Comparative Extraction of Phenolic Compounds from Olive Leaves Using a Sonotrode and an Ultrasonic Bath and the Evaluation of Both Antioxidant and Antimicrobial Activity

This study is part of the project SHEALTHY that has received funding from European Union's Horizon 2020 Research and Innovation Programme under grant agreement No 817936. This study was also supported by project RTI2018-099835-A-I00 financed by MCIN/AEI/10.13039/5011000 11033/FEDER "Una manera de hacer Europa".A sonotrode ultrasound-assisted extraction of phenolic compounds from olive leaves has been developed using a Box-Behnken design to optimize the effects of solvent composition and ultrasound parameters. The determination of single phenolic compounds was performed by HPLC-MS and the highest recovery in total compounds, oleuropein and hydroxytyrosol was achieved using EtOH/H2O (55:45, v/v), 8 min and 100% of amplitude. The optimal conditions were applied on leaves from seven olive cultivars grown under the same conditions and the results were compared with those found by using a conventional ultrasonic bath, obtaining no statistical differences. Moreover, antioxidant activity by FRAP, DPPH and ABTS in these olive leaf extracts was evaluated and they exhibited a significant correlation with oleuropein and total phenolic content. All cultivars of olive leaf extracts were found to be active against S. aureus and methicillin-resistant S. aureus with minimum bactericidal concentration (MBC) values) that ranged from 5.5 to 22.5 mg mL(-1). No extracts showed antimicrobial activity against C. albicans. The percentages of mycelium reduction in B. cinerea ranged from 2.2 and 18.1%. Therefore, sonotrode could be considered as an efficient and fast extraction technique that could be easily scaled-up at industrial level, thus allowing for olive leaves to be revalorized.European Union's Horizon 2020 Research and Innovation Programme 817936MCIN/AEI/FEDER "Una manera de hacer Europa" RTI2018-099835-A-I0

Effect of Lactic Acid Bacteria Fermentation on the Polar Compounds Content with Antioxidant and Antidiabetic Activity of Avocado Seed Extracts

Avocado seeds, a common waste in the avocado processing industry, have been found to have several bioactivities, such as anticancer, antimicrobial, hypocholesterolemic, antioxidant, and antidiabetic activities, among others. Nowadays, this wastage is causing an environmental problem, so the use of new technologies to take advantage of it is a novel field of research. In this study, the submerged fermentation by lactic acid bacteria was used as a novel tool for improving the bioactive compound extraction from avocado seeds. Avocado seeds were fermented by different strains, their polar compounds were identified and quantified by HPLC-ESI-TOF-MS, the antioxidant activity was measured by DPPH and FRAP assays, and the antidiabetic activity was analyzed by the alpha-amylase assay. A total of 32 polar compounds were identified, with 13 of them being described in avocado seeds for the first time. Avocado seeds fermented by Pentosaceus acidilactici showed the highest sum of polar compounds (6279.63 67.74 g/g d.w.), and by extension, of hydroxytyrosol glucoside (2989.76 3.64 g/g d.w.). Lactiplantibacillus plantarum CECT 9567 showed the highest antioxidant activity measured by both DPPH and FRAP assays (6294.67 19.44 and 6846.91 2.13 g TE/g d.w., respectively). Furthermore, Lactiplantibacillus plantarum CECT 748T had the highest antidiabetic activity (52.15% 0.67% inhibition of alpha-amylase activity), attributable to the polyphenols. According to the results, submerged fermentation by lactic acid bacteria led to an interesting increase of the polar compounds’ extractability of avocado seeds, consequently improving the bioactivities of the extracts, which could then be used for food nutraceutical or cosmetic purposes.Project RTI2018-099835-A-I00MCIN/AEI/ 10.13039/501100011033/FEDER, “Una manera de hacer Europ

Essential Oils from Fruit and Vegetables, Aromatic Herbs, and Spices: Composition, Antioxidant, and Antimicrobial Activities

