775. The conversion of flavonols into anthocyanidins

Abstract

Reductive acetylation of flavonols gives acetates of undetermined structure having one acetyl group less than would be expected. Hot mineral acid converts the acetates into the corresponding anthocyanidins smoothly and in good yield ; hydrolysis with caustic alkalis at room temperature, followed by acidification in the cold, leads to a small quantity of anthocyanidin. This appears to be a useful general method for the production of anthocyanidins from flavonols.

Plant Polyphenols Exhibit Lipoprotein-Bound Antioxidant Activity Using an in Vitro Oxidation Model for Heart Disease

“…Pure flavonoids and other antioxidants were obtained from either Sigma Chemical Co. or Aldrich Chemical Co. Cyanidin chloride was synthesized and purified (King and White, 1957). LDL plus VLDL was isolated from the plasma of a single normocholesterolemic subject, who was not consuming antioxidant supplements, by an affinity column (Isolabs, Inc.).…”

CYANIDIN‐3‐LAMINARIOBIOSIDE IN SPANISH RED ONION (Allium cepa. L.)

“…Solvent system abbreviations (Table 1) and the detailed method of analysis were reported previously (Du and Francis, 1973). Authentic cyanidin was obtained from reductive acetylation of quercetin (King and White, 1957). Cyanidin-3-sophoroside was purified from red raspberry (Francis, 1972).…”

The formation of phenolic substances in Eucalyptus gigantea and Eucalyptus sieberiana

“…The free ellagic acid in this region is probably formed as a result of hydrolysis of ellagitannins in the cells, at the time of the intense metabolism (Chattaway, 1952) preceding the death of the living horizontal and vertical parenchyma cells of the sapwood when heartwood is formed. King & White (1957) have also reported that the galloylglucose derivatives in the sapwood cells of quebracho disappeared at the periphery of the heartwood. The amount of combined ellagic acid in the sapwood could give rise to the free ellagic acid in the heartwood but the amount of combined ellagic acid in the latter region has also increased ( Table 2).…”

“…It has also been observed that the amounts of catechin and monomeric leucoanthocyanins decrease from the heartwood boundary to the centre of the tree (Hillis, 1956;King & White, 1957;Hasegawa, 1958;Roux, 1958;Roux & Evelyn, 1958). Occasionally these changes are delayed (Hillis, 1956), which enabled the detection of catechin in the heartwood of a young E. 8ieberiana tree (Hillis & Carle, 1958), whereas it was absent in the heartwood of a larger tree.…”

“…For these and other reasons, it was suggested that the phenolic substances in bark and wood were produced elsewhere. It was further suggested that, in some instances, the leucoanthocyanins were the precursors of heartwood extractives (see also Bate-Smith & Swain, 1953;King & White, 1957;Roux, 1958;Roux & Evelyn, 1958). Recent information obtained with the aid of a staining technique (Hillis, 1958) indicated that the leucoanthocyanins in some eucalypts were synthesized in 8itu.…”