Miguel Angel Meneses

Melaleuca viridiflora (niaouli) is an Australian species that has been introduced into different regions worldwide because of its broad adaptability and potential applications. This work aimed to characterize the chemical and enantiomeric composition of the leaf essential oil from M. viridiflora cultivated in the Americas and to explore its biological properties. The essential oil was isolated by steam distillation and chemically characterized using gas chromatographic techniques, while its enantiomeric profile was established using two chiral stationary phases. Biological activity was investigated by determining the antimicrobial effects against a panel of Gram-positive and Gram-negative bacteria, Candida albicans, and Aspergillus niger using the broth microdilution assay. In addition, the antioxidant capacity was examined by ABTS and DPPH radical-scavenging assays, and acetylcholinesterase inhibitory activity was determined by a spectrophotometric method. Fifty compounds were identified, accounting for 99.07% of the total composition. Sesquiterpene hydrocarbons represented the largest group in terms of number of compounds (16), whereas oxygenated monoterpenes predominated in relative abundance (45.27%). The major constituents were 1,8-cineole (35.66 ± 0.37%), viridiflorol (14.20 ± 0.12%), limonene (11.04 ± 0.06%), α-terpineol (7.89 ± 0.71%), and α-pinene (7.42 ± 0.11%). Six pairs of enantiomers were identified. Overall, the essential oil displayed a biological profile characterized by limited antimicrobial and antioxidant effects but a comparatively more pronounced anticholinesterase activity. Antimicrobial effects were observed at 4000 μg/mL against Listeria monocytogenes, Enterococcus faecium, and Aspergillus niger, while antioxidant activity was weak, with an ABTS SC₅₀ of 1.2 mg/mL. In contrast, the oil exhibited moderate anticholinesterase activity, with an IC₅₀ of 65.98 ± 1.0 μg/mL. Taken together, these findings indicate that the biological profile of M. viridiflora essential oil is primarily distinguished by its anticholinesterase activity rather than by antimicrobial or antioxidant effects. This study provides the first report for Melaleuca viridiflora cultivated in the Americas.

Melaleuca ericifolia Sm., commonly known as paperbark, is a shrub or small tree native to Australia that has been introduced and cultivated in various regions worldwide due to its adaptability and diverse applications. In the present study, the chemical composition and biological activity of the essential oil isolated from this species are investigated. The essential oil was extracted through steam distillation. The qualitative and quantitative chemical composition of the essential oil was determined by gas chromatography. The enantiomeric distribution was determined using two enantioselective chromatographic columns. Antimicrobial activity was determined using the broth microdilution method against four Gram-negative bacilli, a Gram-positive bacillus, three Gram-positive cocci, one fungus and one yeast. The antioxidant activity was determined using ABTS and DPPH assays. Anticholinesterase activity was determined using a spectrophotometric method. The forty-seven compounds identified accounted for 99.74% of the overall composition. Oxygenated monoterpenes were the most representative group in terms of number of compounds (fourteen) and in terms of relative abundance (72.50%). The most abundant constituents were 1,8-cineole (61.85 ± 1.46%), limonene (11.23 ± 0.16%), α-terpineol (7.99 ± 0.10%), α-pinene (4.97 ± 0.17%) and β-pinene (3.71 ± 0.17%). Five pairs of enantiomers were identified in the essential oil from leaves of Melaleuca ericifolia. The essential oil presented MICs of 2000 and 4000 μg/mL against Candida albicans and Aspergillus niger, respectively. The antioxidant activity was weak with a SC₅₀ of 2 mg/mL in the ABTS assay. The essential oil exhibited moderate anticholinesterase activity, with an IC₅₀ of 73.6 ± 1.0 µg/mL. This study provides the first comprehensive analysis of the chemical composition and biological activities of the essential oil isolated from leaves of Melaleuca ericifolia Sm. cultivated in the Americas. Furthermore, the enantiomeric distribution and antioxidant and acetylcholinesterase inhibitory activities of this essential oil are reported for the first time.

This study examines the impact of integrating Generative Artificial Intelligence (AIgen) and Augmented Reality (AR) within a Project-Based Learning (PBL) framework to enhance student motivation and active learning in Chemical Engineering Unit Operations (OU) courses. The research employed a quasi-experimental post-test design without a control group and followed a mixed-methods explanatory approach. The intervention was implemented over two academic semesters at the Universidad Técnica Particular de Loja. The instructional design was structured using the 4PADAFE model, based on the principles of constructive alignment and competency-based education. The intervention was organized into seven sequential phases that integrated pedagogical planning, technological implementation, and evaluation. Students collaboratively developed educational resources, including interactive AR visualizations and AI-generated teaching materials addressing key topics such as fluid flow, heat transfer, and adsorption kinetics. The quantitative component constituted the main analytical approach and assessed changes in motivation using the Instructional Materials Motivation Survey (IMMS), based on Keller’s ARCS model. The instrument’s reliability was supported by high internal consistency (Cronbach’s α > 0.95) and satisfactory factor adequacy indices. The results revealed increases in all motivational dimensions, with mean scores rising from 3.26–3.33 in Phase I to 3.48–3.60 in Phase II. Overall, the findings indicate that the structured integration of AIgen and AR within an aligned problem-based learning (PBL) framework was associated with improvements in student engagement, confidence, and satisfaction. The study provides evaluative evidence supporting the implementation of technology-enhanced teaching strategies in engineering education under real-world classroom conditions.

