Green Rooibos Extract from Aspalathus linearis, and its Component, Aspalathin, Suppress Elevation of Blood Glucose Levels in Mice and Inhibit α-amylase and α-glucosidase Activities in vitro.

Food Science and Technology Research

21

(2)

231-240

Nana Mikam, Junko Tsujimura, Ayumi Sato, Akiko Narasada, Mayumi Shigeta, Motoshi Kato,Shuichi Hata and Eri Hitomi

To evaluate the suppressive effects of green rooibos (Aspalathus linearis) unfermented tea on postprandial
hyperglycemia, we orally administered four carbohydrates with or without green rooibos extract (GRE) and its
major flavonoid aspalathin (Asp). GRE significantly suppressed the elevation of blood glucose levels after glucose,maltose, and starch intake. Asp also lowered the levels for all four carbohydrates. To clarify the mechanismunderlying these results, we performed an intraperitoneal glucose tolerance test (IPGTT) and measured the abilityof GRE and Asp to inhibit the activities of carbohydrate-hydrolyzing enzymes in vitro. In IPGTT, GRE and Asp didnot show suppressive effects on blood glucose, while they dose-dependently inhibited the activities of α-glucosidaseand α-amylase in vitro. These results showed that GRE and Asp suppress the elevation of blood glucose levels. It wasindicated that these effects may result from the suppression of glucose absorption and the inhibition of carbohydratehydrolyzingenzyme activities by GRE and Asp.