Encapsulation of bougainvillea (Bougainvillea spectabilis) flower extract in Urtica dioica L. seed gum: Characterization, antioxidant/antimicrobial properties, and in vitro digestion

Bougainvillea spectabilis extract (BSE), a rich source of bioactive compounds like phenolic, flavonoid, and anthocyanin, was used for encapsulation with Urtica dioica L. seed gum. The extract was obtained using shaking, bath, and probe ultrasound. The results showed that probe ultrasound extract was more efficient, as reflected by the higher value of total phenolic (4354.15 mg GAE/100 g FW), flavonoid (2431.25 mg CE/100 g FW), and anthocyanin content (106.57 mg CGE/100 g FW). BSE was encapsulated in U. dioica L. seed gum at 1:1 and 1:2 core to coating ratio. In both DPPH radical scavenging and FRAP assay, higher antioxidant activity was observed in the encapsulated extract than in the free extract. Encapsulated extracts exhibited 87.9 nm average diameter (polydispersity index below 0.23) and negative zeta potential. The average minimum inhibitory concentration (MIC) of nanoparticles against Staphylococcus aureus, Escherichia coli, Listeria monocytogenes, and Salmonella enterica was 112.5, 87.5, 112.5, and 87.5 mu g/ml, respectively, while MIC of the free extract against S. aureus and E. coli was 150 and 125 mu g/ml, respectively. The phenolic compounds are gradually released from the nanoparticles in the gastric and small intestine phase, whereas free extract released phenolic compounds quickly after entering the gastric phase. Considering antioxidant/antimicrobial activity and release properties, nanoparticles with a 1:1 ratio of core to coating had the potential to use as an effective natural preservative agent in food products besides the delivery of bioactive compounds to the human body.