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Psidium guajava L. (Myrtaceae) leaf contains a wide variety of bioactive compounds that contribute valuable effects on human well-being. This study investigates the influence of guava leaf extract-menthol toner on thermoregulation, including perspiration, skin temperature, and recovery heart rate. This randomised, placebo-controlled clinical trial assessed the effects of the guava leaf extract-menthol toner and placebo with a 1-week washout period. Sixty-four participants were enrolled. The participants exercised on a treadmill until a 75% heart rate reserve was achieved for 5 min, followed by a 5 min post-exercise rest period. The skin temperature and heart rate were then measured before 5 mL of the testing product was sprayed to specific areas of the body, left it for 30 sec before wiped off. Post-exercise perspiration and skin temperatures were collected by sweat patches and measured by the Skin-thermometer ST500, respectively. A 20 min heart rate monitoring period started 10 min after the exercise and measured every 2 min intervals. Use of the toner significantly reduced post-exercise perspiration to approximately half of the baseline and placebo use values (p < 0.05). Furthermore, relative heart rate changes showed no significant differences among the tests (p > 0.05). Skin temperature was also unaffected (p > 0.05). Guava leaf extract-menthol toner reduced perspiration by astringent effects but did not influence heat dissipation and did not affect cardiovascular mechanism compared to the controls. Additional cleaning with guava leaf extract-menthol toner could offer better hygiene after a workout.

Today, there is increasing interest in discovering new bioactive compounds derived from ethnomedicine. Preparations of guava (Psidium guajava L.) leaves have traditionally been used to manage several diseases. The pharmacological research in vitro as well as in vivo has been widely used to demonstrate the potential of the extracts from the leaves for the co-treatment of different ailments with high prevalence worldwide, upholding the traditional medicine in cases such as diabetes mellitus, cardiovascular diseases, cancer, and parasitic infections. Moreover, the biological activity has been attributed to the bioactive composition of the leaves, to some specific phytochemical subclasses, or even to individual compounds. Phenolic compounds in guava leaves have been credited with regulating blood-glucose levels. Thus, the aim of the present review was to compile results from in vitro and in vivo studies carried out with guava leaves over the last decade, relating the effects to their clinical applications in order to focus further research for finding individual bioactive compounds. Some food applications (guava tea and supplementary feed for aquaculture) and some clinical, in vitro, and in vivo outcomes are also included.

Guava (Psidium guajava L.) is a well-known plant containing high levels of natural antioxidants, the phenolic compounds, which have been employed in numerous cosmetic products. However, these molecules are unstable to oxidants, light, temperature, pH, water, and enzymatic activities. Therefore, to enhance their stability and preserve their antioxidant activity, this study investigated the silk fibroin nanoparticles (SFNs) ability to encapsulate, deliver, and heat-protect the phenolic compounds of the guava leaves ethanolic extract. Firstly, the guava ethanolic extract was produced by maceration, which possessed a total phenolic content of 312.6 mg GAE/g DPW and a high antioxidant activity (IC 50 = 5.397 ± 0.618 µg/mL). Then, the extract loaded SFNs were manufactured by desolvation method, and the particles demonstrated appropriate sizes of 200-700 nm with narrow size distribution, spherical shape, silk-II crystalline structure, high drug entrapment efficiency of > 70% (dependent on the fibroin content), and a two-phase sustained drug release for at least 210 min. Using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, the antioxidant activity of the guava extract was well-preserved in the extract loaded SFNs. Finally, after being treated with high temperature of 70 °C for 24 h, the guava extract almost loses all of its antioxidant property (5 times decrement), whereas the extract loaded SFNs could retain the extract activity. Conclusively, the SFNs proved much potential to deliver and heat-protect the guava extract phenolic compounds, and preserve their antioxidant activity. Confirmed by this case, SFNs could be further explored in protecting other natural compounds from environmental factors.

