INTRODUCTION:

Rice (Oryza sativa, Family Graminae) is one of the most important grains in the world. India is second largest producer of Rice in the world. The outer covering of rice kernel after removing the husk is called Rice bran. It is valuable byproduct of rice milling industry because it contains 12-25 % of oil depending on quality. Rice bran wax is the by-product of Rice bran oil refineries .Lots of work is done on RBW in USA, China and Japan but most of those are patented. Nifedipine as a calcium channel blocker used for the treatment of essential hypertension and angina pectoris. It is a BCS Class II drug with poor solubility. The plasma half life of Nifedipine is 2 hrs. Hence, it is an ideal candidate for the preparation of sustained release formulation^{1, 2}.

MATERIALS:

The RBW was obtained as a gift sample from Space lab, Nasik in flakes form. Nifedipine was supplied as a gift sample by Cadila Pharmaceuticals Ltd., Ahmedabad, India.

METHODS:

Characterization of Rice bran Wax: The RBW was characterized for its solubility, melting point, specific gravity, moisture content, saponification value, acid value, ester value, hydroxyl value, unsaponifiable matter, Iodine number etc. Pharmacopoeial standard methods were followed for all these tests².

Solid state compatibility studies:

The compatibility of Nifedipine with RBW was studied. The 50 mg of physical mixtures (1:1) of the RBW and Nifedipine were weighed and transferred to glass vials. These vials were then kept at 60° c for 15 days.

Physical study:

Rice bran wax alone, Nifedipine alone and mixture of RBW and Nifedipine were observed for physical changes like discoloration, liquefaction and gas formation.

The samples were analyzed by Differential scanning Colorimetry and Fourier Transform Infrared Spectroscopy at 0 day and 15 days^{5, 7, 8}.

Differential scanning Colorimetry (DSC):

The DSC measurements were performed on Perkin Elmer coupled to Pyris-6 Software with a thermal analyzer. Accurately weighed samples were placed and sealed in aluminum pans, before heating under nitrogen flow (20 mL/min) at a scanning rate of 10° C/min from 35° C to 300° C for physical mixture and drug and from 35° C to 210° C for RBW. An empty aluminum pan was used as a reference.

Fourier Transform Infrared Spectroscopy:

FT-IR spectra were obtained by FT-IR spectrophotometer (Perkin Elmer). The sample were mixed uniformly with potassium bromide at 1:5 (sample: KBr) ratio. The KBr discs were prepared by compressing the powders (mixture of sample and KBr) at pressure of 5 tons for 5 min in a hydraulic press. The discs were scanned in the range of 500-4000 cm^-1 to obtain FT-IR spectra.

RESULTS AND DISCUSSION:

Characterization of RBW: The Rice Bran Wax was characterized for various properties and specification set as per Pharmacopoeial guidelines. On the basis of results obtained (table:1) it can be suggested that the rice bran wax is a suitable substitute for carnauba wax and it can be used as coating agent, as a base in cosmetic preparation and in some extent it can be used as release retardant agent in sustained release dosage form.

Solid state compatibility studies:

Physical study:

The results of physical studies after keeping the mixture at 60° c for 15 days observed that there is not any change in colour. There was not any indication of liquefaction and gas formation did not take place. This suggests that there is not any physical change which means the mixture is physically compatible.

DSC study: The DSC thermograms of various samples are given in Fig: 1 there is no significant change in the appearance, shift, or disappearance of endo-thermal peaks. The thermal profile of the mixture remained almost unchanged showing peaks of Nifedipine as well as RBW indicating compatibility of the drug with the examined excipients.

FT-IR study: FT-IR spectra of the sample are given in Fig:2 A FT-IR study shows that all characteristics peaks of drug and Excipients are present, showing no signs of interaction indicating compatibility of the drug with all the examined excipients.

Table.1: Observed values of RBW

Sr. No.	Tests	Observed values of Rice Bran Wax
1	Solubility	Insoluble in water Soluble in ether, ethanol and isopropyl alcohol
2	Melting point	80.5 °c
3	Specific gravity	0.912
4	Moisture content	0.074 % w/w
5	Saponification value	80.88
6	Acid value	2.848
7	Ester value	78.04
8	Hydroxyl value	19.62
9	Unsaponifiable matter	40 % w/w
10	Iodine value	10

Fig.1 DSC thermograms of A: Nifedipine, B: Rice bran wax, C: physical mixture of Nifedipine: Rice bran wax

Fig.2FT-IR spectra of A: Nifedipine, B: Rice bran wax, C: physical mixture of Nifedipine: Rice bran wax (1:1)

CONCLUSION:

The solid state compatibility studied (DSC and FT-IR) have suggested that Nifedipine is compatible with RBW. This study indicated potential of RBW in the preparation of sustained release formulations of poorly water soluble drug like Nifedipine.

REFERENCES:

1. Houston, D.F., Eds., In; Rice Chemistry and Technology, 2nd Edn., A.A.C.C., Inc., St. Paul, MN, 1972, 294

2. Pharmacopoeia of India, Govt. of India, 2007. Pages: 151, 990.

3. Raymond C Rowe, Paul J. Sheskey, Paul J Wellen, Handbook of pharmaceutical excipients, fourth edition, Pages: 679.

4. Bodmier R, Hermann J. Encyclopedia of Pharmaceutical Technology. Vol. 16 In; Swarbrick J,Boylan JC, editors. Waxes. New York: Marcel Deckker, Inc.; 1997.p. 335-61.

5. G. Banker and C.T. Rhodes, Modern Pharmaceutics, Marcel Dekker, Inc., 2000.

6. MD Idea Exporting Division uses and application rice bran wax, from octacosanol to phytosterol. http://www.mdidea.com/ products/proper/059.html accessed August 2011.

7. Vali SR, Yi-Hsu J, Kaimal TN, Yaw-Terang C. A process for the preparation of food grade rice bran wax and the determination of its composition. J Am Oil Chem Soc. 2005; 82:57-64.

8. Kanig, JL, Lachman L. Lieberman HA. The theory and practice of Industrial Pharmacy (3ed.). Philadelphia: lea and Febiger; 1986; ISBN 0-8121: p. 977-5.

Received on 13.04.2012 Accepted on 15.05.2012

Asian J. Pharm. Res. 2(2): April-June 2012; Page 83-85