Psidium guajava: a review of its traditional uses, phytochemistry and pharmacology

Antifungal activity of polymeric micelles of silver nanoparticles prepared from Psidium guajava aqueous extract

In the present study, silver nanoparticles (AgNPs) were synthesized by green synthesis using Psidium guajava aqueous extract (PE) as a reducing agent and silver nitrate (AgNO3) as a precursor. The obtained AgNPs showed maximum absorbance at 455 nm. The results from energy-dispersive X-ray spectroscopy demonstrate Ag signal at 88.33% weight. The particle image under scanning electron microscopy is spherical shape. The average size of the freshly prepared AgNPs is 96 ± 4 nm but is dramatically increases during storage due to particle aggregation. Coating AgNPs with polymeric micelles of poloxamer 407 (F127) at the suitable ratio can decrease the size of the freshly prepared AgNPs to 70.4 ± 0.8 nm and significantly prevent AgNPs from aggregation. The obtained coated AgNPs showed high effective on inhibition of Candida albicans. Isotonic solutions of 0.9% NaCl and phosphate buffer solution pH 7.4 can cause some extend of aggregation and increase the particle size of the coated AgNPs but the increased size is in the colloidal range that no precipitation occurs during 90 days at room temperature. From our results, it is suggested that the 1:1 ratio of AgNPs/F127 is the most suitable ratio to obtain the AgNPs loaded polymeric micelles with high stability, small particle size, and high inhibitory activity against C. albicans. These AgNPs are the promising antifungal nanomaterials for further study in animal model.

Antifungal Metabolites From Alternaria atrans: An Endophytic Fungus in Psidium guajava

Six metabolites (1–6), including 1 new fusaric acid derivative, designated atransfusarin (1), and 5 known compounds, (3 R,6 R)-3-benzyl-6-isopropyl-4-methylmorpholine-2,5-dione (2), daucoterol (3), adenosine (4), cerebroside B (5), and 2,3-dihydroxypropyl ( Z,Z)-9,12-octadecadienate (6), were isolated from the solid culture of an endophytic Alternaria atrans MP-7, associated with the medicinal plant Psidium guajava. The structure of the new compound was elucidated by spectral data. The antifungal test indicated that (3 R,6 R)-3-benzyl-6-isopropyl-4-methylmorpholine-2,5-dione (2) showed obvious inhibitory activity against Alternaria solani, Colletotrichum gloeosporioides, and Phyricularia grisea. Compared to fusaric acid (1a), even though the antifungal activity of atransfusarin (1) against A. solani, C. gloeosporioides, and P. grisea was greatly decreased, its inhibitory effect against Botrytis cinerea was still retained.

Essential Oil From Psidium guajava Leaves: An Excellent Source of β-Caryophyllene

The purpose of this study was to investigate the chemical composition of the essential oil extracted from Psidium guajava leaves and to explore the medicinal value of β-caryophyllene in pharmaceutical science. The essential oils of P. guajava leaves were extracted by the hydrodistillation method, using a Clevenger-type apparatus and the chemical composition of essential oils was investigated by gas chromatography–mass spectrometry. The yield of extracted essential oils was 0.6% (w/w) dry weight. The main compounds found in the leaves were β-caryophyllene (20.34%), globulol (8.20%), trans-nerolidol (7.72%), aromadendrene (4.34%), cis-α-bisabolene (3.82%), tetracosane (3.68%), octadecane (3.66%), Z, Z, Z-1,5,9,9-tetramethyl-1,4,7-cycloundecatriene (3.44%), β-bisabolene (3.41%), limonene (3.09%), octacosane (2.88%), δ-cadinene (2.52%), and 1,4-cadadiene (2.04%). The main chemical class of the essential oil was terpenoids, which represent 71.65%, followed by hydrocarbons (26.31%). A total of 50 components were identified, among these β-caryophyllene was found to be dominant, which has great medicinal value, and some other compounds were also identified for the first time in the essential oil of P. guajava leaves.

Antioxidant and Anti-Diabetic Activities of Polysaccharides from Guava Leaves

Guava (Psidium guajava L., Myrtaceae) leaves have been used as a folk herbal tea to treat diabetes for a long time in Asia and North America. In this study, we isolated polysaccharides from guava leaves (GLP), and evaluated its antioxidant activity in vitro and anti-diabetic effects on diabetic mice induced by streptozotocin combined with high-fat diet. The results indicated that GLP exhibited good DPPH, OH, and ABTS free-radical scavenging abilities, and significantly lowered fasting blood sugar, total cholesterol, total triglycerides, glycated serum protein, creatinine, and malonaldehyde. Meanwhile, it significantly increased the total antioxidant activity and superoxide dismutase (SOD) enzyme activity in diabetic mice, as well as ameliorated the damage of liver, kidney, and pancreas. Thus, polysaccharides from guava leaves could be explored as a potential antioxidant or anti-diabetic agents for functional foods or complementary medicine.

Biomimetic total syntheses of chromane meroterpenoids, guadials B and C, guapsidial A and psiguajadial D

The first biomimetic total syntheses of chromane meroterpenoids, guadials B and C, guapsidial A and psiguajadial D have been completed. The key synthetic transformation involves an efficient and high yielding hetero-Diels-Alder reaction. The two structurally isomeric natural products, guadials B and C, were obtained from a common o-quinone methide in the separate reactions with α-pinene and β-pinene, respectively. The two regioisomeric natural products, guapsidial A and psiguajadial D, were achieved in a single chemical operation.

