Analysis of bitter principles

The bitter principles produced in the hairy roots were detected and identified to be amarogentin (2 4) (63) and amaroswerin (2 5) (63) (Fig. 11) by HPLC analysis of the aqueous layer and fraction A (see the part of isolation). Samples (aqueous layer and fraction A) were separately subjected to HPLC on a Nucleosil 100-5Cjg (4.6 mm i. d. x 250 mm) column, mobile phase MeOH-water (9 10), flow rate 0.8 ml /min, column temperature 35 °C, Rt (min) 25 (11.1) and 24 (13.1). Although the contents of these compounds were fairy low (below 0.0001 % as dw), this S. japonica hairy root culture was the first example which succeeded in the production of bitter principles by plant tissue cultures. 

The determination of aldehydes and ketones is of importance in the analysis of those essential oils characterised especially by aldehydic or ketoruc principles, e g.,the citral contained in lemon and lemongrass oils, citronellal in citronella Oil and some eucalyptus oils, benzaldehyde in bitter almond oil, salicylaldehyde in meadow-sweet oil, anisaldehyde in aniseed and fennel oils, cuminaldehyde m cumin oil, cinnamaldehyde in cinnamon oil, carvone in caraway oil, pulegone in pennyroyal oil and methyl nonyl ketone in rue oil The determination of the aldehydes and ketones presents, however, difficulties and the above methods are moderately exact in only a few cases, especially when the content of aldehydes or ketones is considerable The bisulphite method is applicable particularly to the determination of cinnamaldehyde and benzaldehyde in cinnamon oil and bitter almond oil, and, up to a certain pomt, to that of citral in lemongrass Oil. The sulphite method gives good results in the same cases and for the determination of carvone and pulegone... 

Clerodendrin A, which was isolated as a bitter principle from Clerodendron tricotomum, has been assigned the structure (22) on the basis of an 2f-ray analysis of the p-bromobenzoate-chlorohydrin. The full paper describing additional work on the structure of olearin (23) has appeared. The stereochemistry at all but one centre has been determined and olearin has been interrelated with a diterpenoid of known structure from a Dodonaea species. 

This method gave a better correlation with tasting trials than the second method of Rigby and Bethune [110]. In order to avoid assumptions about the chemical nature of the bittering principles in beer the EBC Analysis Committee simplified the regression equation and expressed the results as Bitterness Units [111]. 

Polonsky J, Baskevitch Z, Gottlefb HE, Hagamman EW, Wenkert E (1975) Carbon-13 Nuclear Magnetic Resonance Spectral Analysis of Quassinoid Bitter Principles. J Org Chem 40 2499-2504... 

Gymnocolea inflata (Jungermanniales) contains very bitter principles. One of the bitter substances, gymnocolin (556), possesses structure (556) on the basis of an X-ray crystallographic analysis 26, 28, 157). 

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