Plants are extensively used in traditional medicine, and several plant antimicrobial peptides have been described as potential alternatives to conventional antibiotics. However, after more than four decades of research no plant antimicrobial peptide is currently used for treating bacterial infections, due to their length, post-translational modifications or  high dose requirement for a therapeutic effect . Here we report the design of antimicrobial peptides derived from a guava glycine-rich peptide using a genetic algorithm. This approach yields guavanin peptides, arginine-rich α-helical peptides that possess an unusual hydrophobic counterpart mainly composed of tyrosine residues. Guavanin 2 is characterized as a prototype peptide in terms of structure and activity. Nuclear magnetic resonance analysis indicates that the peptide adopts an α-helical structure in hydrophobic environments. Guavanin 2 is bactericidal at low concentrations, causing membrane disruption and triggering hyperpolarization. This computational approach for the exploration of natural products could be used to design effective peptide antibiotics. Antimicrobial peptides are considered promising alternatives to antibiotics. Here the authors developed a computational algorithm that starts with peptides naturally occurring in plants and optimizes this starting material to yield new variants which are highly distinct from the parent peptide.

Psidium (Myrtaceae) comprises approximately 266 species, distributed in tropical and subtropical regions of the world. Psidium taxa have great ecological, economic, and medicinal relevance due to their essential oils’ chemical diversity and biological potential. This review reports 18 Psidium species growing around the world and the chemical and biological properties of their essential oils. Chemically, 110 oil records are reported with significant variability of volatile constituents, according to their seasonality and collection sites. Monoterpenes and sesquiterpenes with acyclic (C10 and C15), p-menthane, pinane, bisabolane, germacrane, caryophyllane, cadinane, and aromadendrane skeleton-types, were the primary constituents. The essential oils showed various biological activities, including antioxidant, antifungal, antibacterial, phytotoxic, larvicidal, anti-inflammatory, and cytotoxic properties. This review contributes to the Psidium species rational and economic exploration as natural sources to produce new drugs.

Background Guava ( Psidium guajava L.) is a major pantropical fruit crop, valued for its nutritional composition, wider adaptability, and economic significance. Since its introduction in India during the 17 th century, guava cultivars have exhibited a narrow genetic base, with most existing genotypes arising from open-pollinated selections or crosses involving a limited number of genotypes. Furthermore, much of the available germplasm has been named based on fruit characteristics or place/regions of origin, leading to confusion in classification and hindering the precise identification and utilization of genetic resources in guava breeding programs. To address this, 49 morpho-biochemical parameters were assessed in 51 diverse Psidium genotypes, including cultivars, varieties, hybrids, related wild species, and exotic/USDA introductions. Results Substantial variability was observed among globally collected guava germplasm for fruit traits, with fruit weight ranging from 11.67 g ( Psidium molle ) to 379 g (S. N90-53), seed number from 8 (S. N11-3) to 512 (S. N15-3), leaf length from 5.57 to 17.17 cm, leaf width from 2.07 to 7.90 cm, and petiole length from 0.17 to 0.77 cm. Germplasm also differed in qualitative descriptors, including branch orientation, bark colour, leaf morphology, tip structure, and fruit surface traits, with wild species forming distinct morphological groups. Additionally, biochemical traits varied widely, including the contents of total soluble solid (6.8–13.8 °Brix), acidity (0.25–1.60%), total sugars (3.62–9.21 g/100 g FW), ascorbic acid (88.36–302.46 mg/100 g FW), ferric reducing antioxidants power (7.74–20.69 µM TE/g FW), free radical scavenging activity (2,2-diphenyl-1-picrylhydrazyl assay)(85.72–98.47%), lycopene (0.05–8.91 mg/100 g FW), and total carotenoids (0.05–2.76 mg/100 g FW). Besides, principal component analysis indicated PC1 (22.1%) related to fruit size and PC2 (15.2%) to biochemical traits. Furthermore, cluster analysis grouped 51 guava genotypes into three clusters, distinguishing wild from cultivated types. Conclusions The study confirms the presence of wide morpho-biochemical variability in Psidium germplasm, offering valuable genetic resources for genetic improvement programs, aimed at enhanced fruit quality with rich antioxidants, bio-fortification, and the tailoring of novel guava genotypes with reduced seed content, enhanced seed mellowness, and tenet branching, fitting in high-density planting and improved yield efficiency. Graphical Abstract

The use of allelopathic compounds is an alternative for weeds control, since they present low toxicity when compared with the synthetic herbicides, that may cause several damages, as the contamination of the environment. Our objective was to determine the chemical composition and allelopathic properties of the essential oils of Psidium cattleianum , P. myrtoides , P. friedrichsthalianum , and P. gaudichaudianum on the germination and root growth of Lactuca sativa and Sorghum bicolor , and to evaluate their action on the cell cycle of root meristematic cells of L. sativa. The main compound found in all the studied species was (E)-caryophyllene ( P. cattleianum —23.4 %; P. myrtoides —19.3%; P. friedrichsthalianum —24.6% and P. gaudichaudianum —17.0%). The different essential oils were tested at different concentrations on L. sativa and S. bicolor , reducing germination, germination speed index, and root and shoot growth of lettuce and sorghum seedlings. The cytotoxicity and aneugenic potential of these oils were evidenced by the reduction of the mitotic index and increase of the frequency of chromosomal alterations in L. sativa . The essential oils of the species of Psidium studied have potential to be used in weeds control.

