The distribution of monoterpene glycosides in sweet potato

The study investigated the distribution of monoterpene glycoside in a sweet potato tuber. The steamed tuber was divided into 11 parts and powdered after being freeze-dried. Monoterpene glycoside-rich fractions were extracted from the freeze-dried samples using methanol. This fraction was subjected to GC-MS analyses to quantitative liberated monoterpene alcohol before and after enzyme treatment. Nerol and geraniol were liberated efficiently by β-glucosidase while linalool and α-terpineol were done so by β-primeverosidase. However, citronelool was not liberated by either enzyme treatment. These results showed that the monoterpene alcohols except for citronelool existed as glycosides in sweet potato tuber. Consequently, nerol, geraniol, linalool, and α-terpineol contents were compared between different parts of the tuber. The greatest amount of nerol was liberated from the center part of tuber, comprising 38% of the total nerol content. Meanwhile, geraniol, linalool, and α-terpineol were mainly distributed to the skin part, respectively comprising 37%, 66% and 60%. Our results further showed that the center part of the tuber had relatively small amounts of linalool and α-terpineol; in particular, linalool was not found in the center part. These results showed that the distribution of monoterpene glycoside differed among the tuber tissues.