Identification of phenolics responsible for the high antioxidant activity in Burdekin plum (Pleiogynium timoriense) fruit
Joel B. Johnson, Beatriz E. Hoyos, Janice S. Mani, Megan Reynolds, Jens Altvater, Mani Naiker
Abstract
Burdekin plum (Pleiogynium timoriense) is a widespread native edible fruit from Australia; however, there are limited studies exploring the chemical composition of this species. This study investigated the phytochemical composition of Burdekin plum flesh and seeds, finding a high antioxidant activity (12,571 mg Trolox equivalents/100 g as Ferric Reducing Antioxidant Potential), total phenolic content (10,928 mg gallic acid equivalents/100 g) and anthocyanin content (161 mg cyanidin-3-glucoside equivalents/100 g) in the flesh. The seeds also displayed a moderately high antioxidant activity (3,306 mg Trolox equivalents/100 g) and total phenolic content (2,344 mg gallic acid equivalents/100 g). Seventeen phenolic compounds were identified in the flesh and 14 in the seeds using targeted quantitative profiling using liquid chromatography - tandem mass spectrometry (LC-MS/MS). The most abundant compounds were cyanidin-3-glucoside and catechin in the flesh and seeds, respectively. Catechin also showed a high antioxidant activity, along with ellagic acid and gallic acid, while the activity of cyanidin-3-glucoside was relatively lower. Consequently, the main phenolic compounds contributing to the exceptionally high antioxidant activity of Burdekin plum flesh were identified as cyanidin-3-glucoside and ellagic acid. In the seeds, catechin provides a significant contribution to the antioxidant activity.