Incidence and prevalence of dementia: A 2015-2020 population-based study in the Campania Region of Italy

OBJECTIVE

To provide population-based estimates of prevalence and incidence of any dementia and Alzheimer's dementia in the Campania Region (South Italy), and to validate towards a clinical registry.

METHODS

Population-based study, using routinely collected healthcare data of individuals living in the Campania Region (South Italy) from 2015 to 2020. We included individuals aged ≥65 years alive at the prevalence day (1 January 2021) who had at least one administrative record for dementia and/or Alzheimer's dementia from 2015 to 2020. Age-and sex-standardised prevalence rates were calculated using direct standardisation method (European population in 2020 as reference population). To estimate incidence, we tested three possible algorithms, which differed for the duration of the time interval between study baseline (Jan 1, 2015) and index date (first record for dementia and/or Alzheimer's dementia in administrative databases). We employed a clinical database for the validation of our algorithms towards neuropsychological test results.

RESULTS

Among individuals aged over 65, 80,392 had dementia, of which 35,748 had Alzheimer's dementia. The age- and sex-standardized prevalence rates per 1,000 individuals for any dementia and Alzheimer's dementia were 77.64 (95%CI = 77.57; 77.68) and 34.05 (95%CI = 34.01; 34.09), respectively. There were 82.10 incident of any dementia cases per 100,000 per year (0.79 sensitivity and 0.62 specificity), and 59.89 incident cases of any dementia per 100,000 per year (0.80 sensitivity and 0.59 specificity). The capture-recapture method showed very low number of undetected cases (1.7% for any dementia and 3.0% for Alzheimer's dementia). Our algorithms showed acceptable performance with AUC ranging from 0.59 to 0.72, and double likelihood ratio of correctly identifying individuals above and below MMSE standard cut-offs (24 and 26).

CONCLUSIONS

Prevalence and incidence of any dementia and Alzheimer's dementia in the Campania Region (South Italy) from 2015 to 2020 are in line with previous estimates from other countries. Our algorithm, integrating administrative and clinical data, holds potential for assessing dementia's epidemiological burden, identifying risk factors, planning healthcare access, and developing prevention strategies.

Impact of COVID-19 and system recovery in delivering healthcare to people with multiple sclerosis: a population-based Study

BACKGROUND

COVID-19 pandemic has affected the management of multiple sclerosis (MS).

OBJECTIVE

To explore the impact of COVID-19 on healthcare delivery to people with MS and the subsequent recovery of the system.

METHODS

In this population-based study in the Campania Region (Italy), we included people with MS across pre-COVID-19, lockdown, pre-vaccination, and vaccination periods. Differences in continuous outcomes between periods were explored using linear mixed models (annualized hospitalization rate (AHR) and adherence measured as medication possession ratio (MPR)). Differences in disease-modifying treatment (DMT) prescription rates (first DMT prescription, any DMT switch, switch from platform to highly effective DMT, and combination of first DMT prescription and any DMT switch) were assessed using an interrupted time series design.

RESULTS

Compared with pre-COVID-19, AHR decreased during the lockdown (Coeff = 0.64;95%CI = -0.69, -0.59; p < 0.01), and remained lower during pre-vaccination and vaccination periods. Adherence decreased during pre-vaccination (Coeff = -0.04;95%CI = -0.05, -0.03; p < 0.01) and vaccination periods (Coeff = -0.07;95%CI = -0.08, -0.07; p < 0.01). After the lockdown, there was an increase in any DMT switch (IRR 2.05 95%CI 1.38,3.05; p < 0.01), in switch from platform to highly effective DMTs (IRR 4.45;95%CI 2.48,8.26; p < 0.01) and in first DMT prescriptions (IRR 2.48;95%CI 1.64,3.74; p < 0.01).

CONCLUSIONS

DMT prescriptions quickly returned to pre-pandemic levels, reflecting good health system recovery. However, adherence has remained lower than the past, as from suboptimal care. Assessing long-term COVID-19 impact on MS healthcare is warranted.

