Characterization of alkaloids and phenolics in Nitraria roborowskii Kom. fruit by UHPLC-triple-TOF-MS/MS and its sucrase and maltase inhibitory effects.

Nitraria roborowskii Kom (NRK), with high economic and ecological value, is mainly distributed in the Qaidam Basin, China. However, research on its chemical components and bioactivities is still rare. In this study, its chemical constituents (52) including 10 ß-carboline alkaloids, nine cyclic peptides, three indole alkaloids, five pyrrole alkaloids, eight phenolic acids and 17 flavonoids were identified tentatively using UPLC-triple-TOF-MS/MS. Notablely, one new ß-carboline alkaloid and five new cyclic peptides were confirmed using MS/MS fragmentation pathways. In addition, experiments in vitro indicated that NRK-C had strong maltase and sucrase inhibitory activities (IC50 of 0.202 and 0.103 mg/mL, respectively). Polysaccharide tolerance experiments confirmed NRK-C (400 mg/kg) was associated with decreased postprandial blood glucose (PBG) in diabetic mice. These results suggested that NRK fruit might be used as a functional ingredient in food products.

Iridoid- and flavonoid-enriched fractions of Cornus sanguinea and Cornus mas exert antioxidant and anti-inflammatory effects and inhibit key enzymes in the treatment of metabolic disorders.

Background: Berry fruits are recognized as a "superfood" due to their high content of bioactive compounds and health benefits. Scope and approach: Herein, extracts of Cornus sanguinea and Cornus mas fresh and dried fruits obtained by different extraction procedures (ethanolic and hydroalcoholic maceration, ultrasound-assisted extraction, and Soxhlet apparatus) were analysed using liquid chromatography-electrospray ionization-quadrupole-time of flight-mass spectrometry (LC-ESI-QTOF-MS) and compared to identify the main healthy compounds and their impact on the inhibition of key enzymes (pancreatic lipase, α-glucosidase, and α-amylase) associated with metabolic disorders. The antioxidant activity and inhibition of nitric oxide (NO) and NF-κB pathway were also investigated. Key findings and conclusions: Flavonoids, iridoids, and phenolic acids were the main classes of identified compounds. Herein, kaempferol 3-O-galactoside, kaempferol 3-O-glucoside, quercetin, quercetin 3-O-xyloside, and myricetin 3-O-galactoside were detected for the first time in C. sanguinea. Remarkable antioxidant effects and promising α-glucosidase and lipase inhibitory activity were observed with extracts obtained by hydroalcoholic maceration of both Cornus dried fruits. Consequently, these extracts were subjected to fractionation using Amberlite XAD-16 resin. The most promising biological activities, which are attributed to the presence of some flavonoids and iridoids, were detected with the C. sanguinea fractions, in particular SD2(II). The results of this study offer new insights into the potential development of functional foods, nutraceuticals, and food supplements using the Cornus species.

Structurally Diverse Phenolic Amides from the Fruits of Lycium barbarum with Potent α-Glucosidase, Dipeptidyl Peptidase-4 Inhibitory, and PPAR-γ Agonistic Activities.

A total of nine new phenolic amides (1-9), including four pairs of enantiomeric mixtures (3-5 and 8), along with ten known analogues (10-19) were identified from the fruits of Lycium barbarum using bioassay-guided chromatographic fractionation. Their structures were elucidated by comprehensive spectroscopic and spectrometric analyses, chiral HPLC analyses, and quantum NMR, and electronic circular dichroism calculations. Compounds 5-7 are the first example of feruloyl tyramine dimers fused through a cyclobutane ring. The activity results indicated that compounds 1, 11, and 13-17 exhibited remarkable inhibition against α-glucosidase with IC50 of 1.11-33.53 µM, 5-150 times stronger than acarbose (IC50 = 169.78 µM). Meanwhile, compounds 4a, 4b, 5a, 5b, 13, and 14 exerted moderate agonistic activities for peroxisome proliferator-activated receptor (PPAR-γ), with EC50 values of 10.09-44.26 µM. Especially,compound 14 also presented inhibitory activity on dipeptidyl peptidase-4 (DPPIV), with an IC50 value of 47.13 µM. Furthermore, the banding manner of compounds 14 and 17 with the active site of α-glucosidase, DPPIV, and PPAR-γ was explored by employing molecular docking analysis.

