New Taste-Active 3-(O-β-d-Glucosyl)-2-oxoindole-3-acetic Acids and Diarylheptanoids in Cimiciato-Infected Hazelnuts

Abstract

Activity-guided fractionation in combination with sensory analytics, LC-TOF-MS, and 1D/2D-NMR spectroscopy enabled the identification of the bitter tasting diarylheptanoids asadanin, giffonin P, and the previously not reported ( E)-7,9,10,13-tetrahydroxy-1,7-bis(2-hydroxyphenyl)hept-9-en-11-one and 4,12,16-trihydroxy-2-oxatricyclo[13.3.1.1]-nonadeca-1(18),3,5,7(20),8,15,17-heptaen as well as the yet unknown astringent compounds 2-(3-hydroxy-2-oxoindolin-3-yl) acetic acid 3- O-6'-galactopyranosyl-2″-(2″oxoindolin-3″yl) acetate and 3-( O-β-d-glycosyl) dioxindole-3-acetic acid in Cimiciato-infected hazelnuts exhibiting a bitter off-taste. Quantitative LC-MS/MS studies, followed by dose/activity considerations confirmed for the first time asadanin to be the key contributor to the bitter taste of Cimiciato-infected hazelnuts. Furthermore, quantitative studies demonstrated that neither the physical damage alone nor a general microbial infection is able to initiate a stress-induced asadanin generation, but most likely either specific Cimiciato-specific microorganisms associated with the bugs or specific chemical stimulants in the bugs' saliva is the cause triggering asadanin biosynthesis. Finally, also germination was found for the first time to activate diarylheptanoid biosynthesis, resulting in higher contents of bitter tasting phytochemicals and development of the bitter off-taste.

Functional Metabolomics – a Useful Tool to Characterize Stress-Induced Metabolome Alterations Opening New Avenues Towards Tailoring Food Crop Quality

“…In addition, a decrease in flavor quality accompanied by an increase in bitter taste has also been reported in raw hazelnuts (Corylus avellana L.) upon biotic stress challenges, such as upon infection by bugs, belonging to the hemipteran family, like Gonocerus acuteangulatus and Coreus marginatus [99].…”

Identification of bitter‐taste compounds in class‐III caramel colours

“…The threshold concentration experiment was conducted according to the Singldinger et al 27 The taste quality of each purified or authentic compound was determined in bottled water (pH = 4.4) with ascending concentrations. The threshold values of each compound were obtained by averaging threshold values of the sensory panelists.…”

Functional Metabolomics—A Useful Tool to Characterize Stress-Induced Metabolome Alterations Opening New Avenues towards Tailoring Food Crop Quality

“…The increase causes a perceived bitter off-flavor, occurring especially often during the production process for infant diet carrot products [97,98,[109][110][111][112][113][114][115]. In addition, a decrease in flavor quality accompanied by an increase in bitter taste has also been reported in raw hazelnuts (Corylus avellana L.) upon biotic stress challenges, such as upon infection by bugs, belonging to the hemipteran family, like Gonocerus acuteangulatus and Coreus marginatus [116].…”