Antioxidant Capacity and Phenolic Antioxidants of Midwestern Black Raspberries Grown for Direct Markets Are Influenced by Production Site

Abstract

<jats:p>Black raspberries (<jats:italic>Rubus occidentalis</jats:italic> L.) are rich in phytonutrients that have demonstrated chemoprotective properties against certain degenerative diseases. To estimate variability in phytonutritional quality among sources of black raspberry, 19 samples representing four common midwestern cultivars obtained from eight production sites were assayed for their antioxidant capacity [2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing ability of plasma (FRAP) methods], total phenolic content (TP), total monomeric anthocyanin levels (TMA), and levels of cyanidin 3-rutinoside. The antioxidant potential among samples averaged 2.92 ± 0.29 and 4.62 ± 0.88 mmol TE·100 g<jats:sup>−1</jats:sup> fresh weight by the DPPH and FRAP methods, respectively; TP, TMA, and cyanidin 3-rutinoside means averaged 449 ± 62, 336 ± 109, and 244 ± 84 mg·100 g<jats:sup>−1</jats:sup> fresh weight, respectively. Levels of FRAP, TP, TMA, and cyanidin 3-rutinoside were strongly correlated (<jats:italic>r</jats:italic> = +0.85 to +0.96). Mean antioxidant capacities and phenolic constituent levels were similar among ‘Bristol’, ‘Jewel’, and ‘MacBlack’ samples; values for a single sample of ‘Haut’ were lower but comparable to levels found in individual samples of the other three cultivars. Black raspberry production site differences were statistically significant for FRAP, TMA, cyanidin 3-rutinoside, and titratable acidity (TA) levels. Inverse relationships (<jats:italic>r</jats:italic> = –0.65 to –0.74) among black raspberry samples for FRAP, TMA, or cyanidin 3-rutinoside levels versus levels of TA suggested that site differences may be partially attributable to fruit ripeness at harvest. Relationships among these parameters versus regional differences in soil temperatures were also significant but weak. Regardless of its environmental or physiological drivers, point-source variation in fruit phytonutrient contents may be a relevant concern in health-related studies or clinical applications. Moreover, it may impact the nutritional benefits to the consumer and affect the quality advantages associated with direct-marketed black raspberries.</jats:p>

Variation in anthocyanins and total phenolics of black raspberry populations

“…TACY as measured by the pH differential method were lower than total anthocyanin by HPLC/DAD, but measurements were significantly correlated (Spearman rank order correlation R = 0.68, p 6 0.05) as previously demonstrated (Lee & Finn, 2007;Lee, Rennaker, & Wrolstad, 2008). Moreover, values of TACY by pH differential were similar to or slightly lower than those reported by others (Moyer et al, 2002;Ozgen et al, 2008;Wang & Lin, 2000;Wang & Zheng, 2005), ranging from 141 to 627 mg 100 g À1 (n = 31; from 'Earlysweet', 'Munger', 'Jewel', 'Haut', 'MacBlack', and 'Bristol'; all previously reported values by others were converted and expressed as cyanidin-3-glucoside). 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').…”

“…Based on an extracted ion chromatogram of 449.2, minor amounts of cyanidin-3-glucoside were detected. Ozgen et al (2008) found only minor differences in anthocyanin content (measured by pH differential) between the cultivars 'Bristol', 'Jewel', 'MacBlack', and 'Haut', particularly in comparison with differences found among eight different production sites in Ohio (USA). Our data show somewhat larger differences between samples at a single location, however this should be expected with the greater diversity in samples.…”

“…Our data show somewhat larger differences between samples at a single location, however this should be expected with the greater diversity in samples. Ozgen et al (2008) attributed the similarity of their samples to a lack of genetic diversity between cultivars, noting that two of the cultivars they tested ('Bristol' and 'Jewel') are closely related, and citing molecular data (Weber, 2003) that indicate a general lack of genetic diversity among black raspberry cultivars. Our results indicate that similar values for total anthocyanins may be expected from a range of cultivars and that breeding for higher anthocyanin levels in black raspberries using the currently available germplasm is unlikely to be successful.…”

Comparison of antioxidant capacity and phytochemical properties of wild and cultivated red raspberries (Rubus idaeus L.)

“…Previous studies (e.g. Connor et al, 2005a,b;Ö zgen et al, 2008) reported strong relationships among measures of TP content, anthocyanin levels, and antioxidant capacity of Rubus species. From our data we calculated high correlation coefficients (r) between the TP values of red raspberry samples and their respective antioxidant capacities.…”

“…However, phenolic compounds and antioxidant capacities can be influenced, mainly by genetics and environment (Anttonen and Karjalainen, 2005;Connor et al, 2005a,b;McGhie et al, 2002;Ö zgen et al, 2008). Furthermore, Connor et al (2005a) indicated that having high bioactive compounds variability among the accessions is important to obtain superior cultivars, and selection programs are the important resources.…”