Ultrasonic studies of antiprotozoal drug in protic and aprotic solvents at 308.15 K

S. Baluja^†, A. Kulshrestha and M. Bhatt

Department of Chemistry, Saurashtra University, Rajkot-360005, (Gujarat), India.
^† shipra_baluja@rediffmail.com

Abstract — Ultrasonic velocities and density of various concentrations (0.01 to 0.10M) of anti protozoal drog "Diloxanide Furoate" in methanol, dimethyl formamide and 1,4-dioxan have been measured at 308.15 K by using single crystal variable path ultrasonic interferometer operating at 2 MHz and pycnometer respectively. Using these experimental data, some acoustical parameters have been evaluated and they are interpreted in terms of solute-solute and solute-solvent interactions in these solutions.

Keywords — Anti Protozoal Drug; Ultrasonic Studies; Diloxanide Furoate.

I. INTRODUCTION

Diloxanide furoate is a luminal amebicide drug used in the treatment of amebiasis (Fernandes et al., 2009). It is a dichloro acetamide derivative that principally acts in the bowel lumen and is used in the treatment of intestinal amoebicide (Reynolds, 2005). In addition to its anti-protozoal and anti-amoebic effect (Abbas et al., 2011), the drug contains an ester group which has wide usage in flavoring, perfumery, artificial essences, cosmetics, etc. (Abdelaleem and Abdelwahab, 2012).

These properties prompted us to study the molecular interaction of Diloxanide furoate in some protic and aprotic solvents. Ultrasonic velocity measurements in solutions furnish knowledge about ion-ion and ion-solvent interactions.

In the last few years, our investigation groups have carried out some studies on acoustical properties of organic compounds in various solvents (Baluja and Parsania, 1995; Baluja and Oza 2003; Baluja and Shah, 2004, Baluja et al., 2005; Baluja et al., 2009) as well as on some drugs (Godvani et al., 2010; Godvani et al., 2012 ).

In continuation of these investigations, the present paper reports acoustical properties of the anti- protozoal drug "Diloxanide Furoate" in different solvents.

II. EXPERIMENTAL

The solvents methanol, DMF and 1,4-dioxan used in the present work were of AR grade and purified according to the standard procedure (Riddick, 1986). The purity of solvents was checked by GC-MS and was found to be more than 99.97%.

The densities of pure solvents and their solutions were measured by using a single capillary pycnometer, made of borosilicate glass having a bulb capacity of 10 ml. The ultrasonic velocity of pure solvents and their solutions were measured by using a single crystal variable path ultrasonic interferometer operating at 2 MHz. The accuracy of density and velocity are ± 0.0001 g/cm³ and ± 0.1% cm/sec respectively. All the measurements were carried out at 308.15 K. The uncertainty of temperature is ± 0.1 K and of concentration is 0.0001 moles /dm³.

III. THEORY

From the experimental data of density (ρ) and ultrasound velocity (U) of pure solvent and solutions, various acoustical parameters were calculated using following standard equations (Baluja and Oza, 2003).

Isentropic compressibility (κ_S):

κ_S = 1/ (U²ρ) (1)

Intermolecular length (L_f):

L_f = K_J κ_S ^½ (2)

where K_J is Jacobson constant (= 6.0816 x 10⁴).

Rao's molar sound function (R_m):

R_m= (M/ρ)U^1/3 (3)

where M is the molecular weight of solution.

Van der Waal's Constant (b):

b = (M/ρ) (1-RT/MU² (√ (1+MU²/3RT)-1)) (4)

where R is gas constant and T is absolute temperature.

Molar Compressibility (W):

W = (M/ρ) κS^-1/7 (5)

Solvation number (S_n) :

S_n = M₂/M₁ [1- κ_S / κ_S1] [(100- X) /X] (6)

where X is the number of grams of solute in 100 gm of the solution. M₁ and M₂ are the molecular weights and κ_S1 and κ_S are isentropic compressibility of solvent and solute respectively.

IV. RESULTS AND DISCUSSION

Table 1 shows the experimental data of density and ultrasonic velocity (U) of solutions of the anti-protozoal drug at 308.15 K in different solvents; methanol, DMF and 1,4-dioxane. It is observed that in all the three selected solvents, density as well as ultrasonic velocity increase with concentration.

Table-1:- Some acoustical parameters of the drug in methanol, DMF and 1, 4 Dioxan at 308.15 K

Further, intermolecular free length (L_f) and isentropic compressibility (κ_s) values are also reported in Table 1. Both L_f and κ_s decreases with the increase in concentration for all the solutions.

The increase of U and decrease of κ_s and L_f suggest aggregation of solvent molecules around solute molecules indicating thereby the presence of solute-solvent interactions.

Figure 1 shows the variation of some acoustical properties like molar sound function (R_m), molar compressibility (W) and Van der Waals constant (b) with concentration. These parameters are observed to increase linearly (correlation coefficient γ=0.9997 - 0.9999) with the increase of concentration for all the solutions. The linear variation of these acoustical properties indicates the absence of complexes formation in these systems.

Figure 1: The variation of molar compressibility W(A), molar sound function R_m (B) and Vander Waals constant b (C) with concentration.

Figure 2 shows the variation of solvation number (S_n) with concentration. The solvation number (S_n) is a measure of structure-forming or structure-breaking tendency of a solute in solutions. In all the systems, S_n values increases non-linearly with the increase of concentration, which suggests structure-forming tendency of the drug in these solvents.

Figure 2: Variation of solvation number (S_n) with concentration in different solvents.

V. CONCLUSION

It is concluded that, in the studied solvents, the drug exhibited predominance of solute-solvent interactions. Therefore, structure-forming tendency of the drug is observed in the studied solvents and it has a maximum in methanol. The effect of concentration on solute-solvent interaction is also higher in methanol and minimum in DMF solutions. Further, there is no complexes formation in the studied solutions.

ACKNOWLEDGEMENT
Authors are thankful to Head of Chemistry Department for providing facilities

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Received: July 16, 2012
Accepted: December 28, 2012
Recommended by Subject Editor: María Luján Ferreira