The cosmetic industry is constantly searching for bioactive ingredients, namely, those
obtained from natural sources with environmentally friendly connotations and less toxic effects.
A previous study of our research group optimized the extraction of phenolic compounds from
Juglans regia by heat-assisted extraction. Due to its richness in different phenolic compounds, the
present work aimed to develop a formulation containing J. regia leaf extract. The extract’s antioxidant,
anti-tyrosinase, antimicrobial, anti-inflammatory, wound healing, cytotoxicity, and photostability
properties were evaluated. The extract was then incorporated into an O/W base cream, followed by
characterization of the final formulation in terms of its antioxidant properties, phenolic composition,
and stability over time and at different storage conditions. The most abundant compounds in the
hydroethanolic extract were 3-O-caffeoylquinic acid (18.30 0.04 mg/g), quercetin-O-pentoside
(9.64 0.06 mg/g), and quercetin 3-O-glucoside (6.70 0.19 mg/g). Besides those, the extract
presented antioxidant, anti-inflammatory, wound closure, and antibacterial effects against several
skin pathogens. In addition, HaCaT cell viability was maintained up to 98% at 400 g/mL.Within
Proteus vulgaris-infected HaCaT cells, the extract also presented an over 40% bacterial mortality rate
at its nontoxic concentration (200 g/mL). After incorporating the extract, the obtained formulation
presented a good physicochemical profile over time and at different storage conditions while also
maintaining its antioxidant effect; as such, it can be considered stable for topical application. Future
work to evaluate its performance in terms of skin permeation and detailed toxicological studies
with a focus on regulatory requirements, involving skin irritation, eye irritation, genotoxicity, photoirritation,
and dermal absorption, should be conducted, as the prepared formulation demonstrated
relevant properties that deserve to be further explored.
This work was developed within the scope of the project AllNat—“Using natural deep
eutectic solvents for the extraction of bioactive compounds from plant material” (reference POCI-01-
0145-FEDER-030463, PTDC/EQU-EPQ/30463/2017), funded by FEDER funds through
COMPETE2020—Programa Operacional Competitividade e Internacionalização (POCI), Portugal
2020, and by national funds through the Foundation for Science and Technology (FCT/MCTES).
The authors are also grateful to the Foundation for Science and Technology (FCT, Portugal) for the
financial support through national funds FCT/MCTES to the CIMO (UIDB/00690/2020). L. Barros, C.
Pereira, and M. I. Dias are grateful to FCT P.I. for their contracts through the institutional scientific employment
program. F. Mandim is grateful to FCT for her PhD grant (SFRH/BD/146614/2019). This
work was also supported by MICINN for the Juan de la Cierva Formación contract for T. Oludemi
(FJC2019-042549-I). This research was also funded by the Serbian Ministry of Education, Science and
Technological Development (Contract No. 451–03-9/2021–14/200007).