High Carbohydrate High Fat Diet Induced Hepatic Steatosis and Dyslipidemia Were Ameliorated by Psidium guajava Leaf Powder Supplementation in Rats

Psidium guajava leaf is reported to contain many bioactive polyphenols which play an important role in the prevention and treatment of various diseases. Our investigation aimed to study the effect of Psidium guajava leaf powder supplementation on obesity and liver status by using experimental rats. To study the effects of guava leaf supplementation in high fat diet induced obesity, rats were randomly divided into four experimental groups (n=7), control (group I), control + guava leaf (group II), HCHF (group III), and HCHF + guava leaf (group IV). At the end of the experimental period (56 days), glucose intolerance, liver enzymes activities, antioxidant enzymes activities, and lipid and cholesterol profiles were evaluated. Our results revealed that guava leaf powder supplementation showed a significant reduction in fat deposition in obese rats. Moreover, liver enzyme functions were increased in high fat diet fed rats compared to the control rats significantly which were further ameliorated by guava leaf powder supplementation in high fat diet fed rats. High fat diet feeding also decreased the antioxidant enzyme functions and increased the lipid peroxidation products compared to the control rats. Guava leaf powder supplementation in high fat diet fed rats reduced the oxidative stress markers and reestablished antioxidant enzyme system in experimental animals. Guava leaf powder supplementation in high fat diet fed rats also showed a relative decrease in inflammatory cells infiltration and collagen deposition in the liver compared to the high fat diet fed rats. The present study suggests that the supplementation of guava leaf powder prevents obesity, improves glucose intolerance, and decreases inflammation and oxidative stress in liver of high carbohydrate high fat diet fed rats.

Optimization of ultrasound-assisted water extraction of flavonoids from Psidium guajava leaves by response surface analysis

Psidium guajava leaves are rich in health-promoting flavonoids compounds. For better utilization of the resource, the ultrasound-assisted aqueous extraction was investigated using Box-Behnken design under response surface methodology. A high coefficient of determination (R² = 97.8%) indicated good agreement between the experimental and predicted values of flavonoids yield. The optimal extraction parameters to obtain the highest total flavonoids yield were ultrasonic power of 407.41 W, extraction time of 35.15 min, and extraction temperature of 72.69 °C. The average extraction rate of flavonoids could reach 5.12% under the optimum conditions. Besides, HPLC analysis and field emission scanning electron microscopy indicated that the ultrasonic treatment did not change the main component of flavonoids during extraction process and the higher flavonoids content was attributed by the disruption of the cell walls of guava particles. Thus, the extraction method could be applied successfully for large-scale extraction of total flavonoids from guava leaves.

Antidiarrheal and protein conservative activities of Psidium guajava in diarrheal rats

OBJECTIVE

Psidium guajava occurs worldwide in tropical and subtropical areas. It has been used to treat inflammation, diabetes, fever, hypertension and ulcers. However, its antidiarrheal and protein conservative activities still need to be investigated.

METHODS

Fifty-four male rats were divided into normal and diarrheal rats. The normal rats were divided into 4 groups: control, low-dose P. guajava leaf extract (50 mg/kg), high-dose P. guajava leaf extract (100 mg/kg) and gallic acid. Treatments were administrated orally in 1 mL saline for a 1-month period. The diarrheal rats were divided into 5 groups: desmopressin (0.2 mg/kg) drug, low-dose P. guajava leaf extract (50 mg/kg), high-dose P. guajava leaf extract (100 mg/kg), gallic acid and an untreated control. Doses were given daily for a 1-month period while the untreated control received no treatment.

RESULTS

Diarrhea was responsible for an observed decline in kidney weight and serum sodium, potassium and chloride. Further, diarrhea was positively correlated with a significant increase in urine volume, and excretion of electrolytes, serum urea, creatinine and uric acid in the urine. In contrast, there was a proportional increase in the lipid peroxidation value in diarrhea and a significant decline was observed in serum superoxide dismutase, glutathione peroxidase and glutathione levels in diarrhea. Also, diarrhea inhibited blood proteins. The oral intake of P. guajava leaf extract by diarrheal rats restored all of these parameters to near normal levels. High-dose P. guajava leaf extract was more effective than the same compound at a low dose.

CONCLUSION

P. guajava leaf extract elicited antidiarrheal and protein conservative effects.

Potential of guava leaves for mitigating methane emissions and modulating ruminal fermentation characteristics and nutrient degradability

Guava leaves (Psidium guajava, GL), a high-phenolic- and flavonoid-containing plant resource capable of substituting the high-quality forage, may help in mitigating ruminal methane (CH₄) emission without adverse impact on nutrient degradability if supplemented at an appropriate level. In order to test this hypothesis, rumen fermentation, CH₄ production, and nutrient degradability of GL either solely or as a substitute of berseem hay (Trifolium alexandrinum, BH) were evaluated in a diet containing 50:50 concentrate to roughage. Five different levels of GL (0, 12.5, 25, 37.5, and 50%) were tested in vitro after 24 h incubation using a semi-automated gas production (GP) system. The current findings indicated that merely the presence of GL resulted in significantly lower values for cumulative GP (P < 0.001), CH₄ emission (P < 0.05), truly degraded dry matter (TDDM; P < 0.001), truly degraded organic matter (TDOM; P < 0.001), and ammonia nitrogen (NH₃-N) concentration (P < 0.001); however, pH (P < 0.001) and partitioning factor (P < 0.001) were higher. The total and individual volatile fatty acid (VFA) concentrations were drastically declined with GL as compared to BH (P < 0.05). A negative linear correlation was recorded between the levels of GL and GP including CH₄ production (P < 0.05). The addition of GL up to 25% did not pose any negative effect on both TDDM and TDOM values along with NH₃-N concentration. In addition, the inclusion of GL up to 25% did not affect the total or individual VFA concentration. Conclusively, in a medium concentrate diet, use of 25% GL and 25% BH in animal diet could be a promising alternative for mitigating the CH₄ production without any deleterious effect on nutrient degradability.

Effects of the Hydroalcoholic Extract of the Psidium guajava Fruit on Osteoporosis Prevention in Ovariectomized Rats

BACKGROUND

Several plants have been shown to possess antioxidant and estrogenic properties that can be useful in postmenopausal bone-loss prevention. The present study aimed to investigate the anti-osteoporotic effects of the hydroalcoholic extract of the Psidium guajava (PG) fruit in ovariectomized (OVX) rats.

