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Plumbagin, a plant-derived bioactive naphthoquinonoid compound, was converted to a hydroquinonoid derivative, which was studied for its tumour-inhibitory and antileishmanial activities for the first time. A similar chemical transformation was undertaken on an analogous dimeric compound, diospyrin, and its bioassay results were compared with those of the plumbagin derivative. Synthesis of the derivative of plumbagin did not result in a marked enhancement of the tumour-inhibitory activity, whereas the improvement was obvious in the case of diospyrin vis à vis its hydroquinonoid analogue. The conversion of diospyrin to the hydroquinonoid compound also led to a substantial increase in the antileishmanial activity, while a similar conversion of plumbagin failed to do so.

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Two different commercially available sources of alumina and silica were used to study the formation and densification behaviour of mullite prepared by solid-oxide reaction technique in a single firing. Phase analysis and densification studies were carried out on the samples sintered between 1200 and 1600 • C. Effect of addition of 1-6 wt% MgO on the sintered mullite ceramics was also studied. MgO was found to improve the density values for all the compositions till 4 wt% and with higher addition it deteriorated, mainly due to higher extent of liquid phase formation. Mullite formation was found to start below 1200 • C and constituent oxides were found even at 1600 • C; however, addition of 4 wt% MgO was found to complete the mullite formation at 1600 • C for all the compositions. Microstructural studies showed grain growth in the compositions containing MgO and higher impurities due to formation of greater extent of liquid phase.

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