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.