Fertility, pregnancy and childbirth in women with multiple sclerosis: a population-based study from 2018 to 2020

BACKGROUND

We aim to evaluate whether fertility, pregnancy, delivery and breastfeeding have been actually improving in women with multiple sclerosis (MS), compared with general population, and in relation to treatment features.

METHODS

We included 2018-2020 population-level healthcare data on women with MS living in the Campania region (Italy). Fertility, pregnancy and delivery outcomes were obtained from Certificate of Delivery Assistance; breastfeeding was collected up to 6 months after delivery by trained personnel.

RESULTS

Out of 2748 women with MS in childbearing age, 151 women delivered 156 babies. Fertility rate was 0.58 live births per woman with MS, compared with 1.29 in Campania region and 1.25 in Italy. Disease-modifying treatment (DMT) continuation during pregnancy was associated with lower birth weight (coeff -107.09; 95% CI -207.91 to -6.26; p=0.03). Exposure to DMTs with unknown/negative effects on pregnancy was associated with birth defects (OR 8.88; 95% CI 1.35 to 58.41; p=0.02). Birth defects occurred in pregnancies exposed to dimethyl fumarate (2/21 exposed pregnancies), fingolimod (1/11 exposed pregnancies) and natalizumab (2/30 exposed pregnancies). After delivery, 18.8% of women with MS were escalated of DMT efficacy, while 50.7% started on same/similar-efficacy DMTs, and 30.5% did not receive DMT. The probability of breastfeeding was higher in women who were treated with breastfeeding-safe DMTs (OR 5.57; 95% CI 1.09 to 28.55; p=0.03).

CONCLUSIONS

Fertility rate in women with MS remains below the general population. Family planning and subsequent DMT decisions should aim to achieve successful pregnancy, delivery and breastfeeding outcomes, while controlling disease activity.

Emergency medical care for multiple sclerosis: A five-year population study in the Campania Region (South Italy)

BACKGROUND

Emergency hospital admissions are common in multiple sclerosis (MS), and can highlight unmet medical needs.

OBJECTIVES

To evaluate burden, predictors and outcomes of MS emergency admissions.

METHODS

This is a population-based study, conducted in the Campania Region (South Italy) from 2015 to 2019, using hospital discharge records, drug prescriptions and outpatients. The risk of emergency hospital admissions and the likelihood of worse outcomes were evaluated using the Cox regression and multinomial logistic regression models, respectively, in relation to age, sex, disease-modifying treatments (DMTs), comorbidities and adherence.

RESULTS

We recorded 1225 emergency admissions for 1001 patients (out of 5765 prevalent MS patients), overall costing 4,143,764.67 EUR. The risk of emergency admissions increased with age (hazard ratio (HR) = 1.02; 95% confidence interval (CI) = 1.01, 1.03; p < 0.01) and comorbidities (HR = 1.62; p < 0.01), and decreased in patients using DMTs (interferon beta/peg-interferon beta/glatiramer acetate HR = 0.19; p < 0.01; teriflunomide/dimethyl-fumarate/fingolimod HR = 0.18; p < 0.01, and alemtuzumab/cladribine/natalizumab/ocrelizumab HR = 0.21; p < 0.01), and with higher adherence (HR = 0.18; 95% CI = 0.13, 0.26; p < 0.01). Following emergency admission, older age was associated with probability of death (n = 63) (odds ratio (OR) = 1.06; p < 0.01) and discharge to long-term facility (n = 65) (OR = 1.03; p = 0.01).

CONCLUSION

With 17% people with MS requiring emergency medical care over 5 years, improved management of DMTs and comorbidities could potentially reduce their medical, social and financial burden.

Kidney Replacement Treatment in South-Western Italy (Campania): Population-Based Study on Gender and Residence Inequalities in Health Care Access

