Hydroquinone-salicylic acid conjugates as novel anti-melasma actives show superior skin targeting compared to the parent drugs

Biodegradable acids for pyrite depression and green flotation separation - an overview

Exponential increasing demands for base metals have made meaningful processing of their quite low-grade (>1%) resources. Froth flotation is the most important physicochemical pretreatment technique for processing low-grade sulfide ores. In other words, flotation separation can effectively upgrade finely liberated base metal sulfides based on their surface properties. Various sulfide surface characters can be modified by flotation surfactants (collectors, activators, depressants, pH regulators, frothers, etc.). However, these reagents are mostly toxic. Therefore, using biodegradable flotation reagents would be essential for a green transition of ore treatment plants, while flotation circuits deal with massive volumes of water and materials. Pyrite, the most abundant sulfide mineral, is frequently associated with valuable minerals as a troublesome gangue. It causes severe technical and environmental difficulties. Thus, pyrite should be removed early in the beneficiation process to minimize its problematic issues. Recently, conventional inorganic pyrite depressants (such as cyanide, lime, and sulfur-oxy compounds) have been successfully assisted or even replaced with eco-friendly and green reagents (including polysaccharide-based substances and biodegradable acids). Yet, no comprehensive review is specified on the biodegradable acid depression reagents (such as tannic, lactic, humic acids, etc.) for pyrite removal through flotation separation. This study has comprehensively reviewed the previously conducted investigations in this area and provides suggestions for future assessments and developments. This robust review has systematically explored depression performance, various adsorption mechanisms, and aspects of these reagents on pyrite surfaces. Furthermore, factors affecting their efficiency were analyzed, and gaps within each area were highlighted.

Study on the preparation of molecularly imprinted ZrO2-TiO2 photocatalyst and the degradation performance of hydroquinone

In this paper, molecularly imprinted Zr-doped TiO2 photocatalysts (MIP-ZrO2-TiO2) were prepared by the molecularly imprinted sol-gel method for the photocatalytic degradation study of hydroquinone (HQ) as the target pollutant. For the effectiveness of the MIP-ZrO2-TiO2 catalyst in degrading HQ, the effects of Zr doping ratio, imprinted molecule dosage, calcination conditions, and pollutant concentration on its photocatalytic activity were investigated. XRD, TEM, XPS, and other techniques were used to evaluate the materials, and the findings revealed that MIP-ZrO2-TiO2 films with imprinted HQ were successfully produced on the ZrO2-TiO2 surface. The optimal preparation conditions were n(Ti):n(Zr) = 100:8, m(HQ) = 1.5 g, 550 °C for the calcination temperature, and 2 h for the calcination duration. The optimum reaction conditions were 10 mg/L HQ concentration, 1 g/L catalyst dose, and a pH of 6.91. According to the findings of photocatalytic tests, during 30 min of UV lamp (365 nm) irradiation, the degradation rates of MIP-ZrO2-TiO2, ZrO2-TiO2, and TiO2 for HQ were 90.58%, 83.94%, and 58.30%, respectively. The findings revealed that the doping of Zr metal and the addition of imprinted molecules improved the photocatalytic activity of TiO2, which can be used for the efficient treatment of low concentrations of hard-to-degrade hydroquinone.

Supramolecular salicylic acid ameliorates rosacea-like eruptions by suppressing NLRP3-mediated inflammasome activation in mice

BACKGROUND

Rosacea is a chronic inflammatory skin disease with immunological dysfunction. Supramolecular salicylic acid (SSA) has the properties of keratolytic, antibacterial, and anti-inflammatory. However, the mechanism of SSA in the treatment of rosacea is still unclear.

OBJECTIVE

To investigate the efficiencies and molecular mechanisms of SSA in rosacea.

METHODS

Forty mice were randomly divided into four groups (10 in each group): control, LL-37, LL-37 + azelaic acid (AzA), and LL-37 + SSA. Forty μl LL-37 (320 μM) was administered intradermally into the dorsal skin of the mice in the latter 3 groups every 12 h and 4 times altogether (0 h, 12 h, 24 h, 36 h). Twenty % AzA was applied on the eruptions after the first and third LL-37 injection (0 h, 24 h) in LL-37 + AzA group, while 30 % SSA was applied after the first injection (0 h) in LL-37 + SSA group. The redness score and redness area were evaluated. The skin barrier function was measured by the transepidermal water loss (TEWL) and pH. The infiltration of inflammatory cells was evaluated by hematoxylin-eosin staining, and the inflammatory biomarkers were analyzed by RT-PCR and immunohistochemistry.

