The Bitter Glucoside of the Olive

Abstract

The bitter glucoside of olives, olive 'leaves and olive bark was studied by Bourquelot and Vin-tilesco1 2345in 1908. They described it as a noncrystalline, intensely bitter substance, readily soluble in alcohol, fairly soluble in water and practically insoluble in ether. Its specific rotation was given by them as -127°and its reducing power on Fehling's solution as 0.412 that of dextrose. They christened it "oleuropein."Power and Tutin,2,3,4 in 1908, prepared a bitter mixture of several amorphous compounds from olive leaves and bark by the method of Bourquelot and Vintilesco. They inferred that the "oleuropein" of these investigators was not a pure substance. Vanzetti,6 in 1909, obtained an intensely bitter levorotatory amorphous substance from olive twigs. Hilts and Hollingshead6 (1920), in a report of studies on the chemical changes that occur during the ripening and pickling of olives suggested that the bitter principle is a tannin-like substance.

Natural antimicrobials from plants

“…Freezing probably caused a release of the inhibitor due to physical changes in the olive tissue or some chemical alteration. Cruess and Alsberg (1934) contended that the olive contains an emulsin-like enzyme that is liberated by freezing and possibly another enzyme that splits or oxidizes the bitter ester remaining after hydrolysis of the glucoside. Both these two thermal characteristics would suggest its potential use in heated or frozen processed foods.…”

Pure Culture Fermentation of Green Olives1

“…The total amount of fermentable carbohydrates available in olive brines to support microbial activity may depend on residual amounts of the bitter compound remaining in the olives that are brined. The glucoside responsible for the bitterness [discovered and named "oleuropein" by Bourquelot and Vintilesco (8) and studied in the purified state by Cruess and Alsberg (15)] is hydrolyzed by weak acids to yield D-glucose. Lactobacilli could cause this reaction during the acid fermentation and slowly continue to add a secondary supply of fermentable sugar to the brine during the full course of the fermentation, even after the primary source of sugars from the olives is depleted.…”

The isolation of chlorogenic acid from the apple fruit

“…Recent interest in chlorogenic acid has centred on its function as a substrate for polyphenolase and it appears that the darkening of fruits on injury may be due to the oxidation of chlorogenic acid rather than to the oxidation of true tannins (Joslyn & Ponting, 1951). Cruess & Alsberg (1934) consider that a glucoside of caffeic acid and phenol obtained from olives is responsible for the browning of these fruits. Rudkin & Nelson (1947) showed that the addition of small quantities of chlorogenic acid, which they isolated from the sweet potato, in-creased the oxygen uptake of, and also the carbon dioxide given off by, thin slices of the root of this plant.…”