Pouteria macrophylla Fruit Extract Microemulsion for Cutaneous Depigmentation: Evaluation Using a 3D Pigmented Skin Model.

Here, we verify the depigmenting action of Pouteria macrophylla fruit extract (EXT), incorporate it into a safe topical microemulsion and assess its effectiveness in a 3D pigmented skin model. Melanocytes-B16F10- were used to assess the EXT effects on cell viability, melanin synthesis, and melanin synthesis-related gene transcription factor expression, which demonstrated a 32% and 50% reduction of intra and extracellular melanin content, respectively. The developed microemulsion was composed of Cremophor EL®/Span 80 4:1 (w/w), ethyl oleate, and pH 4.5 HEPES buffer and had an average droplet size of 40 nm (PdI 0.40 ± 0.07). Skin irritation test with reconstituted epidermis (Skin Ethic RHETM) showed that the formulation is non-irritating. Tyrosinase inhibition was maintained after skin permeation in vitro, in which microemulsion showed twice the inhibition of the conventional emulsion (20.7 ± 2.2% and 10.7 ± 2.4%, respectively). The depigmenting effect of the microemulsion was finally confirmed in a 3D culture model of pigmented skin, in which histological analysis showed a more pronounced effect than a commercial depigmenting formulation. In conclusion, the developed microemulsion is a promising safe formulation for the administration of cutite fruit extract, which showed remarkable depigmenting potential compared to a commercial formulation.

Use of mixture design in drug-excipient compatibility determinations: Thymol nanoparticles case study.

The objective of this work was to access thymol-excipient compatibility using an alternative protocol of mixture design subsidizing the development of nanostructures lipid carriers containing this drug. Simultaneous DTA-TG analyses associated with infrared spectroscopy were performed according to simplex centroid mixture designs with three components. Two designs were used: the design A containing stearic acid (SA), soybean lecithin (LC), and sodium taurodeoxycholate (TAU) and the design B, where TAU was replaced by polysorbate 80 (P80). Assays allowed for a quantitative evaluation of thermal events involved with thymol (TML) - melting and evaporation -, as well as events related to excipients decomposition and overall system stability. Although the anionic surfactant TAU did not interact with TML in solid state, chemical and physical stability were compromised after drug melting. Alternatively, nonionic surfactant P80 could be a good excipient option, as TML formulation stability was not influenced by it. Fatty acid SA did not compromise TML stability alone, but, when in combination with other formulation components, negative interaction leading to a possible decomposition of the system was observed. Finally, phospholipid LC solubilizes TML extending its evaporation to higher temperatures; hence, drug stability may be increased. In conclusion, the use of mixture design in the evaluation of multicomponent systems is a valuable tool for identification of synergistic effects of excipients, providing more complete information on formulation development. In addition, the association of techniques employed allowed inferring with certainty if thermal interactions could compromise formulation stability.

Development and validation of a selective HPLC-UV method for thymol determination in skin permeation experiments.

Thymol is a natural monoterpene, whose antioxidant and antimicrobial properties suggest a potential use in topical formulations. A simple, precise and selective HPLC method for thymol determination in skin penetration studies was developed and validated in this paper. Separation was achieved with a RP-C18 column, mobile phase comprised of acetonitrile:water (35:65v/v), flow rate of 1.5mL/min, oven temperature at 40°C, injection volume of 30µL and UV detection at 278nm. The validation procedure certified the method was selective for thymol determination even when extracted from skin matrix extracts. It was also linear in a range from 0.5 to 15.0µg/mL, robust, precise and accurate, with recovery rates from the skin layers higher than 90%. Limits of detection and quantification were 0.05 and 0.14µg/mL, respectively. The method showed, therefore, to be adequate for use in further skin permeation studies employing thymol topical formulations.

Acetylcholinesterase inhibitory activity and molecular docking study of 1-nitro-2-phenylethane, the main constituent of Aniba canelilla essential oil.

The odoriferous principle of Aniba canelilla (H.B.K.) Mez is due 1-nitro-2-phenylethane, the main constituent of its essential oil and also responsible for the plant's cinnamon scent. This nitroderivative was previously reported by their antioxidant, antinociception, cardiovascular, and vasorelaxant properties, and now it was tested as the inhibitor of acetylcholinesterase using bioautography on TLC plates. The oil and a purified fraction containing 1-nitro-2-phenylethane were analyzed by GC and GC-MS. The percentage content of 1-nitro-2-phenylethane in the oil and after fractionation was 70.2% and 98.0%, respectively. The results showed that the oil and 1-nitro-2-phenylethane are strong acetylcholinesterase inhibitors with the detection limit of 0.01 ng, equivalent to physostigmine used as the positive control. A molecular docking study was used to determine the position and conformation of the 1-nitro-2-phenylethane inhibitor in the receptor-binding pocket of the acetylcholinesterase enzyme. The nitrogroup of 1-nitro-2-phenylethane was positioned near of the catalytic serine residue of acetylcholinesterase, forming strong hydrogen bond with its hydroxyl group. Therefore, the electronegative character of 1-nitro-2-phenylethane may explain the interaction that occurs with the catalytic serine residue and its significant inhibitory activity of acetylcholinesterase.

Evaluation and theoretical study on the anti-inflammatory mechanism of 1-nitro-2-phenylethane.

In this study, 1-nitro-2-phenylethane was evaluated with respect to its effects in edema models of acute inflammation induced with carrageenan, dextran, and croton oil. 1-Nitro-2-phenylethane produced inhibition of rat paw edema induced by carrageenan and dextran at the doses of 25 and 50 mg/kg. The same doses caused an inhibition of croton oil-induced ear edema in mice. Our results suggest that 1-nitro-2-phenylethane has anti-inflammatory activity, probably of peripheral origin, acting in the synthesis and/or release of inflammatory mediators. A conformational study of 1-nitro-2-phenylethane was carried out using density functional theory calculations, showing three different groups of conformers corresponding to energy minimum geometries. The stereoelectronic repulsions are responsible for conformational preferences and the one most stable conformer. The prostaglandin endoperoxide synthase mechanism is related more to electrophilic than nucleophilic properties.