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This presentation is intended to commemorate the life’s work of a singular individual, Dr. Ralph C. Robbins, who was a pioneer among researchers studying the health benefits of flavonoids, particularly flavonoids such as hesperidin, tangeretin, nobiletin and others which occur in citrus fruits. Dr. Robbins entered the field in 1960, a time when research on health effects of flavonoids seemed to raise more questions than answers. To put Dr. Robbins’ research in perspective, let us first look very briefly at the history of flavonoid research.

Visible and ultraviolet absorption and room temperature fluorescence excitation and emission spectra, obtained from alcoholic solutions of Florida orange juice (OJ) and orange pulpwash (PW), were used to characterize the collaborative study samples. The absorbance sum at 443, 325, and 280 nm and absorbance 443/325 nm ratio were used to estimate the percent total citrus material (TCM), OJ, PW, and dilution of the samples. Six laboratories participated in the study. Known samples of OJ and PW were given to each laboratory for familiarization and instrumental verification. Ten unknown samples (various combinations of OJ and PW) were analyzed by each laboratory. Three duplicate and 2 "closely matched pair" sample set combinations were reported. The results revealed that the method successfully detected the differences in sample formulations. The UV/vis and fluorescence spectrophotometric method has been adopted official first action for detecting adulteration of Florida orange juice with orange pulpwash.

Steam-distilled leaf oils from 11 varieties of citrus were analysed and 28 compounds identified as constituents of one or more oils. Gas-liquid chromatographic (GLC) analyses were carried out on both analytical and semi-preparatory scales. Thin-layer chromatographic (TLC) data was obtained using both silica gel and aluminum oxide coated plates in conjunction with solvent systems of varying polarity. Mass spectral (MS) studies were conducted on a time-of-flight mass spectrometer.

The essential oils of “Valencia” orange peel and leaves were extracted at periodic intervals during the normal growing season, analyzed by gas-liquid chromatography, and qualitative variations noted. The major components of the peel oil from the very small immature fruit were linalool and sabinene, while at the end of the season (+)-limonene was the predominant compound in the mature fruit. The leaf oils did not show a pronounced seasonal variation. Analysis of the oils from petal, pistil, and stamen portions of the blossoms showed differences in their composition.

SUMMARY— Two approaches were used in a study of compounds contributing to the aroma of Hamlin oranges, which had been carefully handled to prevent release of peel‘oil. Volatile aromatic compounds emitted from the oranges on storage, and less volatile aroma compounds present on the cuticle of the fruit were isolated and analyzed. The volatile aroma of the stored oranges seemed to be contributed by ethyl esters, particularly ethyl butyrate, while sesquiterpene hydrocarbons appeared to be responsible for the persistent odor from the cuticle of fresh oranges. Volatile compounds definitely identified include ethyl acetate, ethanol, ethyl butyrate, limonene, ethyl caproate and ethyl caprylate. The sesquiterpene hydrocarbons on the cuticle consisted chiefly of valencene, with lesser amounts of elemene, caryophyllene, farnesene, humulene and cadinene.

Citrus fruit and leaf explants were fed linalool-3- 14 C. Volatile oils were recovered by steam distillation and fractionated by gas—liquid and thin-layer chromatography. α-Terpineol and other terpenoid alcohols were the predominant metabolites in leaves. Fruit also produced α-terpineol, but significant label could also be found in (+)-limonene and other hydrocarbons.