Phenolic profiles and antioxidant abilities of various extracts from white maitake mushrooms (Grifola frondosa)

Abstract

Maitake (Grifola frondosa), a basidiomycete fungus belonging to the Polyporaceae family is consumed as a valuable mushroom in the Asia. Extensive studies focus on the anti‐carcinogenic and immune‐modulatory aspects of the polysaccharide fractions, such as maitake D (MD) and X fractions, that are isolated from a boiling water extract of grey fruiting bodies. However, the non‐polysaccharide bioactive compounds, especially the phenolic compounds, are rarely studied in the maitake mushroom and never studied in the white maitake. The white maitake fruiting body was extracted with 50% ethanol (v/v) and cold water into fractions (F) 1 and 2, respectively. The F2 was further extracted with 75% ethanol (v/v) to remove the polysaccharide, and the soluble fraction was denoted as fraction 3. All fractions were lyophilized for further analysis including the DPPH scavenging ability, total polyphenol, flavonoid and the individual phenolic compound content. Results indicated that the white maitake contained a large amount, 62% w/w, of cold‐water soluble material. The DPPH scavenging effect was F3>F2>>F1as the concentration was equal or greater than 0.4 mg/mL. At 1.2 mg/mL, the DPPH scavenging effect of F3 was almost equal to that of ascorbic acid. The F2 and F3 contained much more total polyphenol and flavonoid than F1. The major phenolic compounds identified were tannic and gallic acids. The F1–3 contained (mg/g extract) 1.33 ± 0.01, 12.33 ± 0.42 and 13.33 ± 0.32 of tannic acid, and 0.43 ± 0.02, 5.68 ± 0.12, and 6.45 ± 0.32 of galllic acid. The antioxidant ability was strongly and positively correlated with the total polyphenol, flavonoid, tannic, and gallic acid content, respectively. Therefore, this study suggests that cold water extract of white maitake exhibited strong DPPH scavenging effect, which was likely to be mainly contributed by tannic and gallic acids.