Modeling Relationships among Active Components in Black Raspberry (Rubus occidentalis L.) Fruit Extracts Using High-Resolution ¹H Nuclear Magnetic Resonance (NMR) Spectroscopy and Multivariate Statistical Analysis

Abstract

A process was developed to ascertain the bioactive components of black raspberry (Rubus occidentalis L.) fruit extracts by relating chemical constituents determined by high-field nuclear magnetic resonance (NMR) spectroscopy to biological responses using partial least-squares regression analysis. To validate our approach, we outlined relationships between phenolic signals in NMR spectra and chemical data for total monomeric anthocyanin (TMA) content and antioxidant capacity by the ferric-reducing antioxidant power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays. Anthocyanins, cyanidin 3-O-rutinoside (Cy 3-rut), cyanidin 3-O-(2(G))-xylosylrutinoside (Cy 3-xylrut), and cyanidin 3-O-glucoside (Cy 3-glc), were significant contributors to the variability in assay results, with the two most important NMR bins corresponding to the methyl peaks in Cy 3-rut (6''') and/or Cy 3-xylrut (6(IV)). Many statistically important bins were common among assay models, but differences in structure-activity relationships resulted in changes in bin ranking. The specificity of these results supported the application of the process to investigate relationships among health-beneficial natural products and potential biological activity.

Variation in anthocyanins and total phenolics of black raspberry populations

“…Cyanidin-3-xylosylrutinoside and cyanidin-3-rutinoside were the major anthocyanins, comprising roughly 90% of the sum of the individual anthocyanins (Table 1). This agrees with other studies indicating that these two anthocyanins comprise the majority of anthocyanins present in black raspberry (Tian et al, 2006;Tulio et al, 2008;Wyzgoski et al, 2010). These two main anthocyanins were also more potent phenolic antioxidants (cyanidin-3-xylosylrutinoside > cyanidin-3-rutinoside) compared to the other anthocyanins present in black raspberry fruit , although it was not clear in this study if the individual anthocyanins antioxidant activities were compared on an equal molar or equal weight basis.…”

“…Total anthocyanins by HPLC in this study were somewhat lower than reported by Wu et al (2006), 687 mg 100 g À1 (n = 1; cultivar unknown), and Hager et al (2008), 1113 mg 100 g À1 (n = 1; 'Munger'). Six individual anthocyanins (cyanidin-3-sambubioside, cyanidin-3-glucoside, cyanidin-3-xylosylrutinoside, cyanidin-3-rutinoside, pelargonidin-3-rutinoside, and peonidin-3-rutinoside; in the order of elution) were detected in juice from the populations in this study as previously reported (Dossett et al, 2008;Hong & Wrolstad, 1990;Tulio et al, 2008;Wu et al, 2006;Wyzgoski et al, 2010). Refer to Dossett et al (2008) for a representative black raspberry chromatogram analyzed under these sample preparation and HPLC conditions.…”

“…This result has also been noted by every study using HPLC to quantify individual anthocyanins in black raspberry fruit and has led, in part, to a focus on the importance and effects of this particular anthocyanin in black raspberry (Ozgen et al, 2008;Tulio et al, 2008;Wyzgoski et al, 2010). In contrast, in NC 84-10-3 (parent) and most of its progenies, the proportions of the two major anthocyanins were reversed from what has been previously reported, with higher amounts of cyanidin-3-xylosylrutinoside than of cyanidin-3-rutinoside.…”

“…The only previous study that attempted to do so used black raspberry germplasm that had been crossed with red raspberry (genotypes n = 124 evaluated) to introduce thornlessness (Scalzo, Currie, Stephens, McGhie, & Alspach, 2008), although, they refer to these crosses as black raspberry. In doing so, cyanidin-3-sophoroside present in red raspberry (Kassim et al, 2009;Mullen, Lean, & Crozier, 2002) but absent from pure black raspberry (Dossett et al, 2008;Hong & Wrolstad, 1990;Tulio et al, 2008;Wyzgoski et al, 2010) was introduced into the material studied by Scalzo et al (2008) and the concentration of anthocyanins in the fruit may have been similarly affected.…”

Characterization of a novel anthocyanin profile in wild black raspberry mutants: An opportunity for studying the genetic control of pigment and color

“…Studies characterizing the types of anthocyanins present in black raspberry fruit date back to at least the 1960s (Nybom, 1968). A number of recent studies have examined the anthocyanin composition of black raspberry fruit using more sophisticated tools than those available 50 years ago and have consistently detected cyanidin-3-glucoside, cyanidin-3-sambubioside, cyanidin-3-rutinoside, cyanidin-3-xylosylrutinoside, pelargonidin-3-rutinoside, and peonidin-3-rutinoside (Dossett, Lee, & Finn, 2008;Tian, Giusti, Stoner, & Schwartz, 2006a, 2006bTulio et al, 2008;Wyzgoski et al, 2010). Wu, Pittman III, and Prior (2006) also found trace levels of pelargonidin-3-glucoside in black raspberry fruit.…”