Investigation of Acid-Base Indicator Property of Plumbagin from Plumbago zeylanica Linn

There has been an increasing interest in the search for colour indicators of natural origin for titrimetric analysis. This is due to some challenges associated with the currently used synthetic ones. This study evaluates and validates the acid-base indicator property of plumbagin isolated from Plumbago zeylanica Linn. Plumbagin (5-hydroxy-2-methyl-1,4-naphthoquinone) was isolated from the roots of Plumbago zeylanica Linn using silica gel chromatography and characterized using spectroscopic methods in comparison with those reported in the literature. Its acid-base indicator property was evaluated alongside phenolphthalein and methyl orange, after it was found to exhibit a sharp change in colour at various pH ranges. The plumbagin indicator was successfully used to assay ibuprofen powder and tablets (400 mg) using the British Pharmacopoeia (2013) method. Data obtained were analyzed statistically by Student’s t-test and one-way ANOVA in GraphPad Prism (version 5.01, 2010). Analysis of the use of the plumbagin indicator in acid-base titrations between strong acids and strong bases and between weak acids and strong bases has been evaluated and validated according to the ICH guidelines. Plumbagin use in ibuprofen powder and tablets has also been verified. Plumbagin has been validated for use as an indicator suitable for different acid-base titrations and the analysis of ibuprofen.