Phytochemical analysis, antioxidant and ALR2 inhibitory activity of Sorbus torminalis (L.) fruits at different maturity stages

Thirty four compounds were identified in Sorbus torminalis (L.) fruit extracts of different maturity types by means of LC-DAD-MS (ESI+) fragmentation analysis. Both immature and mature fruits were rich in flavonoid glycosides esterified with hydroxycinnamic, phenolic and dicarboxylic acids along with benzoic, phenylpropanoic and cinnamoyl quinic acid derivatives with many of them being detected for the first time in Sorbus species and in literature. Extracts and fractions were tested for their antioxidant activity (DPPH, chemiluminescence, Rancimat assays) and the estimation of the phenolic content was carried out through Folin-Ciocalteu reagent. Ethyl acetate fraction exhibited the highest scavenging activity determined as EC₅₀ = 1.58 ± 0.22 μg/mL and EC₅₀ = 1.64 ± 0.24 μg/mL for immature and mature fruits respectively with the DPPH test. Chemiluminescence test indicated the same fraction having the strongest antioxidant activity with an IC₅₀ 0.41 ± 0.06 μg/mL and IC₅₀ 0.50 ± 0.02 μg/mL in both maturity types. The ethyl acetate fraction of the mature fruits is considered the most potent Aldose Reductase 2 (ALR2) inhibitor with 79% demonstrating the high nutritional value of Sorbus torminalis (L.) mature fruits as a defense mechanism against the onset of diabetes mellitus secondary complications leading to the utilization of the plant for nutritional and pharmaceutical purposes.