Transition metal‐catalysed processes have been widely used for the functionalization of inert C−H bonds. Strategies for the functionalization of the benzylic C−H position having a relatively weak C−H ...bond (bond dissociation energy∼ 80–90 kcal/mol) differ from the inert aliphatic and aromatic C−H positions with stronger C−H bonds. The recent advances in the direct activation of the benzylic position through the generation of C(sp3) radicals have demonstrated the potential of electrochemistry and photochemistry as a means for constructing new chemical bonds. This review will cover the recent progress of benzylic C−H functionalization through organic radical strategies employing photochemistry and electrochemistry as sustainable tools. In addition, the mechanistic details of the typical reactions have been included which, in turn, will help the researchers to look at this promising area from a different perspective towards new discoveries and often hidden opportunities.
Background
Over the last months, during the COVID‐19 pandemic, a growing number of chilblain‐like lesions were reported mainly in children and rarely in young adults. The relationship with SARS‐CoV‐2 ...infection was postulated, often without any laboratory, instrumental or clinical confirmation. The disclosure of information about chilblain‐like lesions as a COVID‐19 manifestation in social media has created concern in children’s families and paediatricians.
Objectives
To verify whether the chilblain‐like lesions were caused by SARS‐CoV‐2 infection.
Methods
Prospective study on a case series including children who presented with acral lesions at the Pediatric Dermatology Outpatient and Pediatric Emergency Unit of the University of Bologna, from 1 April to 30 April 2020. We reported demographical, laboratory and clinical features, history of close contact with COVID‐19 patients, presence of similar skin lesions in other family members, precipitating and risk factors for chilblain onset.
Results
We evaluated eight patients (five females, three males) aged between 11 and 15 years. We excluded acute or previous SARS‐CoV‐2 infection with RT‐PCR nasopharyngeal swab, serum antibody levels using chemiluminescent immunoassays. Other acute infections causing purpuric lesions at the extremities were negative in all patients. Skin lesion biopsy for histological and immunohistochemical evaluation was made in two cases and was consistent with chilblain. PCR assay on skin lesion biopsy for parvovirus B19, Mycoplasma pneumoniae and SARS‐CoV‐2 was performed in a patient and resulted negative. We identified common precipitating and risk factors: physical (cold and wet extremities, low BMI), cold and wet indoor and outdoor environment, behaviours, habits and lifestyle. We therefore reached a diagnosis of primary chilblains.
Conclusions
During the COVID‐19 pandemic, a ‘cluster’ of primary chilblains developed in predisposed subjects, mainly teenagers, due to cold exposure in the lockdown period. Laboratory findings support our hypothesis, although it is also possible that an unknown infectious trigger may have contributed to the pathogenesis.
Dental caries and periodontal diseases remain a challenge for oral health, especially given the lack of effective and safe treatment options that are currently available. Against the backdrop of an ...ongoing antimicrobial resistance crisis, a renewed interest in traditional medicinal plants as a potential source of new bioactive compounds has surfaced. In this context, we systematically screened the antimicrobial and anti-biofilm activities of both ethanolic and aqueous extracts of nine Algerian medicinal plants (
Artemisia herba alba, Centaurium erythraea, Juglans regia, Laurus nobilis, Matricaria recutita, Mentha pulegium, Mentha piperita, Origanum vulgare
and
Taraxacum officinale
). To evaluate the activity spectrum of the extracts, the screening was carried out against an extensive collection of
Streptococcus
,
Enterococcus
and
Lacticaseibacillus
isolates recovered from dental plaques of Algerian patients. Broad-spectrum antimicrobial and anti-biofilm properties were observed, especially among ethanolic extracts, which marks them as a promising source for bioactive compounds to control oral biofilms. The ethanolic extract of
O. vulgare
, which showed the most promising effects in the initial screening, was further characterized. We first verified the biocompatibility of this extract using human oral keratinocytes and selected a range of non-cytotoxic concentrations (0.195–0.781 mg/ml) to further validate its anti-biofilm and anti-virulence potential. At these concentrations, the extract not only prevented biofilm formation (10.04 ± 0.75–87.91 ± 9.08% of reduction) of most dental plaque isolates on a polystyrene surface, but also significantly reduced their adherence to hydroxyapatite (34.58 ± 9.09–62.77 ± 0.95%). Moreover, the extract showed curative potential against mature biofilms grown under conditions mimicking the oral niche. In addition to its anti-biofilm properties, we observed an inhibition of glucosyltransferase activity, a reduction in acidogenesis and a downregulation in the expression of multiple virulence-associated genes for extract-treated samples. Since anti-virulence properties are more robust to the development of resistance, they provide an attractive complementation to the antimicrobial activities of the extract. Thymol was identified as an important active compound of the extract using GC–MS analysis, but synergy with other compounds was also detected, suggesting a potential advantage of using the whole extract over purified thymol. Further research into the bioactive compounds of the
O. vulgare
ethanolic extract could yield novel products to fight dental caries.
