Esculin has many pharmacological effects, but these are difficult to observe after oral administration owing to poor lipid solubility. In our previous study, five acylated derivatives with different acyl chain lengths (EA, EP, EO, EL, and EM) were synthesized to improve the lipophilicity of esculin. In this study, the bioavailability and antioxidant activity of the five derivatives were investigated. The logP of esculin, EA, EP, EO, EL, and EM were -1.1 ± 0.1, -0.3 ± 0.14, 0.1 ± 0.17, 1.6 ± 0.09, 2.4 ± 0.11, and 2.8 ± 0.18, and their P were 0.71 ± 0.02, 1.24 ± 0.18, 1.74 ± 0.11, 11.6 ± 3.6, 4.11 ± 1.03, and 2.64 ± 0.97 × 10 cm/s, respectively. Besides, the bioavailability of EO, EL, and EM were seriously affected by carboxylesterase. The results of ABTS, ORAC, and DPPH assays indicated that the antiradical ability of the five derivatives did not exceed that of esculin. However, EA, EP, and EO showed more effective inhibition of AAPH-induced oxidative hemolysis than esculin did (p < 0.05), and EL and EM were less effective than esculin (p < 0.05). The mechanism was related to the distribution and localization of the derivatives in "oil-water interface" between the cytomembrane and the aqueous phase.
BackgroundFlavonoid glycosides have many beneficial effects on health, but these bioactivities tend to decrease after oral administration owing to their poor lipophilicity. In this study, a facile whole-cell-based method was developed for selective preparation of monoester or diester of troxerutin, a flavonoid derivative. In addition, the bioavailabilities and antioxidant properties of troxerutin and its acylated derivatives were also investigated in cells.ResultsPseudomonas aeruginosa and Pseudomonas stutzeri cells showed high catalytic efficiency (substrate conversion > 90%) and different preferences for troxerutin, resulting in the production of its monoester (TME) and diester (TDE), respectively. The logP values of troxerutin, TME, and TDE were − 2.04 ± 0.10, − 0.75 ± 0.08, and 1.51 ± 0.05 and their Papp values were 0.34 × 10−6 ± 0.05, 0.99 × 10−6 ± 0.12, and 1.54 × 10−6 ± 0.17 cm/s, respectively. The results of hydroxyl radical, ABTS, and ORAC assays indicated that the antiradical activities of acylated derivatives did not exceed that of troxerutin, but showed higher inhibition effects upon 2,2′-azobis(2-amidinopropane) dihydrochloride-induced erythrocyte hemolysis than that of troxerutin (P < 0.05).ConclusionA facile and efficient whole-cell biocatalysis method was developed to synthesize troxerutin-acylated derivatives, markedly enhancing the bioavailability and antioxidant activities of troxerutin in cells. Additionally, the mechanism underlying the observed difference in the antioxidant activities of troxerutin and its esters was ascribed to both their free radical scavenging abilities and distribution on the cell membrane surface. Electronic supplementary materialThe online version of this article (10.1186/s12934-018-0976-x) contains supplementary material, which is available to authorized users.
Duck egg white (DEW) is considered as an abandoned protein resource.
Bioflavonoids have many biological and pharmacological activities, but many of them display low bioavailability after oral administration owing to poor lipophilicity of glycoside forms. To improve their lipophilicity, as well as their bioactivity, a new efficient approach was developed for fatty acyl-modification of four vitamin P-like bioflavonoids (troxerutin, rutin, hesperidin, and naringin) using whole-cell biocatalysts in binary solvent systems. Using troxerutin as a typical important bioflavonoid, the acylation activities of 15 strains of different sources were evaluated and Pseudomonas aeruginosa GIM 1.46 showed the highest acylation activity in nonaqueous mediums. 13C NMR, ESI-MS, and FT-IR analysis confirmed that P. aeruginosa catalyzed acylation of troxerutin to produce troxerutin monopropionate (dominant product) and troxerutin dipropionate. In a binary system of n-heptane and pyridine, the cells showed much higher catalytic activity and operational stability than in other solvents, attributing to a proper increase in permeability of cell envelopes and cell viability by using the binary organic solvents. The optimal n-heptane concentration, molar ratio of vinyl propionate to troxerutin, catalyst dosage, and reaction temperature were found as 35%, 30:1, 50 mg/mL, and 40 °C, respectively, under which the troxerutin conversion and the monoester yield reached 94% and 81.1%, respectively.
Puerarin, an important isoflavonoid from the edible root of Pueraria lobata, shows multiple bioactivities but suffers from low bioavailability. In this study, a new whole-cell catalytic method for acylation modification of puerarin was developed. Among the 12 strains tested, Aspergillus oryzae showed the highest catalytic activity and selectively catalyzed acylation of puerarin at the 6″-hydroxyl group. The organic solvents used significantly influenced the catalytic efficiency of the cells. In the green solvent 2-methyltetrahydrofuran, the reaction showed high substrate conversion (92.5%) and regioselectivity (95.8%), with results similar to those with tetrahydrofuran (94.2% and 98.5%, respectively) under optimal conditions. The monoester products showed higher liposolubility in comparison to puerarin, and those with C3−C8 fatty acid chain lengths showed evidently improved antioxidant activity toward erythrocyte hemolysis. Considering the operational stability of the cells and efficiency of the scaled-up reactions, this method is efficient and cost effective, with promising applications in the health food industry.
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