Milica Martinović

Natural deep eutectic solvent (NaDES) extracts exhibit substantial bioactive potential, including antioxidant, UV-protective, and enzyme-inhibitory activities, owing to their rich phytochemical composition. However, their incorporation into appropriate dermal delivery systems is essential to maximize their efficacy. Our previous studies identified emulgels as innovative and effective vehicles for NaDES extracts of green tea and bilberry leaves. In the present study, the in vivo performance of hydroxyethyl cellulose (HEC)-based emulgels containing 12% (w/w) NaDES extracts was evaluated. Formulations stabilized with cetearyl olivate/sorbitan olivate (5%) were compared with those stabilized using cetearyl alcohol/cetearyl glucoside (6%) in a study involving 25 healthy volunteers. Over a 28-day application period, key biophysical skin parameters, including skin pH, transepidermal water loss (TEWL), erythema index (EI), skin capacitance (EC), melanin index (MI), and friction coefficient (F), were monitored. Additionally, a 24 h skin safety assessment and a sensory evaluation were conducted. Both formulations demonstrated excellent safety profiles, with no signs of irritation observed during the 24 h safety study. The emulgels stabilized with cetearyl olivate/sorbitan olivate produced significant improvements in skin biophysical parameters. Skin barrier recovery, indicated by a reduction in TEWL, was achieved within two weeks, while enhanced skin hydration was maintained throughout the study period. Sensory evaluation further demonstrated superior spreadability of the olivate-based formulations. Overall, these findings confirm that HEC-based emulgels are promising dermal delivery systems for NaDES extracts, combining excellent safety, efficacy, and favorable sensory properties.

The aim of this study was to prepare curcumin/2-hydroxypropyl-β-cyclodextrin (HPβCD) inclusion complex, evaluate the antioxidant and antimicrobial activities of curcumin and curcumin in inclusion complex, as well as to examine the effect of curcumin and curcumin inclusion complex on the textural properties of Carbopol^® gel mixture. Curcumin/2-hydroxypropyl-β-cyclodextrin inclusion complex was prepared using the co-precipitation method in a molar ratio of 1:1. The antioxidant activity of curcumin and curcumin in inclusion complex was determined using DPPH, ABTS, and FRAP methods. The micro-dilution method was used to examine in vitro the antimicrobial activity of curcumin and curcumin in inclusion complex. The textural, rheological, and morphological properties of the samples (Gel 1- Carbopol^® gel; Gel 2- Carbopol^® gel with dispersed curcumin inclusion complex; Gel 3- Carbopol^® gel with dispersed curcumin) were examined. The textural properties were evaluated using a texturometer CT3 Texture Analyzer by means of a Texture Profile Analysis (TPA) test. The results showed that curcumin in inclusion complex had higher antioxidant and antimicrobial activity. The SEM confirms the presence of curcumin and inclusion complex in Carbopol^® gel. The rheological analysis confirmed that the structural integrity of Carbopol^® gel was preserved. The highest swelling degree is achieved by Gel 3 formulation. The in vitro release of curcumin from Gel 2 and Gel 3 occurs at the rates of 0.414 µg/h·g_gel and 0.376 µg/h·g_gel, respectively. The textural analysis showed that adding curcumin or its inclusion complex did not significantly change the properties of Carbopol^® gel, indicating potential for topical use.

Natural Deep Eutectic Solvents (NaDES) are biodegradable, non-volatile, thermostable, and easily-prepared mixtures of natural metabolites that form liquids with melting points lower than those of their individual components. As extraction media, they enable the production of extracts with higher contents of bioactive compounds and enhanced biological activities (antioxidant, UV-protective, and enzyme-inhibitory) compared to conventional extracts. The aim of this study was to investigate the effects of emulgels containing NaDES-based extracts on the restoration of skin biophysical parameters impaired by 6% sodium lauryl sulfate-induced irritation. The extracts - bilberry leaf extract obtained using a malic acid-glycerol NaDES and a green tea leaf extract obtained using a tartaric acid-sorbitol NaDES, were incorporated at a concentration of 12% into emulgels stabilized with a combination of cetearyl olivate and sorbitan olivate. During the seven-day in vivo study, using Multiprobe Adapter MPA 9, changes in erythema index (EI), transepidermal water loss (TEWL), and skin pH were monitored at untreated control sites with induced irritation (NCO) and without irritation (NC), as well as at sites treated with placebo (P) and active (A) emulgels were observed on 20 healthy volunteers. An increase in EI, TEWL, and pH was observed at all irritated sites. At the NCO site, five or more days were required for these parameters to return to baseline values, whereas at the A site, all parameters normalized after only one day of application. These findings indicate the pronounced anti-irritant potential of NaDES-based extracts and highlight their significance in the development of effective dermocosmetic formulations.

