Use of Proline to Induce Salt Stress Tolerance in Guava.

Guava is a fruit tree with high potential in the semi-arid region of northeast Brazil. However, qualitative and quantitative water scarcity is a limiting factor for the expansion of irrigated agriculture. Thus, it is necessary to use techniques to mitigate the effects of salt stress, such as foliar application of proline. The objective of this study was to evaluate the effect of foliar application of proline as a mitigator of salt stress effects on the morphophysiology of guava cv. Paluma. The experiment was carried out under field conditions at the 'Rolando Enrique Rivas Castellón' Experimental Farm in São Domingos, PB, Brazil, using a randomized block design in a 5 × 4 factorial scheme referring to five levels of electrical conductivity of irrigation water, ECw (0.8, 1.5, 2.2, 2.9, and 3.5 dS m-1) and four concentrations of proline (0, 8, 16, and 24 mM). Salinity above 0.8 dS m-1 compromised gas exchange, photosynthetic pigment synthesis, photochemical efficiency, and growth of guava plants at 360 days after transplanting. Foliar application of proline at a concentration of 24 mM mitigated the effect of salt stress on the relative water content, stomatal conductance, and carotenoid contents in plants irrigated with 3.6 dS m-1 water. Meanwhile, a proline concentration of up to 18 mM resulted in higher transpiration, CO2 assimilation rate, instantaneous carboxylation efficiency, and absolute growth rate in stem diameter under ECw of 0.8 dS m-1. Proline concentration of up to 24 mM increased the biosynthesis of photosynthetic pigments and the relative growth rate in stem diameter of guava in the period from 190 to 360 days after transplanting.

Can Storage Stability and Simulated Gastrointestinal Behavior Change the Cytotoxic Effects of Concentrated Guava Leaves Extract against Human Lung Cancer Cells?

The influence of storage stability and simulated gastrointestinal behavior of different extracts of guava leaves extracts (NC: not concentrated, and C10 and C20: concentrated by nanofiltration) was evaluated based on their total phenolic compound (TPC) contents and antioxidant activity as well as on their cytotoxic effects on A549 and Vero cells. The results showed that C10 and C20 presented high stability for 125 days probably due to their high TPC contents and antioxidant activity. The simulated gastrointestinal behavior modified their TPC contents; however, after all digestion steps, the TPC values were higher than 70%, which means that they were still available to exert their bioactivities. Additionally, the cytotoxic effects of these extracts were evaluated before and after the simulated gastrointestinal behavior or under different storage conditions. C10 presented the best selectivity indices (SI) values (IC50 Vero cells/IC50 A549 cells) at both conditions suggesting that it can be considered a potential extract to be developed as a functional food due to its resistance to the gastrointestinal digestion and storage conditions tested.

Antidiarrheal effect of Psidium guajava L. extract in acute diarrhea: a systematic review.

Acute diarrheal diseases are a leading cause of childhood mortality and morbidity worldwide. Psidium guajava has been globally used for its antidiarrheal potential. We conducted a systematic review of scientific articles published up to the year 2021, which included in vivo pre-clinical tests and clinical trials involving patients with acute infectious diarrhea to verify the antidiarrheal, antibacterial and antispasmodic effects of galenic preparations or phytopharmaceuticals from P. guajava. PRISMA and Rayyan were used as tools for the selection of studies collected in four databases (Pubmed, Scopus, Web of Science and Science Direct). The keywords used to carry out the search were: 'Psidium guajava', 'guava', 'antidiarrhe*' and 'diarrhe*', joined by Boolean operators 'OR' or 'AND'. The characteristics of studies in animal models of acute diarrhea induction, as well as in vivo and in vitro motility and microbiological tests linked with its main pathophysiological mechanisms, were collected. Twenty-three articles were included. Twenty (87%) of these reported heterogenic preclinical studies, predominating pharmacological studies of efficacy against conventional antidiarrheal agents, which utilized relevant outcomes and models of infectious diarrhea from the top pathogens in the clinic along with classical castor oil-induced diarrhea associated with motility tests. Only three articles (13%) corresponded to clinical trials investigating the efficacy, dose and safety of these preparations. Most studies reported positive results and significant mechanistic evidence from antibacterial, anti-motility, anti-secretory and protective/anti-inflammatory perspectives. However, further studies are needed to define the clinical significance and safety treatment with P. guajava extracts. © 2024 Society of Chemical Industry.

