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Cell and sub‐cellular anatomical adjustments are adaptations utilized by plants to tolerate abiotic stress. Both melatonin and Morinda lucida‐silver nanoparticles (ML‐AgNPs) are recognized as bio‐stimulants. The study examined the morphological changes and adaptive characteristics of these bio‐stimulants under water‐stress Eugenia uniflora. Twenty‐four hours was spent priming the seeds with melatonin (0.06 mg/L), ML‐AgNPs (0.06 mg/L), and a mixture (1:1) of the two. The seeds were sown and subjected to water stress for 7 days. The leaves, stems, and roots of water‐stressed E. uniflora were sectioned, dried, and examined using a microscope. Drought stress led to the production of non‐glandular trichomes on the abaxial and the transformation of paracytic stomata into diacytic stomata. During water stress, melatonin enlarges intercellular gaps and stomata, increases sponge and palisade parenchyma, and thickens epidermis (stem and root) and fibers. The ML‐AgNPs diminished the size of mesophyll, intercellular gaps, stomata, and stem fiber. The ML‐AgNPs increased the size of bulliform cells and activated the mechanical resistance features of sclerophyllous leaves (thick‐celled epidermis and sclerieds) and ray parenchyma (root and stem). Equally, Melatonin and ML‐AgNPs increased stem and root anatomical characteristics (xylem, bark, pith, cortex, epidermis, and vascular bundles). Stomata of E. uniflora are susceptible to alterations and undergo cell division into two new stomata (stomatogensis) in response to varying conditions (melatonin and ML‐AgNPs). Melatonin adopted a strategy for maintaining a high plant water status, possibly by osmoregulation, whereas E. uniflora primed with ML‐AgNPs survived by minimizing transpirational water loss through morphological changes. [ABSTRACT FROM AUTHOR]

This study analysed extracts obtained from the leaves of Eugenia uniflora , E. involucrata , and E. myrcianthes to determine their chemical composition, antioxidative properties, and α-glucosidase inhibitory capacity. By using liquid chromatography with a diode array detector, we identified chlorogenic acids, flavonoids, tannins, proanthocyanidins, saponins, and triterpenes in the extracts. The antioxidant activities of the extracts were found to be directly related to their total phenolic, flavonoid content and enzyme inhibition. The E. uniflora aqueous extract showed significant inhibition of α-glucosidase (IC 50 0.98 µg mL -1 ), indicating its potential as a non-competitive inhibitor for managing Diabetes Mellitus. This study contributes to the existing knowledge on the chemical and biological aspects of Eugenia genus.

Abstract To the moment, there is no ideal substance for home-based denture disinfection. This study assessed in vitro the antimicrobial effect of the hydroalcoholic extract of Eugenia uniflora and the effect on the physical properties of denture polymethylmethacrylate (PMMA). Candida albicans, Staphylococcus aureus, and Klebsiella oxytoca were isolated from samples of saliva collected from denture wearers. The extracts were produced in three concentrations, according to the Brazilian Pharmacopeia. One hundred eighty-eight disc-shaped specimens of thermopolymerizable PMMA were prepared and randomly allocated to five treatment groups: sterile saline solution (0.85%; control); chlorhexidine digluconate (0.2%); and hydroalcoholic extract of E. uniflora (0.2%, 0.8%, and 1.16%). The specimens were disinfected for 8 hours/day for 30 days. Adherence of microorganisms to the surface, PMMA surface roughness, and color stability were assessed. Inferential statistics were performed with one- and two-way ANOVA/Tukey test, and Kruskal Wallis, Mann-Whitney U, and paired t-tests, at α=0.05. The extract of E. uniflora at 0.2% and 1.16% reduced the microbial load of K. oxytoca, while chlorhexidine digluconate significantly reduced microbial load of all microrganisms. Microbial adherence at day 10 was reduced by all experimental substances (p0.05). Nevertheless, all experimental groups produced unacceptable color change at the end of the disinfection protocol (p