Antioxidant Properties of Selected Underutilized Fruit Species of Sri Lanka after Simulated Oral and Gastro-Intestinal Digestion

Background: High consumption of natural antioxidants, particularly phenolic compounds found in fruits and vegetables, makes a significant contribution to plasma antioxidant capacity. The impact of plant phenolics in terms of health benefits is strongly reliant on their level of bioaccessibility and bioavailability.

Objectives: The study was conducted to determine the antioxidative properties and bioaccessibility in six underutilized fruit species, namely (Phyllanthus emblica, Elaeocarpus sirratus, Cynometra cauliflora, Aegle marmelos, Limonia acidissima and Flacoutia indica).

Materials & Methods: The total phenolic content (TPC) of fruit samples was determined after in-vitro simulated oral and gastro-intestinal digestion. The total phenolic content of dialysate and retentates were determined using the Folin-Ciocalteu’s test. 2, 2-diphenyl-1-pycrylehydrazyl (DPPH) and the total antioxidant activity assay (2,2'azinobis3-ethylbenzothiazoline-6-sulphonic acid (ABTS)) were used to assess radical scavenging activity (RSA) and total antioxidant activity (TAA), respectively.

Results: The highest TPC (110.33 mg of gallic acid equivalents (GAE)/g on dry weight (DW) basis), the highest DPPH radical scavenging activity as measured by IC50 value (0.09 mg of dried fruit/mL), and the highest percentage of TAA (90%) were exhibited by P. emblica while the C. cauliflora recorded the lowest. Among the tested fruit species, P. emblica also had maximum bioaccessibility of total polyphenols (83.66 %) and C. cauliflora had the lowest (40.16%).

Conclusions: Phylanthus emblica had the highest TAA and RSA of the tested fruit species while lowest was recorded in C. cauliflora. The TPC, TAA and RSA of all fruit species increased after enzymatic digestion. Further in vitro and in vivo studies should be conducted to assess the bioaccessibility and bioavailability of individual phenolic compounds.