INTRODUCTION:

The toxicology and pharmacologic study of a new antitrichophyton agent. Tolnaftate (TNF) [(2-naphthyl-N-methyl-N-(3-tolyl) thionocarbamate] (Fig.1) has been reported^1-5. TNF has been widely used as topical antifungal drug in the treatment of cutaneous diseases ^6-8. Many antifungal compounds have been shown to act as ergosterol biosynthesis inhibitors, including the azoles which inhibit lanosterol 14-demethylation ^9,
10 and the allylamines which inhibit squalene epoxidase ^{11, 12,13}. The thiocarbamate drugs Tolnaftate ¹⁴ and toiciclate ^{15, 16} are selectively active against dermatophytes ^{17, 18} and are used clinically as a topical treatment for such infections. Their mode of action has not been reported, but ultrastructural studies suggested that it involves a disturbance of cell wall biosynthesis ^{19, 20, 21}. Tolnaftate, discovered in Japan in 1962 by Noguchi and colleagues ^{22, 23}, is a thiocarbamate antifungal. It is therapeutically active against dermatophytes, Epidermophyton, Microsporum, Trichophyton spp., and Malassezia furfur. Tolnaftate is used topically in a concentration of 1% in creams, powders, solutions, aerosols, gels to treat various forms of tinea (tinea pedis, tinea cruris, tinea corporis, tinea manuum) and pityriasis versicolor. Tolnaftate is available over-the-counter and is especially valuable in the prophylaxis and treatment of tinea pedis, which affects approximately 10% of the world population ²⁴.

Tolnaftate has no antibacterial activity and all tested species of Candida were resistant to Tolnaftate ²⁵, apparently due to its poor penetration into Candida cell envelope ²⁶.

To the best of our knowledge, there is no UV method for the analysis of Tolnaftate in pharmaceutical formulations has been reported in literature. The aim of this study is to develop a fast, simple, reliable, selective, sensitive and inexpensive UV spectrophotometrically (Fig.2) method for the determination of Tolnaftate in bulk drug.

Figure 1: Chemical structure of Tolnaftate

Figure 2: Instrumental modules for measuring absorption of UV radiation.²⁷

MATERIALS AND METHOD:

Instrument and materials:

Instruments used were double beam UV-Visible spectrometer, and Shimadzu model 1800. Tolnaftate drug was obtained as a gift sample from Jagsonpal Pharmaceutical Laboratories, New Delhi. Methanol used as solvent was HPLC grade.

Selection of media:

Main criteria for media selection are solubility and stability, i.e. drug should be soluble as well as stable for sufficient time in selected media. Tolnaftate is practically insoluble in water. Tolnaftate drug is soluble in methanol so for present work methanol has been selected as analytical media.

Preparation of standard stock solution:

Accurately weighed quantity of 100 mg Tolnaftate was taken in 100 ml volumetric flask and was dissolved by using 5 ml of methanol and finally the volume was made with methanol upto 100 ml to produce 1mg/ml of solution.

Scanning:

A series of concentration i.e. 1, 2, 3, 4, 5 µg/ml were prepared by using above stock solution and scanned between 200-400 nm. The absorption maxima obtained was 257 nm at 0.612 (Fig. 3, 4) were selected and used for further studies.

Preparation of calibration curve:

A standard solution containing 1mg/ml of Tolnaftate was prepared in methanol by dissolving 50 mg of pure Tolnaftate in 50 ml of methanol. From this solution, working standard solution of concentration 1-5 ug/ml of Tolnaftate was prepared by dilution with methanol. The absorbnce of the solution was measured at 257 nm against blank. All spectral absorbance measurement was made on Shimadzu 1800 UV–visible spectrophotometer. Calibration data are summarized in table 1 and optical characteristics are summarized in table 2.The calibration curve of Tolnaftate are in Fig.5.

Table1: Calibration data for Analysis of Tolnaftate in methanol at λ257

S. No.	Concentration (µg/ml)	Absorbance	Standard Deviation
1	1	0.122	±0.001
2	2	0.249	±0.001
3	3	0.45	±0.01
4	4	0.584	±0.001
5	5	0.612	±0.00152

* n=3 (Average of 3 determinations)

Table 2: Optical Characteristics of Tolnaftate by UV Method

Parameters	Method
λmax(nm)	257nm
Beers law limit (µg/ml)	1-5µg/ml
Correlation coefficient (r²)	0.990
Regression equation (y=mx+c)	Y= 0.148(x)-0.024
Slope(m)	0.148
Intercept(c)	0.024

Fig 3: Ultra violet absorption spectrum of Tolnaftate using methanol

Fig 4: Peak detection of Tolnaftate using methanol

Fig 5: Calibration curve of Tolnaftate by UV method using methanol

Relation between Concentration and Absorbance

CONCLUSION:

Tolnaftate is an antifungal drug. It is used for topical drug in the treatment of cutaneous diseases. The proposed analytical method is simple and accurate for the estimation of Tolnaftate. The drug samples were analyzed by UV spectroscopy using methanol as solvent. We concluded that the suggested method showed high linearity in organic solvent. Moreover, this method is simple and inexpensive and it can be employed for the routine quality control of Tolnaftate in pharmaceutical formulations.

ACKNOWLEDGMENT:

We are thankful to Jagsonpal Pharmaceutical Laboratories, New Delhi for providing the gift sample of Tolnaftate. The authors would like to acknowledge the assistance provided by the Library of Rungta College of Pharmaceutical Sciences and Research, Kohka-Kurud Road, Bhiali, C.G. (India) for collection of literature.

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