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.

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.

Natural products with biological activity, such as essential oils, can be used in the search for and development of ecological herbicides as an alternative to reduce the damage caused by synthetic herbicides. This work to aimed to determine the chemical composition and phytotoxic properties of the essential oils, at concentrations of 3000, 1500, 750, 375 and 187.5 µg/mL, of four cultivars of Psidium guajava (guava) evaluated on germination and root growth of plant models Lactuca sativa and Sorghum bicolor, as well as in the L. sativa cell cycle. Exposure to essential oils reduced germination and root growth in bioassays, especially at the highest concentration (3000 µg/mL). The essential oils interfered in the normal dynamics of the cell cycle of L. sativa at most concentrations, causing a decrease in the mitotic index and increasing of chromosomal alterations, evidencing aneugenic and clastogenic action. The biological activity of the oils was associated with the presence of sesquiterpenes and monoterpenes found here, such as caryophyllene oxide, (E) -caryophyllene, and limonene. Thus, the essential oils of cultivars of guava demonstrated the promising potential for use as natural herbicides.

Essential oils offer a viable alternative to traditional agrochemicals, mitigating problems such as environmental contamination and weed resistance. However, application faces challenges such as low solubility in water and rapid environmental degradation. To overcome these limitations, nanoemulsions containing essential oils from Piper amalago L. and Piper dilatatum Rich were formulated using ultrasonic homogenization. These nanoemulsions were investigated for their herbicidal properties through phytotoxic and cytogenotoxic activity assays using weed plants Bidens pilosa L. and Lolium multiflorum Lam., and model plant Lactuca sativa L. The results indicated that the nanoemulsions presented nanometric-sized droplets (~ 10 nm), PDI close to 0, and greater thermal stability compared to essential oils. The nanoemulsions exerted an inhibitory effect on germination and growth of plants studied, possibly due to cytogenotoxic and mutagenic damages observed. Furthermore, content of photosynthetic pigments was affected, indicating oxidative damage and changes in chlorophyll metabolism.

Synthetic insecticides are widely used against mosquitoes, but misuse has led to environmental and health concerns. Plant-derived alternatives, such as essential oils, seem to offer a safer option, minimizing these problems without compromising efficacy. In this study, we evaluated the essential oil from Siparuna gesnerioides (Kunth) A.DC., a Neotropical plant, for its effectiveness in controlling Aedes (Stegomyia) aegypti (Linnaeus) larvae, a major vector of human diseases. We first assessed the phytochemistry of the essential oil and used in silico approaches to predict potential physiological targets of its larvicidal activities. Selectivity assays were conducted with Belostoma anurum (Herrich-Schäffer), a non-target predatory water bug. The major constituents of S. gesnerioides essential oil were γ-elemene (45.8%) and germacrene D (43.8%). This essential oil effectively killed larvae from both susceptible and resistant mosquito strains (LC50 = 0.070 μg/mL). However, such concentrations killed more than 80% of B. anurum nymphs. Molecular modeling suggested that the essential oil major components (γ-elemene and germacrene D) interact stably with mosquito acetylcholinesterases (AChEs), indicating a potential mechanism of action. Our results reinforce the potential of Siparuna essential oils in mosquito control. Nevertheless, the non-selective impact on mosquito predators, as seen with S. gesnerioides, highlights the need for caution in field applications.

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.