viruses Review Antiviral Bioactive Compounds of Mushrooms and Their Antiviral Mechanisms: A Review Dong Joo Seo 1 and Changsun Choi 2, *   Citation: Seo, D.J.; Choi, C. Antiviral Bioactive Compounds of Mushrooms and Their Antiviral Mechanisms: A Review. Viruses 2021, 13, 350. https://doi.org/10.3390/v13020350 Academic Editors: Mariana Baz and Edin Mifsud Received: 21 December 2020 Accepted: 20 February 2021 Published: 23 February 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 Department of Food Science and Nutrition, College of Health and Welfare and Education, Gwangju University 277 Hyodeok-ro, Nam-gu, Gwangju 61743, Korea; sdj0118@gwangju.ac.kr 2 Department of Food and Nutrition, School of Food Science and Technology, College of Biotechnology and Natural Resources, Chung-Ang University, 4726 Seodongdaero, Daeduck-myun, Anseong-si, Gyeonggi-do 17546, Korea * Correspondence: cchoi@cau.ac.kr; Tel.: +82-31-670-4589; Fax: +82-31-676-8741 Abstract: Mushrooms are used in their natural form as a food supplement and food additive. In addition, several bioactive compounds beneficial for human health have been derived from mushrooms. Among them, polysaccharides, carbohydrate-binding protein, peptides, proteins, enzymes, polyphenols, triterpenes, triterpenoids, and several other compounds exert antiviral activity against DNA and RNA viruses. Their antiviral targets were mostly virus entry, viral genome replication, viral proteins, and cellular proteins and influenced immune modulation, which was evaluated through pre-, simultaneous-, co-, and post-treatment in vitro and in vivo studies. In particular, they treated and relieved the viral diseases caused by herpes simplex virus, influenza virus, and human immunodeficiency virus (HIV). Some mushroom compounds that act against HIV, influenza A virus, and hepatitis C virus showed antiviral effects comparable to those of antiviral drugs. Therefore, bioactive compounds from mushrooms could be candidates for treating viral infections. Keywords: mushroom; bioactive compound; virus; infection; antiviral mechanism 1. Mushrooms and Their Compounds There are approximately 12,000 known species of mushrooms worldwide, of which at least 2000 species are edible [1]. Lentinus (Lentinula), Auricularia, Hericium, Grifola, Flammulina, Pleurotus, Lactarius, Pisolithus, Tremella, Russula, Agaricus, and Cordyceps are well-known edible mushroom species [2]. They are consumed in their natural form or as food supplements. Mushrooms contain moisture (85–95%), carbohydrates (35–70%), protein (15–34.7%), fat (<10%), minerals (6–10.9%), nucleic acids (3–8%), and very low levels of vitamins [1,2]. Since mushrooms have carbohydrates, fiber, protein, essential amino acids, unsaturated fatty acids, minerals, vitamins, and low calories, they are recognized as a healthy food with nutritional benefits [2]. Several bioactive metabolites present in mushrooms are polysaccharides, terpenoids, and phenolic compounds, including flavonoids, glycoproteins, polyketides, steroids, and alkaloids [2]. They have beneficial effects for human health [1,2]. Among them, polysaccharides and terpenoids are important bioactive metabolites. Polysaccharides, such as glucan, β-glucan, mannoglucan, heteroglycan, galactomannan, and lentinan, exhibit immunomodulatory, antioxidant, anti-inflammatory, antitumor, and antiviral activities. Terpenoids affect adipocyte differentiation and exhibit antimicrobial, anticholinesterase, antiviral, anti-inflammatory, and nitric oxide (NO) production inhibitory activity. Phe- nolic compounds showed NO production inhibition, antiviral, anti-inflammatory, and antioxidant activities [1,2]. Viruses 2021, 13, 350. https://doi.org/10.3390/v13020350 https://www.mdpi.com/journal/viruses