The use of essential oils (EOs) in the food industry is a popular research topic, as they have antioxidant and antimicrobial activity and could be used as ingredients directly in food or as bioactive component in food coating and food packaging. Thus, the study of their antioxidant and antimicrobial activity is a crucial step to evaluate their use in food packaging/coating. In this work, we evaluate the antioxidant and antimicrobial activities of 13 EOs from herbs, spices, fruits, and vegetables. Briefly, the EOs from aromatic herbs and spices showed the highest antioxidant and antimicrobial activity. Fennel essential oil reported the lowest antioxidant activity, however it showed very good antimicrobial activity against Botrytis cinerea, one of the post-harvest pathogen microorganisms in fruits and vegetables.In the field of food preservation, encapsulated Essential Oils (EOs) could be the best non-toxic and eco-friendly tool for food preservative applications substituting the chemicals ones that have several disadvantages for the environment and health. Thirteen commercial EOs from plants, fruits, and vegetables were characterized by GC-MS. The antioxidant activity was measured by DPPH and ABTS techniques. Antimicrobial activity was assessed by agar well-diffusion method and the Minimum Inhibitory Concentration (MIC) by agar dilution method against six bacteria, Candida albicans, and Botrytis cinerea. All the EOs tested have demonstrated antioxidant activity in the range of IC50 0.01–105.32 mg/mL. Between them, cinnamon EOs were the best, followed by oregano and thyme EOs. Fennel EO showed the lowest radical scavenging. MIC values ranged from 0.14 to 9 mg/mL. C. cassia, thyme, and oregano EOs were the most effective against the bacterial species tested, and the yeast C. albicans. On the contrary, citric fruit EOs showed low or no inhibition against most bacterial strains. The percentages of inhibition of mycelia growth of B. cinerea ranged from 3.4 to 98.5%. Thyme, oregano, mint, and fennel EOs showed the highest inhibition.European Union’s Horizon 2020 -No 81793

Estudio del potencial probiótico de Lactobacillus plantarum C4

Los probióticos se definen como microorganismos vivos que, cuando son administrados en adecuadas cantidades, confieren beneficios para la salud del huésped. Entre estos efectos beneficiosos figuran la reducción de los síntomas de mala digestión de la lactosa, reducción de hipercolesterolemia, disminución de la duración y gravedad de procesos diarreicos, mejora de la barrera de permeabilidad intestinal, prevención de algunos tipos de cáncer por adsorción o inactivación de agentes genotóxicos, incremento de la resistencia a infecciones intestinales y extraintestinales, atenuación de la enfermedad inflamatoria intestinal, y prevención de alergias (especialmente alimentarias). La cepa C4 de Lactobacillus plantarum ha sido aislada de kéfir y largamente estudiada en nuestro laboratorio por su potencial probiótico. En la presente memoria de tesis doctoral se describen nuevas actividades y propiedades que configuran el potencial probiótico de esta cepa. L. plantarum C4 resistió las condiciones de la digestión gastrointestinal simulada in vitro; en presencia del fructooligosacárido prebiótico FOS se prolongó la viabilidad de la bacteria que adquirió la capacidad de inhibir cepas de las bacterias patógenas intestinales Yersinia enterocolitica, Escherichia coli, Salmonella enterica serovar Typhimurium y Enterococcus faecalis. L. plantarum C4 ejerció antibiosis sobre Clostridium difficile y demostró capacidad para inactivar sus citotoxinas, efectos mediados por la producción de ácidos. Además, L. plantarum C4 inhibió de forma significativa la mutagenicidad del 2-nitrofluoreno sobre la cepa auxotrofa S. typhimurium TA98 en el ensayo de Ames, en condiciones en las que la viabilidad de C4 se vió abolida, lo que sugiere un mecanismo de adsorción que retira el mutágeno. Ensayos de inmunomodulación in vitro, sobre líneas celulares, e in vivo, en animales de experimentación, demostraron un excelente comportamiento de la cepa probiótica, que potenció mecanismos defensivos sin una contrapartida proinflamatoria en las condiciones basales, lo que se reflejó finalmente en un incrementos de la resistencia en el modelo de infección experimental del ratón por Y. enterocolitica. La discusión general de estos resultados pone de manifiesto que L. plantarum utiliza mecanismos directos (antibiosis, inactivación o adsorción de toxinas y de mutágenos) e indirectos (a través de la modulación de mecanismos inmunitarios) para producir los diversos efectos beneficiosos que se describen por primera vez en esta memoria.Tesis Univ. Granada. Programa Oficial de Doctorado en: Biología Fundamental y de Sistema

