Plant-based food represents an excellent source of different nutrients and bioactive compounds, such as phenolics, carotenoids, vitamins, etc., with proven health benefits for humans. The content of selected phytochemicals, polyphenolic profile, and biological activity (antioxidant potential and α-glucosidase inhibitory activity) of fruit extracts of medlar (Mespilus germanica L.), blackthorn (Prunus spinosa L.), and common hawthorn (Crataegus monogyna Jacq.), the neglected Rosaceae species originated from Serbia were studied. Targeted UHPLC/(−)HESI–MS/MS quantitative analysis of phenolic compounds revealed pinocembrin only in medlar fruit extract, and it is the first report of this flavanone in medlar fruits. Total phenolic content did not differ between extracts, whereas significant differences were observed for the contents of total flavonoids, total phenolic acids, and total gallotannins. Monomeric anthocyanins and total anthocyanins were significantly higher in blackthorn compared to medlar and hawthorn fruit extracts (p < 0.05). DPPH^· and ABTS^·+ scavenging activities for examined fruits were modest compared to other natural antioxidants and BHT. The most potent inhibitory activity toward α-glucosidase expressed medlar and blackthorn extracts with IC₅₀ values of 129.46 and 199.84 μg/mL, respectively, which was higher compared to the standard drug acarbose.

Medlar (Mespilus germanica L.) fruit presents a good source of bioactive compounds. This study aimed to optimize the traditional extraction method, maceration, in order to obtain extracts rich in polyphenols. The total phenolic compounds (TPC) from physiologically ripe (PRMFs) and consumable ripe (CRMFs) medlar fruits were extracted to develop models with high accuracy and prediction capacity by response surface methodology (RSM). Furthermore, the main phenolic compounds in the extracts were quantified using HPLC, and the extracts were tested for antioxidant activity and hypoglycemic activity. The extracts were prepared according to a central composite design. The extraction parameters for both PRMFs and CRMFs were time (30–210 min), ethanol concentration (20–80%) and solid-to-solvent ratio (1:10–1:50). The obtained results indicated that the optimal conditions for the extraction were 210 min, 66.55% ethanol, and 1:50 solid-to-solvent ratio (PRMF), and 120 min, 74.96% ethanol, and 1:50 solid-to-solvent ratio (CRMF). Under the optimized conditions, values for TPC were in agreement with the values predicted by RSM. Isoquercitrin, rutin, procyanidin B2, chlorogenic acid and caffeic acid were the most abundant compounds in both PRMF and CRMF optimized extracts. TPC, antioxidant activity, and inhibition of α-glucosidase and α-amylase enzymes did not show significant differences (p > 0.05) among PRMF and CRMF extracts.

Medlar (Mespilus germanica L.) is a plant species that belongs to the Rosaceae family. Despite the nutritional and functional value of the medlar fruit, there is limited research, particularly regarding its potential as a source of dietary fibers, indigestible plant-based components, important for improving health. Fungal cellulase enzymes were used to treat medlar fruit in physiological (PRM) and consumable (CRM) maturity and obtain insoluble dietary fibers (IDF). The yield of obtained insoluble dietary fibers was 83% for both PRM and CRM. Fungal strains Aspergillus welwitschiae have proven to be significant producers of the cellulase enzyme complex and are also safe for use in food production. Swelling capacity exhibited the most pronounced response to the enzymatic treatment; 8.51–8.65% vs. 12.24–12.86% (untreated and treated fruits, respectively). Dietary fibers extracted from medlar fruits exhibited antioxidant activity that can be attributed to the presence of bound polyphenolic compounds within the fiber material. Microscopic analysis and FTIR spectra revealed structural changes in the medlar fibers due to enzyme activity, indicating partial hydrolysis of lignocellulosic components. This process enhances the functional properties of medlar-based IDF, making it a valuable ingredient for fiber-enriched food products.