Structural characterization of slow digestion dextrin synthesized by a combination of α-glucosidase and cyclodextrin glucosyltransferase and its prebiotic potential on the gut microbiota in vitro.

Starch-based dietary fibers are at the forefront of functional ingredient research. In this study, a novel water-soluble slow digestion dextrin (SDD) was synthesized by synergy of α-glucosidase and cyclodextrin glucosyltransferase and characterized. Results showed that SDD exhibited high solubility, low viscosity, and resistance to digestive enzymes, and also showed an increased dietary fiber content of 45.7% compared with that of α-glucosidase catalysis alone. Furthermore, SDD was used as the sole carbon source to ferment selected intestinal strains and human fecal microflora in vitro to investigate its prebiotic effects. It was found that SDD could markedly enriched the abundance of Bifidobacterium, Veillonella, Dialister, and Blautia in human gut microflora and yielded higher total organic acid. The combination of α-glucosidase and cyclodextrin glucosyltransferase in this study showed valuable potential for the preparation of a novel slow digestion dextrin with good physicochemical properties and improved prebiotic effects.

Diagnostic meaning of urinary ethyl glucoside concentrations in relationship to alcoholic beverage consumption.

Incidents and accidents often involve the drinking of alcoholic beverages. We investigated compounds that indicate the consumption of alcoholic beverages even after ethanol (EtOH) becomes undetectable in blood and urine. Ethyl glucoside (EG) has been isolated as a possible drinking marker, and a GC-MS/MS method for EG isomers has been developed. EG isomers in several alcoholic beverages were analyzed. In sake, only αEG was observed in high concentrations. In wine and beer, both α and ßEG were detected. Whisky, however, did not contain EG. EtOH and EG concentrations were analyzed in urine up to 48 h after ingestion. Maximum EtOH concentrations were reached in 1-2 h and was mostly eliminated in 6 h. Maximum EG concentrations were reached in 3-6 h, gradually decreased, and remained low after 24 h. After drinking sake, the αEG concentrations were much higher than that of other alcoholic beverages. After drinking wine or beer, ßEG was detected, but lower than αEG. Also, αEG was detected in urine after drinking whisky that contained no EG. This suggested that αEG may be synthesized in vivo. Disaccharide-degrading enzymes such as α-glucosidase are present in the human small intestine. It was considered that αEG was synthesized when alcohol was consumed with certain foods, such as carbohydrates. In actual forensic autopsy cases, EtOH and EG isomer analysis provided useful information regarding drinking history. In conclusion, it is considered that urinary EG isomers can be used as drinking markers that complement EtOH analysis.

Volatile fingerprints of different parts of Chongming saffron (Crocus sativus) flowers by headspace-gas chromatography-ion mobility spectrometry and in vitro bioactive properties of the saffron tepals.

In this work, the volatile fingerprints of different parts of Chongming saffron flowers (stigmas, stamens, and tepals) were analyzed and compared for the first time by headspace-gas chromatography-ion mobility spectrometry. Three different parts of saffron flowers could be clearly distinguished using principal component analysis based on signal intensity data of gas chromatography-ion mobility spectrometry. Therefore, gas chromatography-ion mobility spectrometry coupled with principal component analysis method could be employed as a new method for authentication and quality control of saffron for the reason of frequent addition with stamens and/or tepals as adulterants in saffron. Moreover, the bioactive composition (total flavonoids, total phenolics, and total anthocyanins) and bioactive properties of saffron tepals were evaluated. The results indicated that aqueous, ethanol, and ethyl acetate extracts of saffron tepals exhibited good radical scavenging (2,2-Diphenyl-1-picrylhydrazyl, ABTS, and OH) and enzyme (α-amylase/α-glucosidase) inhibition activities, which probably were attributed to the bioactive components contained in the extracts. This approach would provide the important information for monitoring the quality of saffron as well as exploring the utilization of saffron tepals in functional food technology. PRACTICAL APPLICATION: This study demonstrated that the HS-GC-IMS method might be used as a new strategy for quality control of saffron, and the saffron tepals were rich source of bioactive components that could be used in health-promoting products.

