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

1 Scope

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

2 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.

3 Conclusion

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

Occurrence of Listeria monocytogenes in green table olives

Microbiological safety of green table olives from different cultivars, prepared by both the Spanish-style and biological methods and fermented with starter cultures of lactic acid bacteria (Lactobacillus plantarum, Lactobacillus casei, and Lactobacillus pentosus), was investigated. The fermentation process was monitored by measuring pH values, titratable acidities, and growth of lactic acid bacteria over time. During fermentation, lactic acid bacteria and yeasts were major microbial populations. Microbiological safety was evaluated by analysis for Listeria monocytogenes with the use of an enrichment method during storage (from 55 days to 18 months). Results demonstrated that L. monocytogenes can survive and grow in green table olives. L. monocytogenes was found in one of the commercial (thermally treated) samples analyzed and in all samples older than 2 months, irrespective of olive cultivar, lactic acid bacteria starter used, pH and titratable acidity of brine samples, or treatment applied.     

Reversal of toxigenic effects of aflatoxin B1 on cockerels by alcoholic extract of African nutmeg,Monodora myristica

The reversal of the toxigenic effects of crystalline aflatoxin B₁ (AFB₁; from Aspergilus flavus) on cockerels using different concentrations of the ethanolic extract from the seeds of African nutmeg, Monodora myristica, was studied in 130 two‐week‐old cockerels, randomly divided into 13 groups (A–M) of ten birds each. Group A (controls) received 100 µl of phosphate‐buffered saline, while those in the test groups B, C and D received 690 ng, 1380 ng or 2010 ng of AFB₁, respectively; groups E to M received the three doses of AFB₁ with either 0.1, 0.2 or 0.3 ml of the extract of M myristica, respectively, 5 min after administration of AFB₁. Jugular blood, collected on days 14 and 21 after administration, was analysed for haematology parameters, serum proteins, alanine aminotransaminase (ALT), aspartate aminotransaminase (AST) and γ‐glutamyl transferase (GGT) levels. The birds were observed daily for clinical signs and mortality for 21 days. Post‐mortem examination was carried out on the livers of dead birds and those sacrificed by exsanguination after the 21 days post‐administration. One hundred per cent mortality was recorded in cockerels that received high doses of only AFB₁ within 72 h (2010 ng per bird), and between 17 and 19 days (1380 ng). The cockerels developed leucocytosis and microcytic hypochromic anaemia. Dosing with 0.2 or 0.3 ml of the extract of M myristica reversed these changes over time, while the lowest dose (0.1 ml) did not. While serum bilirubin levels rose significantly in test cockerels, no significant changes (P > 0.05) were observed in the levels of serum proteins of control and test cockerels, whether or not they received the extract of M myristica. Aflatoxicosis caused significant decreases and increases (P < 0.05) in serum AST and GGT levels, respectively, while the administration of alcoholic extract of M myristica reversed the GGT but not AST levels to normal. Livers from control cockerels and those given 2010 ng of AFB₁ showed no appreciable gross or histological lesions. The other groups showed mild to moderate hepatomegaly, paleness and friability, diffuse vacuolar degeneration and necrosis, Kupffer cell proliferation, presence of megalocytes and multinucleated hepatocytes. Cockerels that received 0.2 or 0.3 ml of extract of M myristica, irrespective of the dose of AFB₁ showed the mildest hepatic lesions. The results of this study show that AFB₁ is highly toxigenic to cockerels and that this could be successfully reversed by the concurrent administration of alcoholic extract of M myristica. It is therefore recommended that reduction of fungal growth on foods and subsequent toxicosis by aeration, cooling, modified atmospheres or by fungistats, is complemented with the use of extracts of spices from M myristica seed, a tree widely distributed along the west coast and central Africa. Copyright © 2004 Society of Chemical Industry     

Linking theory of mind and central coherence bias in autism and in the general population.

Three experiments investigated whether 2 characteristic aspects of the psychological profile of autism, theory-of-mind deficits and weak central coherence, might be functionally related. Experiment 1 showed that in the general population, performance on a proposed test of theory of mind was inversely related to speed on the Embedded Figures Test, a measure of central coherence bias. Experiments 2 and 3 confirmed that poor theory-of-mind performance was linked to weak central coherence among typically developing children and among children with autism; however, the correlations between these measures were reliable only after accounting for differences in individuals' verbal mental ages. This pattern of results is interpreted in terms of a relationship between individual differences in theory of mind and central coherence bias, a relationship that is separate from any developmental differences in these domains. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Selective filling of nanowells in nanowell arrays fabricated using polystyrene nanosphere lithography with cytochrome P450 enzymes

This work describes an original and simple technique for protein immobilization into nanowells, fabricated using nanopatterned array fabrication methods, while ensuring the protein retains normal biological activity. Nanosphere lithography was used to fabricate a nanowell array with nanowells 100?nm in diameter with a periodicity of 500?nm. The base of the nanowells was gold and the surrounding material was silicon dioxide. The different surface chemistries of these materials were used to attach two different self-assembled monolayers (SAM) with different affinities for the protein used here, cytochrome P450 (P450). The nanowell SAM, a methyl terminated thiol, had high affinity for the P450. The surrounding SAM, a polyethylene glycol silane, displayed very little affinity toward the P450 isozyme CYP2C9, as demonstrated by x-ray photoelectron spectroscopy and surface plasmon resonance. The regularity of the nanopatterned array was examined by scanning electron microscopy and atomic force microscopy. P450-mediated metabolism experiments of known substrates demonstrated that the nanowell bound P450 enzyme exceeded its normal activity, as compared to P450 solutions, when bound to the methyl terminated self-assembled monolayer. The nanopatterned array chips bearing P450 display long term stability and give reproducible results making them potentially useful for high-throughput screening assays or as nanoelectrode arrays.     