METHODS

Sixty female Sprague-Dawley rats were randomly divided into 6 groups: a control positive group, a sham-operated group, an OVX group given normal saline (OVX-only group), and 3 treatment groups comprising 2 OVX groups treated orally with 500 and 1000 mg/kg/d of the hydroalcoholic extract of the PG fruit respectively and an OVX group treated with an injection of 0.15 mg/kg of estradiol. The study was conducted over a 12-week period. Samples from the animals' blood, femoral bones, and uteri were collected for stereological and biochemical analyses. The data were analyzed using SPSS, version 19. A P value equal to or less than 0.05 was considered statistically significant.

RESULTS

The results revealed a significant decrease in the levels of calcium, total antioxidant capacity, and phosphorus as well as uterus weight, femoral ash density, femoral volume and weight, and numbers of osteocytes and osteoblasts. Moreover, there was an increase in the levels of alkaline phosphatase and urine deoxypyridinoline together with a rise in the number of osteoclasts in the OVX-only group compared to the control and treatment groups (P≤0.05). The hydroalcoholic extract of the PG fruit increased femoral weight and volume, femoral ash density, numbers of osteocytes and osteoblasts, and trabecular volume of the bones in comparison with the OVX-only group in a dose-dependent manner. No significant difference was observed between the groups in the levels of malondialdehyde and interleukin-6.

CONCLUSION

The hydroalcoholic extract of the PG fruit prevented OVX-induced bone loss in the rats, with no proliferative effect on atrophic uteri; it should, therefore, be considered for treatment purposes.

Characterization of a new heteropolysaccharide from green guava and its application as an α-glucosidase inhibitor for the treatment of type II diabetes

Psidium guajava fruit is a subtropical fruit, functional food and traditional medicine for the adjuvant treatment of diabetes mellitus in China. To investigate the active components responsible for its health benefits, a novel heteropolysaccharide GP70-3 was purified by water extraction, ethanol precipitation and column chromatography. Structural characterization of GP70-3 was elucidated for the first time by monosaccharide composition assay, Fourier transform-infrared spectroscopy (FT-IR), methylation analysis, gas chromatography coupled with mass spectrometry (GC-MS) and nuclear magnetic resonance spectroscopy (NMR). The data revealed that GP70-3 contained a backbone of 1→3,6)-linked β-d-Galp, 1→5)-linked α-l-Araf, 1→6)-linked β-d-Galp and 1→3)-linked β-d-Galp, branched with 1→2,3,5)-linked α-l-Araf, 1→3)-linked α-l-Araf, 1→3)-linked α-l-Rhap, 1→3)-linked β-d-GlcpA, 1→3)-linked β-d-GalpA and terminated with →1)-linked β-d-Galp. Advanced structure studies showed GP70-3 consisted of irregular flakes with rounded-spherical pores. Moreover, GP70-3 exhibited outstanding α-glucosidase inhibitory activity in vitro, with an IC50 value of 2.539 ± 0.144 μM, which was 1867 times higher than that of the positive control acarbose (IC50 value of 4.744 ± 0.026 mM). Therefore, consumption of guava polysaccharides may be beneficial as an α-glucosidase inhibitor for reducing the postprandial blood glucose level and treating type II diabetes.

Medicinal Plants Used for the Traditional Management of Diabetes in the Eastern Cape, South Africa: Pharmacology and Toxicology

The use of medicinal plants for the management of diabetes mellitus is on the rise in the developing countries, including South Africa. There is increasing scientific evidence that supports the claims by the traditional healers. In this review, we compare the families of previously reported anti-diabetic plants in the Eastern Cape by rating the anti-diabetic activity, mode of action and also highlight their therapeutic potentials based on the available evidence on their pharmacology and toxicity. Forty-five plants mentioned in ethnobotanical surveys were subjected to a comprehensive literature search in the available electronic databases such as PubMed, ScienceDirect, Google Scholar and Elsevier, by using “plant name” and “family” as the keywords for the primary searches to determine the plants that have been scientifically investigated for anti-diabetic activity. The search returned 25 families with Asteraceae highly reported, followed by Asphodelaceae and Alliaceae. Most of the plants have been studied for their anti-diabetic potentials in vivo and/or in vitro, with most of the plants having a higher percentage of insulin release and inhibition against carbohydrate digesting enzymes as compared with insulin mimetic and peripheral glucose uptake. Almost all the investigated plants also inhibit oxidative stress as part of their hypoglycemic activity with less toxicity. However, the isolation of their bioactive molecules is still lacking. This review provides a resource to enable thorough assessments of the therapeutic profiles of available medicinal plants used for the management of diabetes in the Eastern Cape, South Africa. Further studies such as the identification of the active ingredients of potent plants still need to be carried out; this may lead to new molecules in drug discovery and development.

Chemical composition, antioxidant activity and antibacterial mechanism of action from Marsilea minuta leaf hexane: methanol extract

BACKGROUND

In the present study, hexane: methanol (50:50) leaf extract of Marisela minuta has been evaluated for its chemical composition, antioxidant effect and the antimicrobial mechanism of action against food borne pathogenic bacteria.

RESULTS

The phytochemical evaluation of extract by GC/MS revealed the major abundance of benzoic acid-4-ethoxyethyl ester (43.39%) and farnesol acetate (18.42%). The extract exhibited potential antioxidant and free radical scavenging properties with promising antibacterial activities against the test pathogens with Pseudomonas aeruginosa being the most susceptible with maximum inhibition zone (17 mm) and IC50 value of 125 µg, respectively. The significant (p < 0.05) increase in intracellular super oxide dismutase (SOD), protein leakage, extracellular alkaline phosphatase and lactate dehydrogenase in treated test pathogens suggested an increase in oxidative stress reveling the mechanism of action of phytochemicals. Scanning electron microscopy analysis of treated pathogens also showed swollen and distorted cells. The bioactive molecules in the extract were efficiently docked with virulent enzymes and farnesol acetate showed best energy value of - 5.19 and - 4.27 kcal/mol towards Topoisomerase IV and SHV-2 respectively. Benzoic acid-4-ethoxyethyl ester showed best binding against TEM-72 with low binding energy value of - 4.35 kcal/mol.