Despite their effectiveness, synthetic preservatives are often associated with adverse health effects, which has led to growing interest in natural alternatives. This study evaluated the antimicrobial activity of an ethanolic extract of Psidium guajava L. leaves incorporated into a shampoo formulation. The ethanolic extract of Psidium guajava L. leaves was tested at concentrations of 0.5%, 2.5%, 5%, 7.5%, and 10% (w/w) under accelerated conditions for three months. Phytochemical screening and HPLC analysis were conducted to identify key bioactive compounds (including phenols, flavonoids, and terpenoids), antimicrobial efficacy testing, and stability testing (such as pH, viscosity, density, and color) were evaluated. At concentration 10%, extract completely inhibited microbial growth over a 28-day period, in comparison with chemical preservatives. Stability testing conducting at accelerated temperatures (40 °C/75% RH) for three months confirmed the physical stability of the formulation and the chemical integrity of ketoconazole. Preservative efficacy tests, performed accordance with USP/BP guidelines against Escherichia coli , Pseudomonas aeruginosa , Staphylococcus aureus , Candida albicans , and Aspergillus brasiliensis , demonstrated that the extract reduced microbial counts beyond USP/BP acceptance criteria, achieving total inhibition of all strains within 28 days. Chemical and biological tests confirmed formulation stability and efficacy over a three-months period. The findings suggest that P. guajava L. extract is a promising natural preservative; however, further studies are needed to assess its long-term stability.

This study investigates the phytochemical, genetic, and antioxidant properties of Psidium guineense , a species native to the tropical dry forests of Ecuador. Leaves were collected, preserved in recognized herbaria, and subjected to Soxhlet extraction using polar and non-polar solvents. Phytochemical screening revealed the presence of secondary metabolites, while GC-MS analysis detected chemical compounds in the extracts. Antioxidant assays demonstrated high phenolic (54.34 ± 0.49 mg GAE/g) and flavonoid (6.43 ± 0.38 mg QE/g) content, with significant antioxidant activity in DPPH (0.57 ± 0.04 mg TE/g), FRAP (105.52 ± 6.85), and ABTS (1.25 ± 0.01 mg TE/g) assays. DNA barcoding of nine loci, (seven from the chloroplast genome and two nuclear genome) using a CTAB extraction protocol and PCR, provides the first genetic characterization of this species, contributing to genetic diversity assessments and phylogenetic studies. These findings underscore the importance of P. guineense as a source of potent bioactive compounds with significant antioxidant potential, highlighting its applicability in nutritional and pharmaceutical industries. Additionally, the genetic insights gained support efforts to expand DNA barcoding databases for tropical biodiversity conservation.

The characteristics of bioactive compounds from guava (Psidium guajava L.) leaf extract, their biological activity, and their technological applications are critical topics in many engineering fields. Guava leaf extract is rich in bioactive compounds, including phenolic acids, flavonoids, tannins, terpenes, alkaloids, etc. Bioactive compounds from guava leaf exhibit notable synergistic effects in enzyme inhibition, as well as antimicrobial and anti-inflammatory activities. Natural bioactive compounds are complicated due to their sensitivity and instability during storage, but their use is promising. Thus, for bioactive compound protection, advanced techniques such as the encapsulation, microemulsion, and nanosuspension of such natural bioactive compounds can be a promising approach. These methods are particularly important for the development of natural preservatives serving as additive agents, which have significant industrial relevance. However, sufficient scientific evidence is required to make a health claim on and to promote the functional benefits of guava leaf extract. This review focuses on recent research into guava leaf extract and its technical roles. Demonstrations of the chemical structure of bioactive compounds are addressed, besides discussing their analytical methods, nutritional bioavailability, biological activity, and synergy effects. Furthermore, this review study considers the methods used to protect the active compounds and technological applications in food, pharmaceuticals, and cosmetic products.