Heinz-Jürgen Bertram

Hydroxy- or methoxy-substituted benzaldoximes and benzaldehyde-O-alkyloximes as tyrosinase inhibitors.

Several benzaldoximes, benzaldehyde-O-ethyloximes, and acetophenonoximes were synthesized and evaluated as tyrosinase inhibitors by an assay based on tyrosinase catalyzed L-DOPA oxidation. Whereas benzaldoxime itself is only a weak inhibitor, its derivatives with one or two hydroxy or methoxy moieties in para and meta positions depress tyrosinase activity. Acetophenonoximes and trisubstituted benzaldoximes show no inhibitory activity. The IC(50) of 3,4-dihydroxybenzaldehyde-O-ethyloxime (0.3 +/- 0.1 micromol L(-1)) is of the same magnitude as tropolone (0.13 +/- 0.08 micromol L(-1)), one of the best tyrosinase inhibitors known so far.

Structure-activity relationships of trigeminal effects for artificial and naturally occurring alkamides related to spilanthol

Twenty six variations of the structure of spilanthol ((E,E,Z)-2,6,8-decatrienoic acid N-isobutylamide) were synthesised starting from the appropriate unsaturated acids by amidation with simple aliphatic amines. The resulting alkamides were evaluated for their trigeminal sensory properties (burning, pungency, tingling, scratching, numbing, warming, mouth-watering, cooling). Spilanthol was the most active tingling and mouth-watering compound. trans-Pellitorine ((E,E)-2,4-decadienoic acid N-isobutylamide) showed mainly the same mouth-watering activity without the strong tingling effect. All other structural variations led to lower intensity of the trigeminal activity.

Structural analogues of homoeriodictyol as flavor modifiers. Part III: short chain gingerdione derivatives.

In order to find new flavor modifiers, various short chain gingerdione derivatives were synthesized as structural analogues of the known bitter masker homoeriodictyol and evaluated by a sensory panel for masking and sweetness enhancing activities. 1-(4-Hydroxy-3-methoxyphenyl)hexa-3,5-dione ([2]-gingerdione) and the homologue 1-(4-hydroxy-3-methoxyphenyl)hepta-3,5-dione ([3]-gingerdione) at concentration ranges 50-500 mg kg (-1) showed the most promising masking activity of 20-30% against bitterness of a 500 mg kg (-1) aqueous caffeine solution. Additionally, both compounds were able to reduce the bitterness of a 5 mg kg (-1) quinine solution by about 20%; however, the bitter tastes of salicine, the model peptide H-Leu-Trp-OH, and KCl solutions were not reduced. Whereas for bitter masking activity a vanillyl moiety seems to be important, some of the tested isovanillyl isomers showed an interesting sweet enhancing effect without exhibiting a significant intrinsic sweetness. The isomer 1-(3-hydroxy-4-methoxyphenyl)hexa-3,5-dione ([2]-isogingerdione) at 100 mg kg (-1) caused a significant and synergistic increase of 27% of sweet taste of a 5% sucrose solution.

Synthesis of polyhydroxylated aromatic mandelic acid amides and their antioxidative potential

Abstract Six hydroxymandelic acid amides of phenolic amines were synthesized by condensation of 3,4-dihydroxymandelic or 4-hydroxy-3-methoxymandelic acid N-succinimidyl esters and several phenolic benzylamino and phenethylamino hydrochlorides in moderate to good yield. The radical scavenging activities determined by 2,2-diphenyl-1-picrylhydrazyl assay and superoxide trapping assay were superior compared to standards l -ascorbic acid, α-tocopherol, and butylated hydroxytoluene (BHT). The antioxidative activities tested by accelerated autoxidation of bulk lipids were 2–3.5 times more potent compared to standards α-tocopherol and BHT. 3,4-Dihydroxymandelic acid dopamide (4b) and 4-hydroxy-3-methoxymandelic acid dopamide (4a) showed the best overall performance as antioxidants.

Extensive Study on the Minor Constituents of the Essential Oil of Eucalyptus dives Schau. Type

Abstract An oil of the piperitone type of Eucalyptus dives produced from trees cultivated in South Africa was analyzed by GC and GC/MS. Seventy-three constituents were characterized with piperitone ranging from 29.2% to 64.9%, depending on whether the oil was produced from dried or fresh leaves. Two novel constituents such as p-menth-5-en-2-one and p-menth-6-en-3-one were characterized as minor constituents of the oil; the former being found in nature for the first time.

The flavour chemistry of culinary Allium preparations

Abstract In culinary preparations cooked, roasted and fried Allium products play a major role in the taste and the aroma of the final product. In this study the correlation of various culinary preparation techniques such as cooking and frying and the resulting differences in the flavour chemistry (volatiles and non-volatiles) are demonstrated. Different preparation techniques performed on shallots, garlic and/or scallions influence the profile of volatiles and non-volatiles in culinary preparations significantly.