Investigating the impact of Psidium guajava leaf hydroalcoholic extract in improving glutamatergic toxicity-induced oxidative stress in Danio rerio larvae.

Glutamate is one of the predominant excitatory neurotransmitters released from the central nervous system; however, at high concentrations, this substance may induce excitotoxicity. This phenomenon is involved in numerous neuropathologies. At present, clinically available pharmacotherapeutic agents to counteract glutamatergic excitotoxicity are not completely effective; therefore, research to develop novel compounds is necessary. In this study, the main objective was to determine the pharmacotherapeutic potential of the hydroalcoholic extract of Psidium guajava (PG) in a model of oxidative stress-induced by exposure to glutamate utilizing Danio rerio larvae (zebrafish) as a model. Data showed that treatment with glutamate produced a significant increase in oxidative stress, chromatin damage, apoptosis, and locomotor dysfunction. All these effects were attenuated by pre-treatment with the classical antioxidant N-acetylcysteine (NAC). Treatment with PG inhibited oxidative stress responsible for cellular damage induced by glutamate. However, exposure to PG failed to prevent glutamate-initiated locomotor damage. Our findings suggest that under conditions of oxidative stress, PG can be considered as a promising candidate for treatment of glutamatergic excitotoxicity and consequent neurodegenerative diseases.

Guava fibre characterization and effects on digestibility, fermentation products, gastrointestinal transit time and palatability of dry diets for dogs.

The use of fruit fibres as a way of reusing industrial waste is attractive and necessary, increasing the efficiency and reducing the environmental impact of the industry. This study characterized guava fibre as a fibrous ingredient and evaluated its effects when included in extruded diets for dogs on nutrient digestibility, faecal traits, fermentation products, gastrointestinal transit time and palatability. Four diets were formulated: CO (control diet, no fibrous ingredients added), GF3 (3% guava fibre), GF6 (6% guava fibre) and GF12 (12% guava fibre). The guava fibre was added to diets in replacement of maize, with small adjustments in the other ingredients to ensure similar contents of protein and fat. The diets were fed to 24 adult Beagle dogs (6 per diet) during 15 days for adaptation followed by 15 days for assessment of digestibility, fermentation end products and gastrointestinal transit time. The palatability of G6 and G12 treatments was evaluated against the CO by the two-pan test. Results were compared by analysis of variance and polynomial contrasts according to the guava fibre inclusion level (p < 0.05). The addition of guava fibre did not change nutrient intake except for the increase on dietary fibre (p < 0.001). Fibre inclusion resulted in a quadratic reduction in total tract apparent digestibility for dry matter, organic matter, crude protein and crude energy (p < 0.001), and on the metabolizable energy content of the foods (p < 0.001). Guava fibre addition did not change the faecal concentration of ammonia, lactic acid, faecal pH and branched chain fatty acids but it decreased acetic and propionic acids concentration (p < 0.01). The inclusion of 12% guava fibre did result in a faster transit time (p = 0.046) compared to the control diet. Guava fibre can be characterized as a novel insoluble non-fermentable fibre source that could be safely used in levels up to 12% in canine extruded diets.

Maltodextrin as a Drying Adjuvant in the Lyophilization of Tropical Red Fruit Blend.

Guava, pitanga and acerola are known for their vitamin content and high levels of bioactive compounds. Thus, the preparation of combinations of these fruits comprises a blend with high nutraceutical potential, yielding a strong and attractive pigmentation material. In this study, the influence of different proportions of maltodextrin on the lyophilization of a blend of guava, acerola and pitanga was evaluated considering not only the physicochemical, physical and colorimetric parameters but also the bioactive compounds in the obtained powders. The blend was formulated from the mixture and homogenization of the three pulps in a ratio of 1:1:1 (m/m), then maltodextrin was added to the blend, resulting in four formulations: blend without adjuvant (BL0), and the others containing 10% (BL10), 20% (BL20) and 30% (BL30) maltodextrin. The formulations were lyophilized and disintegrated to obtain powders. The powders were characterized in terms of water content, water activity, pH, total titratable acidity, ash, total and reducing sugars, ascorbic acid, total phenolic content, flavonoids, anthocyanins, carotenoids, lycopene, color parameters, Hausner factor, Carr index, angle of repose, solubility, wettability and porosity. All evaluated powders showed high levels of bioactive compounds and the increase in maltodextrin concentration promoted positive effects, such as reductions in water content, water activity and porosity and improved flow, cohesiveness and solubility characteristics.

