Luiza Alves Mendes’s research while affiliated with Federal University of Viçosa and other places

The genus Psidium is recognized for its economic value and the species that produce essential oils with notable biological activities. This study investigated the characteristics of the essential oil from the leaves of Psidium myrtoides and Psidium cattleyanum under different drying temperatures. We aimed to understand how drying temperatures affect the yield and composition of the essential oil, as well as its biological activity. The oils obtained from the leaves of P. myrtoides and P. cattleyanum dried in an oven at 40°C showed the highest yields (0.86% and 1.07%, respectively). β-caryophyllene was the major compound in all essential oils of P. myrtoides and P. cattleyanum, except in the oil extracted from P. myrtoides leaves dried at room temperature, where the major compound was α-bisabolol (14.46%). Different phytotoxic effects were observed using the emulsion of these oils in bioassays with Lactuca sativa and Sorghum bicolor, which were associated with the chemical composition and synergy of the identified compounds. The essential oil emulsion from leaves dried at room temperature of both species showed greater phytotoxic activity in the bioassays. Thus, optimizing drying conditions to maximize yield and synergy of compounds from the essential oils of P. myrtoides and P. cattleyanum is an important step in developing environmentally friendly natural agrochemicals. Index terms: Bioassays; chromatography; volatile compounds

The essential oil of Piper amalago L. is recognized for its bioactive compounds with phytotoxic potential against invasive plants. However, little is known about the role of seasonal variation in the action of these compounds. This study aimed to investigate the impact of dry and rainy seasons on the chemical composition, phytotoxic, and cytogenotoxic activity of P. amalago essential oil. Analysis of the chemical composition revealed qualitative and quantitative variations, highlighting β-elemene, germacrene A, linalool, and β-caryophyllene as major compounds. The essential oil from the rainy season showed higher yield compared to that of the dry season. In pre-emergence tests against Bidens pilosa (invasive plant) and Lactuca sativa (non-target plant), negative effects on germination and root and shoot growth were observed, with these effects being more pronounced at higher concentrations, resembling the herbicide glyphosate. The essential oil from the dry season exhibited greater phytotoxic activity on the germination and development of the aerial part of B. pilosa, associated with higher concentrations of linalool and caryophyllene oxide. Additionally, the essential oils of P. amalago induced changes in the mitotic index and aneugenic alterations in L. sativa meristematic cells. These results underscore the bioherbicidal potential of P. amalago essential oil, highlighting its greater efficacy against B. pilosa during the dry season, possibly due to higher levels of linalool and caryophyllene oxide. Key words natural herbicide; weeds; cellular cycle; bioassays

Cyclodextrin enhances the activity of bioactive compounds through the formation of inclusion complexes (ICs), but its effect on diverse compound structures and processing methods is poorly understood. Here, our goal is to provide a comprehensive and cohesive insight into hydroxypropyl-β-cyclodextrin (HPβCD) complexation with cinnamaldehyde (CINN), citral (CIT), or their combination (MIX), prepared via kneading (KN), or freeze-drying (FD) using analytical techniques and computational simulations. Thermodynamic analysis revealed an exothermic and spontaneous (ΔG < 0) complexation process, with CINN-ICs exhibiting greater stability constants at 25 °C than CIT-ICs. Among the methods, CIT-KN displayed the highest efficiency (90.7%) and drug loading (9%), while CINN-KN showcased higher zeta potential (−23.2 mV), controlled release (35%), and antimicrobial activity (against both gram-positive and gram-negative bacteria). Computer simulations confirmed the absence of ternary complexes (CINN+CIT in HPβCD) and revealed the coexistence of association and ICs. Thermal analyses demonstrated high thermal stability (up to 207 °C) of included compounds, enhancing the suitability of these complexes for high-temperature processes. Additionally, CINN-KN incorporation into methylcellulose creates an active film, which effectively inhibited the proliferation of L. monocytogenes and S. Choleraesuis in cheeses (up to 1.3 cm halo inhibition), even following exposure to temperatures as high as 50 °C. Through combined experiments and computations, we uncovered how processing affects ICs performance with bioactive compounds, confirming their associative interactions with HPβCD. Thus, we underscore that the active function of ICs containing bioactive compounds relies not only on compound structure but also on processing methods, involving a collaborative interplay between both factors.

