ChemicalsLtd, Mumbai for the gift samples of Curcumin. Theauthors are also grateful to Prof. (Dr.) Shyam S.Agrawal (Professor, Pharmacology, AMITY) and Dr.Monica Gupta (Lecturer, Pharmaceutical Chemistry, DIPSAR), respectively, for their valuable suggestions,active guidance and facilities provided duringresearch work.

Tables at a glance

Table 1 Table 2 Table 3

Figures at a glance

Figure 1

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