Tropical Red Fruit Blend Foam Mat Drying: Effect of Combination of Additives and Drying Temperatures.

Foam mat drying is a widely used technique for liquid products because it has a number of advantages; however, for an efficient process, the choice of additives and temperatures is extremely important. The objective of this study was to evaluate the effect of additives and drying temperatures on the powders obtained from the blend of tropical red fruits, such as acerola, guava, and pitanga. The foam formulations were prepared by mixing the pulps of the three fruits in equal proportions (1:1:1), all added with 6% albumin and 1% stabilizing agent: E1, gum Arabic; E2, guar gum; E3, gelatin. The combinations were subjected to beating, and subsequently, they were dried in an oven with forced air circulation at four temperatures (50 to 80 °C), with a mat thickness of 0.5 cm. The obtained powders showed low levels of water and water activity and high levels of bioactive compounds, colors with a predominance of yellow, intermediate cohesiveness, poor fluidity, and solubility above 50%. The best temperature for obtaining the powders was 60 °C. The formulation that produced the best results for the production of the tropical red fruit blend powder was the combination of albumin and gelatin.

Antimicrobial Activity of Psidium guajava Aqueous Extract against Sensitive and Resistant Bacterial Strains.

The inappropriate use of antimicrobials, along with environmental conditions, can lead to the emergence of resistant microorganisms. The use of phytopharmaceuticals and herbal medicines has a positive impact and represents a promising alternative. Psidium guajava extracts have been widely reported to have antimicrobial potential; however, studies reporting their activity against resistant bacterial strains are scarce. Because of the emerging resistance, the aim of this study was to analyze the antimicrobial capacity of the aqueous extract of guava leaves against wild-type and resistant bacterial strains. The aqueous extract obtained from the leaves of P. guajava was evaluated by HPLC for the content of total phenolics and tannins, antioxidant activity, and chemical composition. The antimicrobial activity of the extracts was analyzed by the disk diffusion and broth microdilution methods. The results of the chemical analysis of the extracts showed total phenolics content of 17.02 ± 6.87 mg/g of dry extract, total tannin content of 14.09 ± 1.20 mg of tannic acid equivalents/g of dry extract, and moderate antioxidant capacity with an EC50 value of 140 µg/mL. Flavonoids are the major compounds (rutin, hesperidin, and quercetin), followed by phenolic acids. Disk diffusion test results showed the presence of inhibition halos for Gram-positive bacteria (Staphylococcus aureus, sensitive and resistant; Staphylococcus pseudintermedius, sensitive and resistant; and Streptococcus spp., beta-hemolytic), while for Gram-negative bacteria (Escherichia coli, sensitive and resistant), there was no inhibition in the tested concentration range. The Minimal Inhibitory Concentration was 6.8 mg/mL for all Gram-positive strains evaluated. The present study demonstrated the antimicrobial activity of the aqueous extract of P. guajava against sensitive and resistant Gram-positive bacteria. The better antimicrobial activity found in the present study compared with previously reported activity should be highlighted and may be related to the higher concentration of total phenolics present in the tested extract. Moreover, the content of tannins found suggests a species with high quality that produces tannins. These new findings suggest an innovative profile regarding therapeutic resources that can be adopted to combat resistant microbial strains.

Physicochemical Aspects, Bioactive Compounds, Phenolic Profile and In Vitro Antioxidant Activity of Tropical Red Fruits and Their Blend.

