Total Phenols, Antioxidant Capacity and Antibacterial Activity of Manuka Honey Extract.

Aims: To evaluate total phenols content (TPC), antioxidant capacity (TAC) and antibacterial activity of Manuka honey extract (MHE) and to compare such properties with those for unfractionated Manuka honey. Study Design: In vitro study. Place and Duration of Study: School of Biomedical Sciences, Ulster University, Coleraine, UK. Between September 2016 and September 2017. Methodology: MHE was prepared by solvent extraction using ethyl acetate. TPC was determined by Folin-Ciocalteu assay. The iron (III) reducing antioxidant capacity (IRAC) method was used to determine TAC. Antibacterial activity was evaluated using disc diffusion assay and 96-well microtiter plate methods with absorbance measured at 600 nm. Results: The TPC for MHE was 30-fold higher than the value for Manuka honey (33420±1685 mg vs. 1018±78 mg GAE/kg) while TAC values were~ 100-times greater (83,198±7064 vs. 793±104 TEAC, respectively). Antibacterial activity assessed by disc diffusion for Manuka honey (18.5 mm on S. aureus and 20 mm on E. coli) was two times greater than for MHE (9mm for both S. aureus and E. coli). The 96-well microtiter plate assay confirmed the greater antibacterial activity for Manuk

Antioxidant and genoprotective activity of selected cucurbitaceae seed extracts and LC–ESIMS/MS identification of phenolic components

Cucurbitaceae are one of most widely used plant species for human food but lesser known members have not been examined for bioactive components. The purpose of this study was to evaluate the antioxidant and genoprotective activities from three cucurbitaceae seeds extracts and to identify phenolic components by LC–ESIMS/MS analysis. From the results, the yield of seeds extract was 20–41% (w/w) and samples had 16–40% total phenols as gallic acid equivalents (GAE). Compared with methanol solvent, using acidified methanol led to increased extraction yield by 1.4 to 10-fold, higher phenolic content (149.5 ± 1.2 to 396.4 ± 1.9 mg GAE/g), higher DPPH radical quenching and enhanced enoprotective activity using the pBR322 plasmid assay. LC–ESI-MS/MS analysis led to identification of 14–17 components, based on authentic standards and comparison with literature reports, as mainly phenolic acids and esters, flavonol glycosides. This may be the first mass spectrometric profiling of polyphenol components from cucurbitaceae seeds

Determination of Iron (III) Reducing Antioxidant Capacity for Manuka Honey and Comparison with ABTS and Other Methods

Aims: Applying multiple assays with trolox as the sole reference compound is a recent AOAC proposal to improve the reliability of total antioxidant capacity determinations. The aim of this study was to evaluate, iron (III) reducing antioxidant capacity (iRAC) for Manuka honey samples and comparisons with ABTS and other well-known assays. Study Design: In-vitro, laboratory-based study. Place and Duration of Study: School of Biomedical Sciences, Faculty of Life and Health Sciences, Ulster University, Cromore Road, Coleraine, BT52 1SA, UK; September 2015-May 2016. Methodology: Manuka honey rated Unique Manuka Factor (UMF) 5+, 10+, 15+, 18+ and a nonrated (NR) sample were analysed using five assays for total antioxidant capacity namely, iRAC, ABTS, DPPH, FRAP, and Folin assays. Values for total antioxidant capacity were normalized as Trolox Equivalent Antioxidant capacity (TEAC) for comparison within and between assays. Results: The TAC were correlated for all methods (R2 = 0.83-0.99) and also correlated with the total phenols content. Actual TEAC value for a given honey ranged by 21-70-fold depending on the assay method with the following general order of increase; DPPH < FRAP (pH 3.6) < iRAC (pH 7.0) <ABTS (pH7) < Folin (pH ~11). The trends in TAC values are discussed alongside of TEAC values for 50 food items and some challenges for comparing different antioxidant methods are highlighted. Conclusion: Total antioxidant capacity of Manuka honey changes in a regular manner probably affected by assay pH. The findings are important for attempts to standardize antioxidant methods as currently applied to foods, beverages and dietary supplements. Further research is recommended to examine the effect of normalizing antioxidant methods for solvent composition and pH

Comparison of Iron (III) Reducing Antioxidant Capacity (iRAC) and ABTS Radical Quenching Assays for Estimating Antioxidant Activity of Pomegranate