Liposomal formulations developed for dermal delivery of essential oils and/or plant extracts have attracted increasing atten tion in recent years because they provide controlled release of active compounds, improve their stability and interaction with the skin, thereby enhancing the bioavailability and safety profile of plant-derived bioactive compounds. For this study, four liposomal dispersions based on Phosal 40 IP and purified water were prepared: a placebo dispersion, dispersions containing essential oil or the ethanolic extract of Pinus halepensis Miller (Pinaceae), and a dispersion containing both components. The aim of this study was to evaluate the preliminary safety profile of these liposomal dispersions using non-invasive biophysical methods on the skin of 13 healthy volunteers. The essential oil was isolated by steam distillation using Clevenger apparatus, whereas the extract was obtained by Soxhlet extraction with 70% ethanol. A randomized, double-blind, 24-hour occlusive study was conducted on 13 healthy volunteers. Skin safety was assessed by measuring skin pH, transepidermal water loss (TEWL), electrical capacitance (EC), erythema index (EI), and melanin index (MI). None of the tested formulations induced statistically significant changes in the eval uated skin biophysical parameters compared with baseline values and the corresponding controls. Stable TEWL values indicated preserved epidermal barrier integrity, while the absence of significant changes in erythema and MI confirmed that the formulations did not induce skin irritation or pigmentation disorders. The investigated liposomal formulations showed good local tolerability and a favorable preliminary safety profile, providing a basis for their further development as safe topical delivery systems for plant-de rived bioactive compounds.

Cannabidiol (CBD) is one of the major non-psychoactive cannabinoids of industrial hemp (Cannabis sativa L.) due to well-documented anti-inflammatory and antioxidant properties. However, its application is limited by poor aqueous solubility, light sensitivity, and rapid degradation, making CBD a suitable candidate for encapsulation. The aim of this study was to evaluate anti-inflammatory activity of a gel containing a liposomally encapsulated CBD-rich supercritical hemp extract (L-CBD) using carrageenan-induced acute paw edema model in rats. Anti-inflammatory activity was assessed by measuring paw thickness before and 1, 2, 3, and 4 h after inflammation induction. The investigated gel was compared with commercially available hemp extract formulation (K-CBD), a placebo gel containing empty liposomes (L), and ibuprofen cream (IBU) as a positive control. Edema inhibition, lipid peroxidation (TBARS), superoxide dismutase (SOD), catalase (CAT), and reduced glutathione (GSH) levels were evaluated. All tested formulations exhibited a time-dependent anti-inflammatory effect. A statistically significant reduction in paw edema in comparison to untretaed contol was observed from the third hour after carrageenan administration in the L-CBD, IBU, and K-CBD groups. After 4h, the highest edema inhibition was achieved with ibuprofen (77.1%), where as L-CBD and K-CBD produced 60.4% and 56.3% inhibition, respectively. In addition, L-CBD significantly reduced lipid peroxidation and increased SOD and CAT activities compared with the untreated group, while no significant changes in GSH levels were observed. These findings demonstrate that the gel containing a liposomally encapsulated CBD-rich supercritical hemp extract exhibits anti-inflammatory and antioxidant activity, highlighting its potential for the development of novel topical anti-inflammatory formulations.

Tyrosinase is a skin enzyme involved in melanogenesis, whose overactivity can lead to development of hyperpigmentations. Therefore, its inhibition is of dermocosmetic interest. The aim of this study was to examine the potential of green tea leaf extracts to inhibit tyrosinase. The extracts were made using green extraction approach involving natural deep eutectic solvents, NaDES (betaine-urea) as biodegradable and safeextraction solvents. The results have shown that NaDES-based green tea leaves extracts have tyrosinase inhibition potential, with lower IC50 values compared to those of water and ethanol extracts. These results emphasise the potential of NaDES-based extracts as dermocosmetic raw materials.

