Quantification of Triterpenoid Acids in North Carolina Heritage Apple Peels

Abstract

BackgroundPentacyclic triterpenoid acids are found in a variety of medicinal plants and common foods. In particular, oleanolic acid, ursolic acid, and betulinic acid, found in the cuticular wax on apple peels, have anti‐inflammatory, anti‐diabetic, and cancer‐inhibiting properties in murine and in vitro models. This project aimed to find the variation of these three acids in western North Carolina heritage and commercially grown apples from the 2014 season.MethodsA total of 48 North Carolina apple cultivars were studied. Apples peels were collected and stored in −80° C. For extraction and analysis, peel samples were freeze dried, ground, and soaked in ethanol overnight. Samples were then extracted twice with ethanol. The filtrate was dried and resuspended in methanol for reverse‐phase isocratic HPLC analysis. Separation was achieved in 20 minutes with a methanol/water/acetic acid mobile phase (85/15/0.1), monitored at 207 nm.ResultsAll three triterpenoids were quantifiable in the 48 cultivars analyzed. Average total triterpenoid content was 19 mg/g dry peel weight, ranging from 2.0 mg/g (Roxbury Russet) to 36.3 mg/g (Virginia Gold). Betulinic, oleanolic, and ursolic acid averaged 0.26, 3.6, and 14.9 mg/g, respectively. Russet cultivars, such as Roxbury Russet and Sour Rusty Coat tended to contain less total triterpenoids than waxy cultivars such as Virginia Gold and Sweet Sixteen. No substantial differences were observed between green/yellow cultivars and red ones or across the season from early to late cultivars.ConclusionHeritage apple peels are a variable source of potentially salutary pentacyclic triterpenoids. Total amounts may vary almost 20 fold across cultivars with ursolic acid predominating.Support or Funding InformationAppalachian State University Office of Student Research