CONCLUSION

Due to its antioxidant and antibacterial properties, the leaf extract of M. minuta may act as promising natural additives to prevent food spoilage bacteria.

Assessment of Guava (Psidium Guajava L.) Wood Biomass for Briquettes’ Production

Residual biomass from guava (Psidium guajava L.), a common and widespread fruit tree native to Latin America, has been analyzed in the present research in order to determine the biomass quality and its potential use for energy purposes. Obtained biomass was grinded and compacted into the form of fuel briquettes. Determinations of solid biofuel parameters, i.e., physical, mechanical and chemical properties such as calorific value, moisture, ash content, volatile matter, mechanical durability, contents of the main chemical elements and heavy metals were performed according to international standards. As a result, not inconsiderable traces of heavy metals were found, with a concentration of zinc 4.57 mg kg−1 as the highest. Guava’s moisture content (9.8%) comfortably fulfilled the minimum standard requirements and the net calorific value as received (17.11 MJ kg−1) met the average value of a wood. However, measured sulphur content (0.063%) as well as ash content (3.74%) exceeded the maximum allowed limits for the graded wood briquettes and, therefore, guava wood briquettes should be rather categorized as non-woody A class briquettes. The results of the study can contribute significantly to the knowledge of guava wood properties and its potential as renewable solid fuel since there is little published data about it.

Strategies and Research Progress of Chinese Medicine in Prevention and Treatment of Diabetic Peripheral Neuropathy

Diabetic peripheral neuropathy (DPN) seriously affects the quality of life in patients with type 2 diabetes mellitus. This paper reviews the role of Chinese medicine in the main treatment goal of DPN, including protecting pancreatic β-cells, in the use of antioxidation therapy to delay disease progression, and in the endpoint of neural repair and regeneration. We propose that protecting the body from injury caused by high glucose and oxidative stress, and promoting repair and regeneration of nerves should be the research direction for the prevention and treatment of DPN.

The Anti-diarrheal Activity of the Non-toxic Dihuang Powder in Mice

Dihuang powder (DHP) has been used in the traditional Chinese medicine for the treatment of diarrhea in some regions of China. But up to now, the anti-diarrheal activity of DHP haven't been performed with modern pharmacological technology. This study aims to investigate the quality control, the potential toxicity and anti-diarrheal activity of Dihuang powder in mice. High performance liquid chromatography (HPLC) and thin layer chromatography (TLC) were used to detect five active compounds in DHP for quality control, and the acute toxicity and sub-acute toxicity for 28-day oral administration of DHP were then evaluated. The anti-diarrheal activity was investigated using mouse model. Results showed that the levels of quercetin and berberine in DHP were 0.054 and 0.632 mg/g, respectively, and atractylodin, matrine, and patehouli aleohal were also detected in DHP. At the given doses, DHP was safe in terms of acute and sub-acute toxicity. Meanwhile, DHP exhibited strong anti-diarrheal effects as well as decreased gastrointestinal motility and the secretions induced by Sennae and castor oil in a dose-dependent manner. It could decrease the content of IL-1β, IL-6, and TNF-α in the small intestine, and improve the histopathological changes of small intestine and large intestine induced by Sennae. The antinociceptive and anti-inflammatory activities in vivo also were presented. Based on all of the results, we thought that DHP has anti-diarrheal activity, and could be used to treat diarrhea as well as alleviate the pain and inflammation induced by diarrhea. This study provides a theoretical basis for the clinical use of DHP and may assist in the development of new drugs for the treatment of diarrhea. The mechanism of the anti-diarrheal activity should be investigated in the future.

Chemotype diversity of Psidium guajava L

The essential oil of Psidium guajava L. has been studied for pharmacological and industrial purposes, without considering the plant's genotype regarding the heterogeneity of its composition. The present study aimed to characterize the chemotype diversity of the essential oil extracted from the leaves of 22 genotypes of P. guajava grown in two different environments in the state of Espírito Santo, Brazil, and to identify the different chemical markers present in these plants. Essential oil from the leaves of the P. guajava genotypes was extracted by hydrodistillation, and its chemical composition was analyzed by gas chromatography-flame ionization detection (GC-FID) and gas chromatography-mass spectrometry (GC-MS). Thirty-three compounds were identified, comprising 87.5-99.0% of the total composition, with a prevalence of sesquiterpenes in all samples. The major compounds identified consisted of (E)-trans-Caryophyllene, α-Humulene, trans-Nerolidol, β-Bisabolene, β-Bisabolol, and Hinesol, the first of which was identified as a possible chemical marker for the species. Multivariate factor analysis of the chemical composition of P. guajava oil identified three chemotypes: Commercial - PAL, SEC, PS, PET, C7, C11, and C17MI, characterized by high levels of β-Selinene, α-Selinene, Hinesol, and 14-hydroxy-epi-(E)-caryophyllene, with β-Selinene and α-Selinene as the chemical markers; C10 and C13, exhibiting high levels of Elemol, trans-Nerolidol, trans-β-Eudesmol, and (2Z, 6Z)-Farnesol, which were indicated as chemical markers, and Cortibel - C1, C2, C3, C4, C5, C6, C8, C9, C12, C14, C15, C16, C17LI, which retained high levels of α-Cedrene, cis-α-Bergamotene, α-Humulene, Humulene epoxide, epi-α-Cadinol, β-Bisabolol, and α-Bisabolol, with β-Bisabolol and α-Bisabolol as the chemical markers. The use of guava genotypes with different chemotypes, that are agronomically favorable to fruit production and essential oil exploitation adds value to the crop and renders it more sustainable. Given guava crops produce large amounts of leaf biomass, resulting from successive prunings, the extraction of their essential oil, which retains commercially valuable compounds, can be feasible.

