Synthesis and Preliminary Evaluation of Several Chalcone Derivatives as Sunscreen Compounds

Ultrafast excited-state dynamics of 4-hydroxychalcone: role of intramolecular charge transfer and photoacidity

Diarylketones such as benzophenones, oxybenzones, chalcones and their derivatives exhibit promising applications as UV filters/sunscreen agents due to their effective absorption in the UV region and dissipation through non-radiative pathways. However, elucidation of the underlying photoreactive mechanism is non-trivial due to the ultrafast lifetimes of transient species, involvement of non-adiabatic curve crossings among the potential surfaces, etc. In this context, we investigate the excited-state photoreaction dynamics of 4-hydroxychalcone (4-HC) under various environments through femtosecond-transient absorption (fs-TA), nanosecond-transient absorption (ns-TA), and femtosecond-fluorescence upconversion (fs-FL) measurements. Steady-state fluorescence measurements of 4-HC in the presence of 1-methylimidazole (MI)/tert-butylamine (TBA) exhibit dual band emission. The fs-TA measurements of 4-HC in the presence of MI/TBA exhibit distinct spectral and associated lifetimes as compared to 4-HC alone indicating a significant interaction of the hydroxyl proton with bases and influencing the reaction dynamics. The 4-HC:MI/TBA adduct undergoes excited-state intermolecular proton transfer within a time scale of ∼500 fs and subsequently relaxes back to the ground state through a long-lived triplet state. The experimental observations of excited-state reaction dynamics of 4-HC in the presence of MI/TBA bases have been well corroborated with the computational analysis.

Synthesis, Characterization, and Docking Studies of Some New Chalcone Derivatives to Alleviate Skin Damage Due to UV Light

Increasing cases of sunburn is one of the serious problems across the globe. In this connection, there is an urgent requirement for some effective sun screening agents. In the search for the same, nanoemulsions of some new synthesized and characterized chalcone derivatives were prepared and evaluated in vitro and in vivo. In order to meet the said objective, in the first step, vanillin was reacted with 4-aminoacetophenone in the presence of 15% sodium hydroxide and ethanol to synthesize the target compounds (C-1 to C-5). Progress of reaction was monitored using thin-layer chromatography (TLC). The crystals of purified compounds were characterized using spectroscopic techniques such as Infrared (IR) spectroscopy, 1H-NMR spectroscopy, 13C-NMR, and mass spectrometry. We prepared the nanoemulsions of the final compounds (C-1 to C-5) and subsequently evaluated them for in vitro sun protection factor activity. The concentration of the nanoemulsions, consistently ranging from 0.88 to 0.91 mg/mL across all formulations, demonstrated a high degree of consistency. The range of particle size varied from approximately 172 to 183 nm, with low polydispersity index values (approximately 0.11 to 0.15). The negative zeta potentials recorded for all the formulations (ranging from -35.87 mV to -39.30 mV) showed that the nanoemulsions are electrostatically stable enough to keep them from sticking together. The pH values of the nanoemulsions ranged narrowly from approximately 5.00 to 5.16, which indicated the compatibility of emulsion with biological systems and the potential to reduce irritation or instability during administration. The viscosity of the nanoemulsions varied between 2.00 and 2.12 cP. In silico studies were performed using MMP-I and MMP-2 as target receptors. For in vitro SPF evaluation, the Mansur equation was employed. COLIPA guidelines were compiled for in vivo SPF evaluation. The nanoemulsions derived from compounds C-3 and C-4, designated as C-3NE and C-4NE, were more effective as anti-aging agents. Findings suggested the possible scope of further synthesis of newer synthetic derivatives of chalcones for furfur development nanoemulsions for better SPF activity.

Complexation of Flavonoids: Spectral Phenomena, Regioselectivity, Interplay with Charge and Proton Transfer

The review compiles information on the spectral classification of flavonoids, the changes in their electronic structure upon complex formation, and the manifestation of these changes in the absorption and emission spectra. Part of the review is devoted to the regioselectivity of the complex formation process, including types of complexation sites, the structure of chelates and 'open' complexes, and the correlation between the structure of complexes and their spectral properties. The interplay between complex formation and other processes occurring in flavonoids during electronic excitation is also considered, such as intramolecular inter-fragment charge transfer (ICT) and intramolecular proton transfer (ESIPT). The review also contains systematic data on the study of regioselectivity and spectral properties of flavone complexes, obtained by the author and their colleagues over the past decades.

Synthesis and Evaluation of Chalcone Derivatives as Novel Sunscreen Agent

Ultraviolet (UV) irradiation is a serious problem for skin health thus the interest in the research to develop sunscreen agent has been increasing. Chalcone is a promising compound to be developed as its chromophore absorbs in the UV region. Therefore, in the present work, we synthesized eight chalcone derivatives through Claisen-Schmidt condensation at room temperature. The evaluation of the optical properties of each chalcone derivatives in the UV region was conducted through spectroscopic and computational studies. The synthesized chalcones were obtained in good yields and they were active in the UV region. The results revealed that more methoxy substituents to chalcone leads toward red shift. All chalcone derivatives have high molar absorptivity value (21,000-56,000) demonstrating that they have the potential to be used as the sunscreen agent. The cytotoxicity assay showed that chalcone derivatives were demonstrating low toxicity toward normal human fibroblast cell, which is remarkable. Therefore, we concluded that the synthesized chalcones in this work were potential to be developed as novel sunscreen agents in real application.