The aim of this study was to investigate the epidemiology of kidney replacement treatment (KRT) in Italy with a focus on gender and residence. As a population-based study using administrative databases from the Campania region of Italy between 2015 and 2018, the study outcomes included diagnoses of haemodialysis, peritoneal dialysis, kidney transplant, and mortality. A total of 11,713 residents in Campania were on KRT from 2015 to 2018. The annual prevalence ranged between 1000 and 1015 patients per million population (pmp) for haemodialysis, between 115 and 133 pmp for peritoneal dialysis, and between 2081 and 2245 pmp for kidney transplant. The annual incidence ranged between 160 and 185 pmp for de novo haemodialysis and between 59 and 191 pmp for kidney transplant. Annual mortality ranged between 12.8% and 14.2% in haemodialysis, between 5.2% and 13.8% in peritoneal dialysis, and between 2.4% and 3.3% in kidney transplant. In Cox regression targeting mortality, significant HRs were found for age (95%CI = 1.05/1.05), kidney transplant (compared to haemodialysis: 0.37/0.47), residence in suburban areas (1.03/1.24), and de novo dialysis incidence in years 2015–2018 (1.01/1.17). The annual rate of kidney transplant was 2.6%. In regression targeting kidney transplant rate, significant HRs were found for female gender (0.67/0.92), age (0.93/0.94), residence in suburban areas (0.65/0.98), and de novo incidence of dialysis in 2015–2018 (0.49/0.71). The existence of socioeconomic inequities in KRT is suggested by the evidence that gender and suburban residence predicted mortality and/or access to kidney transplant.

Multiple Sclerosis in the Campania Region (South Italy): Algorithm Validation and 2015-2017 Prevalence

We aim to validate a case-finding algorithm to detect individuals with multiple sclerosis (MS) using routinely collected healthcare data, and to assess the prevalence of MS in the Campania Region (South Italy). To identify individuals with MS living in the Campania Region, we employed an algorithm using different routinely collected healthcare administrative databases (hospital discharges, drug prescriptions, outpatient consultations with payment exemptions), from 1 January 2015 to 31 December 2017. The algorithm was validated towards the clinical registry from the largest regional MS centre (n = 1460). We used the direct method to standardise the prevalence rate and the capture-recapture method to estimate the proportion of undetected cases. The case-finding algorithm including individuals with at least one MS record during the study period captured 5362 MS patients (females = 64.4%; age = 44.6 ± 12.9 years), with 99.0% sensitivity (95% CI = 98.3%, 99.4%). Standardised prevalence rate per 100,000 people was 89.8 (95% CI = 87.4, 92.2) (111.8 for females [95% CI = 108.1, 115.6] and 66.2 for males [95% CI = 63.2, 69.2]). The number of expected MS cases was 2.7% higher than cases we detected. We developed a case-finding algorithm for MS using routinely collected healthcare data from the Campania Region, which was validated towards a clinical dataset, with high sensitivity and low proportion of undetected cases. Our prevalence estimates are in line with those reported by international studies conducted using similar methods. In the future, this cohort could be used for studies with high granularity of clinical, environmental, healthcare resource utilisation, and pharmacoeconomic variables.

Prevalence of multiple sclerosis in the South of Italy based on healthcare administrative data

Background

Multiple sclerosis (MS) is an heterogenous disease whose prevalence varies in Europe. Hereby, we aimed to estimate prevalence of MS in the Campania Region of Italy.

Methods

To identify individuals with MS living in the Campania Region of Italy, we extracted data from the following healthcare administrative databases: hospital discharge records, regional drug registry, and specialist outpatient visits from Jan-2015 to 3Dec-2017. Individuals alive on the 1-Jan-2018 were included to capture prevalence on this date. Age-sex standardised prevalence rates were calculated using the direct standardisation method; the European population in 2018 was considered as reference population. To assess differences in the prevalence ratios across the five provinces of the region, standardised morbility ratios (SMR) were calculated. To calculate 95% confidence intervals (95%CI) for the standardised rates, the Byar’s approximation method based on the Poisson distribution was used.

Results

We identified 5,361 individuals with MS (females 64.5%, age 45.6±12.7 years). Standardised prevalence rate per 100,000 people was 90.0 cases (95%CI=87.60, 92.40) (112.07 for females [95%CI=108.36, 115.88] and 66.20 for males [95%CI=63.26, 69.25]). The SMR in the province of Naples, the most densely populated, was 0.90 (95%CI=0.86, 0.96), whereas the highest SMR was found in the province of Salerno (SMR=1.30; 95%CI=1.23, 1.38), and the lowest in the province of Caserta (SMR=0.89; 95%CI=0.82-0.96).

