Ultrasound assisted extraction and liposome encapsulation of olive leaves and orange peels: How to transform biomass waste into valuable resources with antimicrobial activity

Impact of pharmacokinetic enhancement strategies on the antimicrobial and antioxidant activities of hydroxytyrosol

Hydroxytyrosol (HTyr), a plant-derived phenolic compound found in Olea europaea L. products and by-products, is well-known for its antioxidant activity and a wide range of biological effects, including anti-inflammatory, anticancer, antiviral, cardioprotective, neuroprotective, and antibacterial properties. However, due to its high hydrophilicity, HTyr exhibits unfavorable pharmacokinetic properties, preventing its potential therapeutic use. Various strategies can be employed to address these limitations. In this study, we evaluated the effect of two specific approaches on the HTyr antimicrobial and antioxidant activities: chemical modification of HTyr by lipophilization of the alcoholic moiety and encapsulation in liposomes. Based on our experience in the synthesis and biological activities of HTyr derivatives, the attention was focused on HTyr oleate (HTyr-OL), having a C-18 unsaturated alkylic chain responsible for an increased lipophilicity compared to HTyr. This structural feature enhanced antimicrobial activity against both tested strains of S. aureus, ATCC 25923 (wild-type strain) and ATCC 33591 (MRSA), and comparable antioxidant activity against two different radicals, Galvinoxyl radical and 1,1-diphenyl-2-picrylhydrazyl radical. Moreover, liposomes as delivery systems for HTyr and HTyr-OL were developed using both natural and synthetic amphiphiles, and the impact of encapsulation on their activities was further investigated. The experimental results showed that the antimicrobial properties of HTyr and HTyr-OL against S. aureus strains were not enhanced after encapsulation in liposomes, while the high antioxidant activity of HTyr-OL was preserved when conveyed in liposomes.

From Waste to Value: Optimization of Ultrasound-Assisted Extraction of Anthocyanins and Flavonols from Pistacia lentiscus L. Oilcakes

Pistacia lentiscus L., commonly known as the mastic tree or lentisk, is a woody Mediterranean plant revered for its ecological relevance as well as for its extensive ethnobotanical heritage. Historically, the fruits and the resin of P. lentiscus have been widely utilized in traditional medicine, underscoring its important role in local healing practices. Given these properties, this study explored an innovative approach to efficiently extract anthocyanins and flavonols from P. lentiscus oilcakes utilizing ultrasound-assisted extraction (UAE) as an alternative to conventional solvent extraction. Liquid chromatography-mass spectrometry (LC-MS) and high-performance liquid chromatography with diode-array detection (HPLC-DAD) were used to identify and quantify the anthocyanins and flavonols, revealing the successful extraction of eight distinct anthocyanins and twenty flavonols. A Fractional Factorial Design (FFD) followed by a Box-Behnken design (BBD) were applied to optimize the yield of anthocyanins and flavonols. The optimal extraction conditions found were to be an extraction time of 15 min with 70% ethanol as the solvent and a liquid-to-solid ratio of 0.012 L g-1, which resulted in a maximum extraction yield of 19.78 mg g-1 dry extract for the Total Flavonol Content and over 25.4 mg g-1 dry extract for the Total Flavonol and Anthocyanin Content. By elucidating the optimal conditions for extracting anthocyanins and flavonol glycosides, this study opens promising avenues for utilizing P. lentiscus oilcake by-products, supporting sustainable practices, and advancing the valorization of Mediterranean bio-resources for health-promoting applications.

Encapsulation of Olea europaea Leaf Polyphenols in Liposomes: A Study on Their Antimicrobial Activity to Turn a Byproduct into a Tool to Treat Bacterial Infection

According to the innovative and sustainable perspective of the circular economy model, Olea europaea leaves, a solid byproduct generated every year in large amounts by the olive oil production chain, are considered a valuable source of bioactive compounds, such as polyphenols, with many potential applications. In particular, the following study aimed to valorize olive leaves in order to obtain products with potential antibacterial activity. In this study, olive leaf extracts, rich in polyphenols, were prepared by ultrasound-assisted extraction using green solvents, such as ethanol and water. The extracts were found to be rich in polyphenols up to 26.7 mgGAE/gleaves; in particular, hydroxytyrosol-hexose isomers (up to 6.6 mg/gdry extract) and oleuropein (up to 324.1 mg/gdry extract) turned out to be the most abundant polyphenolic compounds in all of the extracts. The extracts were embedded in liposomes formulated with natural phosphocholine and cholesterol, in the presence or in the absence of a synthetic galactosylated amphiphile. All liposomes, prepared according to the thin-layer evaporation method coupled with an extrusion protocol, showed a narrow size distribution with a particle diameter between 79 and 120 nm and a good polydispersity index (0.10-0.20). Furthermore, all developed liposomes exhibited a great storage stability up to 90 days at 4 °C and at different pH values, with no significant changes in their size and polydispersity index. The effect of the encapsulation in liposomes of O. europaea leaf extracts on their antimicrobial activity was examined in vitro against two strains of Staphylococcus aureus: ATCC 25923 (wild-type strain) and ATCC 33591 (methicillin-resistant S. aureus, MRSA). The extracts demonstrated good antimicrobial activity against both bacterial strains under investigation, with the minimum inhibitory concentration ranging from 140 to 240 μgextract/mL and the minimum bactericidal concentration ranging from 180 to 310 μgextract/mL, depending on the specific extract and the bacterium tested. Moreover, a possible synergistic effect between the bioactive compounds inside the extracts tested was highlighted. Notably, their inclusion in galactosylated liposomes highlighted comparable or slightly increased antimicrobial activity compared to the free extracts against both bacterial strains tested.

