Abstract
RESEARCH BACKGROUND: In India, widespread dietary deficiency in calcium and vitamin D is a significant public health concern. Over the past five decades, evidence has shown a decline in dietary calcium intake in rural, tribal and urban populations. This persistent deficiency poses a serious risk to bone health and contributes to the development of rickets, osteoporosis and osteopenia, as well as potential disturbances in metabolic rates and physiological functions. A key factor in this decline appears to be the reduced consumption of calcium-rich dairy products. As a result, research is exploring alternative, highly bioavailable sources of calcium, such as those derived from fish bone waste. The potential of nano-calcium supplements to improve absorption and bone density compared to traditional supplements is an area of active investigation. EXPERIMENTAL APPROACH: Nano-calcium powder was synthesised from the bones of two commercial fish species, Daysciaena albida and Otolithes ruber, ethically sourced from the Kerala coast following relevant regulations. Alkali extraction method was used and the resulting nano-calcium powder was characterized by various physiological and chemical analyses. RESULTS AND CONCLUSIONS: The yield percentage of two samples was different. Notably, both samples had different colour properties, proximate composition and results of scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX). The nano-calcium from D. albida also contains slightly more calcium and phosphorus than that from O. ruber. The nanoparticles of the calcium from D. albida (d=153.8 nm) were also smaller than the nanoparticles of the calcium from O. ruber (d=337.1 nm). Interestingly, further analyses using techniques such as Fourier transform infrared spectroscopy (FTIR), zeta potential, thermogravimetric analysis (TGA) and X-ray diffraction (XRD) showed significant similarity between the nano-calcium samples from D. albida and O. ruber, despite the initial differences in yield, composition and particle size. This result suggests that the choice of fish species significantly affects the yield, composition and properties of the synthesised nano-calcium powder with D. albida appearing to be a more favorable source, but both products can exhibit similar functionality and warrant further investigation. NOVELTY AND SCIENTIFIC CONTRIBUTION: This is the first report on the extraction and characterization of biogenic nano-calcium from two commercial fish, Daysciaena albida and Otolithes ruber from the Malabar Coast, India. The extracted nano-calcium powders from these two fish are a good source of calcium and help overcome calcium-related disorders.