The combination of fruit pulps from different species, in addition to multiplying the offer of flavors, aromas and textures, favors the nutritional spectrum and the diversity of bioactive principles. The objective was to evaluate and compare the physicochemical characteristics, bioactive compounds, profile of phenolic compounds and in vitro antioxidant activity of pulps of three species of tropical red fruits (acerola, guava and pitanga) and of the blend produced from the combination. The pulps showed significant values of bioactive compounds, with emphasis on acerola, which had the highest levels in all parameters, except for lycopene, with the highest content in pitanga pulp. Nineteen phenolic compounds were identified, being phenolic acids, flavanols, anthocyanin and stilbene; of these, eighteen were quantified in acerola, nine in guava, twelve in pitanga and fourteen in the blend. The blend combined positive characteristics conferred by the individual pulps, with low pH favorable for conservation, high levels of total soluble solids and sugars, greater diversity of phenolic compounds and antioxidant activity close to that of acerola pulp. Pearson's correlation between antioxidant activity and ascorbic acid content, total phenolic compounds, flavonoids, anthocyanins and carotenoids for the samples were positive, indicating their use as a source of bioactive compounds.

Lycopene from Red Guava (Psidium guajava L.): From Hepatoprotective Effect to Its Use as Promising Self-Emulsifying Drug Delivery System for Anti-Inflammatory and Antioxidant Applications.

Lycopene is a carotenoid with potential use in the treatment of chronic illnesses. Here, different formulations of lycopene were studied: lycopene-rich extract from red guava (LEG), purified lycopene from red guava (LPG) and a self-emulsifying drug delivery system loaded with LPG (nanoLPG). The effects of administering orally various doses of LEG to hypercholesterolemic hamsters were evaluated regarding the liver function of the animals. The cytotoxicity of LPG in Vero cells was analyzed by a crystal violet assay and by fluorescence microscopy. In addition, nanoLPG was employed in stability tests. LPG and nanoLPG were tested for their cytotoxic effect on human keratinocytes and antioxidant capacity on cells in an endothelial dysfunction model in an isolated rat aorta. Finally, the effect of different nanoLPG concentrations on the expression of immune-related genes (IL-10, TNF-α, COX-2 and IFN-γ) from peripheral blood mononuclear cells (PBMC) using real-time PCR was also analyzed. Results suggest that LEG, despite not being able to improve blood markers indicative of liver function in hypercholesterolemic hamsters, reduced hepatic degenerative changes. Additionally, LPG did not show cytotoxicity in Vero cells. In relation to nanoLPG, the effects produced by heat stress evaluated by Dynamics Light Scattering (DLS) and visually were loss of color, texture change and phase separation after 15 days without interfering with the droplet size, so the formulation proved to be efficient in stabilizing the encapsulated lycopene. Although LPG and nanoLPG showed moderate toxicity to keratinocytes, which may be related to cell lineage characteristics, both revealed potent antioxidant activity. LPG and nanoLPG showed vasoprotective effects in aortic preparations. The gene expression assay indicates that, although no significant differences were observed in the expression of IL-10 and TNF-α, the PBMCs treated with nanoLPG showed a reduction in transcriptional levels of IFN-γ and an increased expression of COX-2. Thus, the work adds evidence to the safety of the use of lycopene by humans and shows that tested formulations, mainly nanoLPG due to its stability, stand out as promising and biosafe products for the treatment of diseases that have oxidative stress and inflammation in their etiopathology.

Hydrogen peroxide in the induction of tolerance of guava seedlings to salt stress / Peróxido de hidrogênio na indução de tolerância de mudas de goiabeira ao estresse salino

Guava cultivation plays a significant role in the socioeconomic development of the Brazilian semi-arid region, contributing to employment opportunities and income generation. However, this region often faces the challenge of high levels of dissolved salts in water sources, necessitating strategies to mitigate the adverse effects of salt stress on plants. This study aimed to assess the impact of foliar application of hydrogen peroxide on gas exchange, photochemical efficiency, growth, and quality of guava seedlings subjected to salt stress. The experiment was conducted under greenhouse conditions in Pombal - PB, Brazil, following a randomized block design. The treatments comprised a 5 × 4 factorial arrangement, representing five levels of electrical conductivity in the irrigation water (ECw: 0.3, 1.3, 2.3, 3.3, and 4.3 dS m-1) and four concentrations of hydrogen peroxide (H2O2: 0, 25, 50, and 75 µM). Each treatment was replicated four times, with two plants per plot. Irrigation with water having an electrical conductivity of 0.3 dS m-1 significantly inhibited gas exchange, photochemical efficiency, and growth of guava seedlings after 91 days of emergence. Foliar application of hydrogen peroxide at concentrations up to 75 µM did not alleviate the effects of salt stress during the seedling formation phase of guava plants. Guava cv. Paluma was found to be sensitive to water salinity during the seedling formation phase, with a threshold level of 0.3 dS m-1 and a decrease in the growth rate of 11.48% per unit increase in salinity.(AU)