Exploring Antimicrobial Compounds from Agri-Food Wastes for Sustainable Applications

Transforming agri-food wastes into valuable products is crucial due to their significant environmental impact, when discarded, including energy consumption, water use, and carbon emissions. This review aims to explore the current research on the recovery of bioactive molecules with antimicrobial properties from agri-food waste and by-products, and discusses future opportunities for promoting a circular economy in its production and processing. Mainly, antibacterial molecules extracted from agri-food wastes are phenolic compounds, essential oils, and saponins. Their extraction and antimicrobial activity against a wide spectrum of bacteria is analyzed in depth. Also, their possible mechanisms of activity are described and classified based on their effect on bacteria, such as the (i) alteration of the cell membrane, (ii) inhibition of energy metabolism and DNA synthesis, and iii) disruption of quorum sensing and biofilm formation. These bioactive molecules have a wide range of possible applications ranging from cosmetics to food packaging. However, despite their potential, the amount of wastes transformed into valuable compounds is very low, due to the high costs relating to their extraction, technical challenges in managing supply chain complexity, limited infrastructure, policy and regulatory barriers, and public perception. For these reasons, further research is needed to develop cost-effective, scalable technologies for biomass valorization.

Innovative Approaches to Enhancing the Biomedical Properties of Liposomes

Liposomes represent a promising class of drug delivery systems that enhance the therapeutic efficacy and safety of various pharmaceutical agents. Also, they offer numerous advantages compared to traditional drug delivery methods, including targeted delivery to specific sites, controlled release, and fewer side effects. This review meticulously examines the methodologies employed in the preparation and characterization of liposomal formulations. With the rising incidence of adverse drug reactions, there is a pressing need for innovative delivery strategies that prioritize selectivity, specificity, and safety. Nanomedicine promises to revolutionize diagnostics and treatments, addressing current limitations and improving disease management, including cancer, which remains a major global health challenge. This paper aims to conduct a comprehensive study on the interest of biomedical research regarding nanotechnology and its implications for further applications.

Targeted breast cancer therapy using novel nanovesicle formulations of Olea europaea extract

Olive leaf is a byproduct of the olive tree that is rich in phenolic compounds with potential anticarcinogenic effects against various cancers, including breast cancer. Nevertheless, the ingestion or topical application of such plant extracts faces certain limitations. These limitations can be addressed by encapsulating the extracts in nanovesicles to enhance their release and bioavailability. This study aims to develop nanovesicles using Olea europaea leaf extract to exploit its potential anti-cancer properties. Soy lecithin was used to form liposomes for encapsulation of the olive leaf extract. In addition, ethanol and glycerol were added to form ethosomes and glycerosomes, respectively. The antiproliferative effect of both the free extract and the three formed nanovesicles was tested in MCF7 and MCF10A cell lines. To comprehend the mechanisms leading to reduced cell viability after exposure to olive leaf extract and its nanovesicles, levels of reactive oxygen species (ROS), mitochondrial membrane potential, and apoptotic stage were evaluated. The results suggest that both, the nanovesicles and the free extract, are antiproliferative agents against MCF7 tumour cells. However, when examining the impact of olive leaf extract and the formulated nanovesicles on MCF10A cells, no reduction in cell viability was observed. Our findings indicate that the anti-tumour effect of the extract and its nanovesicles may be due to increased oxidative stress, mediated by mitochondrial damage. The mechanism through which olive leaf extract exerts its antiproliferative effect on the breast cancer tumour line implies that apoptosis may be induced by the extract via the involvement of a mitochondria-dependent ROS-mediated pathway.

Ultrasonic-assisted extraction of grape seed procyanidins, preparation of liposomes, and evaluation of their antioxidant capacity

The residue remaining after oil extraction from grape seed contain abundant procyanidins. An ultrasonic-assisted enzyme method was performed to achieve a high extraction efficiency of procyanidins when the optimal extraction conditions were 8 U/g of cellulase, ultrasound power of 200 W, ultrasonic temperature of 50 ℃, and ultrasonic reaction time of 40 min. The effects of free procyanidins on both radical scavenging activity and thermal stability at 40, 60, and 80 ℃ of the procyanidins-loaded liposomal systems prepared by the ultrasonic-assisted method were discussed. The presence of procyanidins at concentrations ranging from 0.02 to 0.10 mg/mL was observed to be effective at inhibiting lipid oxidation by 15.15 % to 69.70 % in a linoleic acid model system during reaction for 168 h, as measured using the ferric thiocyanate method. The procyanidins-loaded liposomal systems prepared by the ultrasonic-assisted method were characterized by measuring the mean particle size and encapsulation efficiency. Moreover, the holographic plots showed that the effect-response points of procyanidins combined with α-tocopherol in liposomes were lower than the addition line and 95 % confidence interval limits. At the same time, there were significant differences between the theoretical IC50add value and the experimental IC50mix value. The interaction index (γ) of all combinations was observed to be less than 1. These results indicated that there was a synergistic antioxidant effect between procyanidins combined with α-tocopherol, which will show promising prospects in practical applications. In addition, particle size differentiation and morphology agglomeration were observed at different time points of antioxidant activity determination (0, 48, 96 h).