Characterization of Rajath Bhasma and Evaluation of Its Toxicity in Zebrafish Embryos and Its Antimicrobial Activity

Abstract

Siddha medicine was developed by ancient Tamil sages known as 'Siddhars' and has been in use for more than 5,000 years [1]. It involves the use of gold, zinc and silver formulated with honey, ghee, or milk to cure diseases [2,3]. Prototypical examples include Swarna Bhasma (gold ash), Jasada Bhasma (zinc ash), and Rajath Bhasma (silver ash), which are prepared by processing a fine powder of gold, zinc, and silver with plant extract, followed by repeated incineration at high temperature (~1,000°C). During incineration, the size of the fine powder of gold, zinc, and silver is reduced to that of chemically synthesized nanoparticles (1-100 nm). This fine powder is composed of individual particles of around 50-70 nm in size; however, these particles are prone to forming large aggregates, unlike chemically synthesized nanoparticles [4].Compared with gold-derived Swarna Bhasma and zinc-derived Jasada Bhasma, the silver-derived medicine Rajath Bhasma has superior and broad-spectrum antimicrobial, antifungal, and antiviral activities [5] and hence numerous applications. Notably, Rajath Bhasma has been used to treat various disorders including anxiety, aging, and infertility [6][7][8]. The physical characteristics of a silver preparation are believed to markedly influence its therapeutic properties; however, despite its widespread use in India, the exact chemical composition/structure of Rajath Bhasma and its biological activities are largely unknown. Current tools for characterizing these particles at the nanoscale level have furthered the understanding of the parameters directly or indirectly influencing the efficacy of these ancestral medicines. Accordingly, efforts have been made to study these particles at the nanoscale level. For example, Mitra et al. [9] have characterized Swarna Bhasma (gold ash) and Jasada Bhasma (zinc ash) and Rohit et al. [10] reported the synthesis of Rajath Bhasma through a simple characterization method.In general, Rajath Bhasma is safe for therapeutic applications [9]; however, in vivo studies are required to accurately predict its toxicity. Zebrafish embryos are a well-established in vivo model for evaluating teratogenicity.In India, nanotechnology has been used in therapeutic applications for several millennia. One example of a traditional nanomedicine is Rajath Bhasma (also called calcined silver ash), which is used as an antimicrobial and for the treatment of various ailments and conditions such as memory loss, eye diseases, and dehydration. In this study, we aimed to characterize the physical composition and morphology of Rajath Bhasma and its suitability for use as a non-toxic antimicrobial agent. First, Rajath Bhasma was physically characterized via i) Fourier-transform infrared spectroscopy to analyze the surface functional groups, ii) scanning electron microscopy coupled with energydispersive X-ray spectroscopy to observe the morphology and elemental composition, and iii) X-ray diffraction to determine the crystalline phases. Thereafter, functional characterization was performed thr...