Conclusions

Prevalence of MS in the Campania Region is lower than previous estimates from smaller areas in the North of Italy, suggesting a longitudinal gradient. Differences within the Region could be explained by genetic/environmental background and healthcare organization (e.g., missing diagnoses). In the future, healthcare administrative databases could be used to monitor MS prevalence/incidence and to plan healthcare resource utilization.

Key messages

Prevalence of MS in the Campania Region is 90 cases per 100,000 people. It is lower than previous estimates from smaller areas in the North of Italy, suggesting a longitudinal gradient. Differences within the Region could be explained by genetic/environmental background and healthcare organization (e.g., missing diagnoses).

Cytotoxic and antioxidant activity of 4-methylthio-3-butenyl isothiocyanate from Raphanus sativus L. (Kaiware Daikon) sprouts

There is high current interest in the chemopreventive potential of Brassica vegetables (cruciferae), particularly due to their content in glucosinolates (GL), which upon myrosinase hydrolysis release the corresponding isythiocyanates (ITC). Some ITCs, such as sulforaphane (SFN) from broccoli ( Brassica oleacea italica), have been found to possess anticancer activity through induction of apoptosis in selected cell lines, as well as indirect antioxidant activity through induction of phase II detoxifying enzymes. Japanese daikon ( Raphanus sativus L.) is possibly the vegetable with the highest per capita consumption within the Brassicaceae family. Thanks to a recently improved gram scale production process, it was possible to prepare sufficient amounts of the GL glucoraphasatin (GRH) as well as the corresponding ITC 4-methylthio-3-butenyl isothiocyanate (GRH-ITC) from its sprouts. This paper reports a study on the cytotoxic and apoptotic activities of GRH-ITC compared with the oxidized counterpart 4-methylsulfinyl-3-butenyl isothiocyanate (GRE-ITC) on three human colon carcinoma cell lines (LoVo, HCT-116, and HT-29) together with a detailed kinetic investigation of the direct antioxidant/radical scavenging ability of GRH and GRH-ITC. Both GRH-ITC and GRE-ITC reduced cell proliferation in a dose-dependent manner and induced apoptosis in the three cancer cell lines. The compounds significantly ( p < 0.05) increased Bax and decreased Bcl2 protein expression, as well as producing caspase-9 and PARP-1 cleavage after 3 days of exposure in the three cancer cell lines. GRH-ITC treatment was shown to have no toxicity with regard to normal human lymphocytes (-15 +/- 5%) in comparison with SFN (complete growth inhibition). GRH and GRH-ITC were able to quench the 2,2-diphenyl-1-picrylhydrazyl radical, with second-order rate constants of 14.0 +/- 2.8 and 43.1 +/- 9.5 M(-1) s(-1), respectively (at 298 K in methanol), whereas the corresponding value measured here for the reference antioxidant alpha-tocopherol was 425 +/- 40 M (-1) s (-1). GRH reacted with H2O2 and tert-butyl hydroperoxide in water (pH 7.4) at 37 degrees C, with rate constants of 1.9 +/- 0.3 x 10(-2) and 9.5 +/- 0.3 x 10(-4) M(-1) s (-1) (paralleling recently developed synthetic antioxidants) being quantitatively (>97%) converted to GRE. It is demonstrated that GRH-ITC has interesting antioxidant/radical scavenging properties, associated with a selective cytotoxic/apoptotic activity toward three human colon carcinoma cell lines, and very limited toxicity on normal human T-lymphocytes.

