antioxidants Article Antioxidant, Anti-Inflammatory, and Anti-Aging Potential of a Kalmia angustifolia Extract and Identification of Some Major Compounds Alexe Grenier 1,2 , Jean Legault 3 , André Pichette 3 , Lorry Jean 3 , Audrey Bélanger 3 and Roxane Pouliot 1,2, *   Citation: Grenier, A.; Legault, J.; Pichette, A.; Jean, L.; Bélanger, A.; Pouliot, R. Antioxidant, Anti-Inflammatory, and Anti-Aging Potential of a Kalmia angustifolia Extract and Identification of Some Major Compounds. Antioxidants 2021, 10, 1373. https://doi.org/10.3390/ antiox10091373 Academic Editor: Stanley Omaye Received: 26 July 2021 Accepted: 26 August 2021 Published: 28 August 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Centre de Recherche en Organogénèse Expérimentale de l’Université Laval/LOEX, Axe Médecine Régénératrice, Centre de Recherche du CHU de Québec Université Laval, Québec, QC GIJ 1Z4, Canada; alexe.grenier.1@ulaval.ca 2 Faculté de Pharmacie, Université Laval, Québec, QC G1V 0A6, Canada 3 Centre de Recherche sur la Boréalie (CREB), Laboratoire d’Analyse et de Séparation des Essences Végétales (LASEVE), Département des Sciences Fondamentales, Université du Québec à Chicoutimi, Chicoutimi, QC G7H 2B1, Canada; jean_legault@uqac.ca (J.L.); andre_pichette@uqac.ca (A.P.); lorry.jean1@uqac.ca (L.J.); audrey1_belanger@uqac.ca (A.B.) * Correspondence: roxane.pouliot@pha.ulaval.ca; Tel.: +1-418-525-4444 (ext. 61706) Abstract: Skin aging is the most visible element of the aging process, giving rise to a major concern for many people. Plants from the Ericaceae family generally have antioxidant and anti-inflammatory properties, making them potential anti-aging active ingredients. This study aimed to evaluate the safety and anti-aging efficacy of a Kalmia angustifolia extract using reconstructed skin substitutes. The safety evaluation was performed using a 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bro- mide (MTT) assay, while the efficacy was determined by assessing antioxidant and anti-inflammatory activity and analyzing skin substitutes reconstructed according to the self-assembly method by histology and immunofluorescence staining (elastin, collagen-1, collagen-3, aquaporin-3). The cell viability assay established the safety of the extract at a concentration up to 200 μg/mL. The Oxygen Radical Absorbance Capacity (ORAC) assay and a cell-based assay using 2’,7’-dichlorofluorescein- diacetate (DCFH-DA) revealed a strong antioxidant activity with an ORAC value of 16 μmol Trolox Equivalent/mg and a half-maximal inhibitory concentration (IC 50 ) of 0.37 ± 0.02 μg/mL, while an interesting anti-inflammatory activity was found in the inhibition of NO production, with an inhibition percentage of NO production of 49 ± 2% at 80 μg/mL. The isolation and characterization of the extract allowed the identification of compounds that could be responsible for these biologi- cal activities, with two of them being identified for the first time in K. angustifolia: avicularin and epicatechin-(2β-O-7, 4β-6)-ent-epicatechin. Histological analyses of skin substitutes treated with the extract showed an increase in dermal thickness compared with the controls. K. angustifolia extract enhanced the expression of elastin and collagen-1, which are usually decreased with skin aging. These results suggest that K. angustifolia has promising antioxidant efficacy and anti-aging potential. Keywords: skin substitutes; skin aging; natural products; active ingredients; Sheep Laurel; antioxi- dant activity; anti-inflammatory activity; tissue engineering 1. Introduction Skin aging is a natural physiological process of concern for many people. It is the first visible sign of advancing age and skin degeneration. Thus, the formulation of anti-aging cosmetic products has gained importance in the last few years due to the desire to limit this appearance of aging. Skin aging is characterized by multiple changes at a biological level, which include a decrease in cell proliferation, resulting in epidermal atrophy, and a decrease in dermal components such as fibroblasts and elastin and collagen fibers, and thus a decrease in dermal thickness in older adults [1,2]. Antioxidants 2021, 10, 1373. https://doi.org/10.3390/antiox10091373 https://www.mdpi.com/journal/antioxidants