The present investigation aimed to develop inclusion complexes (ICs) from Psidium gaudichaudianum (GAU) essential oil (EO) and its major compound β-caryophyllene (β-CAR), and to evaluate their herbicidal (against Lolium multiflorum and Bidens pilosa) and cytogenotoxic (on Lactuca sativa) activities. The ICs were obtained using 2-hydroxypropyl-β-cyclodextrin (HPβCD) and they were prepared to avoid or reduce the volatility and degradation of GAU EO and β-CAR. The ICs obtained showed a complexation efficiency of 91.5 and 83.9% for GAU EO and β-CAR, respectively. The IC of GAU EO at a concentration of 3000 µg mL⁻¹ displayed a significant effect against weed species B. pilosa and L. multiflorum. However, the β-CAR IC at a concentration of 3000 µg mL⁻¹ was effective only on L. multiflorum. In addition, the cytogenotoxic activity evaluation revealed that there was a reduction in the mitotic index and an increase in chromosomal abnormalities. The produced ICs were able to protect the EO and β-CAR from volatility and degradation, with a high thermal stability, and they also enabled the solubilization of the EO and β-CAR in water without the addition of an organic solvent. Therefore, it is possible to indicate the obtained products as potential candidates for commercial exploration since the ICs allow the complexed EO to exhibit a more stable chemical constitution than pure EO under storage conditions.

Essential oils (EO) have diverse applications, such as antibacterial and antifungal activity. However, they are susceptible to oxidation in the presence of air, light, and moisture. In addition, they are thermally unstable. In this sense, it is necessary to develop techniques to increase the lifespan of EO. In this work, EO was obtained from cloves and characterized by different techniques. The major compounds found were eugenol (83%), eugenol acetate (9%), and β-caryophyllene (8%). The EO was encapsulated by extrusion using a microfluidic device. The sodium alginate was used as wall material, and the CaCl 2 solution was used as a crosslinking agent. The microcapsule presented sizes of 164.7 ± 0.3 µm, with an encapsulation yield of 64 ± 14%. Functional characteristic groups of EO were observed in the microcapsule by infrared and Raman spectroscopies. The microcapsule increased the thermal decomposition of the EO from 162 to 230 °C. Release kinetics of the capsule was performed, with an equilibrium time of 72 h and release of 54% of the EO. Finally, the pure EO and encapsulated EO-microcapsules were applied in the Aedes aegypti larvae control, showing mean lethal concentration necessary to eliminate 50% (LC 50) values of 74.4 and 96.9 µg mL-1 and lethal concentration necessary to eliminate 90% (LC 90) of 106.2 and 133.3 µg mL-1 for pure EO and encapsulated EO, respectively. Therefore, it was concluded that these microcapsules have the potential for application in the Aedes aegypti larvae control.

As plantas do gênero Psidium (Myrtaceae) apresentam, dentre seus usos relevantes, atividades biológicas relacionadas aos seus compostos ativos, com destaque ao óleo essencial (OE) presente na folha. Os OEs extraídos das folhas de Psidium guajava, Psidium cattleyanum e Psidium gaudichaudianum possuem aplicações em larvas de Aedes aegypti, herbicida e citogenotóxica. Para ampliar as aplicações do OE, que é insolúvel em água e facilmente degradado por fatores externos, métodos de proteção podem ser utilizados para formar cápsulas ou complexos de inclusão (CIs). Um oligossacarídeo que pode ser utilizado para complexar o OE é a 2-hidroxipropil-β-ciclodextrina (HPβCD), que é derivada do amido. Para produzir os CIs, os métodos físicos como maceração (KN) e liofilização (FD) podem ser empregados. A fim de comprovar se os CIs foram preparados corretamente, técnicas analíticas podem ser utilizadas, como a espectroscopia na região do UV-Vis, FTIR, TGA, DLS e XRD. Os OEs e CIs de Psidium produzidos podem ser aplicados em larvas de Aedes aegypti, em plantas invasoras como Lolium multiflorum e Bidens pilosa e em células meristemáticas da raiz de Lactuca sativa, sendo verificado a influência na normalidade do ciclo celular. Considerando a importância dos óleos essenciais, dos complexos de inclusão e de suas potenciais aplicações, este capítulo aborda os assuntos mais relevantes numa revisão da literatura sobre esse assunto.