The applicative characteristics of topical preparations can be assessed using sensory analysis as a subjective method and texture analysis as an objective method. In this study, the sensory and textural properties of an emulgel containing 6% (w/w) plum seed oil, as the natural oil obtained from renewable resources, were compared to a placebo emulgel, in which the plum seed oil was replaced by caprylic/capric triglycerides, commonly used in cosmetic formulations. Both emulgels were semi-solid in consistency, slightly shiny, easy to spread, and demonstrated rapid absorption, low stickiness, and low oiliness. The results indicated that plum seed oil had a comparable influence on the sensory and textural properties of the final product to that of caprylic/capric triglycerides. Differences in sensory characteristics were noted in terms of density, with participants reporting a lower density for the emulgel containing plum seed oil. Texture analysis was conducted 7 days, 14 days, and 28 days after preparation of samples. The texture analysis revealed that the presence of plum seed oil was associated with lower hardness (initial hardness of active emulgel was 0.25 ± 0.01 N while the hardness of placebo emulgel was 0.39 ± 0.04 N), leading to better spreadability. Apart from an increase in cohesiveness over time, likely due to the restructuring of the gel matrix, (from 0.85 ± 0.06 mJ to 1.38 ± 0.31 mJ, and from 0.83 ± 0.04 mJ to 1.62 ± 0.45 mJ for placebo and active emulgel respectively), other texture parameters remained statistically unchanged, indicating the physical stability of the emulgels during the study.

Natural plant oils are commonly used in skincare products for their emollient properties. Plum seed oil is a promising cosmetic ingredient since it represents a sustainable material derived from fruit processing waste, recognized in the CosIng Database for its skin-conditioning function. The aim of this study was to incorporate plum seed oil into a topical emulgel and assess its biophysical effects on the skin. An in vivo study on healthy volunteers evaluated the safety (irritation potential) and long-term efficacy (impact on biophysical skin parameters during 28-day application) of emulgel containing 6% (w/w) plum seed oil as a natural emollient and active ingredient. Results showed that plum seed oil exhibited no irritation potential during a 24-hour safety assessment since transepidermal water loss (TEWL) decreased (p <0.05), and erythema index didn’t change significantly. Results of 28-day efficacy study suggested, potential anti-irritant effects after long-term usage. In addition, pH, skin integrity and skin color were preserved during the study, while skin hydration was increased. To our knowledge, this is the first study to employ non-invasive biophysical methods to assess the influence of plum seed oil in cosmetic formulations. These findings point plum seed oil’s potential as a natural, sustainable, safe and effective raw material for cosmetics.

Natural deep eutectic solvents (NaDES) represent novel biodegradable green extraction solvents obtained from natural metabolites such as sugars and organic acids. NaDES-based extracts have demonstrated better performance in in vitro assays compared to those obtained using conventional solvents. In this study, extracts of bilberry leaves (BL), bilberry fruits (BF), and green tea leaves (TL) were prepared using the following NaDES, respectively—malic acid + glycerol (MG), citric acid + sorbitol (CS), and tartaric acid + sorbitol (TS), whose formation was confirmed via FTIR spectroscopy. With the aim to evaluate the effect of gels loaded with NaDES extracts on skin biophysical parameters 2 h prior their application, as well as their anti-irritation potential against sodium lauryl sulfate–induced irritation, an in vivo study involving human volunteers was conducted. The results indicated that all extract-loaded gels exhibited notable anti-irritation potential, reducing artificially induced irritation and improving elevated skin parameters including transepidermal water loss (TEWL), erythema index (EI), and pH. The ΔTEWL at CS–BF site was 8.20 ± 0.34, while at TS–TL was 5.63 ± 0.30. The short-term efficacy study revealed increased skin hydration across all treated sites, preservation of skin pH within physiological limits, and reduction in EI at the site treated with TS–TL gel. Further in vivo studies are planned for confirming long-term skin effects.