Pomegranate juice (PJ) has total antioxidant capacity which is reportedly higher compared to other common beverages. This short study aimed to assess the total antioxidant capacity of commercial PJ and pomegranate fruit using a newly described method for iron (III) reducing antioxidant capacity (iRAC) and to compare with the ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid)) and Folin–Ciocalteu assays. Commercial PJ, freeze-dried pomegranate, and oven-dried pomegranate were analyzed. The calibration results for iRAC were comparable to ABTS and Folin–Ciocalteu methods in terms of linearity (R2 > 0.99), sensitivity and precision. The total antioxidant capacity for PJ expressed as trolox equivalent antioxidant capacity (TEAC) was 33.4 ± 0.5 mM with the iRAC method and 36.3 ± 2.1 mM using the ABTS method. For dried pomegranates, total antioxidant capacity on a dry weight basis (DB) was 89–110 mmol/100 g DB or 76.0 ± 4.3 mmol/100 g DB using iRAC and ABTS methods, respectively. Freeze-dried pomegranate had 15% higher total antioxidant capacity compared with oven-dried pomegranate. In conclusion, pomegranate has high total antioxidant capacity as evaluated by the iRAC and ABTS methods, though variations occur due to the type of cultivar, geographic origin, processing and other factors. The study is relevant for attempts to refine food composition data for pomegranate and other functional food

Antioxidant, Anticancer and Antibacterial Activity of Withania somnifera Aqueous Root Extract

Aims: To evaluate total antioxidant capacity, anticancer activity and antibacterial effects Withania somnifera aqueous-root extracts. Study Design: In vitro study. Place of Study: School of Biomedical Sciences, Ulster University, UK. Methodology: Total antioxidant capacity (TAC) of whole powder and freeze dried W. somnifera aqueous-root extracts was determined using FRAP, DPPH, Folin and ABTS assays. Anticancer activity was accessed using MDA-MB-231 breast cells and Sulforhodamine B staining for cell viability. Antibacterial activity was by disk diffusion assay with penicillin, amoxicillin and streptomycin as positive controls. Results: The TAC for W. somnifera extract was 86, 47, 195,or 443 gallic acid equivalents per 100g dry basis (mgGAE/ 100 g) using FRAP, DPPH, Folin or ABTS assays, respectively. Corresponding TAC values for freeze dried W. somnifera aqueous-root extract were, 418, 553, 1898 or, 1770 (mgGAE/100 g). W. somnifera aqueous-root extract inhibited MDA-MB-231 cell proliferation in a dose-dependent manner with IC50 = 0.19 mg/ml (21 µM GAE). Nil antibacterial effects were detected for freeze dried W. somnifera extract (0-1 mg/ml) across six species of bacteria tested. Conclusion: Withania somnifera root water extract showed significant antioxidant and anticancer activity for MDA-MB-231 breast cancer cells but no antibacterial activity under the conditions of this study

Antibacterial activity of Manuka honey and its components: An overview

The importance of honey for medicinal purposes is well documented in some of the world’s oldest literature. Honey is well known and studied for its antimicrobial properties. The medicinal properties in honey originate from the floral source used by bees. Manuka honey is a dark monofloral honey rich in phenolic content, and currently it is gaining much attention for its antimicrobial activity. Researchers have found that honey is effective against a wide range of pathogens. The antibacterial potency of Manuka honey was found to be related to the Unique Manuka Factor (UMF) rating, which is correlated with the methylglyoxal and total phenols content. It is reported that different types of Manuka honey have differing effects and Gram-negative bacteria are more resistant than Gram-positive bacteria. Bacterial resistance to honey as antimicrobial agent has yet to be identified, possibly due to the presence of a complex mixture of methylglyoxal and other components. Honey is also reported to alter a bacterium’s shape and size through septal ring alteration, which affects cell morphology and growth. Research has shown that Manuka honey of different UMF values has medicinal properties of interest and it can be beneficial when used as a combination treatment with other antimicrobial agent

Effect of pH on the Radical Quenching Capacity of Tea Infusions Using the ABTS•+ Assay

