Differential partitioning of triterpenes and triterpene esters in apple peel

Authors: Poirier, Brenton; BUCHANAN, DAVID - Retired ARS Employee; Rudell, David; Mattheis, James

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/22/2018
Publication Date: 1/22/2018
Citation: Poirier, B.C., Buchanan, D.A., Rudell Jr, D.R., Mattheis, J.P. 2018. Differential partitioning of triterpenes and triterpene esters in apple peel. Journal of Agricultural and Food Chemistry. https://doi.org/10.1021/acs.jafc.7b04509.
DOI: https://doi.org/10.1021/acs.jafc.7b04509

Interpretive Summary: The natural wax coating of apple fruit is a critical factor for maintaining quality and appearance during growth and storage. Apple wax has many components that together protect the fruit from water loss and impact how ripening occurs. Under some situations, this natural wax coating forms irregularly and results in poor fruit quality after fruit are removed from cold storage. To address this problem, scientists at the USDA, ARS Tree Fruit Research Laboratory in Wenatchee, WA identified novel components in the wax and peel tissue. This new information allows additional insight as to how wax is formed and factors that may influence wax production. Together these findings may contribute to development of improved cold storage and handling practices that will reduce fruit loss as well as provide consistent, high eating quality of apples in the domestic and international marketplace.

Technical Abstract: Apple peel functions as a protective barrier against biotic and abiotic stresses, and preserving the integrity and appearance of peel critical for market acceptance. Peel epidermal cells and epicuticular wax are a rich source of secondary metabolites, including triterpenes. Several studies have outlined the dietary health benefits of ursane-type triterpenes in apple. Changes in triterpene metabolism have also been associated with the development of superficial scald, a postharvest apple peel browning disorder, and postharvest applications of diphenylamine and 1-methylcyclopropene. Previously, studies have generated metabolite profiles for whole apple peel or apple wax. In this study, we report separate metabolic analyses of isolated wax fractions and peel epidermis. We identified several unreported ursane-type triterpene esters, and our analysis reveals spatial distribution of triterpenes and triterpene conjugates that may be used to interpret the results of other metabolic studies.