Nonanthocyanin Secondary Metabolites of Black Raspberry (<i>Rubus occidentalis</i> L.) Fruits: Identification by HPLC-DAD, NMR, HPLC-ESI-MS, and ESI-MS/MS Analyses

Nonanthocyanin secondary metabolites potentially contributing to the antiproliferative bioactivity of black raspberry (Rubus occidentalis L.) fruits were extracted in ethyl acetate and isolated by semipreparative and analytical HPLC and analyzed by NMR, HPLC-ESI-MS, and ESI-MS/MS techniques. Here we present complete and partial structures of a variety of the chemical entities such as quercetin 3-glucoside, quercetin 3-rutinoside, myricetin glucoside, dihydrokaempferol glucoside, benzoic acid β-d-glucopyranosyl ester, 3,4-dihydroxybenzoic acid, epicatechin, caffeic acid, <i>p-</i>coumaric acid, <i>p-</i>coumaryl glucoside, <i>p-</i>coumaryl sugar ester, ellagic acid, methyl ellagic acid acetylpentose, methyl ellagic acid valerylpentose, <i>trans</i>-piceid, phloretin glucoside (phloridzin), dihydrosinapic acid, salicylic acid β-d-glucopyranosyl ester, a salicylic acid derivative without attached sugar, <i>p-</i>alkylphenyl glucoside, and a citric acid derivative. To our knowledge, 15 of these compounds were not previously reported in black raspberry fruits

NMR-Based Metabolomic Investigation of Bioactivity of Chemical Constituents in Black Raspberry (Rubus occidentalis L.) Fruit Extracts

Black raspberry (Rubus occidentalis L.) (BR) fruit extracts with differing compound profiles have shown variable antiproliferative activities against HT-29 colon cancer cell lines. This study used partial least-squares (PLS) regression analysis to develop a high-resolution ¹H NMR-based multivariate statistical model for discerning the biological activity of BR constituents. This model identified specific bioactive compounds and ascertained their relative contribution against cancer cell proliferation. Cyanidin 3-rutinoside and cyanidin 3-xylosylrutinoside were the predominant contributors to the extract bioactivity, but salicylic acid derivatives (e.g., salicylic acid glucosyl ester), quercetin 3-glucoside, quercetin 3-rutinoside, <i>p</i>-coumaric acid, epicatechin, methyl ellagic acid derivatives (e.g., methyl ellagic acetyl pentose), and citric acid derivatives also contributed significantly to the antiproliferative activity of the berry extracts. This approach enabled the identification of new bioactive components in BR fruits and demonstrates the utility of the method for assessing chemopreventive compounds in foods and food products