Anthocyanidins pelargonidin

FIGURE 3.2 General phenylpropanoid and flavonoid bios5mthetic pathways. The B-ring hydroxylation steps are not shown. For formation of anthocyanins from leucoanthocyanidins two routes are represented a simplified scheme via the anthocyanidin (pelargonidin) and the likely in vivo route via the pseudobase. Enzyme abbreviations are defined in the text and in Table 3.1. 

Anthocyanidins Pelargonidin Cyanidin Peonidin Delphinidin Petunidin Malvidin... 

Six anthocyanidins are commonly found in plants and plant-derived foods and beverages pelargonidin, cyanidin, delphinidin, peonidin, petunidin, and malvidin. Their structures differ in the number and position of hydroxyl and methoxyl groups on the flavan nucleus. The most commonly occurring anthocyanidin is cyanidin, and all these anthocyanidins are found in plants as glycosides with or without acylation, leading to around 400 different stractures. 

FIGURE 13.4 Typical structures for main classes of flavonoids naringin chalcone, 4,6,4 -trihydroxyaurone, apigenin (flavone), and pelargonidin (anthocyanidin). 

Flavan-3,4-diols FIavan-3,4-diols, also known as leucoanthocyanidins, are not particularly prevalent in the plant kingdom, instead being themselves precursors of flavan-3-ols (catechins), anthocyanidins, and condensed tannins (proanthocyanidins) (see Fig. 5.4). Flavan-3,4-diols are synthesized from dihydroflavonol precursors by the enzyme dihydroflavonol 4-reductase (DFR), through an NADPH-dependent reaction (Anderson and Markham 2006). The substrate binding affinity of DFR is paramount in determining which types of downstream anthocyanins are synthesized, with many fruits and flowers unable to synthesize pelargonidin type anthocyanins, because their particular DFR enzymes cannot accept dihydrokaempferol as a substrate (Anderson and Markham 2006). 

The scavenging ability toward O2 can also be measured by using electron spin resonance (ESR) spectrometry. The 02 anion is trapped with 5,5-dimethyl-1-pyrroline TV-oxidc (DMPO), and the resultant DMPO-OH adduct is detected by ESR using manganese oxide as internal standard. Noda and others (1997) used this technique to evaluate antioxidant activities of pomegranate fruit extract and its anthocyanidins (delphinidin, cyanidin, and pelargonidin). 

Noda Y, Kaneyuki T, Mori A and Packer L. 2002. Antioxidant activities of pomegranate fruit extract and its anthocyanidins delphinidin, cyanidin, and pelargonidin. J Agric Food Chem 50(1) 166-171. 

Fig. 2.112. The structures of the flavan-3-ol(4a — 8)pelargonidin 3-0-/f-glucopyranosides (1-4) isolated from strawberry extract. The letter A denotes the aglycone ring systems belonging to the anthocyanidin substructure, whereas the letter F denotes the aglycone ring system belonging to the flavanol substructure. Reprinted with permission from T. Fossen et al. [252].

Parasitic plants often use chemicals released by their host plant to stimulate seed germination, to locate the host, or for haustorial development. Many different compounds are involved, including strigolactones, quinones, coumarins, flavonoids, and other phenolics. Flavonoids contribute to signaling in some species but not others. Haustorial development in Triphysaria versicolor can be induced in vitro by the anthocyanidins petunidin, cyanidin, pelargonidin, delphinidin, as well as their glycosides obtained from the host plant.Anthocyanins are not usually found in root exudates, however, and thus the mechanism by which they affect natural signals for parasitic plants in the soil is not clear. 

Two classes of dimeric anthocyanins isolated from plants (section 10.2.6) have been identified in plants for the first time. One class includes pigments where an anthocyanin and a flavone or flavonol are linked to each end of a dicarboxylic acyl unit. The other class includes four different catechins linked covalently to pelargonidin 3-glucoside. During the last decade, seven new desoxyanthocyanidins and a novel type of anthocyanidin called P)Tanoanthocyanidins have been reported (Section 10.2.2). Toward the end of the 20th century, several color-stable 4-substituted anthocyanins, pyranoanthocyanins, were discovered in small amounts in red wine and grape pomace.Recently, similar compounds have been isolated from extracts of petals of Rosa hybrida cv. M me Violet, scales of red onion, and strawberries. About 94% of the new anthocyanins in the period of this review are based on only six anthocyanidins (Table 10.2). 

In addition to the 18 anthocyanidins listed previously, Table 10.1 contains seven new desoxyanthocyanidins and a novel type of anthocyanidin called pyranoanthocyanidins. While 31 monomeric anthocyanidins have been properly identified, most of the anthocyanins are based on cyanidin (30%i), delphinidin (22%i), and pelargonidin (18%), respectively (Figure 10.2). Altogether 20%i of the anthocyanins are based on the three common anthocyanidins (peonidin, malvidin, and petunidin) that are methylated. Around 3, 3, and 2% of the anthocyanins or anthocyanidins are labeled as 3-desoxyanthocyanidins, rare methylated anthocyanidins, and 6-hydroxyanthocyanidins, respectively. 

FIGURE 10.2 The number of anthocyanins based on the various anthocyanidins. The upper dark part of each bar represents the anthocyanins reported later than 1992. Pg, pelargonidin Cy, cyanidin Pn, peonidin, Dp, delphinidin Pt, petunidin Mv, malvidin RMS, rare methylated structures 60H, 6-hydroxy- Des, desoxy- Pyr, pyrano- Sp, sphagnorubins. See Table 10.1 for structures. 

From species in Labiatae, the 3-[6-(p-coumaryl)glucoside]-5-[4,6-di-(malonyl)glucoside] of cyanidin, delphinidin, and pelargonidin, and the 3-[6-(caffeyl)glucoside]-5-[4,6-di-(malonyl)glucoside] of the two latter anthocyanidins have been reported.The location of malonyl to the glucose 4-position has also been reported for cyanidin 3-[4-(malonyl)-... 

The fundamental nucleus in anthocyanidins (aglycones) is flavylium chloride. Most of the anthocyanidins are derivatives of 3,5,7-trihydroxyflavylium chloride. Thus, the hydroxylation patterns in the natural anthocyanidins fall into the three basic groups of pelargonidin, cyanidin and delphinidin. Anthocyanidins are rarely found in fresh plant material because of their instability [19]. 

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