# Antioxidant and Antibacterial Properties of Extracts and Bioactive Compounds in Bryophytes
## 3 Antioxidant Activity  
Secondary metabolites compounds function as a nonenzymatic defence that protects bryophytes against various environmental stresses [1; 21]. In general, plants are known to produce several secondary metabolites that can act as antioxidant scavengers (e.g., phenolic compound; flavonoids; terpenes). Bryophytes have evolved the capacity to synthesize antioxidative molecules as a mechanism to deal with the formation of free radicals (e.g., reactive oxygen species, hydrogen peroxide) derived from abiotic stresses (i.e., light, desiccation, pollution). Several studies indicated that secondary metabolites in bryophytes are synthesized in response to oxidative stress-inducing agents such as UV radiations [22; 23; 24] and cadmium [24]. This feature has prompted researchers to deepen knowledge about the antioxidant potential of bryophytes for therapeutic purposes. The vast majority of the research has focused on the in vitro antioxidant activity of bryophytes extracts and pure isolated compounds through multiple chemical methods such as 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, 2,2-azinobis-(3-ethylbenzothazoline-6  
Figure 2: Schematization of indirect induction of cytoprotective proteins through Keq1/Nrf2/ARE system by antioxidant compounds. sulfonate) (ABST) assay, lipid peroxidation test (LPT), \(\beta\)-carotene assay (Tables 1 and 2) (for in-depth methodological review read [25]) [26; 27; 28; 29; 30; 31; 32; 33]. The extraction methods mostly rely on solvents such as ethanol, methanol, water, and acetone which are the most common solvents used for in vitro antioxidant testing [25]. Extracts, depending on the solvent used and the selected species contain variable concentrations of phenolics, polyphenols, biphenyls and terpenoids which are responsible for the antioxidant activity (Tables 1 and 2). A study of [31] that focused on the chemical composition of pure ethanol extracts, revealed the presence of several glycosidic flavonoids (e.g., apigenin hexoside, kaempfer 3-galactosidaseoside). Another study obtained similar results from water:ethanol extracts of several moss species [34]. Among the 3000 compounds isolated and characterized in bryophytes [35], only a few molecules have been tested for their antioxidant activity (Table 2) [36; 37; 38; 39; 40; 41; 42]. The majority of the pure tested compounds were isolated from liverworks, while only two compounds, Ohiesin G and D, were from the moss _Polytrichastrum alpinum_. Interestingly, some of these studies found that terpenoids, (bis)bibenzyls isolated from liverworks had higher or similar antioxidant activity with respect to natural reference antioxidant compounds (ascorbic acid, \(\alpha\)-tocopherol) (Table 2). Specifically, [36] isolated two sesquiterpenoids identified as (-)-herbertenediol and (-)-mastigophoreene C and D that were found to have a DPPH activity comparable to that of quercetin and higher than ascorbic acid (DPPH IC\({}_{50}\) from 1.9 \(\pm\) 0.6 to 2.7 \(\pm\) 0.8 \(\mu\)g/mL). In a study by [37], researchers isolated a caffeine ester, named subulatin, from the liverworks _Jungermannia subulata; Lophocolea heterophylla_ and _Scapania parvietxta_. The compound inhibited lipid peroxidation at percentages comparable to those of \(\alpha\)-tocopherol in an erythocite membrane ghost system. [40] carried out wide testing on several pure compounds: the macrocyclic (bis)bibenzyls marchantins A, B, D, E, riccardi C, isoricciardin C; the bisbibenzyl paleatin B; the prenylated biphenyls radualininin H. The result evidenced an antioxidant activity ranging from 0.4 to 15.7 \(\mu\)mol/L on the arachidonic acid peroxidation test, with marchantin A and perrotettin D showing the highest activity (IC\({}_{50}\) 0.4 and 0.72 \(\mu\)mol/L). In a study from [41], researchers tested the antioxidant activity of marchantin H. They found a DPPH IC\({}_{0.20}\) 0.51 \(\pm\) 0.03 \(\mu\)M respect to 3.80 \(\pm\) 0.33 \(\mu\)M measured in \(\alpha\)-tocopherol (Table 2).