Characterisation of Single-step Charcoal-purified Cosmetic-grade C- Phycocyanin Produced from Native Spirulina platensis in Bangladesh

C-Phycocyanin (C-PC), a water-soluble phycobiliprotein from Spirulina , possesses significant commercial value for food, cosmetic, and pharmaceutical applications due to its natural blue colouration and bioactive properties. However, conventional production methods, involving freeze/spray-drying and complex, multi-step purification processes, impose substantial costs that limit widespread commercialisation, particularly in resource-limited settings. This study presents the first characterisation of C-PC from a local Spirulina (Arthrospira) platensis strain in Bangladesh, systematically evaluating cost-effective drying, extraction, and purification methods. Among employed drying techniques, low-humidity air-drying at 25°C preserved approximately 95.4% of extractable C-PC content (160.87 mg g ^-1 DW) relative to freeze-drying (168.59 mg g ^-1 DW). Biomass drying at 25°C was accelerated with humidity reduction (< 25%), and the drying time (24 h) was comparable to other reported methods. Shaking-assisted aqueous extraction of C-PC at a 1:30 solvent-to-biomass ratio for 16 hours at 25°C exceeded 85% C-PC extraction efficiency, with food-grade purity (≥ 0.86). Single-step purification of crude C-PC extracts at 25°C using activated charcoal adsorption (ACA) with 60 g L ^-1 charcoal for 16 h yielded cosmetic-grade C-PC (≥ 2.19) with more than 70% recovery. UV-Vis, fluorescence, and infrared spectra of the lyophilised C-PC preparations confirmed structural integrity comparable to the analytical reference standard. Purified C-PC exhibited moderate antioxidant activity (IC ₅₀ 574.4 - 620.1 µg mL ^-1 ) in DPPH radical scavenging assay and moderate cytotoxicity (LC ₅₀ 78.6 - 122.5 µg mL⁻¹) in brine shrimp lethality bioassays. Additionally, heavy metal content in the fresh Spirulina biomass remained within regulatory limits. The optimised combination of low-humidity air-drying, stirred aqueous extraction, and single-step ACA purification for C-PC production provides a green, cost-effective, scalable approach for commercial applications, addressing economic constraints for developing countries.