| Summary: | Abstract Mushrooms have been consumed as delicacies since ancient times; however, little knowledge is available on the nutritional and bioactive properties of commercially grown mushroom species in Sri Lanka; button (Agaricus bisporus), oyster (Pleurotus ostreatus), Makandura white (Calocybe sp.), and Reishi (Ganoderma lucidum). Samples from four mushroom species were analysed for proximate composition, mineral and fatty acid content, and antioxidant, antidiabetic, and microstructural properties. Carbohydrate, protein, fat, ash, and dietary fibre content in mushroom species ranged from 64.83–79.97%, 10.53–23.29%, 0.57–4.37%, 2.80–11.00%, and 33.04 to 75.33%, respectively. The highest (P ≤ 0.05) protein and ash content were observed in A. bisporus, and G. lucidum had the highest (P ≤ 0.05) fat and dietary fibre content. When considering the micronutrients, G. lucidum comprised higher (P ≤ 0.05) Ca, Mg, Mn, and Cu, while A. bisporus had higher (P ≤ 0.05) Fe and Zn contents than other species. Essential omega-6 fatty acid, linoleic (18:2n-6) content was in the range of 37- 81% in studied mushroom samples. Results obtained from FTIR (Fourier transform infrared spectroscopy) in conjunction with ATR (Attenuated total reflectance) revealed the presence of functional groups associated with fat (̴1740 cm−1), protein (̴1560 cm−1), polysaccharides (1500–750 cm−1) and moisture (̴3300 cm−1) in mushroom samples. According to the results, P. ostreatus showed the highest (P ≤ 0.05) polysaccharide content, while G. lucidum showed the lowest (P ≤ 0.05). The highest (P ≤ 0.05) total phenolic content (TPC) (3.95 ± 0.05 mg GAE/g DW) and total flavonoid content (TFC) (2.17 ± 0.06 mg CE/g DW) were observed in P. ostreatus. Antioxidant activity measured by DPPH, ABTS, and FRAP methods was higher (P ≤ 0.05) in P. ostreatus and A. bisporus compared to the other two species. Among all the studied mushroom species, G. lucidum showed the highest (P ≤ 0.05) α-amylase (IC50 = 77.51 ± 6.80 µg/mL) and α-glucosidase (IC50 = 0.4113 ± 0.08 µg/mL) inhibition activities. This study reveals the potential of using A. bisporus, G. lucidum, and P. ostreatus for nutritional, functional, and therapeutic uses. Graphical Abstract
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