A Focus on Four Popular “Functional Foods” as Part of a Strategy to Combat Metabolic Disease Through the Increased Consumption of Fruits and Vegetables

Fruit and vegetable consumption is on the rise as an increasing number of people recognize their health promoting effects, which are mediated through phytochemicals with disease combatting properties. The aim of this paper is to identify the potential benefits of fruits and vegetables in chronic diseases such as diabetes mellitus and hypertension. An electronic search of databases such as Pubmed Central, Science Direct and Web of Science from the last 5 years was conducted. Four commonly consumed edible fruit and vegetables, namely, Hypoxis hemmerocallidea (African potato), Moringa oleifera (Moringa), Persea americana (Avocado) and Psidium guajava (Guava) and their potential role in the prevention and management of metabolic syndrome and other disorders, are presented. In this narrative review plant uses extend beyond traditional medicine and include usage in food preparation, beverages, as part of fragrances, culinary flavouring, as well as cosmetic use, but more importantly have potential in contributing to the amelioration of the deleterious effects of diseases/health conditions. In addressing disease states, including metabolic syndrome and other disorders, the interest in medicinal plants continues to grow with the possibility of novel compounds and/or new drug discovery. Alternative and affordable methods of large scale harvesting of medicinal plants, as well as identification and specificity of bioactive compounds as future therapeutics are essential for sustainability.

In Vitro and In Vivo Inhibition of Intestinal Glucose Transport by Guava (Psidium Guajava) Extracts

SCOPE

Known pharmacological activities of guava (Psidium guajava) include modulation of blood glucose levels. However, mechanistic details remain unclear in many cases.

METHODS AND RESULTS

This study investigated the effects of different guava leaf and fruit extracts on intestinal glucose transport in vitro and on postprandial glucose levels in vivo. Substantial dose- and time-dependent glucose transport inhibition (up to 80%) was observed for both guava fruit and leaf extracts, at conceivable physiological concentrations in Caco-2 cells. Using sodium-containing (both glucose transporters, sodium-dependent glucose transporter 1 [SGLT1] and glucose transporter 2 [GLUT2], are active) and sodium-free (only GLUT2 is active) conditions, we show that inhibition of GLUT2 was greater than that of SGLT1. Inhibitory properties of guava extracts also remained stable after digestive juice treatment, indicating a good chemical stability of the active substances. Furthermore, we could unequivocally show that guava extracts significantly reduced blood glucose levels (≈fourfold reduction) in a time-dependent manner in vivo (C57BL/6N mice). Extracts were characterized with respect to their main putative bioactive compounds (polyphenols) using HPLC and LC-MS.

CONCLUSION

The data demonstrated that guava leaf and fruit extracts can potentially contribute to the regulation of blood glucose levels.

Effects of Psidium guajava leaf extract on secretion systems of Gram-negative enteropathogenic bacteria

We screened a total of 672 plant-tissue extracts to search for phytochemicals that inhibit the function of the type III secretion system (T3SS) of enteropathogenic Escherichia coli (EPEC) and enterohemorrhagic E. coli (EHEC). Among candidates examined, we found that an extract from the leaves of Psidium guajava (guava) inhibited the secretion of the EspB protein from EPEC and EHEC without affecting bacterial growth. The guava extract (GE) also inhibited EPEC and EHEC from adhering to and injecting EspB protein into HEp-2 cells. GE seemed to block the translocation of EspB from the bacterial cells to the culture medium. In addition to EPEC and EHEC, GE also inhibited the T3SS of Yersinia pseudotuberculosis and Salmonella enterica serovar Typhimurium. After exposure to GE, Y. pseudotuberculosis stopped the secretion of Yop proteins and lost its ability to induce the apoptosis of mouse bone marrow-derived macrophages. S. Typhimurium exposed to GE ceased the secretion of Sip proteins and lost its ability to invade HEp-2 cells. GE inhibited EspC secretion, the type V secretion protein of EPEC, but not Shiga toxin2 from EHEC. Thus, our results suggest that guava leaves contain a novel type of antimicrobial compound that could be used for the therapeutic treatment and prevention of gram-negative enteropathogenic bacterial infections.

Potential Functional Byproducts from Guava Purée Processing

The valorization of guava waste requires compositional and functional studies. We tested three byproducts of guava purée processing, namely refiner, siever, and decanter. We analyzed the chemical composition and quantified the prebiotic activity score and selected carbohydrates; we also determined the water holding (WHC), oil holding (OHC), cation exchange capacities, bile acid binding, and glucose dialysis retardation (GDR) of the solid fraction and the antioxidative and α-amylase inhibitory capacities (AIC) of the ethanolic extract. Refiner contained 7.7% lipid, 7.08% protein and a relatively high phytate content; it had a high prebiotic activity score and possessed the highest binding capacity with deoxycholic acid. Siever contained high levels of low molecular weight carbohydrates and total tannin but relatively low crude fiber and cellulose contents. It had the highest binding with chenodeoxycholic acid (74.8%), and exhibited the highest 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity. Decanter was rich in cellulose and had a high prebiotic activity score. The WHC and OHC values of decanter were within a narrow range and also exhibited the highest binding with cholic acid (86.6%), and the highest values of GDR and AIC. The refiner waste could be included in animal feed but requires further processing to reduce the high phytate levels. All three guava byproducts had the potential to be a source of antioxidant dietary fiber (DF), a finding that warrants further in vivo study.

PRACTICAL APPLICATION

To differing extents, the guava byproducts exhibited useful physicochemical binding properties and so possessed the potential for health-promoting activity. These byproducts could also be upgraded to other marketable products so the manufacturers of processed guava might be able to develop their businesses sustainably by making better use of them.

An overview of anti-diabetic plants used in Gabon: Pharmacology and toxicology

ETHNOPHARMACOLOGICAL RELEVANCE

The management of diabetes mellitus management in African communities, especially in Gabon, is not well established as more than 60% of population rely on traditional treatments as primary healthcare. The aim of this review was to collect and present the scientific evidence for the use of medicinal plants that are in currect by Gabonese traditional healers to manage diabetes or hyperglycaemia based here on the pharmacological and toxicological profiles of plants with anti-diabetic activity. There are presented in order to promote their therapeutic value, ensure a safer use by population and provide some bases for further study on high potential plants reviewed.

