Comparative bioactivity screening and chitosan nanoparticle formulation of pharmacy-grade medicinal tea extracts used for common cold.

Medicinal teas are widely used for the symptomatic relief of common cold; however, comparative data on standardized pharmacy-grade products remain limited. In this study, 40 aqueous and ethanolic extracts prepared from 20 pharmacy-grade herbal drugs used for common cold were evaluated for their antimicrobial and antioxidant activities. Antimicrobial effects were determined by the microdilution method against bacterial and fungal strains, while antioxidant capacity was assessed using DPPH, FRAP, CUPRAC, ABTS, and TPC assays. Ethanolic extracts showed higher antioxidant activity than aqueous extracts, with mean DPPH IC50 values of 0.10 vs 0.16 mg/mL, FRAP values of 2.16 vs 0.14 mM Fe+2/mg, and ABTS values of 77.5% vs 66.0%, respectively. Ethanolic extracts also exhibited stronger antimicrobial activity, with MIC values of 39.06-625 μg/mL versus 312.5-1250 μg/mL for aqueous extracts. Extracts of Melissa officinalis, Mentha piperita, and Echinacea purpurea demonstrated the most prominent results. Chitosan nanoparticles (NPs) of the six most active extracts obtained from these three plants were prepared, with particle sizes of 289.29-354.36 nm, zeta potentials of 2.27-2.78 mV, PDI of 0.202-0.258, and encapsulation efficiencies of 68.27-74.57%. HPLC-DAD analysis of the active extracts identified rosmarinic acid, chlorogenic acid, rutin, luteolin, and hesperidin as major phenolics.