Investigating structural aspects to understand the putative/claimed non-toxicity of the Hg-based Ayurvedic drugRasasindurausing XAFS

Abstract

XANES- and EXAFS-based analysis of the Ayurvedic Hg-based nano-drugRasasindurahas been performed to seek evidence of its non-toxicity.Rasasindurais determined to be composed of single-phase α-HgS nanoparticles (size ∼24 nm), free of Hg0or organic molecules; its structure is determined to be robust (<3% defects). The non-existence of Hg0implies the absence of Hg-based toxicity and establishes that chemical form, rather than content of heavy metals, is the correct parameter for evaluating the toxicity in these drugs. The stable α-HgS form (strong Hg—S covalent bond and robust particle character) ensures the integrity of the drug during delivery and prevention of its reduction to Hg0within the human body. Further, these comparative studies establish that structural parameters (size dispersion, coordination configuration) are better controlled inRasasindura. This places the Ayurvedic synthesis method on par with contemporary techniques of nanoparticle synthesis.