Novel formulation of oleaster bark (Elaeagnus angustifolia) extract-oil-emulsion gel immobilized into coconut shell hydrochar

Abstract This study introduced a novel formulation involving the use of oleaster bark ethanol extract-oil-emulsion gel immobilized into coconut shell hydrochar. The characterization of fish oil (FO)-emulsion gel (Eg) incorporating Elaeagnus angustifolia ethanol extract immobilized within coconut shell hydrochar pores and assesses its antimicrobial efficacy against Acinetobacter baumannii , Staphylococcus aureus , Candida albicans and C. tropicalis was explored. The oil extracted from the gonad of Kolyos fish ( Scomber japonicus ) was emulsified and then bioactively enriched with ethanol extract of E. angustifolia . Gonad emulsion containing E. angustifolia extract was gelled with gelatin and finally immobilized into hydrochar (H). This study examined the characteristics and surface analysis of coconut hydrochar (CH)–based E. angustifolia ethanol extract-Eg (H-E-Eg) using FTIR and SEM. Stability, particle size distribution, and zeta potential of H-E-Eg were determined. Notably, the stability of H-E-Eg was demonstrated with a zeta potential of − 16.4 mV. Additionally, for the first time, this study investigated the time-dependent inactivation of the pathogens when exposed to H-E-Eg. A significant reduction was detected at 30 min and 1 h in A. baumannii (84.6% and 89.06%), S. aureus (74.075 and 82.12%) compared to C. albicans (8.3% and 9.09%) and C. tropicalis (46.12% and 43.2%), respectively. The maximum logarithmic decrease of A. baumanni was calculated as 0.9 log at the end of the 1st hour. In conclusion, E. angustifolia extract-emulsion gel immobilized on coconut shell hydrochar is a functional product for industries seeking sustainable and natural solutions for antimicrobial products, as well as for researchers interested in the bioactivity of plant extracts and innovative formulation techniques. Graphical Abstract