Chemical characterization of the antioxidant and α-glucosidase inhibitory active fraction of Malus transitoria leaves.

Chinese Tibetan tea made from the tender leaves of Malus transitoria is a widely consumed health drink, but there are few reports on its chemical composition and biological activity. In this study, we found that a 50% ethanol extract of M. transitoria had good antioxidant and α-glucosidase inhibitory activities in vitro. Guided by in vitro bioassays, chromatographic separation and purification were conducted, and the most active fraction in M. transitoria was determined. UPLC-Orbitrap-MS/MS was used to further quickly and comprehensively characterize the chemical composition. Library searches, MS/MS fragmentation patterns of two isolated reference compounds, and bibliography were used to annotate 81 compounds, of which 2 were new compounds, and 79 were identified from M. transitoria for the first time. This study provides a scientific basis for the development of antioxidant and anti-diabetic functional foods from M. transitoria.

Reusable Fluorescent Nanobiosensor Integrated in a Multiwell Plate for Screening and Quantification of Antidiabetic Drugs.

A highly stable and reusable fluorescent multisample nanobiosensor for the detection of α-glucosidase inhibitors has been developed by coupling fluorescent liposomal nanoparticles based on conjugated polymers (L-CPNs) to the enzyme α-glucosidase, one of the main target enzymes in the treatment of type 2 diabetes. The mechanism of sensing is based on the fluorescence "turn-on" of L-CPNs by p-nitrophenol (PNP), the end product of the enzymatic hydrolysis of p-nitrophenyl-α-d-glucopyranoside. L-CPNs, composed of lipid vesicles coated with a blue-emitting cationic polyfluorene, were designed and characterized to obtain a good response to PNP. Two nanobiosensor configurations were developed in this study. In the first step, a single-sample nanobiosensor composed of L-CPNs and α-glucosidase entrapped in a sol-gel glass was developed in order to characterize and optimize the device. In the second part, the nanobiosensor was integrated and adapted to a multiwell microplate and the possibility of reusing it and performing multiple measurements simultaneously with samples containing different α-glucosidase inhibitors was investigated. Using super-resolution confocal microscopy, L-CPNs could be visualized within the sol-gel matrix, and the quenching of their fluorescence, induced by the substrate, was directly observed in situ. The device was also shown to be useful not only as a platform for screening of antidiabetic drugs but also for quantifying their presence. The latter application was successfully tested with the currently available drug, acarbose.

Steroidal saponins from Trillium govanianum as α-amylase, α-glucosidase, and dipeptidyl peptidase IV inhibitory agents.

