Go wild for Ethiopian antioxidant mushrooms, say researchers
The research, published in the journal Food Chemistry, looked at the antioxidant activities, phenolic profile and ergothioneine content of two cultivated mushroom varieties (P. ostreatus and L. edodes) and five wild (L. sulphureus, A. campestris, T. clypeatus, T. microcarpus and T. letestui).
The scientists found that the wild A. campestris variety had the highest antioxidant activity and greatest total phenolics and flavonoids content. While all the mushrooms contained ergothioneine, the cultivated oyster mushroom P. ostreatus contained the most by far.
The antioxidant race
This method revealed that the scavenging effect was high for the wild A. campestris, with the wild L. sulphureus showing the least scavenging power overall. Aside from L. sulphurous, all the wild edible mushrooms had a better scavenging effect than their cultivated counter parts. In tracking the presence of reductants (antioxidants), once again wild A. campestris came out on top, while the wild L. sulphurous came last.
A. campestris had the highest phenolic content among the mushroom species evaluated, followed by the wild varieties T. letestui and T. clypeatus . The researchers said this indicated the correlation between total phenolics with antioxidant activity. L. sulphureus with least antioxidant activity also had the least phenolic content. A. campestris also had the greatest total flavonoid content, followed by T. letestui.
However, in terms of ergothioneine content, it was the cultivated oyster mushroom, P. ostreatus, which came out best. “Both the cultivated mushrooms (oyster and shiitake) had better ergothioneine than all the wild edible mushrooms evaluated,” the researchers said. Meanwhile its wild cousins, T. clypeatus and L. sulphureus, had the least.
The researchers said consumption of the mushrooms could help protect against oxidative damage. “Cells lacking ergothioneine were readily susceptible to oxidative stress, and thereby resulting in increased mitochondrial DNA damage, protein oxidation and lipid per-oxidation. Since mushrooms are an abundant source of antioxidants, including ergothioneine, it is another reason to incorporate mushrooms into the human diet. Besides, ergothioneine may be a new vitamin with physiologic roles in antioxidant cytoprotection,” they wrote.
The researchers from Addis Ababa University and Pennsylvanian State University collected the samples from the Addis Ababa, Kaffa zone and Benishangul Gumuz region of Ethiopia. They were obtained personally by the researchers or from local people or markets. Mycological experts were recruited in order to help identify the wild mushrooms.
The samples were then dried in a drying oven until they had a consistent weight, then milled to fine powder. The researchers employed a methanolic solution to test the radical scavenging of each powdered mushroom. The solution starts as a deep purple colour and fades when an antioxidant is present. A similar method was used to track the presence of reductants (antioxidants), with a ferricyanide solution (Fe2+) turning from a yellow colour to shades of green and blue depending on the reducing power of each compound.
Source: Food Chemistry
Published online ahead of print, http://dx.doi.org/10.1016/j.foodchem.2014.02.014
“Antioxidant property of edible mushrooms collected from Ethiopia”
Authors: A. Z. Woldegiorgis, D. Abate, G.D. Haki and G. R. Ziegler