MATERIALS AND METHODS

Ethnobotanical studies were sourced using databases such as Online Wiley library, Pubmed, Google Scholar, PROTA, books and unpublished data including Ph.D. and Master thesis, African and Asian journals. Keywords including 'Diabetes', 'Gabon', 'Toxicity', 'Constituents', 'hyperglycaemia' were used.

RESULTS

A total of 69 plants currently used in Gabon with potential anti-diabetic activity have been identified in the literature, all of which have been used in in vivo or in vitro studies. Most of the plants have been studied in human or animal models for their ability to reduce blood glucose, stimulate insulin secretion or inhibit carbohydrates enzymes. Active substances have been identified in 12 out of 69 plants outlined in this review, these include Allium cepa and Tabernanthe iboga. Only eight plants have their active substances tested for anti-diabetic activity and are suitables for further investigation. Toxicological data is scarce and is dose-related to the functional parameters of major organs such as kidney and liver.

CONCLUSION

An in-depth understanding on the pharmacology and toxicology of Gabonese anti-diabetic plants is lacking yet there is a great scope for new treatments. With further research, the use of Gabonese anti-diabetic plants is important to ensure the safety of the diabetic patients in Gabon.

Antibacterial Activity of Azadirachta indica, Pongamia pinnata, Psidium guajava, and Mangifera indica and their mechanism of action against Streptococcus mutans

Background:

Curative plants have reportedly been used to make chewing sticks/toothbrushes intended for the treatment of oral diseases.

Objective:

The in vitro antibacterial activities of Azadirachta indica, Pongamia pinnata, Psidium guajava, and Mangifera indica were evaluated against Streptococcus mutans, along with the cytotoxicity and antioxidant and synergistic potentials. The effect of M. indica on the expression of crucial virulence genes spaP and gtfB of S. mutans was determined.

Materials and Methods:

The antibacterial activity was determined using a modified microdilution method. The antioxidant potential was evaluated using diphenyl picrylhydrazyl (DPPH), Griess reagent, and nitroblue tetrazolium calorimetric assays. The synergistic activity was investigated using a modified checkerboard method, while the cytotoxicity was determined according to a cell proliferation 2,3-Bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide salt assay. Reverse transcription was the chosen method for determining the difference in expression of the spaP and gtfB genes after treatment with the plant sample.

Results:

M. indica and A. indica had the highest antibacterial activity at concentrations of 0.3 mg/ml and 6.25 mg/ml, respectively. A. indica had the best free radical scavenging of DPPH, exhibiting 50% inhibition at 28.72 μg/ml; while M. indica showed better superoxide scavenging potential than the positive control quercetin. Both M. indica and A. indica had adequate activity against the nitric oxide-free radical (12.87 and 18.89 μg/ml, respectively). M. indica selectively reduced the expression of the gtfB gene, indicating a mechanism involving Glucotranferases, specifically targeting bacterial attachment.

SUMMARY

Mangifera indica and Azadirachta indica had very good antibacterial activity against Streptococcus mutans and moderate toxicity against Vero cells

M. indica had the best antioxidant capacity overall

M. indica reduced the expression of gtfB gene at 0.5 mg/ml.

Abbreviations used: AA: Ascorbic acid; BHI: Brain–heart infusion; CHX: Chlorhexidine; DPPH: Diphenyl picrylhydrazyl; DMSO: Dimethlysulfoxide; NBT: Nitroblue tetrazolium; NO: Nitric oxide;

Quantification of Phenolic Compounds and In Vitro Radical Scavenging Abilities with Leaf Extracts from Two Varieties of Psidium guajava L

Guava leaf (Psidium guajava L.) extracts are used in both traditional medicine and the pharmaceutical industry. The antioxidant compounds in P. guajava leaves can have positive effects including anti-inflammatory, anti-hyperglycemic, hepatoprotective, analgesic, anti-cancer effects, as well as protecting against cardiovascular diseases. In the present study, phenolic compounds and in vitro antioxidant capacity were measured in extracts obtained with polar and non-polar solvents from leaves of two varieties of guava, Calvillo Siglo XXI and Hidrozac. The quantity of total phenolics and total flavonoids were expressed as equivalents of gallic acid and quercetin, respectively. Hydroxyl radical, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH), and Oxygen Radical Absorbance Capacity using fluorescein (ORAC-FL) in vitro tests were used to assess the radical scavenging abilities of the extracts. The total phenolics were higher in the aqueous fraction of the variety Calvillo Siglo XXI, while in the Hidrozac variety total phenolics were higher in the acetone and chloroform fractions. Total flavonoids were higher in all fractions in the variety Calvillo Siglo XXI. Total phenolics showed a highly positive correlation for ORAC-FL, and a moderately positive correlation with hydroxyl radicals. Finally, total flavonoids showed a slightly positive correlation for ORAC-FL and hydroxyl radicals. Both varieties of guava leaf extract showed excellent antioxidant properties.

Quickly Screening for Potential α-Glucosidase Inhibitors from Guava Leaves Tea by Bioaffinity Ultrafiltration Coupled with HPLC-ESI-TOF/MS Method

Guava leaves tea (GLT) has a potential antihyperglycemic effect. Nevertheless, it is unclear which compound plays a key role in reducing blood sugar. In this study, GLT extract (IC₅₀ = 19.37 ± 0.21 μg/mL) exhibited a stronger inhibitory potency against α-glucosidase than did acarbose (positive control) at IC₅₀ = 178.52 ± 1.37 μg/mL. To rapidly identify the specific α-glucosidase inhibitor components from GLT, an approach based on bioaffinity ultrafiltration combined with high performance liquid chromatography coupled to electrospray ionization-time-of-flight-mass spectrometry (BAUF-HPLC-ESI-TOF/MS) was developed. Under the optimal bioaffinity ultrafiltration conditions, 11 corresponding potential α-glucosidase inhibitors with high affinity degrees (ADs) were screened and identified from the GLT extract. Quercetin (IC₅₀ = 4.51 ± 0.71 μg/mL) and procyanidin B3 (IC₅₀ = 28.67 ± 5.81 μg/mL) were determined to be primarily responsible for the antihyperglycemic effect, which further verified the established screening method. Moreover, structure-activity relationships were discussed. In conclusion, the BAUF-HPLC-ESI-TOF/MS method could be applied to determine the potential α-glucosidase inhibitors from complex natural products quickly.