Essential oils are a source of promising bioactive compounds for the development of environmentally friendly herbicides. However, the low solubility, high volatility, and degradability make it impossible to apply essential oils under field conditions. Encapsulation in nanoemulsions and inclusion complexes can overcome these disadvantages by increasing the stability of these products. Recent studies have shown the ability of some protected essential oils to suppress weed development. This chapter reviews the processes of encapsulation and use of these essential oils. Inclusion complexes can be prepared using oligosaccharides such as cyclodextrins by the molecular inclusion method, while nanoemulsions can be obtained through low and high-energy methods. The development of nanoemulsions and inclusion complexes can increase the solubility and physicochemical stability of essential oils, providing stable formulations for use in agricultural fields.

Terpenoids are essential for plant growth, development, defense, and adaptation mechanisms. Psidium cattleyanum (Myrtaceae) is a fleshy fruit tree species endemics from Atlantic Forest, known for its pleasant fragrance and sweet taste, attributed to terpenoids in its leaves and fruits. In this study, we conducted genome-wide identification, evolutionary and expression analyses of the terpene synthase gene (TPS) family in P. cattleyanum red guava (var. cattleyanum), and yellow guava (var. lucidum Hort.) morphotypes. We identified 32 full-length TPS in red guava (RedTPS) and 30 in yellow guava (YlwTPS). We showed different expression patterns of TPS paralogous in the two morphotypes, suggesting the existence of distinct gene regulation mechanisms and their influence on the final essential oil content in both morphotypes. Moreover, the oil profile of red guava was dominated by 1,8-cineole and linalool and yellow guava was enriched in α-pinene, coincident in proportion to TPS-b1 genes, which encode enzymes that produce cyclic monoterpenes, suggesting a lineage-specific subfamily expansion of this family. Finally, we identified amino acid residues near the catalytic center and functional areas under positive selection. Our findings provide valuable insights into the terpene biosynthesis in a Neotropical Myrtaceae species and their potential involvement in adaptation mechanisms.

Diploid and polyploid species derived from the euploid series x = 11 occur in the genus Psidium, as well as intraspecific cytotypes. Euploidy in the genus can alter the gene copy number, resulting in several “omics” variations. We revisited the euploidy, reported genomic (nuclear 2C value, GC%, and copy number of secondary metabolism genes) and epigenomic (5-mC%) differences in Psidium, and related them to essential oil yield and composition. Mean 2C values ranged from 0.90 pg (P. guajava) to 7.40 pg (P. gaudichaudianum). 2C value is intraspecifically varied in P. cattleyanum and P. gaudichaudianum, evidencing cytotypes that can be formed from euploid (non-reduced) and/or aneuploid reproductive cells. GC% ranged from 34.33% (P. guineense) to 48.95% (P. myrtoides), and intraspecific variations occurred even for species without 2C value intraspecific variation. Essential oil yield increased in relation to 2C value and to GC%. We showed that P. guajava (diploid) possesses two and P. guineense (tetraploid) four copies of the one specific TPS gene, as well as eight and sixteen copies respectively of the conserved regions that occur in eight TPS genes. We provide a wide “omics'' characterization of Psidium and show the outcome of the genome and epigenome variation in secondary metabolism.