The unusual reaction of semiquinone radicals with molecular oxygen

Hydroquinones (benzene-1,4-diols) are naturally occurring chain-breaking antioxidants, whose reactions with peroxyl radicals yield 1,4-semiquinone radicals. Unlike the 1,2-semiquinone radicals derived from catechols (benzene-1,2-diols), the 1,4-semiquinone radicals do not always trap another peroxyl radical, and instead the stoichiometric factor of hydroquinones varies widely between 0 and 2 as a function of ring-substitution and reaction conditions. This variable antioxidant behavior has been attributed to the competing reaction of the 1,4-semiquinone radical with molecular oxygen. Herein we report the results of experiments and theoretical calculations focused on understanding this key reaction. Our experiments, which include detailed kinetic and mechanistic investigations by laser flash photolysis and inhibited autoxidation studies, and our theoretical calculations, which include detailed studies of the reactions of both 1,4-semiquinones and 1,2-semiquinones with O2, provide many important insights. They show that the reaction of O2 with 2,5-di-tert-butyl-1,4-semiquinone radical (used as model compound) has a rate constant of 2.4 +/- 0.9 x 10(5) M-1 s-1 in acetonitrile and as high as 2.0 +/- 0.9 x 10(6) M-1 s-1 in chlorobenzene, i.e., similar to that previously reported in water at pH approximately 7. These results, considered alongside our theoretical calculations, suggest that the reaction occurs by an unusual hydrogen atom abstraction mechanism, taking place in a two-step process consisting first of addition of O2 to the semiquinone radical and second an intramolecular H-atom transfer concerted with elimination of hydroperoxyl to yield the quinone. This reaction appears to be much more facile for 1,4-semiquinones than for their 1,2-isomers.

Monitoring of environmental pollutants by bioluminescent bacteria

This review deals with the applications of bioluminescent bacteria to the environmental analyses, published during the years 2000-2007. The ecotoxicological assessment, by bioassays, of the environmental risks and the luminescent approaches are reported. The review includes a brief introduction to the characteristics and applications of bioassays, a description of the characteristics and applications of natural bioluminescent bacteria (BLB), and a collection of the main applications to organic and inorganic pollutants. The light-emitting genetically modified bacteria applications, as well as the bioluminescent immobilized systems and biosensors are outlined. Considerations about commercially available BLB and BLB catalogues are also reported. Most of the environmental applications, here mentioned, of luminescent organisms are on wastewater, seawater, surface and ground water, tap water, soil and sediments, air. Comparison to other bioindicators and bioassay has been also made. Various tables have been inserted, to make easier to take a rapid glance at all possible references concerning the topic of specific interest.

Kinetic and Thermochemical Study of the Antioxidant Activity of Sulfur-Containing Analogues of Vitamin E

Sulfur-containing analogues of vitamin E (thiachromanols), either linked or not to a catechol moiety, were synthesized and their hydrogen-atom donating ability evaluated. The determination of the O--H bond dissociation enthalpy (BDE) of the alpha-tocopherol analogue 4 by the electron paramagnetic resonance (EPR) equilibration technique provided a value of 78.9 kcal mol(-1), that is, approximately 1.8 kcal mol(-1) higher than that of alpha-tocopherol. The kinetic rate constants for the reaction with peroxyl radicals (kinh), measured by inhibited autoxidation studies, showed that thiachromanols react 2.5 times slower than the corresponding tocopherols, in agreement with the higher BDE value. This behavior was explained, on the basis of crystallographic analyses and DFT calculations, in terms of a change in the molecular geometry caused by insertion of a sulfur atom into the framework of vitamin E. This behavior implies a greater deviation of the condensed ring from coplanarity with the aromatic ring, thus giving rise to a decrease in the conjugative stabilization of the phenoxyl radical and consequently to an increase in the O--H bond strength. Although less reactive than tocopherols, thiachromanols may, however, act as bimodal antioxidants as a result of the hydroperoxide decomposing ability of the sulfur atom.

Synthesis and antioxidant activity of [60]fullerene-BHT conjugates

Fullerene derivatives incorporating one or two 3,5-di-tert-butyl-4-hydroxyphenyl groups were synthesized by 1,3-dipolar cycloaddition of azomethine ylides to C(60). The O-H bond dissociation enthalpies (BDEs) of these compounds were estimated by studying, by means of EPR spectroscopy, the equilibration of each of these phenols and 2,6-di-tert-butyl-4-methylphenol (BHT) with the corresponding phenoxyl radicals. The antioxidant activity of the investigated phenols was also determined by measuring the rate constants for their reaction with peroxyl radicals in controlled autoxidation experiments and compared to that recorded under identical experimental settings for [60]fullerene itself and unlinked BHT. The results indicate that linking of the BHT structure to C(60) does not substantially alter the thermochemistry and kinetics of its reaction with peroxyl radicals, but such adducts may behave as interesting bimodal radical scavengers. The inherent rate constant for trapping of peroxyl radicals by C(60) per se (k(inh)=3.1+/-1.1 x 10(2) m(-1) s(-1)) indicates that, contrary to previous reports, [60]fullerene is an extremely weak chain-breaking antioxidant.