Interrelationships among skeletal maturity status, body size, ventilator thresholds (VT) and peak oxygen uptake (VO2peak) were considered in 47 adolescent male soccer players aged 12.5-15.4 years. ...Body mass, stature, and the triceps and subscapular skinfolds were measured. The latter were used to estimate fat mass and fat-free mass. Skeletal age was assessed with the Fels method. VO2peak and VO2 at the first (VT1) and second (VT2) ventilatory thresholds were determined during an incremental maximal exercise test on a motorized treadmill. Ratio standards and allometric models were used in the analysis. Scaling exponents suggested linearity for all combinations between size descriptors and physiological variables, except between log-transformed values of VT1 and body mass (mL·kg-0.801·min, 95%CI: 0.649 to 0.952). Early maturing players attained greater values than players classified as "on-time" in skeletal maturity for the three ventilatory parameters expressed in absolute terms (d ranged from 0.65 to 0.71). The differences were attenuated after normalizing for mass descriptors using ratio standards and scaled variables (d ranged from 0.00 to 0.31). The results suggested significant variability between maturity groups when moving from VT1 to maximal metabolic conditions expressed by unit of stature (VT1: t = -2.413, p = 0.02, d = 0.60; VT2: t = -2.488, p = 0.02, d = 0.65; VO2peak: t = -2.475, p = 0.02, d = 0.65). Skeletal maturity status and associated variation in overall body size affects VT1, VT2 and VO2peak. The observed scaling of ventilatory outputs for body size may be related to the better running economy and smaller body size of average maturing athletes.
Many speleothems can be assigned to one of two morphological groups: massive speleothems, which consist of compact bulks of material, and coralloids, which are domal to digitate in form. Faster ...growth on protrusions of the substrate occurs in the typical growth layers of coralloids (where those layers are termed “coralloid accretions”), but it is not observed in the typical layers of massive speleothems, which in contrast tend to smoothen the speleothem surface (and can therefore be defined as “smoothing accretions”). The different growth rates on different areas of the substrate are explainable by various mechanisms of CaCO3 deposition (e.g., differential aerosol deposition, differential CO2 and/or H2O loss from a capillary film of solution, deposition in subaqueous environments). To identify the causes of formation of coralloids rather than massive speleothems, this article provides data about δ13C and δ18O at coeval points of both smoothing and coralloid accretions, examining the relationship between isotopic composition and the substrate morphology. In subaerial speleothems, data show enrichment in heavy isotopes both along the direction of water flow and toward the protrusions. The first effect is due to H2O evaporation and CO2 degassing during a gravity-driven flow of water (gravity stage) and is observed in smoothing accretions; the second effect is due to evaporation and degassing during water movement by capillary action from recesses to prominences (capillary stage) and is observed in subaerial coralloids. Both effects coexist in smoothing accretions interspersed among coralloid ones (intermediate stage). Thus this study supports the origin of subaerial coralloids from dominantly capillary water and disproves their origin by deposition of aerosol from the cave air. On the other hand, subaqueous coralloids seem to form by a differential mass-transfer from a still bulk of water toward different zones of the substrate along diffusion flux vectors of nutrients perpendicular to the iso-depleted surfaces. Finally, this isotopic method has proved useful to investigate the controls on speleothem morphology and to obtain additional insights on the evolution of aqueous solutions inside caves.
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