Bioactive phytochemicals and their bioaccessibility in four unexploited tropical fruits grown in Queensland, Australia

Tropical fruits are a popular target for health-conscious consumers worldwide. The phytochemical composition, in particular polyphenols and carotenoids, of these “exotics” is of emerging interest due to the potential health benefits of these compounds. The anthocyanin, quercetin glycoside and carotenoid composition in hog plum (Spondia dulcis), peanut butter fruit (Bunchosia armeniaca), chupa-chupa (Martisia cordata) and kwai muk (Artocarpus hypargyreus) grown in North Queensland was determined in the present study. Additionally, the release/ bioaccessibility of the determined phytochemicals as an initial measure to predict their availability for intestinal absorption was assessed using an in-vitro digestion model. Six anthocyanins could be identified in Kwai muk with cyanidin-3-glucoside as the predominant pigment (80% of total amount). Quercetin glycosides ranged between 5.6 and 8.4 mg 100 g^-1 fresh weight (fw). Lycopene was identified as the main carotenoid in peanut butter fruit (21.3 mg 100 g^-1 fw), whereas β-carotene was predominant in chupa-chupa (5.84 mg 100 g^-1 fw), kwai muk (1.66 mg 100 g^-1 fw) and hog plum (0.21 mg 100 g^-1 fw). The lycopene content in peanut butter fruit was considerable and even higher than that reported for tomatoes, a popular dietary source of lycopene. Total anthocyanins (10.5 mg 100 g^-1 fw) and quercetin glycosides were in the same range as reported for other fruits such as gooseberries, red currants and blueberries. Between 1-3% of carotenoids, 7-25% of quercetin glycosides and 37% of anthocyanins were released/bioaccessible after the in vitro digestion procedure. The observed low release of carotenoids from unprocessed fruits is in the same range as reported for unprocessed carrots. However, processing (e.g., blending, thermal treatment) and the addition of lipids can significantly increase the release/bioaccessibility of these lipophilic compounds. The present study clearly identified peanut butter fruit as a promising candidate for follow-up studies, in vitro and in vivo, evaluating its potential as a novel dietary source of lycopene.