Formulation and stability of bioactive nanoemulsions using gum extracts from Acacia tortilis subsp. raddiana

• Solvent polarity governs A. tortilis gum composition and emulsification. • 80:20 ethanol–water extract forms stable nanoemulsions with 182 nm droplets. • 80:20 extract reduced interfacial tension and improved emulsion stability. • Emulsification enhanced antioxidant and antibacterial activities. • FTIR and SEM confirm interfacial films via phenolic–protein synergy. This study evaluated how ethanol–water polarity (0:100–100:0, v/v) influences the emulsifying, antioxidant, and antimicrobial properties of Acacia tortilis subsp. raddiana gum exudate. The 80:20 ethanol–water mixture maximized extraction yield (83%) and produced nanoemulsions with the smallest droplet size (Z-average 182 nm; PDI 0.31), highly negative ζ-potential (−46 mV), and low centrifugal separation (Ke = 3.7%). Over 30 days, emulsions remained stable with modest size increases (249 nm at 5°C; 386 nm at 25°C) and consistent ζ-potential (−42 to −44 mV). Antioxidant activity was mechanism-dependent: the aqueous extract exhibited superior radical scavenging capacity (DPPH IC 50 = 3.3 µg/mL), reflecting efficient hydrogen atom transfer, while the 80:20 extract demonstrated higher reducing power (FRAP = 7.0 mM Trolox equivalents), indicating enhanced single electron transfer capability. The 80:20 extract exhibited antibacterial activity against Staphylococcus aureus (19 mm inhibition zones) and Pseudomonas aeruginosa (20 mm), with comparable or enhanced activity upon emulsification (20–23 mm). These findings demonstrate that solvent engineering of arid-land gum exudate yields a multifunctional, clean-label emulsifier for food and nutraceutical applications.