A goiabeira é uma cultura importante no cenário socioeconômico da região semiárida brasileira, sendo uma fonte de geração de emprego e renda. Contudo, nesta região é comum a ocorrência de fontes hídricas com altos teores de sais dissolvidos e assim são necessárias estratégias que visem minimizar os efeitos deletérios do estresse salino nas plantas. Neste contexto, objetivou-se com este trabalho avaliar os efeitos da aplicação foliar com peróxido de hidrogênio nas trocas gasosas, eficiência fotoquímica, crescimento e qualidade de mudas de goiabeira sob estresse salino. O experimento foi conduzido sob condições de casa de vegetação em Pombal, Paraíba, utilizando-se o delineamento de blocos casualizados, com tratamentos arranjados em esquema fatorial 5 × 4, referentes a cinco níveis de condutividade elétrica da água - CEa (0,3; 1,3; 2,3; 3,3 e 4,3 dS m-1) e quatro concentrações de peróxido de hidrogênio ­ H2O2 (0, 25, 50 e 75 µM) com quatro repetições e duas plantas por parcela. A irrigação com água de condutividade elétrica a partir de 0,3 dS m-1 inibiu as trocas gasosas, eficiência fotoquímica e crescimento de mudas de goiabeira, aos 91 dias após a emergência. A aplicação foliar de peróxido de hidrogênio em concentrações de até 75 µM não amenizou os efeitos do estresse salino em plantas de goiabeira na fase de formação de mudas. A goiabeira cv. Paluma é classificada como sensível a salinidade da água na fase de formação de mudas, sendo o nível limiar de 0,3 dS m-1 e diminuição por aumento unitário de 11,48%.(AU)

Self-Emulsifying Micellization of Crude Extracts from Apple (Malus domestica cv. Anna), Plum (Prunus domestica cv. Satsuma), and Guava (Psidium guajava L.) Fruits.

Micellar microemulsions are thermodynamically stable self-emulsifying systems that have been used to successfully improve the low oral bioavailability of several bioactive phytochemicals, such as antioxidant polyphenols. However, most studies have reported the micellization of single-compounds or purified chemical fractions; thus, the stability, phytochemical-loading efficiency, and bioactivity of complex crude extracts remain largely unexplored. In this study, we evaluated the effects of micellar emulsification of tropical apple (Malus domestica cv. Anna), plum (Prunus domestica cv. Satsuma), and guava (Psidium guajava L.) extracts regarding particle size and stability, polyphenol-loading efficiency, antioxidant capacity, and cytotoxic activity in human and murine cells. Simple food-grade extraction protocols were implemented to obtain apple, plum, and guava extracts. Total polyphenols, flavonoids, and antioxidant activity (DPPH) were determined in the fruit extracts, and their polyphenol profile was further characterized by liquid chromatography (HPLC-DAD). The dried extracts were mixed into a food-grade, self-emulsifying system, and their cytotoxicity in human and murine cell lines was compared. Our research showed that complex fruit matrixes were successfully emulsified into thermodynamically stable polysorbate-based nanometric micelles with uniform size distribution and consistent pH stability, with potential applications in food and biomedical industries.

Repeatability estimates in longitudinal data on guava trees

The use of longitudinal measurements is an essential practice both in Psidium guajava L. breeding and in other perennial crops in which covariance structures can be introduced to explain the form of dependence between measurements. Hence, this study aimed to analyze six covariance structures to identify one that best described the correlation between the repeated measurements in time in traits of guava full-sib families. The repeatability coefficient for each trait was estimated and the minimum number of evaluations required for estimates representing the population was determined. The work was performed based on average data of three yield-related variables from nine harvests of a guava tree population evaluated from 2011 to 2018. The best model was chosen based on the Akaike and Schwarz Bayesian information criterion. The autoregressive covariance structure best represented the dependencies among families between crops for all traits. The number of variables of fruits and total yield per plant presented repeatability estimates higher than 0.5 and may be essential traits for indirect selection of others, such as fruit mass, which had an estimated repeatability of 0.24, proving low regularity in the repetition of the character from one cycle to another. It was also possible to define four harvests as the minimum acceptable number of observations necessary on the same individual for these traits; therefore, the repetitions represented the individuals.(AU)

