# Antioxidant and Antibacterial Properties of Extracts and Bioactive Compounds in Bryophytes
###### Abstract  
Today global health problems such as increased risks of oxidative stress-related diseases and antibiotic resistance are issues of serious concern. Oxidative stress is considered to be the underlying cause of many contemporary pathological conditions such as neurological disorders, ischemia, cancer, etc. Antibiotic-resistant bacteria are a concerning issue in clinical practice, causing an increase in deadly infections. Bryophytes synthesize an outstanding number of secondary metabolites that have shown several potential therapeutic and nutraceuticaltical applications. Research in the field has led to the isolation and characterization of several compounds (flavonoids, terpenoids, and biphenyls). Some of these compounds have shown promising in vitro antibacterial activities and antioxidant potential comparable to known natural antioxidants such as ascorbic acid and \(\alpha\)-tocopherol. However, the process of developing new drugs from naturally occurring molecules is often an impervious path. In this paper, the current state of research of bryophytic antioxidant and antibacterial applications is discussed.  
bryophytes; antimicrobial; antibacterial; antioxidant; bioactive compounds +
Footnote †: journal: Medical  
implied in several processes related to tumorigenesis such as cell motility, tumour proliferation, and metastasis [10]. Furthermore, oxidative damage to mitochondrial DNA might cause dysfunctions in the mitochondrial respiratory chain causing further ROS generation and, ultimately, oncogenicity [11]. As a consequence of the increased risks of diseases related to oxidative stress, extensive research has been conducted on non-toxic natural antioxidants that can help to cope with oxidative stress [12].  
Antioxidant compounds can act directly and indirectly on the redox balance of cells (Figures 1 and 2) [13]. Some compounds are capable of directly antagonizing and reducing ROS. For example, compounds having phenolic groups in their structures' phenolic groups (e.g., flavonoids, phenols) act as hydrogen donors to free radicals, stabilizing the excess electron on the aromatic ring by resonance. Other compounds such as flavonoids act indirectly by chelating metal ions that can alter the redox balance in cells (e.g., zinc, copper) [14]. Furthermore, it is known that the Keap1/Nrf2/ARE system is involved in the activation of antioxidant responses in cells [15]. Compounds such as polyphenols, biphenyls and terpenoids are inducers of Nrf2-ARE system, enhancing the expression of the antioxidants cytoprotective proteins (e.g., glutathione-S-transferase; glutathione reductase; gamma-glutamylcisteine; NAD(P)H:quinone oxidoreductase; superoxide dismutase; catalase), granting long-term protection from oxidative stress [16]. Due to its central role in redox homeostasis, dysregulations of the Keap/Nrf2/ARE system have been linked to oxidative stress-related diseases [17].  
Furthermore, for decades antibiotics have been employed both therapeutically and prophylatically against human diseases as well as in agriculture and for animals [18; 19]. As a consequence, several antibiotic-resistant strains have begun to spread, and bacterial infections have again become a threat [20]. Bryophytes, being rich in secondary metabolites that show several biological activities [3], might be a valuable source to discover novel drugs that aid coping with both prevention of oxidative stress-related diseases and antibiotic resistance issues. The present review is intended to revise the research state-of-the-art of antioxidant and antibacterial compounds found in bryophytes and to outline future investigation needed in the field of applications of bryophytes in nutraceuticalals and pharmaceutics.  
Figure 1: Schematization of direct antioxidant activity through ROS scavenging and metal chelation.