OBJECTIVE: To provide the scientific basis for the utility of rhizome of Trillium govanianum as nutraceutical supplements in managing physiological glycemic levels. METHODS: The in vitro enzyme inhibitory activity of the extract, fractions, and the isolated steroidal saponins from the rhizome part of T. govanianum was carried out against α-amylase, α-glucosidase, and dipeptidyl peptidase IV. The molecular interactions, binding score, and pharmacokinetic parameters (absorption, distribution metabolism, and excretion) of steroidal saponins were analyzed by the Schrodinger molecular docking software. KEY FINDINGS: Current study explained that the extract, fractions, and isolated steroidal saponins from T. govanianum possess good α-amylase and α-glucosidase inhibitory activity while moderate dipeptidyl peptidase IV inhibitory activity. Moreover, in vitro results revealed that borassoside E (IC50 7.15 ± 1.78 µM), protodioscin (IC50 6.72 ± 0.04 µM), and diosgenin (IC50 12.75 ± 2.70 µM) are most effective in inhibiting the activity of α-amylase, α-glucosidase, and dipeptidyl peptidase IV, respectively. Current in silico and in vitro studies established an association between the steroidal saponins from T. govanianum and their molecular interactions with α-amylase, α-glucosidase, and dipeptidyl peptidase IV. CONCLUSION: The results of this investigation suggest that fractions and steroidal saponins from T. govanianum exhibit good antidiabetic activity which could be used as nutraceutical supplements for the management of systemic glucose level.

Consumer-perception, nutritional, and functional studies of a yogurt with restructured elderberry juice.

We investigated the effects of supplementation of yogurt with elderberry juice (Sambucus nigra L.), in both natural and restructured forms, on certain technological, physicochemical, sensory, and health-promoting properties of yogurt, including antioxidant activity and inhibition of angiotensin-converting enzyme (ACE), α-amylase, and α-glucosidase activity. Consumer acceptance of the yogurt-juice products was assessed. Gel-strength restructured elderberry juice retained a spherical shape and most of the juice, despite decreasing in mass from 57.2 to 50.9 g during storage. As a result, yogurt supplemented with 10 and 25% restructured elderberry juice appeared to be more desirable from a sensory and technological perspective than yogurt with natural juice. Yogurt supplemented with restructured elderberry juice had a high water-holding capacity (94.4-96.4%), exhibited no spontaneous whey syneresis, and maintained a dense consistency (up to 5,626 g). Consumer penalty analysis of the just-about-right diagnostic attributes indicated that the flavor of these yogurts may not be sufficiently refreshing. High correlation was demonstrated between ACE inhibition, ABTS, α-amylase, and α-glucosidase in yogurt supplemented with restructured juice. An in vitro gastrointestinal simulation estimated bioaccessibility of antioxidants to be in the range of 62 to 66%. This model fermented yogurt supplemented with restructured elderberry juice is a novel dairy-juice beverage that represents a new approach for the development of functional fruit yogurt beverages.

Emerging strategies for the activity assay and inhibitor screening of alpha-glucosidase.

The high incidence of diabetes mellitus has caused widespread concern around the world, and has quickly become one of the most prevalent and costly chronic diseases. Alpha-glucosidase has been considered as the main target enzyme in the prevention and treatment of type 2 diabetes, and the inhibition of alpha-glucosidase activity can control postprandial blood glucose levels of diabetics and keep blood glucose levels normal. However, most of the current antidiabetic drugs in the clinic have many side effects. Recently, the screening of alpha-glucosidase inhibitors, from natural products, with excellent activity and less side effects has been successfully achieved, which also proposes more requirements and challenges for the approaches of alpha-glucosidase inhibitor (AGI) screening because of the trace level of active compounds in natural products, large-scale sample screening, and complex matrix of natural products. In this review, we comprehensively summarized the available strategies for the assay of alpha-glucosidase activity and AGI screening for the first time, including classic strategies such as high throughput screening methods (e.g. capillary electrophoresis strategies, HPLC/LC-MS strategies), emerging sensing strategies (e.g. colorimetric sensing, fluorescence sensing, electrochemical sensing, and surface plasmon resonance sensing) and other strategies. Finally, future opportunities and challenges in future research are tentatively proposed.

Ratiometric fluorescence monitoring of α-glucosidase activity based on oxidase-like property of MnO2 nanosheet and its application for inhibitor screening.