Aims: The aims of this study were to assess the impact of pH on the free radical quenching activity of tea infusions using a modified 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid (ABTS) assay and three antioxidant compounds as reference. Study Design: In-vitro method. Place and Duration of Study: Faculty of Life and Health Science, School of Biomedical Sciences, Ulster University, UK. From Sept 2014 and May 2016. Methodology: Free radical quenching capacity of tea (Earl grey, black tea, Ceylon tea, & green tea) infusions were investigated using persulfate activated ABTS with acetate buffer (pH 4.5) or phosphate buffer saline (pH 7.0) as solvent. Tests were performed using 96-well microplates, 20 µl of sample and 280 µl of ABTS reagent, and calibrated using ascorbic acid, trolox or gallic acid as reference antioxidants. Results: Gallic acid free radical quenching was pH dependent and unsuitable as reference. The free radical quenching capacity of trolox and ascorbic acid was not significantly different at pH 4.5 and pH 7.0. The radical quenching capacity of tea infusions expressed as Trolox Equivalent Antioxidant Capacity (TEAC) or Ascorbic Acid Equivalent Antioxidant Capacity (AAEAC) was greater by 50-300% at pH 7 compared to pH 4.5. Conclusion: The modified ABTS assay is suitable for examining the influence of pH on free radical quenching ability of tea samples. Gallic acid was not a suitable reference compound. The radical quenching capacity of tea infusions increases with rising pH

Antioxidant, Anticancer and Antimicrobial, Effects of Rubia cordifolia Aqueous Root Extract

Received 15th October 2015 Accepted 29th October 2015 Published 10th November 2015Aims: To evaluate the total antioxidant capacity (TAC) of Rubia cordifolia root extracts, to test anticancer activity against MDA-MB-231 breast cancer cell lines, and to evaluate antimicrobial activity of the same extract versus six Gram-positive and negative bacteria. Study Design: In vitro. Place of Study and Duration: School of Biomedical Sciences, Ulster University, July 2014-Sept 2015. Methodology: TAC was tested using ABTS, DPPH, FRAP and Folin assays and values were expressed as mg-gallic acid equivalents per 100 g (GAE/100 g) of sample. Anticancer properties were examined against MDA-MB-231 breast cancer cell lines using Sulforhodamine B assay. Antimicrobial activity was examined using a disk diffusion assay with three Gram-positive (Staphylococcus epidermidis, Staphylococcus aureus and Bacillus cereus) and three Gram-negative (Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi) bacteria. Results: TAC of dry extracts of Rubia cordifolia ranged from 523±43 to 4513±208 (mg GAE mg/100 g) depending on the method of analysis, ABTS> FRAP> Folin > DPPH methods. R. cordifolia dry extract showed cytotoxicity against MDA-MB-231 with IC50 = 44 µg/ml or 5.1µM GAE. No antimicrobial activity was observed against the three Gram-positive, or three Gram-negative bacterial species using the water extract or R. cordifolia. Conclusion: R. cordifolia aqueous extract possess high total antioxidant capacity but values depend on the method of analysis. R. cordifolia extract inhibits MDA-MB-231 breast cancer cells proliferation but nil anti-bacterial activity was observed for three Gram-positive and three Gram-negative bacterial strains tested

Rapid Colorimetric Determination of Methylglyoxal Equivalents for Manuka Honey

Aims: Realization of a rapid colorimetric assay for monitoring levels of methylglyoxal and other dicarbonyl compounds from Manuka honey. Methods: N-acetyl cysteine (NAC) and 2, 4-dinitrophenylhydrazine (DNPH) were adopted as reagents for methylglyoxal colorimetric analysis of honey at 288 or 525 nm, respectively. Results and Discussion: NAC and DNPH produced linear responses for methylglyoxal with:(i) regression coefficient (R2) equal to 0.99 or 0.97, (ii) molar absorptivity (measure of sensitivity) equal to 287±11 or 14189±498 M-1 cm-1, (iii) a minimum detectable concentration (MDC) of 0.18 mM vs 7.3 µM, (iv) upper linearity limit of linearity (ULL) equal to 4mM or 83 µM, and (v) a day-to-day precision of 16.0 and 18.3%, respectively. Low interferences occurred with reducing sugars, glyoxal or 3-deoxy-D-glucosone. For honey with a unique manuka factor (UMF) rating 5+ to UMF18+, the net concentration of dicarbonyl compounds ranged from 1069 mg-methylglyoxal equivalence per kg (mg MeGEq /kg) to 2208 (mg MeGEq /kg) using the NAC assay. For the DNPH assay, the apparent dicarbonyl concentration was 350 to 1009-mg MeGEq /kg honey. Measures of methylglyoxal equivalences were strongly correlated with the UMF rating for honeys (R2=0.98-0.99). Conclusion: The proposed colorimetric analysis of methylglyoxal equivalence in Manuka honey is feasible proposition. Further work is needed for method validation