Delphinidine chloride

Delphinidin chloride has a further OH group in the position indicated. The important relations between cyanidin, quercitin, catechin, and luteolin should be studied from the point of view of plant physiology. 

The red, violet, and blue pigments of flower petals are called anthocyanins, and are glycosides of various benzopyrilium cations. Delphinidin chloride 9.7, for example, is a blue pigment. Khellin 9.8 is a natural product which has found clinical application in the treatment of bronchial asthma and has been the starting point for the design of many totally synthetic chromones with improved biological properties. 

Many of the beautiful colors of butterflies wings, autumn leaves, and flowers are due to the presence of flavone derivatives called anthocyanins. When antho-cyanins are hydrolyzed in hydrochloric acid (to remove sugar residues), they produce aromatic oxygen-containing salts. One of these is delphinidin chloride. Explain why delphinidin chloride is aromatic. What is the hybridization of the heterocyclic oxygen in this compound ... 

Solution Delphinidin chloride is aromatic for the same reason that naphthalene is aromatic two overlapping aromatic sextets of tt electrons that have a pair of electrons in common. 

The hybridization of the heterocyclic oxygen in delphinidin chloride is sp, as is the hybridization of the carbons in the compound. Thus, a pair of electrons from oxygen is in a p orbital, which allows them to participate in the ir cloud. The other lone-pair electrons of oxygen are in a sp2 orbital, with the other two sp2 orbitals forming c bonds with two carbon atoms. Since oxygen contributes two electrons to the tt cloud, it has a formal charge of +1. 

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]. 

Experimental structural results indicate that the unknown, PA-X, may have a structure similar to delphinidin, since the same substitution pattern was observed [82]. The absorption maxima of PA-X showed a 25 nm bathochromic shift upon the addition of A1C13, thus indicating the presence of an ortho-dihydroxyl group in the B-ring [84]. Further analysis suggests that PA-X may also be similar to 8-methoxy-7,3, 4 -trihydroxy-flavylium chloride and 3,8-dimethoxy-7,3, 4 -trihydroxyflavylium chloride which were isolated from the heartwood of Acaria saxatilis by Fourie et al. 

Anthocyanidins (aglycones), flavyliun salts (chlorides), are shown generally by (1), the anthocyanins (3-monoglucosides) by (2), and 3,5-diglucosides by (3). The major anthocyanidins are cyanidin, delphinidin, malvidin, pelargonidin, peonidin and petunidin and the substituents in their structures are shown below for the formula (1). Table 3... 

Delphinidin (3,3, 4, 5,5, 7-hexahydroxyflavylium). Formula, see anthocyanins, Ci3H, 07, Mr 303.25, as chloride C,5Hi,C107, Mr 338.70) chocolate-brown prisms of needles with metallic luster (from 5% aq. HCl), mp. >350 °C, uv ,a, 544 nm, well soluble in alcohols and ethyl acetate see also anthocyanins. 

Petunidin (delphinidin 3 -methyl ether, 3,3 4, 5,7-pentahydroxy-5 -methoxyflavylium). Formula see anthocyanins, CisHjjO,, Mr 317.28, as chloride (CiftHijClO, Mr 352.73) gray-brown platelets or prisms (aqueous HCl). P. is isolated from Petunia hybrids see anthocyanins. 

Compments. The primary anthocyanins of V. vinifera grapes appear to be the monoglucoside oenin and some diglucoside. Levy el al. (1931) found a small amount of delphinidin and its 3 -methyl ester in the Fogarina (i.e., Fogaruna ) grape. The absorption curve of natural and synthetic oenin chloride (malvidin) from 420 m. to 600 m/i. and the distribution numbers in a special solvent were identical for the synthetic and natural product. The picrate consisted of only about 45% oenin— the remainder may be petunidin (delphinidin 3 -methyl ester) and delphinidin. 

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