In recent years, α-glucosidase (α-Glu) inhibitor has been widely used in clinic for diabetic and HIV therapy. Although different systems have been constructed for sensitive and selective detection of α-Glu and screening its inhibitor, the method based on ratiometric fluorescence for α-glucosidase inhibitor screening remains poorly investigated. Herein, we constructed a new MnO2 nanosheet (NS)-based ratiometric fluorescent sensor for α-glucosidase activity assay and its inhibitor screening. MnO2 NS as an oxidase-mimicking nanomaterial directly oxidized o-phenylenediamine (OPD) into 2,3-diaminophenazine (DAP) which had a strong fluorescence emission at 575 nm, whereas the fluorescence of Ag nanoclusters (NCs) at 450 nm was then quenched by the generated DAP through inner filter effect (IFE). When 2-O-α-d-glucopyranosyl-l-ascorbic acid (AAG) as α-Glu substrate and α-Glu were introduced into the above system, MnO2 NS would be reduced to Mn2+ and lose the oxidase-like property since ascorbic acids (AA) were released with the hydrolysis of AAG by α-Glu. Thus, DAP would not be produced and IFE was stopped accompanying with the fluorescence decrease of DAP and fluorescence increase of AgNCs. A ratiometric fluorescent α-Glu nanosensor was thus developed. The fluorescence intensity ratio of DAP to AgNCs linearly decreased with the increasing of α-Glu concentrations in the range of 0.2-8 U mL-1, and limit of detection was 0.03 U mL-1. This proposed sensing approach was also expanded to α-Glu inhibitor screening and showed excellent applicability. As a typical α-Glu inhibitor, acarbose was investigated with a low detection limit of 10-8 M. The constructed sensor platform was proven to be sensitive and selective as well as simple, label-free and low-cost, making it promising for the accurate diagnosis of relevant disease and discovery of potential drugs.

Improved sperm motility after 4 h of ejaculatory abstinence: role of accessory sex gland secretions.

Various studies have sought to determine the typical v. optimal abstinence period after which semen samples should be collected, with many contradictory results reported. Several factors influence the semen microenvironment, and thus sperm parameters. In this study we focused on the secretions of the prostate, seminal vesicles and the epididymis. Semen samples were obtained from healthy normozoospermic males (n=16) after 4-day and 4-h periods of ejaculatory abstinence, and standard semen analysis was performed using computer-aided sperm analysis, whereas seminal plasma citric acid, neutral α-glucosidase and fructose concentrations were measured using assay kits. There were significant decreases in total sperm count (P<0.001), sperm concentration (P<0.05) and semen volume (P<0.05) after 4h compared with 4 days ejaculatory abstinence. Furthermore, increases were observed in total sperm motility (P<0.05) and sperm progressive motility (P<0.01) after a 4-h abstinence period, accompanied by significant reductions in citric acid (P<0.05), α-glucosidase (P<0.01) and fructose (P<0.01) concentrations. In addition, due to the decreased number of spermatozoa, these concentrations translated to a significant decrease in fructose (P<0.05) per spermatozoon, indicating an intrinsic mechanism capitalising on alternative sources of energy for increased metabolic function and subsequent sperm motility.

Use of a deoxynojirimycin-fluorophore conjugate as a cell-specific imaging probe targeting α-glucosidase on cell membranes.

Molecules designed for cell-specific imaging were studied, taking advantage of an enzyme-inhibitor interaction. 1-Deoxynojirimycin (DNJ) can be actively captured by cells which express the surface membrane protein α-glucosidase. New probes composed of DNJ for recognition linked to a fluorophore signal portion were prepared (DNJ-CF31, DNJ-Dans 2 and DNJ-DEAC 3). Docking simulations revealed that the inhibitors acarbose and miglitol and the inhibitor portion of the probes bind at the same position in the pocket of α-glucosidase (human-derived PDB: 3TON). The ability of probes 1-3 to detect the difference between HeLa cells (from human cervical cancer tissue), Neuro-2a cells (from a mouse neuroblastoma C1300 tumor), N1E-115 cells (from a mouse brain neuroblastoma C1300 tumor), A1 cells (from the astrocyte of a newborn mouse brain), and Caco-2 cells (from a human colon carcinoma) was evaluated, and cell-specific fluorescence imaging was possible for conjugate probes 1 and 2. Caco-2 cells treated with probes 1 and 2 showed blue and green fluorescence, respectively, from the cell membrane, and did not stain the Caco-2 cells inside. These results show that DNJ-CF31 and DNJ-Dans 2 recognize an α-glucosidase protein on the surface of Caco-2 cells. Probes 1 and 2 did not stain any part of the other cells. This cell-specific imaging strategy is applicable for a variety of therapeutic agents for many diseases.

