Towards medicinal tea from untapped Namibian Ganoderma: Phenolics and in vitro antioxidant activity of wild and cultivated mushrooms

Abstract

Ganoderma is a genus of mushrooms that is prized in developed nations, especially those in Asia, due to its health-promoting properties, which are attributed to bioactive compounds such as phenolics. However, in developing countries, particularly in Africa, Ganoderma mushrooms are untapped and are barely identified. In this study, we identified Ganoderma species collected from different host trees in the wild in Namibia, cultivated them on one substrate and determined their water absorption and solubility indices. Total phenolics (TP), total flavonoids (TF), condensed tannins (CT) and in vitro antioxidant activity (AA) were determined in hot water infusions made from wild and cultivated Ganoderma mushrooms. Folin–Ciocalteu, aluminium chloride, vanillin-HCl, and DPPH assay methods were used to determine TP, TF, CT and AA, respectively. Wild species had 6.12–11.70% moisture, 1.91–5.32% ash, 11.55–24.40 (g of absorbed water/g of dry sample) water absorption index, 3.60–24.10% water solubility index, 18.37–44.78 (mg GAE/g of sample) TP, 0.09–1.67 (mg QE/g of sample) TF, 2.97–6.37 (mg CAE/g of sample) CT and 40.8–49.3% AA. Cultivated species had 9.64 13.45% moisture, 2.34–6.20% ash, 13.55–28.30 water absorption index, 6.40–25.35% water solubility index, 36.70–52.73 (mg GAE/g of sample) TP, 0.41–0.86 (mg QE/g of sample) TF, 11.38–15.29 (mg CAE/g of sample) CT and 53.6–63.7% AA. Infusions prepared from cultivated Ganoderma species had higher levels of TP, CT and AA, but lower levels of TF than those prepared from wild Ganoderma species, suggesting that they have potential as nutraceuticals.

Ganoderma adspersum (Ganodermataceae): Investigation of Its Secondary Metabolites and the Antioxidant, Antimicrobial, and Cytotoxic Potential of Its Extracts

“…The difference in that case was that the mushroom material was not wild but from mycelial cultures. The results of recent studies confirm the aforementioned conclusion [ 49 , 50 ]. Furthermore, it has also been reported that the freshness (i.e., fresh or dry) of the mushroom material plays a key role in the amounts of bioactive components recovered [ 51 ].…”

The contribution of fungi to the global economy

“…The reported bioactivities include antibacterial, antidiabetic, antifungal, antihypercholesterolemial, antioxidant, antiparasitic, antitumor, antiviral, cardiovascular, hepatoprotective, immunomodulatory and radical scavenging effects (Hyde et al 2019;Zeb and Lee 2021;Niego et al 2021). The bioactive principles causative for those effects are polysaccharides, proteins (El Enshasy and Hatti-Kaul 2013), glycoproteins (Cohen et al 2014), phenolic compounds (Gupta et al 2018;Hamwenye et al 2022), ergosterol (Diallo et al 2020) and other terpenoids, or unsaturated fatty acids (Galappaththi et al 2022). The health-promoting properties of many fungi are the driving force for increasing their market value and incorporation into the nutraceutical industry (Niego et al 2021).…”