In this in vitro experimental study, we compared four extraction techniques -dynamic maceration (DME), ultrasound-assisted (UAE), microwave-assisted (MAE), and pressurized liquid extraction (PLE)- to obtain bioactive extracts from two native Ecuadorian plants, Piper carpunya and Simira ecuadorensis. The effect of extraction techniques was evaluated separately for each specie based on extraction yield, total phenolic content (TPC), antioxidant capacity (DPPH, ABTS, FRAP, and ORAC assays), antimicrobial activity, and chemical composition. All analyses were performed in triplicate and analyzed statistically (ANOVA, p < 0.05). UAE and MAE exhibited the highest extraction yield, while PLE provided extracts with the greatest TPC. However, UAE extracts, particularly for S. ecuadorensis, exhibited superior antioxidant capacity across assays. GC/MS analysis revealed alkanes as predominant constituents, along with minor phenolic and ester compounds. Antimicrobial activity was observed in both species, especially against Listeria monocytogenes and Pseudomonas aeruginosa, with UAE and MAE extracts being most effective. Compounds such as isoelemicin, phytol, and ethyl linolenate may contribute to the observed bioactivities. These findings highlight the potential of P. carpunya and S. ecuadorensis as natural sources of antioxidants and antimicrobials for food and pharmaceutical applications.

The essential oil isolated from clove (Syzygium aromaticum) is used in food, medicine, cosmetics, agriculture, and aromatherapy for its antimicrobial, antioxidant, and analgesic properties. This systematic review, following the PRISMA 2020 methodology, evaluates the application of clove essential oil in meat and meat products to determine its effectiveness in preventing oxidative damage and improving product quality. A search was performed in various databases, obtaining 639 studies. After removing duplicates and applying inclusion and exclusion criteria, 43 relevant articles were selected. Studies published between 1999 and 2024 that evaluated clove essential oil in meat for human consumption were included, excluding research on extracts other than essential oil or supplements for animal feed. The studies suggest that clove essential oil improves parameters such as oxidative stability, colour preservation, and the reduction in reactive compounds such as thiobarbituric acid-reactive substances, thereby increasing the shelf life and safety of meat and meat products. Oxidation is reduced through free radical inhibition and lipid protection. The main variability detected includes the type of meat, application method and storage conditions. The concentrations used ranged from 2.65 mL/kg to 5%. Although variability in methodologies and concentrations used is a limitation for meta-analysis, the findings support the potential of clove essential oil as a natural alternative for preserving meat products, responding to consumer demand for safer foods free of synthetic preservatives.

Background: Clove (Syzygium aromaticum) essential oil is widely recognized for its potent antimicrobial properties, making it a valuable natural preservative in food products, particularly in meat and meat derivatives, where it helps extend shelf life and enhance food safety. Methods: This systematic review aims to evaluate the application of clove essential oil in meat and meat products, following the PRISMA 2020 methodology, to analyze its antimicrobial efficacy and its impact on the preservation of these products. The information search was carried out in the PubMed, ScienceDirect, SCOPUS, and Web of Science databases and included research articles in English published between 1999 and 2024, and 37 studies were confirmed as eligible. Results: Due to the heterogeneity of methodologies and concentrations evaluated, a narrative analysis was chosen, organizing the studies into three categories according to the application of the essential oil: direct addition, use in edible films and coatings, and encapsulation. The analysis included the main components of the essential oil, the activity analysis method, a concentration evaluation, storage conditions, the activities obtained, and a sensory evaluation. However, variability in methodologies and concentrations made direct comparison between studies difficult. Conclusions: Overall, this review confirms the effectiveness of clove essential oil in preserving meat and meat products but highlights the need to standardize its concentration and application conditions to optimize its use in the food industry.

Citrus x limonia is an aromatic species, known locally in Ecuador as limón mandarina or limón chino. In the present study, the chemical composition and biological activity of the essential oil isolated from this species were determined. The essential oil was extracted through hydrodistillation. The chemical composition and enantiomeric distribution of the essential oil were determined by gas chromatography. Antimicrobial activity was determined using the broth microdilution method against tree Gram-positive cocci, a Gram-positive bacillus, four Gram-negative bacilli, a fungus, and a yeast. The antioxidant activity was determined through ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) and DPPH (2,2-diphenyl-1-picrylhydrazyl) methods. The spectrophotometric method was used to determine anticholinesterase activity. In the essential oil, thirty-nine compounds were identified, which represented 99.35% of the total composition. Monoterpene hydrocarbons were the most representative group in terms of number of compounds (thirteen) and in terms of relative abundance (91.39%). The main constituents were found to be limonene (57.38 ± 1.09%), γ-terpinene (13.01 ± 0.37%), and β-pinene (12.04 ± 0.63%). Five pairs of enantiomers were identified in the essential oil from fruits of Citrus x limonia. The essential oil presented a minimum inhibitory concentration of 4000 μg/mL against Aspergillus niger. The antioxidant activity of essential oil was weak per the ABTS method, with a SC₅₀ of 1.26 mg/mL. Additionally, the essential oil exhibited moderate anticholinesterase activity, with an IC₅₀ of 203.9 ± 1.03 µg/mL. This study provides the first comprehensive analysis of the chemical composition and biological activities of the essential oil from fruits of Citrus x limonia.