Skin protective effect of guava leaves against UV-induced melanogenesis via inhibition of ORAI1 channel and tyrosinase activity

Ultraviolet (UV) irradiation is a major environmental factor affecting photoageing, which is characterized by skin wrinkle formation and hyperpigmentation. Although many factors are involved in the photoageing process, UV irradiation is thought to play a major role in melanogenesis. Tyrosinase is the key enzyme in melanin synthesis; therefore, many whitening agents target tyrosinase through various mechanisms, such as direct interference of tyrosinase catalytic activity or inhibition of tyrosinase mRNA expression. Furthermore, the highly selective calcium channel ORAI1 has been shown to be associated with UV-induced melanogenesis. Thus, ORAI1 antagonists may have applications in the prevention of melanogenesis. Here, we aimed to identify the antimelanogenesis agents from methanolic extract of guava leaves (Psidium guajava) that can inhibit tyrosinase and ORAI1 channel. The n-butanol (47.47%±7.503% inhibition at 10 μg/mL) and hexane (57.88%±7.09% inhibition at 10 μg/mL) fractions were found to inhibit ORAI1 channel activity. In addition, both fractions showed effective tyrosinase inhibitory activity (68.3%±0.50% and 56.9%±1.53% inhibition, respectively). We also confirmed that the hexane fraction decreased the melanin content induced by UVB irradiation and the ET-1-induced melanogenesis in murine B16F10 melanoma cells. These results suggest that the leaves of P. guajava can be used to protect against direct and indirect UV-induced melanogenesis.

Three new flavonoids, proanthocyanidin, and accompanying phenolic constituents from Feijoa sellowiana

Our investigation of phenolic constituents of fruits, flower buds, and leaves of Feijoa sellowiana led to the isolation of twenty-one phenolics including three new gossypetin glycosides 1–3, and also the purification of a proanthocyanidin fraction. A high-performance liquid chromatography method for simultaneous analysis of phenolic constituents was established and then used to investigate the phenolic profiles of the parts of the plant species, to show the presence of characteristic flavonoids and ellagic acid derivatives or ellagitannins in the extracts from fruits, flower buds, and leaves. The branch extract profile also suggested the presence of alkylated ellagic acids as characteristic constituents. Inhibitory effects of feijoa flavonoids on mushroom tyrosinase were seen, although in some cases this may have resulted from direct interaction with the enzyme. Cytotoxic effect of the proanthocyanidin fraction was also shown.

Diversity of Neopestalotiopsis and Pestalotiopsis spp., Causal Agents of Guava Scab in Colombia

Common guava (Psidium guajava L.) is a fruit tree of global economic importance. It is grown in Asia, South and Central America, and Hawaii for its exquisite aroma and flavor, and nutritional and medical properties. However, guava production is limited by guava scab, caused by fungi in the Pestalotiopsis genus. Characteristic symptoms of guava scab are corky, ovoid or round lesions on fruit surfaces. These lesions may thicken, affecting the flesh below and reducing fruit quality and commercial value. We characterized 81 isolates isolated from guava scab lesions on guava leaves and fruit in different regions of Colombia, and identified them as Pestalotiopsis and Neopestalotiopsis spp. We analyzed the morphology, pathogenicity, and genetic diversity of the isolates based on the sequences of the internal transcribed spacer, β-tubulin, and elongation factor genes. Isolates were morphologically, pathogenically, and genetically diverse but the diversity did not correlate with geographical origin, or guava cultivar or tissue from which the isolates were recovered. Selected monosporic isolates included in the multiple-gene analysis were identified as belonging to two genera: Neopestalotiopsis (65 isolates with versicolorous conidia) and Pestalotiopsis (4 isolates with concolorous conidia).

Antioxidant and mercury chelating activity of Psidium guajava var. pomifera L. leaves hydroalcoholic extract

Mercury (Hg) is widely distributed in the environment and is known to produce several adverse effects in organisms. The aim of the present study was to examine the in vitro antioxidant activity and Hg chelating ability of the hydroalcoholic extract of Psidium guajava leaves (HEPG). In addition, the potential protective effects of HEPG against Hg(II) were evaluated using a yeast model (Saccharomyces cerevisiae). HEPG was found to exert significant antioxidant activity in 2,2-diphenyl-1-picrylhydrazyl scavenger and inhibition of lipid peroxidation induced by Fe(II) assays in a concentration-dependent manner. The extract also exhibited significant Hg(II) chelating activity. In yeast, Hg(II) induced a significant decrease in cell viability. In contrast, HEPG partially prevented the fall in cell viability induced by Hg(II). In conclusion, HEPG exhibited protective effects against Hg(II)-mediated toxicity, which may be related to both antioxidant and Hg(II)-chelating activities.

Complex Enzyme-Assisted Extraction Releases Antioxidative Phenolic Compositions from Guava Leaves

Phenolics in food and fruit tree leaves exist in free, soluble-conjugate, and insoluble-bound forms. In this study, in order to enhance the bioavailability of insoluble-bound phenolics from guava leaves (GL), the ability of enzyme-assisted extraction in improving the release of insoluble-bound phenolics was investigated. Compared to untreated GL, single xylanase-assisted extraction did not change the composition and yield of soluble phenolics, whereas single cellulase or β-glucosidase-assisted extraction significantly enhanced the soluble phenolics content of PGL. However, complex enzyme-assisted extraction (CEAE) greatly improved the soluble phenolics content, flavonoids content, ABTS, DPPH, and FRAP by 103.2%, 81.6%, 104.4%, 126.5%, and 90.3%, respectively. Interestingly, after CEAE, a major proportion of phenolics existed in the soluble form, and rarely in the insoluble-bound form. Especially, the contents of quercetin and kaempferol with higher bio-activity were enhanced by 3.5- and 2.2-fold, respectively. More importantly, total soluble phenolics extracts of GL following CEAE exhibited the highest antioxidant activity and protective effect against supercoiled DNA damage. This enzyme-assisted extraction technology can be useful for extracting biochemical components from plant matrix, and has good potential for use in the food and pharmaceutical industries.

