Metabolomics-guided discrimination of constituents in five commercial apple (Malus × domestica Borkh.) cultivars: Assessment of their antioxidant, neuroprotective, and antidiabetic activities for potential use as functional food

Abstract

Apples (Malus × domestica Borkh.) are available in different cultivars, we investigated the similarities and differences in the chemical composition and biological activities of the extracted apple oils by hydrodistillation and hexane extraction. The aroma constituents obtained by hydrodistillation and n-hexane extraction of five commercial Egyptian apple cultivars namely Pink Lady (Cripps pink), Red Delicious, Ambrosia, Golden Delicious, and Granny Smith were investigated by Gas chromatography-mass spectrometry (GC-MS). The total phenolic (TPC) and total flavonoid contents (TFC), in vitro antioxidant analysis, and enzyme inhibition assays were performed. Results showed that TPC and TFC were the highest in the hexane extract of pink ladies with values of 12.42 (mg GAE/g FW) and 1.35 (mg RE/g FW), respectively. Similarly, pink lady hexane extract showed the highest efficacy in antioxidant assays like 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS), Cupric reducing antioxidant capacity (CUPRAC), ferric reducing antioxidant power (FRAP), metal chelation, and phosphomolybdenum tests with values of 25.21 mg TE/g, 39.82 mg TE/g, 19.27 mg TE/g, 28.16 mg EDTAE/g, and 1.36 mmol TE/g, respectively. Assessments of enzyme inhibition potential of the hexane extracts of the five cultivars on acetylcholinesterase (AChE) showed efficacy for ambrosia only with inhibition value at 2.53 mg GALAE/g. All other cultivars showed comparable efficacies in inhibiting tyrosinase, amylase, and glucosidase enzymes. Significant differences were observed in the chemical composition of the five apple cultivars which were reflected by differences in their antioxidant and enzyme inhibition capacities. Results of biological studies were further confirmed with in silico investigations.