Liposomal Encapsulation of Carob (Ceratonia siliqua L.) Pulp Extract: Design, Characterization, and Controlled Release Assessment

Abstract

Background: Carob (Ceratonia siliqua L.) pulp flour is primarily used in the food industry. As a rich source of bioactive compounds, particularly polyphenols, it holds promise for pharmaceutical formulation research and development. Objectives: This study focused on developing liposomal particles loaded with carob pulp extract using the proliposome method, followed by modifications through UV irradiation and sonication. Methods: The resulting liposomes were analyzed for encapsulation efficiency, vesicle size, polydispersity index (PDI), mobility, zeta potential, viscosity, surface tension, density, antioxidant activity, FT-IR spectra, and release kinetics under simulated gastrointestinal conditions. In addition, nanoparticle tracking analysis and transmission electron microscopy (TEM) were used for liposomal characterization. Results: The findings revealed a high encapsulation efficiency across all samples (>70%). The particle size and PDI measurements confirmed the presence of a multilamellar and uniform liposomal system before post-processing modifications. The medium value of zeta potential suggested a moderately electrostatically stabilized liposomal suspension. The sonicated liposomes demonstrated a higher concentration of vesicles in comparison to non-treated and UV-irradiated samples. TEM analysis revealed purified liposomal vesicles with preserved structural integrity. Encapsulation, as well as UV irradiation and sonication of liposomes, did not diminish the extract's anti-DPPH activity. However, the ABTS radical scavenging potential of the pure extract was significantly lower compared to its encapsulated counterparts. UV irradiation and sonication notably reduced the anti-ABTS capacity of the extract-liposome system. Monitoring the release of bioactive compounds demonstrated controlled delivery from liposomal particles under simulated gastrointestinal conditions. Conclusions: Overall, liposomal formulations of carob pulp extract exhibit significant potential for further development as a functional food ingredient or for use in the prevention and treatment of various diseases.

Keywords: antioxidant activity; carob pulp extract; controlled release; encapsulation efficiency; liposomal formulation.

Figure 1

Principal scheme of the carob extract-loaded liposome preparation and modification methods.

Figure 2

Storage stability of developed carob extract-loaded liposomes (non-treated, UV-irradiated, and sonicated samples): (A) vesicle size, (B) polydispersity index, (C) mobility, and (D) zeta potential monitored during 60 days of storage at 4 °C.

Figure 3

Size distribution (A), concentration (B), and representative video frame capture (C) of non-treated, UV-irradiated, and sonicated carob extract-loaded liposomes. Data on size distribution and concentration represent the mean values of three independent measurements obtained by nanoparticle tracking analysis.

Figure 4

FT-IR spectroscopic analysis of pure carob extract, phospholipids (Ph), and developed carob extract-loaded liposomes (non-treated, UV-irradiated, and sonicated samples).

Figure 5

Representative transmission electron microscopy images showing non-treated (A), UV-irradiated (B), and sonicated (C) carob extract-loaded liposomes. Bar—1 µm. The arrow represents the common appearance of liposomes in a corresponding sample. The triangle represents impurities or debris from the ultrasound probe within the liposomes.

Figure 6

The radical scavenging capacity of pure carob extract and developed carob extract-loaded liposomes (non-treated, UV-irradiated, and sonicated samples); different letters (a–c, for both assays separately) indicate that there was a statistically significant difference based on Duncan’s post hoc test at p < 0.05 level, n = 3, mean value ± standard deviation.

Figure 7

Release profiles of polyphenols from carob extract and developed carob extract-loaded liposomes (non-treated, UV-irradiated, and sonicated samples) in (A) simulated gastric fluid (SGF, pH 1.5, monitored for 3 h) and (B) simulated intestinal fluid (SIF, pH 7.4, monitored for 8 h) at 37 °C.

Figure 7

Release profiles of polyphenols from carob extract and developed carob extract-loaded liposomes (non-treated, UV-irradiated, and sonicated samples) in (A) simulated gastric fluid (SGF, pH 1.5, monitored for 3 h) and (B) simulated intestinal fluid (SIF, pH 7.4, monitored for 8 h) at 37 °C.