Purple Beautyberry is a shrub grown in the United States as an ornamental plant, with uniquely bright, purple-violet fruit that is edible, but not currently utilized. This coloration is rare in nature, and is interesting for natural food coloring applications, but no compositional studies were found. Our objective was to analyze the fruit color and pigments, and to quantify total phenolics that may contribute to the bright coloration.
Fruit was powderized with liquid nitrogen followed by acetone extraction and chloroform partitioning. The top aqueous layer was collected, solvents were evaporated, and the extract was taken to 100 mL with acidified water. Crude extracts underwent C18 resin purification before chromatographic analysis on an uHPLC-PDA-ESI-MS/MS with a C18 column using a mobile phase of 4.5% formic acid and acetonitrile (flow rate of 0.3 mL/min). Alkaline hydrolysis was conducted with 10% KOH in the dark. Total phenolics (TP) were determined by Folin-Ciocaliteau colorimetry and total monomeric anthocyanins (TMA) by the pH differential method. Color (CIEL*c*h) of fruits (fresh and frozen/thawed), and extracts were measured with a Minolta RC400 colorimeter and SpectraMax 190 Microplate Reader.
Chromatographic results showed two major and one minor peak (520 nm) identified as anthocyanins. The mass to charge values [M]+ m/z of 625(pk 1) and 711(pk 3) of the two major peaks were putatively characterized as peonidin dihexose and peonidin dihexose acylated with malonic acid. Alkaline hydrolysis resulted in loss of acylated peaks 2 and 3, which is consistent with anthocyanins sharing a single aglycone(peonidin). The TMA (5.6 mg/100g) and TP (54.8 mg/100 g) were modest compared to plants in the same family (Lamiaceae) (TMA 0-15mg /100g, TP 400-2500 mg/100 g) and berries (TMA 100-700mg/100g, TP 10-500 mg/100g). The color of the fresh fruit was magenta (L*=60, C*=78, h=331), frozen fruit was deep violet (L*=32, C*=37, h=349), and the extract was bright pink (L*=63, C*=36, h= 7, pH 2).
Anthocyanin pigments (peonidin derivatives) were identified in Purple Beautyberries. Despite a modest anthocyanin and phenolic content, the fruit exhibits intense colorations, which merits additional attention. The prevalence of anthocyanins and polyphenols could provide an additional, low-cost source for food colorants.