| Summary: | <i>Fomes fomentarius</i>, usually referred to as tinder conk, is a common wood-based fungus rich in many interesting phytochemicals and with an unique porous structure. Dry or wet ball milling of this sponge on a planetary mill results in small particles with sizes in the range of 10 µm or below. Suspended in water and without preservatives or other stabilizers, the resulting micro-suspensions are sterile for around six days, probably due to the increased temperatures of around 80 °C especially during the wet milling process. The suspensions also exhibit excellent antioxidant activities as determined in the DPPH, ferric reducing antioxidant potential (FRAP) and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) assays. In the DPPH assay, IC<sub>50</sub> values of 0.02—0.04% <i>w/v</i> and 0.04% <i>w/v</i> were observed for dry and wet milled samples, respectively. In the FRAP assay, IC<sub>50</sub> values of <0.02% <i>w/v</i> and 0.04% <i>w/v</i> were observed for dry and wet milled samples, respectively. In contrast, the ABTS assay provided IC<sub>50</sub> values of 0.04% <i>w/v</i> and 0.005% <i>w/v</i>, respectively. Notably, this activity is mostly—albeit not exclusively—associated with the highly porous particles and their large surfaces, although some active ingredients also diffuse into the surrounding aqueous medium. Such suspensions of natural particles carrying otherwise insoluble antioxidants on their surfaces provide an interesting avenue to unleash the antioxidant potential of materials such as sponges and barks. As dry milling also enables longer storage and transport, applications in the fields of medicine, nutrition, agriculture, materials and cosmetics are feasible.
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