Visualization of anthocyanin species in rabbiteye blueberry Vaccinium ashei by matrix-assisted laser desorption/ionization imaging mass spectrometry

Abstract

Anthocyanins are naturally occurring compounds that impart color to fruits, vegetables, and plants, and are believed to have a number of beneficial health effects in both humans and animals. Because of these properties, pharmacokinetic analysis of anthocyanins in tissue has been performed to quantify and identify anthocyanin species although, currently, no methods exist for investigating tissue localization of anthocyanin species or for elucidating the mechanisms of anthocyanin activity. Imaging mass spectrometry (IMS) is powerful tool for determining and visualizing the distribution of a wide range of biomolecules. To investigate whether anthocyanin species could be identified and visualized by IMS, we performed matrix-assisted laser desorption/ionization (MALDI)-IMS analysis, by tandem mass spectrometry (MALDI-IMS-MS), of ten anthocyanin molecular species in rabbiteye blueberry (Vaccinium ashei). The distribution patterns of each anthocyanin species were different in the exocarp and endocarp of blueberry sections. Anthocyanin species composed of delphinidin and petunidin were localized mainly in the exocarp. In contrast, those species composed of cyanidin, peonidin, and malvidin were localized in both the exocarp and the endocarp. Moreover, MALDI-IMS analysis of anthocyanidins in a blueberry section indicated that the distribution patterns of each anthocyanidin species were nearly identical with those of the corresponding anthocyanins. These results suggested that the different distribution patterns of anthocyanin species in the exocarp and endocarp depended on the aglycone rather than on the sugar moieties. This study is the first to visualize anthocyanin molecular species in fruits.

LC–MS/MS and UPLC–UV Evaluation of Anthocyanins and Anthocyanidins during Rabbiteye Blueberry Juice Processing

“…Press cake samples contained 3-fold greater total anthocyanidins (265.6 mg 100 g −1 ) than the control (85.1 mg 100 g −1 ). Since berry skins account for 10% to 20% of the berry weight (13.0 ± 0.6% herein [58]) and as the main location for anthocyanins in the berry, the majority of anthocyanins were left behind in the press cake, as previously demonstrated [19,37,48]. Cyanidin was the most abundant anthocyanidin (77.7 mg 100 g −1 ) recovered from PRC.…”

“…Malvidin (26.6 mg 100 g −1 ) and petunidin (25.9 mg 100 g −1 ) were the most abundant anthocyanidins in the control samples, while peonidin (4.1 mg 100 g −1 ) was the least abundant. Markedly higher amounts of anthocyanidins detected in the press cake are due to the majority of anthocyanins being located in the skins of the berries [37]. Press cake samples contained 3-fold greater total anthocyanidins (265.6 mg 100 g −1 ) than the control (85.1 mg 100 g −1 ).…”

“…Using the semi-quantitative LC-MS/MS peak area abundance data to compare anthocyanins, the most abundant major anthocyanin identified in the control rabbiteye sample was malvidin-3-pyranoside (Table 3). Malvidin-3-galactoside was the most abundant anthocyanin found in NHB blueberries [37]. Although peak resolution did not allow for the separation of the two 6 carbon sugars, herein, malvidin-3-galactoside was included in the recovery of malvidin-3-pyranoside.…”

“…Significant anthocyanin losses have also occurred in NHB blueberry juice and products [19,37,48,56,57]. There was 58.8% loss of monomeric anthocyanins in enzyme-treated, non-clarified, batch-pasteurized NHB blueberry juice prepared from frozen blanched berries, but only 27.5% loss in centrifuge-clarified juice [48].…”

“…A slightly different process using thawed, blanched NHB blueberries treated with pectinase, pressed, then clarified and followed by HTST (90 • C) pasteurization resulted in higher losses of 77.6% and 84.3% anthocyanin glycosides and anthocyanins, respectively [19]. There was a 68.0% total anthocyanin loss in juice created with individually quick frozen (IQF) NHB blueberries that were partially thawed, heated to 43 • C, treated with pectinase, pressed, then HTST pasteurized (90 • C) [37]. In puree/juice made with NHB berries that were manually crushed and machine-juiced, not filtered or clarified, then batch-pasteurized at 92 • C, there was a substantial 95.7% loss of total anthocyanins [57].…”