Fermentation of Orange Peels by Lactic Acid Bacteria: Impact on Phenolic Composition and Antioxidant Activity

Orange processing generates peel by-products rich in phenolic compounds, particularly flavanones like hesperidin and narirutin, offering potential health benefits. Utilizing these byproducts is of significant interest in supporting Spain’s circular bioeconomy. Therefore, the aim of this study was to investigate the fermentation of orange peels by different lactic acid bacteria (LAB) strains and its impact on phenolic composition and antioxidant activity. Three different LAB strains, two Lactiplantibacillus plantarum, and one Levilactobacillus brevis were utilized. The phenolic compounds were measured by HPLC-ESI-TOF-MS, and antioxidant activity was assessed using DPPH and ABTS methods. The growth of the LAB strains varied, showing initial increases followed by gradual declines, with strain-specific patterns observed. Medium acidification occurred during fermentation. A phenolic analysis revealed an 11% increase in phenolic acids in peels fermented by La. plantarum CECT 9567-C4 after 24 h, attributed to glycosylation by LAB enzymes. The flavonoid content exhibited diverse trends, with Le. brevis showing an 8% increase. The antioxidant assays demonstrated strain- and time-dependent variations. Positive correlations were found between antioxidant activity and total phenolic compounds. The results underscore the importance of bacterial selection and fermentation time for tailored phenolic composition and antioxidant activity in orange peel extracts. LAB fermentation, particularly with La. plantarum CECT 9567 and Le. brevis, holds promise for enhancing the recovery of phenolic compounds and augmenting antioxidant activity in orange peels, suggesting potential applications in food and beverage processing. Orange processing generates peel by-products rich in phenolic compounds, particularly flavanones like hesperidin and narirutin, offering potential health benefits. Utilizing these byproducts is of significant interest in supporting Spain’s circular bioeconomy. Therefore, the aim of this study was to investigate the fermentation of orange peels by different lactic acid bacteria (LAB) strains and its impact on phenolic composition and antioxidant activity. Three different LAB strains, two Lactiplantibacillus plantarum, and one Levilactobacillus brevis were utilized. The phenolic compounds were measured by HPLC-ESI-TOF-MS, and antioxidant activity was assessed using DPPH and ABTS methods. The growth of the LAB strains varied, showing initial increases followed by gradual declines, with strain-specific patterns observed. Medium acidification occurred during fermentation. A phenolic analysis revealed an 11% increase in phenolic acids in peels fermented by La. plantarum CECT 9567-C4 after 24 h, attributed to glycosylation by LAB enzymes. The flavonoid content exhibited diverse trends, with Le. brevis showing an 8% increase. The antioxidant assays demonstrated strain- and time-dependent variations. Positive correlations were found between antioxidant activity and total phenolic compounds. The results underscore the importance of bacterial selection and fermentation time for tailored phenolic composition and antioxidant activity in orange peel extracts. LAB fermentation, particularly with La. plantarum CECT 9567 and Le. brevis, holds promise for enhancing the recovery of phenolic compounds and augmenting antioxidant activity in orange peels, suggesting potential applications in food and beverage processing.Research Fellowship from the Government of Spain (FPU19/02009

Impact of Lactic Acid Bacteria Fermentation on Phenolic Compounds and Antioxidant Activity of Avocado Leaf Extracts