Citrus x limonia is an aromatic species belonging to the Rutaceae family. In the present study, the chemical composition, enantiomeric distribution, and biological activity of the essential oil isolated from leaves of Citrus x limonia were determined. The essential oil was extracted through hydrodistillation. The chemical composition of the essential oil was determined by gas chromatography (GC) coupled to a flame ionization detector (GC-FID), and a mass spectrometer detector (GC-MS) using a nonpolar column. The enantiomeric distribution was performed using two enantioselective chromatographic columns. Antimicrobial activity was determined using the broth microdilution method. The antimicrobial activity was tested against eight bacteria and two fungi. The antioxidant activity was determined through ABTS and DPPH methods. The spectrophotometric method was used to determine anticholinesterase activity. In the essential oil, forty-three compounds were identified. These compounds represent 99.13% of the total composition. Monoterpene hydrocarbons were the most representative group in number of compounds (fourteen) and in terms of relative abundance (65.67%). The main constituent is found to be limonene (25.37 ± 0.80%), β-pinene (23.29 ± 0.15%) and sabinene (8.35 ± 0.10%). Six pairs of enantiomers were identified in the essential oil from fruits of Citrus x limonia. The essential oil showed moderate antibacterial activity against Gram-positive cocci Enterococcus faecalis, and Gram-positive bacillus Lysteria monocytogenes with a MIC of 1000 μg/mL. The oil exhibited strong antifungal activity against fungi Aspergillus niger, and yeasts Candida albicans with a MIC of 250 and 500 μg/mL, respectively. The antioxidant activity of essential oil was weak in ABTS method with a SC₅₀ of 9.12 mg/mL. Additionally, the essential oil presented moderate anticholinesterase activity with an IC₅₀ of 71.02 ± 1.02 µg/mL.

This study investigated the valorization of Ilex guayusa leaves by producing a low-caffeine, antioxidant-rich product through the supercritical antisolvent extraction (SAE) process. The objective was to concentrate the antioxidants while selectively reducing the caffeine. The SAE treatments were conducted using an ethanolic extract of guayusa leaves under varying pressure (80 bar–150 bar) and temperature (35–45 °C) conditions to improve the recovery of chlorogenic acid (CGA) and caffeine fractionation. The co-precipitation of antioxidants with polyvinylpyrrolidone (PVP) (ratio 1:1–1:2 mass/mass) as an encapsulant was also studied. The SAE precipitates were analyzed for their recovery yield, CGA and caffeine contents, antioxidant activity, and total phenols. Based on the statistical analysis, the optimal conditions for the SAE were 120 bar and 45 °C. Under these conditions, the CGA concentration increased from 43.02 mg/g extract to 237 mg/g precipitate, while the caffeine was reduced to less than 1% mass. Co-precipitation with PVP improved the recovery yield by more than two times than the SAE alone while maintaining the caffeine content below 1% mass. Additionally, the co-precipitation with PVP facilitated the formation of spherical microparticles, indicating successful encapsulation of the bioactive compounds, with an IC₅₀ of 0.51 ± 0.01 mg/mL for DPPH and 0.18 ± 0.01 mg/mL for ABTS. These results highlight the effectiveness of the SAE co-precipitation process in developing low-caffeine functional ingredients with potential food and pharmaceutical applications.

Beet is a nutritious and health-promoting food with important bioactive compounds in its industrial by-products. The encapsulation of antioxidants from beet by-products has been proposed for valorization. For this, an ethanol–water extract was mixed with polyvinylpyrrolidone (PVP) (used as a carrier agent) and then encapsulated. The encapsulation was performed by spray drying, where the effects of temperature (140–160 °C), extract input flow rate (10–30%), and extraction solvent (ethanol–water 50/50 v/v and ethanol) were evaluated for the total phenol content and the spray-drying yield. The yields obtained were between 60 and 89%, and total phenols were between 136 and 1026 mg gallic acid equivalents/g of encapsulated product. Both responses were affected (p < 0.05) by the extraction solvent. The optimal spray-drying conditions were determined by response surface methodology (RSM). The encapsulated product obtained at optimal conditions was characterized by infrared spectrometry, X-ray fluorescence, Ultra-High Performance Liquid Chromatography, and scanning electron microscopy analysis. The results show that the encapsulated product has a high content of total phenols and compounds such as betanin, isobetanin, and neobetanin. Considering the results of physicochemical properties and the bioactive compounds, the optimized encapsulated product could be applied in the food industry as a bioactive ingredient or natural colorant. However, the further investigation of alternative carrier agents needs to be performed to reduce caking.