Abstract
As part of an ongoing study of new insulin mimetic agents from medicinal plants, the 70% EtOH extract of Symplocos cochinchinensis was found to have a stimulatory effect on glucose uptake in 3T3-L1 adipocyte cells. The intensive targeted isolation of this active extract resulted in ten new hydroxyoleoside-type compounds conjugated with a phenolic acid and monoterpene (1–6 and 8–11), as well as four known compounds (7 and 12–14). The chemical structures of the new compounds were determined based on spectroscopic data analysis (1H and 13C NMR, HSQC, HMBC, NOESY and MS). The absolute configurations of the isolated compounds were determined by electronic circular dichroism (ECD) analysis of derivatives obtained after a series of reactions, such as those with dirhodium (ІІ) tetrakis (trifluoroacetate) and dimolybdenum (ІІ) tetraacetate. In vitro, compounds 3, 7 and 8 moderately increased the 2-deoxy-2-[(7-nitro-2,1,3-benzoxadiazol-4-yl)amino]-D-glucose (2-NBDG) uptake level in differentiated 3T3-L1 adipocytes. For further studies, we evaluated their effects on the expression of glucose transporter-4 (GLUT4), its translocation, protein tyrosine phosphatase 1B (PTP1B) inhibition and expression of phosphorylated Akt. Our results strongly suggest that the traditional uses of this plant can be described as active constituents by hydroxyoleoside-type compounds.
Highlights
The number of people with diabetes mellitus is growing rapidly, and the incidence rate of diabetes is accelerating, especially as the elderly and obese population increases1
Food intake and body weight decrease when insulin is selectively delivered to the brain, but not when it is delivered to the whole body4. These results suggest that insulin mimetics that separate glucose-lowering action from the weight gain are a very good pharmacological solution for overcoming insulin resistance as the side effects of diabetes therapies
The 70% EtOH extract of the aerial part of S. cochinchinensis was separated by silica gel, Sephadex LH-20, ODS open column chromatography and preparative HPLC to yield ten new 10-hydroxyoleoside-type seco-iridoids, symplocochinsides A-F [1,2,3,4,5,6] and G-J [8,9,10,11], together with four known compounds (Fig. 1)
Summary
The number of people with diabetes mellitus is growing rapidly, and the incidence rate of diabetes is accelerating, especially as the elderly and obese population increases. While many diabetes medications lower blood glucose levels in the short term, they often cause weight gain as a side effect and prolonged use worsens the insulin resistance of diabetic patients. Food intake and body weight decrease when insulin is selectively delivered to the brain, but not when it is delivered to the whole body4 These results suggest that insulin mimetics that separate glucose-lowering action from the weight gain are a very good pharmacological solution for overcoming insulin resistance as the side effects of diabetes therapies. Moore (www.theplantlist.org) is an evergreen tree that grows up to 35 meters in height and belongs to the Symplocaceae family. This plant is distributed in East Asia, including China, Japan, India, Vietnam and Malaysia. Recent reports on the antidiabetic activity of oleuropein, which is abundant in olive tree leaves, led us to isolate active compounds by a special dereplication method aimed at seco-iridoids
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