The growing global consumption of avocados, associated with contents including bioactive compounds with numerous health-promoting properties, is producing a large amount of agro wastes around the world. Different management approaches are available for the recovery of bioactive compounds from wastes as potential ingredients for use in the production of functional foods and nutraceuticals. Lactic acid fermentation can be used to exploit nutritional potential and add value to agro wastes. In this study, fermentations with lactic acid bacteria were carried out in avocado leaves, and the total phenolic content and the antioxidant activity were determined by DPPH and FRAP assays from hydroalcoholic extracts obtained from fermented avocado leaves. Fifteen new phenolic compounds were identified for the first time in avocado leaves by HPLC-ESI-TOF-MS. L. plantarum CECT 748T and P. pentosaceus CECT 4695T showed the highest antioxidant activity. The sum of phenolic compounds was increased by 71, 62, 55 and 21% in fermentations with P. pentosaceus CECT 4695T, L. brevis CECT 5354, P. acidilactici CECT 5765T and L. plantarum CECT 9567, respectively, while it was reduced in the fermentation with L. plantarum 748T by 21% as demonstrated by HPLC-ESI-TOFMS. Biotransformations induced by bacterial metabolism modified the phenolic compound profile of avocado leaves in a strain-specific-dependent manner. P. pentosaceus CECT 4695T significantly increased kaempferol, P. pentosaceus 4695T, L. brevis 5354 and L. plantarum 9567 increased rutin, and dihydro-p-coumaric acid was increased by the five selected lactic acid bacteria. Total flavonoids were highly increased after fermentations with the five selected lactic acid bacteria but flavonoid glucosides were decreased by L. plantarum 748T, which was related to its higher antioxidant activity. Our results suggest that lactic acid bacteria led the hydrolysis of compounds by enzymatic activity such as glycosidases or decarboxylase and the release of phenolics bound to the plant cell wall, thus improving their bioavailability.projectRTI2018-099835-A-I00 financed byMCIN/AEI/10.13039/ 501100011033/ FEDER “Unamanera de hacer Europa

Impact of Lactic Acid Bacteria Fermentation on Phenolic Compounds and Antioxidant Activity of Avocado Leaf Extracts

The growing global consumption of avocados, associated with contents including bioactive compounds with numerous health-promoting properties, is producing a large amount of agro wastes around the world. Different management approaches are available for the recovery of bioactive compounds from wastes as potential ingredients for use in the production of functional foods and nutraceuticals. Lactic acid fermentation can be used to exploit nutritional potential and add value to agro wastes. In this study, fermentations with lactic acid bacteria were carried out in avocado leaves, and the total phenolic content and the antioxidant activity were determined by DPPH and FRAP assays from hydroalcoholic extracts obtained from fermented avocado leaves. Fifteen new phenolic compounds were identified for the first time in avocado leaves by HPLC-ESI-TOF-MS. L. plantarum CECT 748T and P. pentosaceus CECT 4695T showed the highest antioxidant activity. The sum of phenolic compounds was increased by 71, 62, 55 and 21% in fermentations with P. pentosaceus CECT 4695T, L. brevis CECT 5354, P. acidilactici CECT 5765T and L. plantarum CECT 9567, respectively, while it was reduced in the fermentation with L. plantarum 748T by 21% as demonstrated by HPLC-ESI-TOF-MS. Biotransformations induced by bacterial metabolism modified the phenolic compound profile of avocado leaves in a strain-specific-dependent manner. P. pentosaceus CECT 4695T significantly increased kaempferol, P. pentosaceus 4695T, L. brevis 5354 and L. plantarum 9567 increased rutin, and dihydro-p-coumaric acid was increased by the five selected lactic acid bacteria. Total flavonoids were highly increased after fermentations with the five selected lactic acid bacteria but flavonoid glucosides were decreased by L. plantarum 748T, which was related to its higher antioxidant activity. Our results suggest that lactic acid bacteria led the hydrolysis of compounds by enzymatic activity such as glycosidases or decarboxylase and the release of phenolics bound to the plant cell wall, thus improving their bioavailability