Seminal plasma neutral alpha-glucosidase activity as an early predictor of patency and natural pregnancy after microsurgical vasoepididymostomy.

Microsurgical vasoepididymostomy (MVE) is recommended as a first-line option for treatment of epididymal obstructive azoospermia (EOA). However, early indicators for predicting patency and natural pregnancy are unclear. Our aim was to explore the early predictive value of seminal plasma neutral alpha-glucosidase (NAG) activity for patency and natural pregnancy after MVE. Eighty-four patients with EOA who underwent MVE were enrolled in this study. The post-operative patency and natural pregnancy rates were 60.71% and 33.33% respectively. The presence of motile epididymal spermatozoa at the anastomosis site and NAG activity measured at the first month after MVE were early and independent predictors of patency and natural pregnancy. The areas under the receiver operating characteristic curves (AUCs) of NAG activity for prediction of patency and natural pregnancy were 0.78 (95% confidence interval [CI]: 0.68-0.88) and 0.82 (95% CI: 0.73-0.92). The best cut-off values of NAG activity for predicting patency and pregnancy were 15.9 and 17.0 m IU/ejaculate respectively. In conclusion， NAG activity measured at the first month after MVE is an early and independent predictor of patency and natural pregnancy.

Influence of preparation procedures on the phenolic content, antioxidant and antidiabetic activities of green and black teas

The influence of common tea preparation procedures (temperature, infusion time, consumption time interval and tea bag/loose-leaf) and the type of water used, on the total phenolic content (TPC), the radical scavenging activity and the α-glucosidase inhibitory activity were assessed. Higher TPC and antioxidant activity were obtained when using lower mineralized waters. Tea bags also evidenced higher antioxidant activity than loose-leaf samples. Under the same conditions (90 ºC and five minutes of infusion time) green tea contains almost twice the quantity of polyphenols and the free radical scavenging ability of black tea. In the α-glucosidase assay all infusions were active (97-100 %). Furthermore, HPLC allowed to identify some of the polyphenols present in both teas and to monitor their composition change with time. After twenty-four hours, the antioxidant activity was maintained without significant changes, but a small decrease in enzyme inhibition was observed, although this activity was still very high

[Automatic detection and clinical application of semen biochemical markers].

Human seminal plasma is rich in potential biological markers for male infertility and male reproductive system diseases, which have an application value in the diagnosis and treatment of male infertility. The methods for the detection of semen biochemical markers have been developed from the manual, semi-automatic to the present automatic means. The automatic detection of semen biochemical markers is known for its advantages of simple reagent composition and small amount of reagents for each test, simple setting of parameters, whole automatic procedure with few errors, short detection time contributive to batch detection and reduction of manpower cost, simple calibration and quality control procedure to ensure accurate and reliable results, output of results in the order of the samples in favor of clinical diagnosis and treatment, and open reagents applicable to various automatic biochemistry analyzers. At present, the automatic method is applied in the detection of such semen biochemical markers as seminal plasma total and neutral alpha-glucosidase, acid phosphatase, fructose, γ-glutamyl transpeptidase, zinc, citric acid, uric acid, superoxide dismutase and carnitine, sperm acrosin and lactate dehydrogenase C4, and semen free elastase, which can be used to evaluate the secretory functions of the epididymis, seminal vesicle and prostate, sperm acrosome and energy metabolism function, seminal plasma antioxidative function, and infection or silent infection in the male genital tract.