RESULTS

SSA alleviated LL-37-induced rosacea-like inflammation. The increased TEWL and pH induced by LL-37 were also reversed by SSA. In addition, SSA reduced inflammatory cell infiltration and suppressed the production of Toll-like receptor 2, Matrix metallopeptidase 9, kallikrein 5, LL-37 associated with rosacea, and inhibited LL-37-induced NOD-like receptor family, pyrin domain containing 3 (NLRP3)-mediated inflammasome activation in mice.

CONCLUSIONS

Our findings indicated that SSA ameliorated LL-37-induced rosacea-like lesions by suppressing NLRP3-mediated inflammasome activation in mice.

Topical treatment strategies to manipulate human skin pigmentation

Skin pigmentation is a result of melanin produced by melanocytes in the epidermis. Melanocyte activity, along with the type and distribution of melanins, is the main driver for diversity of skin pigmentation. Dark melanin acts to protect against the deleterious effects of ultraviolet (UV) radiation, including photo-aging and skin cancer formation. In turn, UV radiation activates skin melanocytes to induce further pigmentation (i.e., "tanning pathway"). The well-characterized MSH/MC1R-cAMP-MITF pathway regulates UV-induced melanization. Pharmacologic activation of this pathway ("sunless tanning") represents a potential strategy for skin cancer prevention, particularly in those with light skin or the "red hair" phenotype who tan poorly after UV exposure due to MC1R inactivating polymorphisms. Skin hyperpigmentation can also occur as a result of inflammatory processes and dermatological disorders such as melasma. While primarily of cosmetic concern, these conditions can dramatically impact quality of life of affected patients. Several topical agents are utilized to treat skin pigmentation disorders. Here, we review melanogenesis induced by UV exposure and the agents that target this pathway.

Fast synthesis of amides from ethyl salicylate under microwave radiation in a solvent-free system

In this study, amide bond formation, one of the most important reaction in organic chemistry, it was evaluated using ethyl salicylate and ten different primary amines under microwave radiation in a free-solvent system.

The first clinical experience on efficacy of topical flutamide on melasma compared with topical hydroquinone: a randomized clinical trial

Background

Treatment of melasma is unsatisfactory most of the times. Hormonal role is shown to exist in pathogenesis of the melasma, and sex-hormone related drugs may have an effect on melasma.

Aim

To investigate efficacy of 1% flutamide cream versus 4% hydroquinone cream on melasma.

Methods

In a parallel randomized clinical trial, 74 women with melasma were allocated to receive a sunscreen along with 4% hydroquinone cream or 1% flutamide cream. Melasma Area and Severity Index (MASI), mexameter melanin assay, and patient satisfaction were investigated.

Results

Mean age of the participants was 33.8 years. Mean length of time suffering from Melasma was 96.3 months. The subjects reported in average 1.1 hours per day of exposure to sunlight. Mean standardized total patient satisfaction score was 28.8 (standard deviation [SD] 17.2) in flutamide group patients versus 18 (SD 15.5) in control group (P<0.01). Regardless of treatment group, the skin darkness assessed upon MASI scales was reduced over the treatment course (P<0.001). Using mixed effects, longitudinal modeling showed better treatment efficacy based on MASI scale for flutamide group compared to the hydroquinone group (P<0.05). However, longitudinal analysis of mexameter scores did not reveal any significant difference in melanin measurements between flutamide and hydroquinone.

Conclusion

Topical flutamide appeared as effective as topical hydroquinone in treating melasma using mexameter assessment but with a better MASI improvement trend and higher patient satisfaction in flutamide treatment versus topical hydroquinone. As the present study is possibly the first clinical experience on efficacy of topical flutamide on melasma, it would be quite unreasonable to recommend clinical use of it before future studies replicate the results on its efficacy and safety.

Prodrug strategies for enhancing the percutaneous absorption of drugs

The transdermal application of drugs has attracted increasing interest over the last decade or so, due to the advantages it offers, compared to other delivery methods. The development of an efficient means of transdermal delivery can increase drug concentrations, while reducing their systemic distribution, thereby avoiding certain limitations of oral administration. The efficient barrier function of the skin, however, limits the use of most drugs as transdermal agents. This limitation has led to the development of various strategies to enhance drug-skin permeation, including the use of penetration enhancers. This method unfortunately has certain proven disadvantages, such as the increased absorption of unwanted components, besides the drug, which may induce skin damage and irritancy. The prodrug approach to increase the skin’s permeability to drugs represents a very promising alternative to penetration enhancers. The concept involves the chemical modification of a drug into a bioreversible entity that changes both its pharmaceutical and pharmacokinetic characteristics to enhance its delivery through the skin. In this review; we report on the in vitro attempts and successes over the last decade by using the prodrug strategy for the percutaneous delivery of pharmacological molecules.