Antioxidant profile of ethoxyquin and some of its S, Se, and Te analogues

6-(Ethylthio)-, 6-(ethylseleno)-, and 6-(ethyltelluro)-2,2,4-trimethyl-1,2-dihydroquinoline-three heavier chalcogen analogues of ethoxyquin-were prepared by dilithiation of the corresponding 6-bromodihydroquinoline followed either by treatment with the corresponding diethyl dichalcogenide (sulfur derivative) or by insertion of selenium/tellurium into the carbon-lithium bond, oxidation to a diaryl dichalcogenide, borohydride reduction, and finally alkylation of the resulting areneselenolate/arenetellurolate. Ethoxyquin, its heavier chalcogen analogues, and the corresponding 6-PhS, 6-PhSe, and 6-PhTe derivatives were assayed for both their chain-breaking antioxidative capacity and their ability to catalyze reduction of hydrogen peroxide in the presence of a stoichiometric amount of a thiol reducing agent (thiol peroxidase activity). Ethoxyquin itself turned out to be the best inhibitor of azo-initiated peroxidation of linoleic acid in a water/chlorobenzene two-phase system. In the absence of N-acetylcysteine as a coantioxidant in the aqueous phase, it inhibited peroxidation as efficiently as alpha-tocopherol but with a more than 2-fold longer inhibition time. In the presence of 0.25 mM coantioxidant in the aqueous phase, the inhibition time was further increased by almost a factor of 2. This is probably due to thiol-mediated regeneration of the active antioxidant across the lipid-aqueous interphase. The ethyltelluro analogue 1d of ethoxyquin was a similarly efficient quencher of peroxyl radicals compared to the parent in the two-phase system, but less regenerable. Ethoxyquin was found to inhibit azo-initiated oxidation of styrene in the homogeneous phase (chlorobenzene) almost as efficiently (kinh = (2.0 +/- 0.2) x 106 M-1 s-1) as alpha-tocopherol with a stoichiometric factor n = 2.2 +/- 0.1. At the end of the inhibition period, autoxidation was additionally retarded, probably by ethoxyquin nitroxide formed during the course of peroxidation. The N-H bond dissociation enthalpy of ethoxyquin (81.3 +/- 0.3 kcal/mol) was determined by a radical equilibration method using 2,6-dimethoxyphenol and 2,6-di-tert-butyl-4-methylphenol as equilibration partners. Among the investigated compounds, only the tellurium analogues 1d and, less efficiently, 1g had a capacity to catalyze reduction of hydrogen peroxide in the presence of thiophenol. Therefore, analogue 1d is the only antioxidant which is multifunctional (chain-breaking and preventive) in character and which can act in a truly catalytic fashion to decompose both peroxyl radicals and organic hydroperoxides in the presence of suitable thiol reducing agents.

