# Physicochemical, Functional, and Antioxidative Characteristics of Oyster Mushrooms
## 6 Antioxidant Activity of Oyster Mushrooms  
The antioxidant activity of _Pleurotus_ species shows marked variations due to their unique bioactive compound profiles. _P. ostreatus_ protects against oxidative damage by scavenging reactive oxygen species (ROS), thereby mitigating oxidative stress. The high antioxidant activity is attributed to phenolic compounds such as flavonoids, effective free radical scavengers. Polysaccharides, particularly \(\beta\)-glucans, contribute to radical scavenging activity and inhibition of lipid peroxidation [21; 25; 65; 66]. _P. djamor (Pink Oyster Mushroom)_ exhibits antioxidant effects but is less effective in scavenging ROS than _P. ostreatus_ and _P. citrinopileatus_, suggesting limited application in high antioxidant demand scenarios. This is due to moderate levels of phenolic compounds and flavonoids compared to other species. The presence of ascorbic acid enhances its antioxidant potential, although to a lesser extent [50; 51; 66]. _P. citrinopileatus (Golden Oyster Mushroom)_ has an excellent antioxidant profile, positioning it as an exceptional candidate to combat oxidative stress. Rich in phenolic compounds and polysaccharides, it has a robust free radical scavenging capacity. It is particularly effective in inhibiting lipid peroxidation, which increases its value in functional and therapeutic foods [57; 58; 67]. The antioxidant efficacy of P. species is inextricably linked to their bioactive composition. _P. ostreatus_ is a reliable source of balanced antioxidant activity. _P. djamor_ has a moderate effect but does not have the biochemical richness of other species. _P. citrinopileatus_ stands out due to its superior phenolic content, which is superior in preventing oxidative damage and controlling lipid peroxidation. These results highlight the critical role of bioactive compounds in enhancing mushrooms' therapeutic and nutritional value. Research indicates that _P. ostreatus_ extracts also contain alkaloids (187.6 mg/100 g), tannins (25.12 mg/100 g), saponins (0.16 mg/100 g), flavonoids (104.83 mg/100 g), and cardiac glycosides (20.18 mg/100 g) [39]. Analysis of the quantitative composition of ethanol extracts from another species--_P. pulmonarius_--showed that the amount of tannins (18.74 mg/100 g) and cardiac glycosides (24.19 mg/100 g) may be even higher than in _P. ostreatus_[68]. Due to cardiac glycoside contents in _P. ostreatus_, this raw material may play a particular role in producing functional and therapeutic foods aimed at people with heart diseases, which can only be used according to the recommended medical dosage regimen. Research results confirm that cardiac glycosides such as digitoxin, digoxin, ouabain, and oleandrin may also effectively combat certain types of cancer, such as ovarian cancer and leukaemia [69]. It was also confirmed that _P. ostreattus_ and _P. pulmomarius_ mushrooms can be a significant source of phlobatannins (16.96 mg/100 g and 15.81 mg/100 g, respectively)--bioactive substances with high antioxidant properties [68]. Phlobatannins are increasingly credited with significant anti-inflammatory, analgesic, and wound-healing properties [70; 71]. Animal studies have confirmed that the bioactive substances contained _in P. ostreatus_ can also have a hepatoprotective effect. In an experiment in which rats under metabolic and oxidative stress took crushed raw or cooked powder of _P. ostreatus_ (at a dose of 250 mg/kg body weight), a decrease in the levels of alanine aminotransferase (ALAT) and aspartate aminotransferase (AST) was observed [72]. The obtained result indicates that consuming _P. ostreatus_ may reduce the risk of developing inflammatory processes in the liver and toxic liver damage [73]. The results of studies conducted on an animal model have shown that consuming _P. ostreatus_ mushrooms can have a therapeutic effect in treating hyperlipidaemia and limiting the accompanying oxidative stress.