Spectrophotometric Determination of Tetrahydrocurcumin using Sulfa Drugs as Coupling Reagents

Abstract

Tetrahydrocurcumin (THC), is a cosmeceutical which is colourless and is reduced form of yellow curcuminoids extracted from the roots of Curcuma longa, commonly called turmeric. A study was made of the application of diazotization-coupling spectrophotometric technique for the determination of tetrahydrocurcumin, using sulfanilamide (SAA), sulfadoxine (SDX) and sulfamethoxazole (SMX) - the widely used sulfa drugs as coupling agents. The methods are based on the interaction of diazotized drugs with THC in alkaline medium to produce a red colour product having maximum absorption at 500 nm. The colour developed was stable for 6 h at 27°C. Beer's law was obeyed in the concentration range 1.0-14.0 ug ml^-1 for SAA and SMX and 2.0-16.0 ug ml^-1 for SDX at the wavelength of maximum absorption at 500 nm. The method was also successfully tried for the determination of THC in presence of common excipients used as additives, which did not interfere in the proposed methods.
Introduction: In recent years, there is a resurgence globally for alternate medicines where the people who obtained health care from physicians, pharmacists and other professionals needed to be supported by safe and cost effective and more accessible health products. It is in this delicate balance of health care and surge for alternate medicine, the field of "nutraceuticals" emerges.

 Objectives This paper is an attempt to meet an ever-increasing demand for the analytical control of    commercialized health care products by developing simple, sensitive, selective, rapid and reliable spectrophotometrie procedures for the determination of the newly introduced cosmeceutical product. Survey of literature revealed that no analytical method has been developed so far for the determination of the THC using sulfanilamides as spectrophotometric reagents.

Methods: The methods involve coupling of diazotized sulfanilamides with tetrahydrocurcumin in alkaline medium to produce red colour. The proposed methods have distinct advantages of sensitivity and stability. Besides, the methods do not require heating or distillation and exhibit reliability due to reproducibility.

Results: A red coloured product with maximum absorption at 500 mm was formed when sulfanilamide, sulfadoxine, sulfamethoxazole reacted with tetrahydrocurcumin in sodium hydroxide medium.

Conclusions: The herbal renaissance has produced a profound effect on the Western medical system, which is now trying to acknowledge methods of healing that was in existence for millennia in the traditional medicine throughout the world, especially Asia. The surge in research on drugs from natural sources is now moving out of the herbalists shop away from the core texts into the drugs research laboratories. With increasing consumer awareness, the pharmaceutical industries in drug control authority have long been interested in the development of simple and sensitive methods for the assay and evaluation of drugs in bulk and in dosage forms, to assure high standard in quality control. In the present context, determination or estimation of cosmeceuticals is of paramount importance. Simple methods based on spectrophotometry may dominate as analytical tool for the evaluation of cosmeceuticals. Our methods are a step forward towards this direction. The proposed spectrophotometric methods have adequate sensitivity and accuracy for determination of tetrahydrocurcumin. Their analytical characteristics such as sensitivity, selectivity and stability are far superior to other existing spectrophotometric methods.