Mineral composition and production of guava under salt stress and salicylic acid / Composição mineral e produção de goiabeira sob estresse salino e ácido salicílico

The limitation in the quality of water sources for irrigation in the semi-arid region of northeastern Brazil is increasingly present, so it is necessary to use water with high concentrations of salts for agricultural production, which makes the use of elicitors essential to mitigate the harmful effects of salinity on plants. Given the above, the objective of this study was to evaluate the effects of foliar application of salicylic acid on the mineral composition and production of guava plants under salt stress conditions in the post-grafting phase. The experiment was carried out under greenhouse conditions, in a randomized block design, in a 2 × 4 factorial scheme, with two levels of electrical conductivity of irrigation water (0.6 and 3.2 dS m-1) and four concentrations of salicylic acid (0, 1.2, 2.4, and 3.6 mM), with three replicates. During the flowering stage of guava, N, P, and K contents accumulated in the leaves according to the following order of concentration: N > K > P. Foliar application of 1.2 mM of salicylic acid increases the leaf contents of N, P, and K in guava plants grown under irrigation with water of 0.6 dS m-1. Water salinity of 3.2 dS m-1 reduces the growth and production components of guava plants.

A limitação na qualidade das fontes hídricas para irrigação na região semiárida do Nordeste é cada vez mais presente, tornando-se necessário o uso de águas com altas concentrações de sais para produção agrícola, o que torna indispensável à utilização de elicitores para atenuar os efeitos deletérios da salinidade sobre as plantas. Diante do exposto, objetivou-se com esse trabalho avaliar os efeitos da aplicação foliar de ácido salicílico na composição mineral e na produção de plantas de goiabeira sob condições de estresse salino na fase pós-enxertia. O experimento foi conduzido em casa de vegetação, no delineamento experimental de blocos casualizados, em esquema fatorial 2 × 4, sendo dois níveis de condutividade elétrica da água de irrigação (0,6 e 3,2 dS m-1) e quatro concentrações de ácido salicílico (0; 1,2; 2,4 e 3,6 mM), com três repetições. Durante a fase de floração da goiabeira, os teores de N, P, K, se acumularam nas folhas segundo a ordem de concentração N > K > P. A aplicação foliar de 1,2 mM de ácido salicílico aumentou os teores foliares de nitrogênio, fósforo e potássio nas plantas de goiabeira cultivadas sob irrigação com água de 0,6 dS m-1. A salinidade da água de 3,2 dS m-1 diminuiu o crescimento e os componentes de produção das plantas de goiabeira.

Morphology of 'Crioula' guava seedlings under irrigation with increasing salinity water and nitrogen/potassium fertilization / Morfologia de goiabeira 'Crioula' sob irrigação com águas de salinidades crescentes e adubação nitrogenada-potássica

Abstract Several studies have been conducted evaluating the management of fertilizers as strategies to mitigate the deleterious effects of salt stress, so the objective of this work was to evaluate the quality of 'Crioula' guava seedlings under irrigation with water of different salinity levels and fertilized with combinations of nitrogen and potassium. The experiment was performed in a protected (screened) environment using a randomized block design and analyzed in a 5 × 4 factorial scheme, with four replicates, with the plot formed by two plants. The treatments were formed from the combination of the factor electrical conductivity of irrigation water (ECw 0.3, 1.1, 1.9, 2.7 and 3.5 dS m-1), with the factor combinations (C) of nitrogen (N) and potassium (K2O) doses, being C1 = 70% N + 50% K2O, C2 = 100% N + 75% K2O, C3= 130% N + 100% K2O and C4= 160% N + 125% K2O. The recommended dose of 100% N and K, respectively, was 541.1 mg N dm-3 soil and 798.6 mg K dm-3 soil. The combinations of N and K fertilization corresponding to 70% N + 50% K2O and 100% N + 75% K2O of the recommended doses promoted greater growth of 'Crioula' guava seedlings. Water with ECw of 2.1 dS m-1 promotes the formation of quality 'Crioula' guava seedlings.

