Evaluation of the Antioxidant Capacity, Antimicrobial Effect, and In Vitro Digestion Process of Bioactive Compounds of Cherry Laurel Leaves Extracts

Abstract

Cherry laurel is a less known fruit species with an astringent taste and is mostly consumed as fresh fruit only in the Black Sea and Marmara regions of Turkey. Cherry laurel (Laurocerasus officinalis Roemer) leaves can be prepared in different forms such as infusion by steeping the dried leaf in boiled water and as an extract for its further use as a food supplement or ingredient. In this study, aqueous and ethanol extracts of cherry laurel leaves were prepared and examined in terms of total phenolic compound (TPC), total flavonoid compound (TFC), antioxidant capacities using 2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and the copper reducing antioxidant capacity (CUPRAC) assays after submitting to in vitro digestion. Additionally, the antimicrobial potential of the leaves extract was evaluated. The TPC of ethanol and aqueous extracts were found at 17.62 and 0.83 mg gallic acid equivalent GAE.g-1 leaves and the TFC of ethanol and aqueous extracts were determined as 11.61 and 0.47 mg catechin equivalent CE.g-1 leaves, respectively. In terms of antioxidant activity results, ethanol and aqueous extracts had 41.11 and 0.77 mg Trolox equivalent TE.g-1 leaves for the DPPH assay, and 67.05 and 1.63 mg TE.g-1 leaves for the CUPRAC assay. After gastric digestion post-gastric (PG), compared to the initial values significantly lower recovery of the TPC (11.2 and 41%) and TFC (5.8 and 14.9 %) was observed for ethanol and aqueous extracts. The recovery of TPC, TFC values after the intestinal fraction was lower compared to the PG fraction for ethanol extracts, whereas for aqueous extracts they were higher compared to the PG fraction. The highest inhibition zone was observed against Listeria monocytogenes and Aspergillus niger when 10% extract concentration was applied. The experimental data verified that these extracts displayed remarkable antioxidant and antimicrobial activities, and the extraction method was important in terms of the bioaccessibility of bioactive compounds.