Hydrogen Peroxide Levels in Freshly Brewed Coffee and the Effects of Storage

SummaryOne of the world’s most consumed beverages, coffee has its origins as early as the 15th century Ethiopia. Although there are studies on caffeine and other components of coffee such as cafestol and kahweol, up until recently knowledge of the presence of hydrogen peroxide (H2O2) in coffee was confined to the scientific community and some informed public. It is a general belief that H2O2 is formed only after long periods of storage or with certain roasting practices. The present study is focused on dispelling the myths of H2O2 in coffee. We first measured H2O2 in freshly brewed coffee from different companies using the ferrous oxidation-xylenol orange binding (FOX) assay. Following this, we examined the time-dependent accumulation of H2O2 and its changes with temperature. Further, H2O2 was estimated in coffee obtained from several local vendors. Contrary to the general belief that the accumulation of H2O2 is an aging phenomenon of coffee, we found this toxicant even in freshly brewed coffee. This was true for all brands tested, and the H2O2 content increased upon storage. The highest increase was seen in coffee stored on the hot plate compared to the ones kept at room temperature (22-25 °C) or in the cold (0-4 °C). The H2O2 content of coffee from different vendors ranged between 0.29 and 0.82 mM, which is 5- to 20-fold higher than the typical H2O2 concentrations at which significant cytotoxic effects have been reported for assay systems using the human Fanconi deficient (PD20 FANCD2−/−) fibroblasts and other cell types. Our findings are deemed to shine new light on the probable toxic effects of a commonly consumed beverage like coffee, and the time and temperature dependent variations of keeping. While there are documented benefits of consumption of coffee, the possible H2O2-medicated toxic effects are critical and should be considered. Future studies are warranted to delineate the contribution of H2O2 in the healthy wellbeing of individuals who consume coffee extensively.

LC-MS Analysis, 15-Lipoxygenase Inhibition, Cytotoxicity, and Genotoxicity of Dissotis multiflora (Sm) Triana (Melastomataceae) and Paullinia pinnata Linn (Sapindaceae)

This study aims to evaluate the anti-inflammatory, cytotoxicity, and genotoxicity activities of Dissotis multiflora (Sm) Triana and Paullinia pinnata Linn used traditionally in Cameroon to treat infectious diseases. Phytochemical screening was carried out using the LC-MS procedure. The ferrous oxidation-xylenol orange (FOX) assay was used to determine the 15-lipoxygenase (15-LOX) inhibitory activity of the plant samples. The tetrazolium-based colorimetric (MTT) assay was performed using Vero cells. The Ames test was carried out using Salmonella typhimurium TA98 and TA100 tester strains. LC-MS chromatogram of D. multiflora led to the identification of four known compounds, namely, 5-(3,5-dinitrophenyl)-2H-tetrazol (2), 2,2'-{[2-(6-amino-9H-purine-9-yl)ethyl]imino}diethanol (14), 1,2,5-oxadiazolo [3,4-b]pyrazine, 5,6-di (3,5-dimethyl-1-piperidyl) (19), and nimbolinin D (20) while four compounds were also identified in P. pinnata known as 2-hydroxycarbamoyl-4-methyl-pentanoic acid (2), pheophorbide A (16), 1-[4-({2-[(1-methyl-1H-indol-5-yl)amino]-4-pyrimidinyl}oxy)-1-naphthyl]-3-[1-(4 methylphenyl)-3-(2-methyl-2-propanyl)-1H-pyrazol-5-yl]urea (17), and nimbolinin D (18). D. multiflora and P. pinnata inhibited 15-LOX activity in concentration-dependent manner. The LC50 (concentration that kills 50% of cells) values of the extracts ranged from 0.13 ± 00 to 1 ± 00 mg/mL for P. pinnata and D. multiflora, respectively. P. pinnata was cytotoxic at concentrations tested while D. multiflora was not. The selectivity index (SI) values ranged from 0.16 to 10.30 on Vero cell lines. No genotoxic effect was observed against both strains tested. These extracts are sources of compounds which can be used to control infectious diseases and associated inflammation. However, caution should be taken while using P. pinnata for medicinal purposes.

DETECTION OF HYDROPEROXIDES IN SOLUTIONS OF PHOTOOXIDIZED PSORALEN

Photooxidized psoralen solutions possess a variety of biological effects, which implementation mechanism may presumably involve hydroperoxides. Here, the hydroperoxide content in photooxidized psoralen solutions was assessed using photometric FOX assay (from Ferrous Oxidation + Xylenol Orange). FOX reagent with 10× content of Xylenol Orange, modified for quantitative analysis of up to 50 μM of hydroperoxides in aqueous phase was used in experiments. During photooxidation of 0.1 mM psoralen in phosphate buffer solution, hydroperoxide production increases with dose of UVA irradiation (~2.5 μM eq. of H2O2 for dose of 252 kJ/m2 and ~11 μM eq. of H2O2 for dose of 1512 kJ/m2) and reaches ~16.5 μM eq. of H2O2 at the highest dose investigated (3024 kJ/m2). A comparison of kinetics of psoralen photolysis and hydroperoxide generation allows us to suggest that generation of hydroperoxide results from the secondary photochemical processes involving psoralen photoproducts, presumably from photoinduced autooxidation of aldehydic photoproducts of psoralen.