Ultrasonication study for suspending single-walled carbon nanotubes in water

A systematic calorimetry-based technique was developed to standardize single-walled carbon nanotube (SWNT) dispersion protocol. Simple calorimetric experiments were performed to benchmark the performance of the ultra-dismembrator. Temperature profiles for the sonication period were utilized to estimate energy input to the system. Energy loss profile was generated for the ultradismembrator in use and a calibration relationship was formulated that could standardize the sonication process. The standardized protocol was used to prepare aqueous SWNT suspensions-sonicating SWNTs in a varied range of input energy (18-100 kJ) in water. SWNT mass fractions suspended for each energy input was accurately measured and the suspended SWNT samples were characterized for morphology, surface potential, cluster size and structure, and chemical functionality using high resolution transmission electron microscopy (HRTEM), electrophoresis, dynamic and static light scattering (DLS/SLS), and Raman spectroscopy. The study demonstrated that suspended mass of SWNTs increased up to 18 kJ of energy input with no further increase upon continued energy input. The physicochemical properties showed similar trend for energy input. The aggregate cluster size, surface potential behavior, as well as the Raman defect properties plateaued after the initial energy input. The significant changes observed were limited to morphological properties, i.e., shorter length, debundled, and sharp edged SWNTs and fractal cluster formation (lower D(f)) with increased input energy.     

Inclusive recovery planning for incremental systemic change: A methodology,early outcomes,and limitations from the Falkland Islands' Covid-19 recovery planning experience

Crises do not affect populations equally but expose and exacerbate long-standing vulnerabilities and inequalities. Recovery language such as ‘build back better’, or ‘bounce forward’ has been criticised for neglecting underlying inequalities. This paper reports on the process and early outcomes of an inclusive Community Recovery Planning process for the Falkland Islands, in response to Covid-19. The Falkland Islands is home to a complex community, with close ties and short power distances (due to its small size and remoteness), with differences institutionalised in citizenship statuses and entitlements, and shaped by geopolitical tensions. We aimed to use the ‘pandemic as a portal’, seeking out previously ‘less heard’ voices, to make visible previously hidden impacts, and initiate incremental systemic change to tackle them. Community Impact Assessments evidenced specific areas of vulnerability (e.g., housing and income insecurity) and inequalities, largely shaped by differing citizenship status. In tandem with other government currents, the Community Recovery Planning process has contributed to progressive policy changes in Equalities legislation and Income Support. We offer this paper as a demonstration of our methodology for inclusive recovery planning that could be adapted elsewhere. We argue that the inclusion of previously unheard voices contributed to incremental systemic change to reduce inequalities.     

Chemical and Physical Properties of Copper-Based Catalysts for CO Shift Reaction and Methanol Synthesis

The modern low-pressure methanol synthesis catalysts are based on copper-containing systems such as Cu/ZnO/Al₂O₃ and Cu/ZnO/Cr₂O₃ with various compositions. These catalysts are also highly active for the low-temperature CO shift reaction. For both reactions the nature of the active sites is still an open question.     

A novel approach for the fabrication of carbon nanofibre/ceramic porous structures

This paper describes the fabrication of hybrid ceramic/carbon scaffolds in which carbon nanofibres and multi-walled carbon nanotubes fully cover the internal walls of a microporous ceramic structure that provides mechanical stability. Freeze casting is used to fabricate a porous, lamellar ceramic (Al₂O₃) structure with aligned pores whose width can be controlled between 10 and 90 μm. Subsequently, a two step chemical vapour deposition process that uses iron as a catalyst is used to grow the carbon nanostructures inside the scaffold. This catalyst remains in the scaffold after the growth process. The formation of the alumina scaffold and the influence of its structure on the growth of nanofibres and tubes are investigated. A set of growth conditions is determined to produce a dense covering of the internal walls of the porous ceramic with the carbon nanostructures. The limiting pore size for this process is located around 25 μm.     

Light‐Activated Triazabutadienes for the Modification of a Viral Surface

Chemical crosslinking is a versatile tool for the examination of biochemical interactions, in particular host–pathogen interactions. We report the critical first step toward the goal of probing these interactions by the synthesis and use of a new heterobifunctional crosslinker containing a triazabutadiene scaffold. The triazabutadiene is stable to protein conjugation and liberates a reactive aryl diazonium species upon irradiation with 350 nm light. We highlight the use of this technology by modifying the surface of several proteins, including the dengue virus envelope protein.