Regenerable Chain-Breaking 2,3-Dihydrobenzo[b]selenophene-5-ol Antioxidants

A series of 2,3-dihydrobenzo[b]selenophene-5-ol antioxidants was prepared by subjecting suitably substituted allyl 4-methoxyphenyl selenides to microwave-induced seleno-Claisen rearrangement/intramolecular Markovnikov hydroselenation followed by boron tribromide-induced O-demethylation. The novel antioxidants were assayed for their capacity to inhibit azo-initiated peroxidation of linoleic acid in a water/chlorobenzene two-phase system containing N-acetylcysteine as a thiol reducing agent in the aqueous phase. Antioxidant efficiency as determined by the inhibited rate of peroxidation, Rinh, increased with increasing methyl substitution (Rinh=46-26 microM/h), but none of the compounds could match alpha-tocopherol (Rinh=22 microM/h). Regenerability as determined by the inhibition time, Tinh, in the presence of the thiol regenerating agent decreased with increasing methyl substitution. Thus, under conditions where the unsubstituted compound 5a inhibited peroxidation for more than 320 min, alpha-tocopherol worked for 90 min and the trimethylated antioxidant 5g for 60 min only. Sampling of the aqueous phase at intervals during peroxidation using antioxidant 5a showed that N-acetylcysteine was continuously oxidized with time to the corresponding disulfide. In the absence of the regenerating agent, compounds 5 inhibited peroxidation for 50-60 min only. A (RO)B3LYP/LANL2DZdp//B3LYP/LANL2DZ model was used for the calculation of homolytic O-H bond dissociation enthalpies (BDE) and adiabatic ionization potentials (IP) of phenolic antioxidants 5. Both BDE (80.6-76.3 kcal/mol) and IP (163.2-156.0 kcal/mol) decrease with increasing methyl substitution. The phenoxyl radical corresponding to phenol 5g gave an intense ESR signal centered at g=2.0099. The H-O bond dissociation enthalpy of the phenol was determined by a radical equilibration method using BHA as an equilibration partner. The observed BDE (77.6+/-0.5 kcal/mol) is in reasonable agreement with calculations (76.3 kcal/mol). As judged by calculated log P values, the lipophilicity of compounds 5 increased slightly when methyl groups were introduced into the phenolic moiety (2.9>C log P<4.2). The capacity of compounds 5a (kinh=3.8x10(5) M-1 s-1) and 5g (kinh=1.5x10(6) M-1 s-1) to inhibit azo-initiated autoxidation of styrene in the homogeneous phase (chlorobenzene) was also studied. More efficient regeneration at the lipid-aqueous interphase is the most likely explanation why the intrinsically poorest antioxidant 5a can outperform its analogues as well as alpha-TOC in the two-phase system. Possible mechanisms of regeneration are discussed and evaluated.

Electronic and Hydrogen Bonding Effects on the Chain-Breaking Activity of Sulfur-Containing Phenolic Antioxidants

A kinetic and thermodynamic investigation of phenols para-substituted with thiyl (SR), sulfinyl (SOR), and sulfonyl (SO(2)R) groups and ortho-substituted with thiyl groups is reported. The effect of the sulfur substituents on the O-H bond dissociation enthalpy values, BDE(O-H), was measured by means of the EPR radical equilibration technique and the reactivity toward peroxyl radicals, k(inh), of these phenolic antioxidants was determined by inhibited autoxidation studies. An inverse correlation between these two parameters was found. A p-SMe substituent decreased the BDE(O-H) value to a lesser extent than a p-OMe group (-3.6 vs -4.4 kcal/mol), whereas the effect of the same groups in an ortho position showed an opposite trend (-0.85 vs -0.2 kcal/mol). The latter result is explained in terms of the different strength of the intramolecular hydrogen bond between the OH proton and the sulfur or oxygen substituents in ortho derivatives. ESI-MS analysis of the products formed by reacting the sulfides with peroxyl radicals from the azoinitiator AIBN revealed the formation of a complex mixture of products, which may play an important role in determining the overall antioxidant activity of the parent compounds.

Synthesis and Antioxidant Profile of all-rac-α-Selenotocopherol

all-rac-alpha-Selenotocopherol (6c) has been synthesized in 11 steps in 6.6% total yield. Key steps include chloromethylation to approach the persubstituted aromatic 9b and cyclization of alcohol precursor 10 by radical homolytic substitution at selenium to form the selenotocopherol heterocycle. Determination of the OH bond dissociation enthalpy (BDE) of 6c by electron paramagnetic resonance (EPR) equilibration techniques gave a value of 78.1 +/- 0.3 kcal mol(-1), approximately 1 kcal mol(-1) higher than that of alpha-tocopherol. Kinetic studies performed by measuring oxygen uptake of the induced oxidation of styrene in the presence of an antioxidant showed that selenotocopherol (6c) was a slightly poorer inhibitor than alpha-tocopherol, in agreement with the BDE values. In contrast to simpler selenotocopherol analogues, 6c was not regenerable in the presence of a stoichiometric coreductant in a two-phase lipid peroxidation model.