Improved synthesis of the antifungal isobutyl o-coumarate catalyzed by the Aspergillus terreus type B feruloyl esterase

BACKGROUND Hydroxycinnamic acids and some of their derivatives are molecules with interesting biological activities; for instance, hydroxylated hydroxycinnamic esters have proved to have antifungal properties, and thus the generation of these molecules is of industrial importance. In this study, the direct esterification capacity of the pure recombinant type B feruloyl esterase from Aspergillus terreus (AtFAE B) was evaluated by its ability to catalyze the synthesis of isobutyl o-coumarate, an interesting antifungal molecule. A ternary solvent system (isooctane/isobutanol/water) was employed to improve the synthesis of isobutyl o-coumarate, assessing different substrate concentrations, enzyme load, water percentages and pH and temperature values. RESULTS AtFAE B showed the highest initial rate at 18% (v/v) isobutanol and 50 mM o-coumaric acid, 0.04 mg/ml of enzyme, 4% (v/v) water without buffer and 40C. AtFAE B half-lives at 30C, 40C and 50C were 16.5 h, 1.75 h and 3.5 min, respectively. Thus, we decided to evaluate the bioconversion yield at 30C, where the enzyme showed the highest operational stability. At this temperature, we obtained a yield of ~80% after only 8 h of reaction, using a 78:18:4 isooctane:isobutanol:water ternary solvent system, with 50 mM of o-coumaric acid.CONCLUSIONS Under these improved conditions, the productivity was 1.06 g isobutyl o-coumarate/L*h with a biocatalyst yield of 209.6 kg isobutyl o-coumarate/kg free AtFAE B, demonstrating the promising potential of AtFAE B to accept the non-canonical o-coumaric acid as the substrate and to achieve the synthesis of isobutyl o-coum

Damage and drying modify the composition of Mikania glomerata and Mikania laevigata leaves

ABSTRACT This study compared the influence of mechanical damage and drying on the chemical composition of Mikania glomerata Spreng. and Mikania laevigata Sch.Bip. ex Baker, Asteraceae, leaves. Leaves were collected 1-24 h after damage. Oven-drying at 40ºC and shade-drying at ambient temperature were compared to lyophilization. Samples were extracted in 70% ethanol and analyzed by ultra-high-performance liquid chromatography with mass spectrometry. Significant (p < 0.05) increases of caffeoylquinic acids were observed in damaged leaves of both species and coumarin decreased in M. laevigata, indicating stress. Although the final water content was similar, the drying method affected the leaf composition. In shade-dried leaves of M. laevigata coumarin decreased and the presence of umbelliferone was observed; caffeoylquinic acid contents increased for 288 h in in both species. Apparently, enzymes were inactivated after 6 h in oven drying, stabilizing their chemical composition, while shade drying allowed enzymatic and microbial activity to continue; illustrating the importance of post harvesting procedures on the quality of medicinal plants.