Characterization of the nutritional components of seabuckthorn ( hippophae rhamnoides L.) fruits.

摘要

We compared the nutritional components of the fruits of H. rhamnoides subsp. mongolica and H. rhamnoides subsp. rhamnoides grown in Japan. Sugars and acids that are important in fruit flavour were measured in both subspecies. The glucose content was the highest among the sugars, suggesting that the flavour of the fruit might be improved by enhancing the accumulation of sweeter sugars, such as fructose and sucrose. The fruits of H. rhamnoides subsp. mongolica had higher concentrations of sugars and a lower acid content than H. rhamnoides subsp. rhamnoides, indicating that the former have better flavour. Seabuckthorn fruits also contained high levels of ascorbic acid. The ascorbic acid content was lower in the fruits of H. rhamnoides subsp. mongolica than in the fruits of H. rhamnoides subsp. rhamnoides. The metabolic pathway for the biosynthesis of ascorbic acid in this species was investigated. Galacturonate reductase (GalUR), L-galactose dehydrogenase [galactose 1-dehydrogenase] (L-GDH), and myo-inositol oxygenase [inositol oxygenase] (MIOX) are potential key enzymes in the galacturonate, mannose/L-galactose, and myo-inositol pathways for ascorbic acid synthesis, respectively. The activity of each of these enzymes was detected in fruits, with the MIOX activity being much higher than the GalUR or L-GDH activities. The GalUR activity increased during ripening, whereas the ascorbic acid decreased, suggesting that there is no relationship between the biosynthesis of ascorbic acid and the degradation of cell wall pectin. It is possible that the substrate for the biosynthesis of ascorbic acid in seabuckthorn fruit is supplied from MIOX and/or L-GDH.