New Highly Stable Dimeric 3‐Deoxyanthocyanidin Pigments from Sorghum bicolor Leaf Sheath

Abstract

The growing interest in natural alternatives to synthetic petroleum-based dyes for food applications necessitates looking at nontraditional sources of natural colors. Certain sorghum varieties accumulate large amounts of poorly characterized pigments in their nongrain tissue. We used High Performance Liquid Chromatography-Tandem Mass Spectroscopy to characterize sorghum leaf sheath pigments and measured the stability of isolated pigments in the presence of bisulfite at pH 1.0 to 7.0 over a 4-wk period. Two new 3-deoxyanthocyanidin compounds were identified: apigeninidin-flavene dimer and apigenin-7-O-methylflavene dimer. The dimeric molecules had near identical UV-Vis absorbance profiles at pH 1.0 to 7.0, with no obvious sign of chalcone or quinoidal base formation even at the neutral pH, indicating unusually strong resistance to hydrophilic attack. The dimeric 3-deoxyanthocyanidins were also highly resistant to nucleophilic attack by SO(2); for example, apigeninidin-flavene dimer lost less than 20% of absorbance, compared to apigeninidin monomer, which lost more than 80% of absorbance at λ(max) within 1 h in the presence of SO(2). The increased molecular complexity of the dimeric 3-deoxyanthocyanidins compared to their monomers may be responsible for their unusual stability in the presence of bisulfite; these compounds present new interesting opportunities for food applications.

Sorghum Grain: From Genotype, Nutrition, and Phenolic Profile to Its Health Benefits and Food Applications

“…Their derivatives including the methoxylated form (7‐methoxy‐apigeninidin, 7‐methoxy‐luteolinidin, and 5‐methoxy‐luteolinidin), glycosides (apigeninidin 5‐glucoside and luteolinidin 5‐glucoside), and methoxylated glycosides (7‐methoxy‐apigeninidin 5‐glucoside, 7‐methoxy‐luteolinidin 5‐glucoside, and 5‐methoxy‐luteolinidin 7‐glucoside) have also been reported and in relatively moderate or small quantities (Dykes et al., ; Dykes et al., ; Petti et al., ; Wu & Prior, ). Moreover, other novel derivatives such as dimeric 3‐deoxyanthocyanidins (for example, apigeninidin‐flavene dimer) and pyranic 3‐deoxyanthocyanidins (an additional ring connected to the C‐4 and C‐5 position) have also been reported and demonstrated promising color stability (Bai et al., ; Geera, Ojwang, & Awika, ; Khalil, Baltenweck‐Guyot, Ocampo‐Torres, & Albrecht, ).…”

“…Among the red pericarp sorghum genotypes, black sorghum (genotypically red but phenotypically black) bran has the highest levels of 3‐deoxyanthocyanidins (1,790 to 6,120 µg/g), at least twice higher than red (both genotypically and phenotypically red) and brown sorghum (red genotype with pigmentated testa) bran (Table ) (Awika et al., ; Dykes et al., ; Dykes et al., ; Dykes et al., ). In addition, 3‐deoxyanthocyanidins are also distributed in other plant tissues of sorghum such as the sheath and leaves, with a concentration up to 90,000 µg/g (Geera et al., ; Petti et al., ).…”

Clinical Efficacy of a West African Sorghum bicolor-Based Traditional Herbal Preparation Jobelyn Shows Increased Hemoglobin and CD4+ T-Lymphocyte Counts in HIV-Positive Patients

“…[3][4][5][6] The suggested mechanism of action was an immune-boosting effect, which is interesting in light of the presence of antiviral peptides in some parts of the sorghum plant, 7 as well as unique polyphenol compounds identified in Jobelyn. 8,9 Evidence in vitro for many biological properties of Jobelyn was recently published. The data include immune modulation, activation of natural killer cells involved in antiviral immune defense actions, and up-regulating of the production of antiviral chemokines.…”

3‐Deoxyanthocyanidin Colorant: Nature, Health, Synthesis, and Food Applications

“…For example, apigeninidin extracted from sorghum has demonstrated good stability at pH 6 to 10, with increased color intensity at alkaline pH (Akogou, Kayodé, den Besten, Linnemann, & Fogliano, ). Second, 3‐deoxyanthocyanidins are resistant to common food bleaching additives such as ascorbic acid and sulfites (Ojwang & Awika, , ), especially the complex dimeric 3‐deoxyanthocyanidins which have shown stronger resistance to bleaching in a wide pH range of 1 to 7 (Geera et al., ). Third, they have promising thermal stability and are resistant to severe heat treatments (Akogou et al., ; Yang, Dykes, & Awika, ).…”