Durable Antihyperglycemic Effect of 6-O-Caffeoylsophorose with .ALPHA.-Glucosidase Inhibitory Activity in Rats

Abstract

To evaluate the duration of antihyperglycemic effects of 6-O-caffeoylsophorose (CS), a newly identified natural α-glucosidase inhibitor from fermented purple-sweet potato, a single oral administration of CS was given to maltose-loaded Sprague-Dawley rats. Administration of CS (200 mg/kg) 30 min or 60 min before maltose administration produced an elevation of blood glucose level by administration of 2 g/kg of maltose in rats that was significantly lower than for no administration (control). In contrast, simultaneous or pro-administration of CS with maltose eliminated the antihyperglycemic effect. CS significantly reduced rat intestinal α-glucosidase activity in all of the small intestinal mucosal regions with a maximal reduction ratio of ca. 40% up to 60 min after CS administration. Thereafter, the intestinal α-glucosidase activity tended to return to basal level. These findings suggest that the antihyperglycemic effect of CS is restricted to pre-administration within 60 min.Keywords: α-glucosidase, caffeoylsophorose, antihyperglycemic effect, diabetes *To whom correspondence should be addressed. Email: tfujise@nakamura-u.ac.jp IntroductionAnthocyanins, one of the families of polyphenol compounds found in fruits and plants, are valued for their beneficial health effects. Pharmacologically, anthocyanins are reputed to be antimutagenic (Yoshimoto et al., 2001) and to have antioxidative effects (Oki et al., 2002). Crude anthocyanin extract of Ipomoea batatas cv Ayamurasaki has also been demonstrated to have considerable antihyperglycemic effect in Sprague Dawley (SD) rats (Matsui et al., 2002). In our previous reports, (Matsui et al., 2001a;Matsui et al., 2001b;Matsui et al., 2002) the main compounds showing antihyperglycemic effects in the extract were found to be acylated anthocyanins, both of which possess α-glucosidase (AGH, EC 3.3.1.20) inhibitory activity: YGM-3 (Cyanidin; 3-O-(2-O-(6-O-E-feruloyl-β-D-glucopyranosyl)-6-O-Ecaffeoyl-β-D-glucopyranoside)-5-O-β-D-gluconopyranoside) and YGM-6 (Peonidin; 3-O-(2-O-(6-O-E-feruloyl-β-D-glucopyranosyl) -6-O-E-caffeoyl-β-D-glucopyranoside)-5-O-β-D-gluconopyranoside).Further study regarding the structure-AGH inhibition relationship revealed that the acylated moieties (e.g., 6-O-E-caffeoyl-β-D-glucopyranoside) were responsible for eliciting AGH inhibition (Matsui et al., 2001b; Terahara et al., 2003). 6-O-Caffeoylsophorose (CS), which is a constituent of YGM-3 and YGM-6, was successfully produced by fermentation of purple-fleshed sweet potato and was identified for the first time as a natural compound and proven to be a potent AGH inhibitor Terahara et al., 2003).Recently, AGH inhibitors have attracted much attention as being effective drugs for noninsulin-dependent diabetes mellitus (NIDDM), as they can suppress or delay excessive postprandial elevation of blood glucose level (BGL) without promoting insulin secretion. In addition, the effective use of long-term therapeutic drug acarbose treatment in the prevention of NIDDM was reported (Chiasson et al., 2002). Clinical ...

Suppression of blood glucose level by a new fermented tea obtained by tea‐rolling processing of loquat (Eriobotrya japonica) and green tea leaves in disaccharide‐loaded Sprague‐Dawley rats

“…This revealed that pre‐administration of LG tea within 30 min, except for simultaneous administration, was effective in producing an acute antihyperglycaemic effect in the present SD rat experiments. In a previous report we showed that acarbose (3 mg kg −1 ) continued to have an ameliorative effect on BGL rise even when administered 120 min before maltose administration, along with the long‐term suppression of intestinal α‐glucosidase activity for up to 120 min 17. However, to clarify the mechanism underlying the durability of BGL reduction by LG tea for up to 30 min, further experiments, including intestinal α‐glucosidase activity, are now in progress.…”

Functional New Acylated Sophoroses and Deglucosylated Anthocyanins in a Fermented Red Vinegar

“…Peonidin 3-caffeoylsophoroside-5-glucoside (YGM-5b), and peonidin 3-dicaffeoylsophoroside-5-glucoside (YGM-4b), peonidin 3-caffeoyl-p-hydroxybenzoylsophoroside-5-glucoside (YGM-5a) and peonidin 3-caffeoyl-feruloylsophoroside-5-gluco-side (YGM-6) are major anthocyanins in the purple-fleshed sweet potato. The YGMs have not only high stability (6, 7) but also multifaceted biological actions including antioxidant capacity (6-9) and other functions (10,11) as well as antidiabetic effect (12)(13)(14)(15). In particular, the first finding that the acylated anthocyanins and their acylated moieties could lower the excess postprandial blood glucose level via R-glucosidase inhibition (13)(14)(15) led us to investigate antihyperglycemic potential of other acylated moieties from anthocyanins in this study.…”

“…The YGMs have not only high stability (6, 7) but also multifaceted biological actions including antioxidant capacity (6-9) and other functions (10,11) as well as antidiabetic effect (12)(13)(14)(15). In particular, the first finding that the acylated anthocyanins and their acylated moieties could lower the excess postprandial blood glucose level via R-glucosidase inhibition (13)(14)(15) led us to investigate antihyperglycemic potential of other acylated moieties from anthocyanins in this study. In addition, caffeoylquinic acids are also known to exhibit antioxidant capacity (16,17), and other physiological functions including antihepatotoxic effect (18)(19)(20).…”