Resumo Diversos estudos vêm sendo desenvolvido avaliando o manejo de adubos como estratégias para mitigar os efeitos deletérios do estresse salino, neste sentido, objetivou-se com este trabalho avaliar a qualidade de mudas de goiabeira Crioula sob irrigação com águas de diferentes níveis salinos e adubadas com combinações de nitrogênio e potássio. O experimento foi conduzido em ambiente protegido (telado) utilizando-se o delineamento de blocos casualizados e analisados em esquema fatorial 5 × 4, com quatro repetições, com a parcela formada por duas plantas. Os tratamentos foram formados pela combinação do fator condutividade elétrica da água de irrigação (CEa), com valores de 0,3; 1,1; 1,9; 2,7 e 3,5 dS m-1; e o fator combinações (C) de doses de nitrogênio (N) e potássio (K2O), sendo C1 = 70% N + 50% K2O; C2 = 100% N + 75% K2O; C3= 130% N + 100% K2O e C4= 160% N + 125% K2O. A dose recomendada de 100% de N e K, respectivamente, foi de 541,1 e 798,6 mg de K dm-3 de solo. As combinações de adubação nitrogenada e potássica de 70% N + 50% K2O e 100% N + 75% K2O, em relação às doses recomendadas, resultaram em um maior crescimento de mudas de goiabeira Crioula. Água com CEa média de 2,1 dS m-1 foi capaz de promove a formação de mudas de qualidade de goiabeira Crioula.

Meloidogyne enterolobii-induced Changes in Guava Root Exudates Are Associated With Root Rotting Caused by Neocosmospora falciformis.

Despite the worldwide importance of disease complexes involving root-feeding nematodes and soilborne fungi, there have been few in-depth studies on how these organisms interact at the molecular level. Previous studies of guava decline have shown that root exudates from Meloidogyne enterolobii-parasitized guava plants (NP plants), but not from nematode-free plants (NF plants), enable the fungus Neocosmospora falciformis to rot guava roots, leading to plant death. To further characterize this interaction, NP and NF root exudates were lyophilized; extracted with distinct solvents; quantified regarding amino acids, soluble carbohydrates, sucrose, phenols, and alkaloids; and submitted to a bioassay to determine their ability to enable N. falciformis to rot the guava seedlings' roots. NP root exudates were richer than NF root exudates in amino acids, carbohydrates, and sucrose. Only the fractions NP-03 and NP-04 enabled fungal root rotting. NP-03 was then sequentially fractionated through chromatographic silica columns. At each step, the main fractions were reassessed in bioassay. The final fraction that enabled fungal root rotting was submitted to analysis using high performance liquid chromatography, nuclear magnetic resonance, mass spectrometry, energy-dispersive X-ray fluorescence, and computational calculations, leading to the identification of 1,5-dinitrobiuret as the predominant substance. In conclusion, parasitism by M. enterolobii causes an enrichment of guava root exudates that likely favors microorganisms capable of producing 1,5-dinitrobiuret in the rhizosphere. The accumulation of biuret, a known phytotoxic substance, possibly hampers root physiology and the innate immunity of guava to N. falciformis.

Influence of the Extraction Method on the Polyphenolic Profile and the Antioxidant Activity of Psidium guajava L. Leaf Extracts.

The leaves of Psidium guajava L. are an agro-industrial by-product with an outstanding content of polyphenolic compounds; however, there are many factors which can affect the phytochemical profile when valuing this type of plant material, such as temperatures and extraction times involving in the extraction methods applied. In this context, this study analyzed the impact of different extraction methods (Soxhlet, maceration and ultrasound-assisted extraction) on the phytochemical profile (FTIR and UPLC-MS) and the antioxidant activity (ABTS, FRAP and Folin-Ciocalteu) of guava leaf extracts. A yield of phenolic compounds per gram of guava leaf was obtained within the range of 16 to 45 mg/g; on the other hand, the IC50 values determined with the ABTS assay ranged between 78 ± 4 to 152 ± 12 µg/mL. The methanolic extract obtained by Soxhlet was the one with the best reducing power, both in the FRAP assay and in the Folin-Ciocalteu assay. Finally, bioactive compounds such as quercetin, kaempferol and avicularin were identified in the guava leaf extract. It was concluded that the purification of polyphenolics compounds improves the antioxidant capacity, and that the extraction method greatly influences the phytochemical profile and activity of the extracts.

