Synthesis of an anionic hydride from monomeric silsesquioxanes is described. The novel compound, dubbed "silica hydride" is the first of several newly synthesized compounds from an interstitially embedded hydride family. It is a hydride-based compound with H- ions interstitially embedded in a matrix of caged silica. This compound exhibits profoundly different characteristics than other known compounds in hydride family. Unlike saline hydrides, the silica hydride demonstrates no overt or violent reaction with water or air. However it is capable of generating aqueous reductive potential readings of -750 mV for extended time periods. In vitro biological testing demonstrated no cytotoxicity induced by the compound while demonstrating efficacy as an antioxidant. In vivo studies of the compound have shown that it has a significant ability to reduce lactic acid build up in muscles by one-half after exercise. The synthesis of the silica hydride resulted in an approximately 16.8% w/w hydride content, as determined by density changes, proton NMR spectroscopy and ion beam analyses. Scanning and tunneling electron microscopy, Rutherford backscattering spectroscopy (RBS), forward recoil (FReS) ion beam analyses, in addition to Fourier transform infrared spectroscopy, reduction potential and Si-29 CP-MAS solid state NMR were additionally used to characterize the compound. (C) 2003 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.