Hydroethanolic extract of Psidium guajava leaf for induced osteoarthritis using a guinea pig model

We investigated the therapeutic effects of an extract of Psidium guajava (guava) leaf on experimentally induced osteoarthritis in guinea pig. The left knee of 30 male guinea pigs was anesthetized and the cranial cruciate ligament was severed. The animals were followed for 8 weeks until osteoarthritis was confirmed by radiography and histopathology. Animals were divided randomly into five groups; group 1, the ligament was severed and untreated; group 2, the ligament was severed and treated with piascledine, an extract of soybean and avocado; group 3, the ligament was severed and treated with 200 mg/kg hydroethanolic extract of guava; group 4, the ligament was severed and treated with 400 mg/kg hydroethanolic extract of guava; and group 5, control animals without surgery or extracts. Radiological and histopathological evaluations after 8 weeks showed reduced severity of osteoarthritis in the piascledine treatment group compared to group 1. The guava extract also reduce the severity of osteoarthritis compared to controls. Histopathological examination of treatment and control groups showed that treatment the guava extract improved lesions significantly. Hydroethanolic extracts of guava leaf appears to prevent osteoarthritis by inhibition of free radical formation in the knee joint.

Antibacterial activities of medicinal plants used in Mexican traditional medicine

ETHNOPHARMACOLOGICAL RELEVANCE

We provide an extensive summary of the in vitro antibacterial properties of medicinal plants popularly used in Mexico to treat infections, and we discuss the ethnomedical information that has been published for these species.

MATERIALS AND METHODS

We carried out a bibliographic investigation by analyzing local and international peer-reviewed papers selected by consulting internationally accepted scientific databases from 1995 to 2014. We provide specific information about the evaluated plant parts, the type of extracts, the tested bacterial strains, and the inhibitory concentrations for each one of the species. We recorded the ethnomedical information for the active species, as well as their popular names and local distribution. Information about the plant compounds that has been identified is included in the manuscript. This review also incorporates an extensive summary of the available toxicological reports on the recorded species, as well as the worldwide registries of plant patents used for treating bacterial infections. In addition, we provide a list with the top plant species with antibacterial activities in this review RESULTS: We documented the in vitro antibacterial activities of 343 plant species pertaining to 92 botanical families against 72 bacterial species, focusing particularly on Staphylococcus aureus, Mycobacterium tuberculosis, Escherichia coli and Pseudomonas aeruginosa. The plant families Asteraceae, Fabaceae, Lamiaceae and Euphorbiaceae included the largest number of active species. Information related to popular uses reveals that the majority of the plants, in addition to treating infections, are used to treat other conditions. The distribution of Mexican plants extended from those that were reported to grow in just one state to those that grow in all 32 Mexican states. From 75 plant species, 225 compounds were identified. Out of the total plant species, only 140 (40.57%) had at least one report about their toxic effects. From 1994 to July 2014 a total of 11,836 worldwide antibacterial patents prepared from different sources were recorded; only 36 antibacterial patents from plants were registered over the same time period. We offered some insights on the most important findings regarding the antibacterial effects, current state of the art, and research perspectives of top plant species with antibacterial activities in vitro.

CONCLUSIONS

Studies of the antibacterial in vitro activity of medicinal plants popularly used in Mexico to treat infections indicate that both the selection of plant material and the investigation methodologies vary. Standardized experimental procedures as well as in vivo pharmacokinetic studies to document the effectiveness of plant extracts and compounds are necessary. This review presents extensive information about the medicinal plants possessing antibacterial activity that has been scientifically studied and are popularly used in Mexico. We anticipate that this review will be of use for future studies because it constitutes a valuable information tool for selecting the most significant plants and their potential antibacterial properties.

Chemical Compositions, Antioxidant and Antimicrobial Activities of Essential Oils of Psidium guajava L. Leaves from Different Geographic Regions in China

Hydrodistilled essential oils (EO) of Psidium guajava L. leaves from different regions in China were analyzed by GC and GC/MS. The samples from Guangdong Province displayed high EO yields (0.61 - 0.75%, v/w). A total of 50 components, representing over 98.00% of the EOs, were identified and semi-quantitatived. The major constituents of EOs included β-caryophyllene (17.17 - 31.38%), γ-gurjunene (9.17 - 15.22%), τ-cadinol (1.35 - 10.02%) and calamenene (2.13 - 7.80%). The terpenoids in all sample oils were dominated by sesquiterpenes hydrocarbons (70.18 - 84.35%), followed by oxygenated sesquiterpenes (9.89 - 22.19%). The similarities and differences among EOs from different samples were evaluated by hierarchical cluster analysis and principal component analysis methods. The IC₅₀ values of EOs from different regions were between 18.52 - 33.72 mg/ml (DPPH) and 13.12 - 25.15 mg/ml (ABTS⁺ ). The FRAP value of EO from Guangdong Province was 7.34 - 9.13 mmol Vc/g DM, while the FRAP value of EO from Taiwan Province was 2.29 - 2.36 mmol Vc/g DM. The antimicrobial tests revealed that EO had a higher antimicrobial activity against all Gram-positive bacteria and two fungi. Moreover, EO from P. guajava leaves of Guangdong Province showed the highest antimicrobial activity. These properties can be considered in the design of industrial products and for further application in the food, pharmaceutical and cosmetic industries.