Bitter friends are not always toxic: The loss of acetic acid bacteria and the absence of Komagataeibacter in the gut microbiota of the polyphagous fly Anastrepha ludens could inhibit its development in Psidium guajava in contrast to A. striata and A. fraterculus that flourish in this host.

The gut microbiota is key for the homeostasis of many phytophagous insects, but there are few studies comparing its role on host use by stenophagous or polyphagous frugivores. Guava (Psidium guajava) is a fruit infested in nature by the tephritids Anastrepha striata and A. fraterculus. In contrast, the extremely polyphagous A. ludens infests guava only under artificial conditions, but unlike A. striata and the Mexican A. fraterculus, it infests bitter oranges (Citrus x aurantium). We used these models to analyze whether the gut microbiota could explain the differences in host use observed in these flies. We compared the gut microbiota of the larvae of the three species when they developed in guava and the microbiota of the fruit pulp larvae fed on. We also compared the gut microbiota of A. ludens developing in C. x aurantium with the pulp microbiota of this widely used host. The three flies modified the composition of the host pulp microbiota (i.e., pulp the larvae fed on). We observed a depletion of Acetic Acid Bacteria (AAB) associated with a deleterious phenotype in A. ludens when infesting P. guajava. In contrast, the ability of A. striata and A. fraterculus to infest this fruit is likely associated to a symbiotic interaction with species of the Komagataeibacter genus, which are known to degrade a wide spectrum of tannins and polyphenols. The three flies establish genera specific symbiotic associations with AABs. In the case of A. ludens, the association is with Gluconobacter and Acetobacter, but importantly, it cannot be colonized by Komagataeibacter, a factor likely inhibiting its development in guava.

Antidepressant-Like Effect and Phenolic Profile of Brazilian Native and Exotic Species from Psidium Genus.

Depression is one of the disorders involving mental health that most affects the population worldwide. Considering the available pharmacological therapies for the treatment of depression are ineffective in most patients, the search for new alternatives is crucial. In line with this, we investigated the phenolic profile, antidepressant-like, and antioxidant effects triggered by the administration of aqueous extracts from Psidium guajava L. (GUA), Psidium cattleianum Sw. (CAT), and Psidium guineense Sabine (GUI) leaves in mice. Our results show that quercetin is the major compound of GUA and GUI, and o-coumaric acid in CAT extracts. The acute and subchronic administrations of the three plant extracts exerted an antidepressant-like effect in mice exposed to the tail suspension test, without changes on locomotor performance evaluated by the open field test. Furthermore, the GUI and CAT decreased oxidative stress markers, mainly lipid peroxidation and nitrites in the hippocampus, prefrontal cortex, liver, and plasma. Notably, GUA and CAT increased non-protein thiols in all tissues. Therefore, the Psidium extracts demonstrated an antidepressant-like effect in mice, and the antioxidant capacity of the extracts seems to underlie the behavioral effect.

Integrating proteomics and metabolomics approaches to elucidate the ripening process in white Psidium guajava.

Psidium guajava (guava) exhibits a high content of biomolecules with nutraceutical properties. However, the biochemistry and molecular foundation of guava ripening is unknown. We performed comparative proteomics and metabolomics studies in different fruit tissues at two ripening stages to understand this process in white guava. Our results, suggest the positive contribution of ethylene and abscisic acid (ABA) signaling to the regulation of biochemical changes during guava ripening. We characterized the modulation of several metabolic pathways, including those of sugar and chlorophyll metabolism, abiotic and biotic stress responses, and biosynthesis of carotenoids and secondary metabolites, among others. In addition to ethylene and ABA, we also found a differential accumulation of other growth regulators such as brassinosteroids, cytokinin, methyl-jasmonate, gibberellins and proteins, and discuss their possible implications in the intricate biochemical network associated with guava ripening process. This integrative approach represents a global overview of the metabolic pathway dynamics during guava ripening.