René Fumeaux

Epicatechin B-Ring Conjugates: First Enantioselective Synthesis and Evidence for Their Occurrence in Human Biological Fluids

Herein, the first enantioselective total synthesis of a number of biologically relevant (-)-epicatechin conjugates is described. The success of this synthesis relied on (i) optimized conditions for the stereospecific cyclization step leading to the catechin C ring; on (ii) efficient conjugation reactions; and on (iii) optimized deprotection sequences. These standard compounds have been subsequently used to elucidate for the first time the pattern of (-)-epicatechin conjugates present in four different human biological fluids following (-)-epicatechin absorption.

Hydrolysis of Chicoric and Caftaric Acids with Esterases and Lactobacillus johnsonii in Vitro and in a Gastrointestinal Model

Chicoric acid (ChA) and caftaric acid (CafA) were identified as bioactive components of chicory and have been ascribed a number of health benefits. This study investigated the hydrolysis of ChA and CafA with enzymes and a probiotic bacterium Lactobacillus johnsonii (La1). Esterase from Aspergillus japonicus (24 U/mg) hydrolyzed 100% of ChA (5 mM) and CafA (5 mM) after 3 h, at pH 7.0 and 37 °C. Under the same reaction conditions, 100% hydrolysis of ChA and CafA was achieved with a spray-dried preparation of La1. The addition of La1 (100 mg/mL, 3.3 E9 cfu/g) to CafA solution in a gastrointestinal model (GI model) resulted in 65% hydrolysis of CafA. This model simulates the physicochemical conditions of the human gastrointestinal tract. No hydrolysis of CafA was observed after passage through the GI model in the absence of La1. The results of this study support the hypothesis that ChA and CafA are degraded by gut microflora before absorption and metabolization.

Chemo-enzymatic synthesis of α-terpineol thioacetate and thiol derivatives and their use as flavouring compounds

Reaction of (R,S)‐α‐terpineol with thioacetic acid in food‐grade n‐hexane resulted into two α‐terpineol thioacetate derivatives with the same molecular weight. After 5 h of reaction time, (R,S)‐α‐terpineol was completely transformed and the mixture analysed by different chromatographic techniques. The aroma character of the α‐terpineol thioacetates was described as exotic, sweet, blackcurrant, roasted and sulphury. Of eight lipases and two esterases assayed, only non‐immobilized pig liver esterase (PLE) hydrolysed α‐terpineol thioacetates into the corresponding α‐terpineol thiols. When reactions were performed in 0.2 m phosphate buffer at pH 8.0 and 30 °C with non‐immobilized PLE, α‐terpineol thiols were produced in an optimal yield of 88% after 24 h of reaction time. The aroma character of α‐terpineol thiols was described as green, exotic and fresh grapefruit. Flavouring powders were prepared by freeze‐drying the α‐terpineol thioacetates and α‐terpineol thiols in the presence of maltodextrine. Preliminary applications showed that these flavouring preparations could be used to improve the flavour quality of lighter cooked notes and tropical fruit aromas. Copyright