Colorimetric in situ assay of membrane-bound enzyme based on lipid bilayer inhibition of ion transport.

Membrane-bound enzymes (MBEs), which make up a very high proportion of intracellular enzymes, catalyze a variety of activities that are currently analyzed by various techniques after purification. However, due to their amphipathic character, the purification of MBEs is difficult. Therefore, the most productive approach represents in situ analysis of MBEs in the cellular membrane. Methods: In this study, using membrane-bound α-glucosidase (α-Glu) as an example, we have developed a colorimetric in situ assay for MBEs based on the inhibitory effect of lipid bilayer on ion transport. The enzyme substrate could mediate the self-assembly of phospholipid PEG derivative around magnetic nanospheres that were modified with boronic acid. The formation of lipid bilayer could inhibit the leaking of iron ions under acidic conditions. However, the product of the catalytic reaction had no capability for self-assembly of the lipid bilayer, leading to the release of iron ions from the magnetic nanospheres under acidic pH. Results: The colorimetric in situ assay for MBEs could not only analyze the activity of membrane-bound α-Glu located on Caco-2 cells but could also evaluate the α-Glu inhibitors in cell medium. Conclusions: The simple, economic, and efficient method proposed here offers a potential application for high-throughput testing of α-Glu and its inhibitors. Our study also outlines a strategy for exploring the colorimetric method to detect the activities of MBEs in situ.

Fabrication of reusable electrochemical biosensor and its application for the assay of α-glucosidase activity.

A reusable biosensor has been fabricated in this work for the assay of α-glucosidase activity and the inhibitor screening. In this design, the aptamer of ATP is split as split aptamer 1 (Apt 1) and split aptamer 2 (Apt 2), and Apt 2 can link gold nanoparticles (AuNPs) modified with Apt 1 and 4-aminophenyl-α-d-glucopyranoside (pAPG). Consequently, the functional AuNPs can be immobilized onto the surface of gold electrode, allowing for salt-induced regeneration. In the presence of α-glucosidase, the glycosyl of pAPG is cut off, and the electroactive phenolic hydroxyls appear to give a strong current signal. Furthermore, the biosensor can be recovered very easily by incubating it in water to dissociate the AuNPs modified with Apt 1 and pAPG. So, a new biosensor for α-glucosidase activity detection and inhibitor screening is developed based on enzyme-activated signal generation and recovery. The biosensor may also exhibit good sensitivity for α-glucosidase determination with the detection limit 0.005 U/mL and can be reused by water-washing regeneration with good repeatability. Meanwhile this biosensor can also be utilized for inhibitor screening, which may have potential for clinical applications.

Seasonal variation in Hibiscus sabdariffa (Roselle) calyx phytochemical profile, soluble solids and α-glucosidase inhibition.

Seasonal variations in crops can alter the profile and amount of constituent compounds and consequentially any biological activity. Differences in phytochemical profile, total phenolic content and inhibitory activity on α-glucosidase (maltase) of Hibiscus sabdariffa calyces grown in South Western Nigeria were determined over wet and dry seasons. The phenolic profile, organic acids and sugars were analysed using HPLC, while inhibition of rat intestinal maltase was measured enzymically. There was a significant increase (1.4-fold; p ≤ 0.05) in total anthocyanin content in the dry compared to wet planting seasons, and maltase inhibition from the dry season was slightly more potent (1.15-fold, p ≤ 0.05). Fructose (1.8-fold), glucose (1.8-fold) and malic acid (3.7-fold) were significantly higher (p ≤ 0.05) but citric acid was lower (62-fold, p ≤ 0.008) in the dry season. Environmental conditions provoke metabolic responses in Hibiscus sabdariffa affecting constituent phytochemicals and nutritional value.