Syntheses of alpha-tocopheryl glycosides by glucosidases.

Enzymatic syntheses of water-soluble alpha-tocopheryl glycosides were carried out in di-isopropyl ether using amyloglucosidase from Rhizopus mold or beta-glucosidase isolated from sweet almond. Optimum conditions for the amyloglucosidase were: alpha-tocopherol 0.5 mmol, D-glucose 0.5 mmol, 400 activity unit (AU) amyloglucosidase, 0.2 mM pH 7 phosphate buffer and 72 h; and for the beta-glucosidase: alpha-tocopherol 0.5 mmol, D: -glucose 0.5 mmol, 110 AU beta-glucosidase, 0.1 mM pH 6 phosphate buffer and 72 h. Out of 11 carbohydrates employed, amyloglucosidase reacted only with D-glucose to give 50% of 6-O-(alpha-D-glucopyranosyl)alpha-tocopherol. However, the beta-glucosidase gave 6-O-(beta-D-glucopyranosyl)alpha-tocopherol, 6-O-(alpha-D-galactopyranosyl)alpha-tocopherol, 6-O-(beta-D-galactopyranosyl)alpha-tocopherol, 6-O-(alpha-D-mannopyranosyl)alpha-tocopherol and 6-O-(beta-D-mannopyranosyl)alpha-tocopherol in yields ranging from 10-25%. Water solubility of 6-O-(alpha-D-glucopyranosyl)alpha-tocopherol was 26 g/l at 25 degrees C. alpha-Tocopheryl glycosides showed antioxidant activities with IC(50) values from 0.5 to 1 mM and angiotensin-converting enzyme (ACE) inhibitory activity with IC(50) values from 1.3 to 2.6 mM.