antioxidants Article Antitussive, Antioxidant, and Anti-Inﬂammatory Effects of a Walnut (Juglans regia L.) Septum Extract Rich in Bioactive Compounds Ionel Fizes , an 1,† , Marius Emil Rusu 2,† , Carmen Georgiu 3, *, Anca Pop 1 , Maria-Georgia S , tefan 1 , Dana-Maria Muntean 2 , Simona Mirel 4 , Oliviu Vostinaru 5, *, Béla Kiss 1 and Daniela-Saveta Popa 1   Citation: Fizes , an, I.; Rusu, M.E.; Georgiu, C.; Pop, A.; S , tefan, M.-G.; Muntean, D.-M.; Mirel, S.; Vostinaru, O.; Kiss, B.; Popa, D.-S. Antitussive, Antioxidant, and Anti-Inﬂammatory Effects of a Walnut (Juglans regia L.) Septum Extract Rich in Bioactive Compounds. Antioxidants 2021, 10, 119. https://doi.org/10.3390/ antiox10010119 Received: 27 December 2020 Accepted: 12 January 2021 Published: 15 January 2021 Publisher’s Note: MDPI stays neu- tral with regard to jurisdictional clai- ms in published maps and institutio- nal afﬁliations. Copyright: © 2021 by the authors. Li- censee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and con- ditions of the Creative Commons At- tribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Department of Toxicology, Faculty of Pharmacy, Iuliu Hatieganu University of Medicine and Pharmacy, 8 Victor Babes, 400012 Cluj-Napoca, Romania; ionel.ﬁzesan@umfcluj.ro (I.F.); anca.pop@umfcluj.ro (A.P.); stefan.georgia@umfcluj.ro (M.-G.S , .); kbela@umfcluj.ro (B.K.); dpopa@umfcluj.ro (D.-S.P.) 2 Department of Pharmaceutical Technology and Biopharmaceutics, Faculty of Pharmacy, Iuliu Hatieganu University of Medicine and Pharmacy, 8 Victor Babes, 400012 Cluj-Napoca, Romania; rusu.marius@umfcluj.ro (M.E.R.); dana.muntean@umfcluj.ro (D.-M.M.) 3 Department of Pathological Anatomy, Faculty of Medicine, Iuliu Hatieganu University of Medicine and Pharmacy, 8 Victor Babes, 400012 Cluj-Napoca, Romania 4 Department of Medical Devices, Faculty of Pharmacy, Iuliu Hatieganu University of Medicine and Pharmacy, 8 Victor Babes, 400012 Cluj-Napoca, Romania; smirel@umfcluj.ro 5 Department of Pharmacology, Physiology and Physiopathology, Faculty of Pharmacy, Iuliu Hatieganu University of Medicine and Pharmacy, 8 Victor Babes, 400012 Cluj-Napoca, Romania * Correspondence: cgeorgiu@umfcluj.ro (C.G.); oliviu.vostinaru@umfcluj.ro (O.V.); Tel.: +40-741-185163 (O.V.) † These authors contributed equally to this work. Abstract: The antitussive, antioxidant, and anti-inﬂammatory effects of a walnut (Juglans regia L.) septum extract (WSE), rich in bioactive compounds were investigated using the citric acid aerosol- induced cough experimental model in rodents. Wistar male rats were treated orally for three days with distilled water (control), codeine (reference), and WSE in graded doses. On the third day, all rats were exposed to citric acid aerosols, the number of coughs being recorded. Each animal was sacriﬁced after exposure, and blood and lung tissue samples were collected for histopathological analysis and the assessment of oxidative stress and inﬂammatory biomarkers. The results of the experiment showed a signiﬁcant antitussive effect of WSE, superior to codeine. This activity could be due to cellular protective effect and anti-inﬂammatory effect via the stimulation of the antioxidant enzyme system and the decrease of IL-6 and CXC-R1 concentration in the lung tissue of WSE-treated animals. The antioxidant and anti-inﬂammatory effects of WSE were conﬁrmed by biochemical assays and histopathological analysis. This is the ﬁrst scientiﬁc study reporting the antitussive effect of walnut septum, a new potential source of non-opioid antitussive drug candidates, and a valuable bioactive by-product that could be used in the treatment of respiratory diseases. Keywords: walnut; by-products; antitussive; ROS; NOx; IL-6; CXC-R1; histopathological analysis 1. Introduction Natural products such as endogenous or exogenous metabolites of animals and plants, played a signiﬁcant role in the discovery of medicines as more than half of the medicines in use were developed from natural products [1]. Famous examples are aspirin, a product derived from salicylic acid, present in the bark of several species of genus Salix [2], codeine, a naturally occurring alkaloid found in plants of Papaver spp. [3], quinine, a component of the bark of trees in the genus Cinchona [4], or penicillin, the ﬁrst antibiotic compound isolated from the fungus Penicillium [5]. The isolation and use of bioactive compounds from natural products can mitigate the high cost of chemical synthetic drugs in the development of new medications. Antioxidants 2021, 10, 119. https://doi.org/10.3390/antiox10010119 https://www.mdpi.com/journal/antioxidants