Hypoglycemic activity of extracts of Chamaecyparis obtusa var. formosana leaf in rats with hyperglycemia induced by high-fat diets and streptozotocin.

Chamaecyparis obtusa var. formosana is a species indigenous to Taiwan and has been used as a medicinal plant. It has been claimed that the hot water extracts of C. obtusa var. formosana leaves (CoLE) with flavonoids and proanthocyanidins have anti-oxidant and anti-hyperglycemic activities in vitro. This study further examines the anti-hyperglycemic activity of CoLE and its possible mechanisms in hyperglycemic rats. Hyperglycemia of rats was induced by streptozotocin (STZ) and high-fat diets (HFD). Hyperglycemic rats treated orally with 30 and 150 mg/kg CoLE were classified into LCO and HCO groups, respectively. After three-month treatment, both LCO and HCO groups showed improved glucose metabolism in oral glucose tolerance and postprandial blood glucose tests. Decrease in HOMA-IR, leptin and adiponectin levels of the HCO group revealed amelioration of insulin and leptin resistance. Obesity and accumulation of visceral fats induced by STZ and HFD could be alleviated in both HCO and LCO groups. These anti-diabetic effects might be contributed by inhibition of intestinal digested enzymes and protein tyrosine phosphatases (PTPases). Although other studies are necessary, these findings suggest that CoLE could be potentially used as a health complement for treating diabetes without significant toxicity.

Antihyperglycemic activities of twig extract of indigenous cinnamon (Cinnamomum osmophloeum) on high-fat diet and streptozotocin-induced hyperglycemic rats.

BACKGROUND: Cinnamomum osmophloeum (indigenous cinnamon) is an endemic species in Taiwan and its twigs contain abundant A-type proanthocyanidins. C. osmophloeum twig extracts (CoTEs) were found to have α-glucosidase and α-amylase inhibitory activities in vitro. The aim of this study is to further investigate the antihyperglycemic activity of CoTEs in hyperglycemic rats. RESULTS: Hyperglycemic rats were divided into three groups and were treated orally with high-dosage CoTEs (HCO, 150 mg kg-1 ), low-dosage CoTEs (LCO, 30 mg kg-1 ) and positive control (PC, 30 mg kg-1 pioglitazone). The HCO group showed improved glucose tolerance in an oral glucose tolerance test after 1 month of treatment, contributed by the inhibition of intestinal disaccharidases, amylase, and lipase. Compared with the PC group, both the HCO and LCO groups had decreased weight of visceral fats and lower atherogenic index; while their low-density lipoprotein-cholesterol, food intake, feed efficiency, and biochemical parameters remained unchanged compared with the NC group. Furthermore, the HCO group had decreased weight gain and the LCO group had decreased serum leptin level. CONCLUSION: These results suggest that CoTE has potential antihyperglycemic activities for treating hyperglycemia without weight gain. © 2018 Society of Chemical Industry.

Characteristics of proanthocyanidins in leaves of Chamaecyparis obtusa var. formosana as strong α-glucosidase inhibitors.

BACKGROUND: In recent decades, there has been a growing demand for natural products with a view to using them as α-glucosidase inhibitors for reducing postprandial hyperglycemia. In this study, the hot water extract (HWE) from Chamaecyparis obtusa var. formosana (Hayata) Rehder (Cupressaceae) leaves and its soluble fractions were screened for α-glucosidase inhibition properties. The n-butanol-soluble fraction of HWE was further fractionated into 14 subfractions (B1-B14) using a Sephadex LH-20 column. The α-glucosidase-inhibitory activities and proanthocyanidin contents of all subfractions were determined. The structural characteristics of proanthocyanidins in proanthocyanidin-rich fractions were also elucidated. RESULTS: HWE produced a dose-dependent inhibition of α-glucosidase at low dose. Its IC50 value was 1.4 µg mL-1 , showing high inhibitory activity. Subfractions B7-B14 displayed powerful α-glucosidase-inhibitory activities with IC50 values ranging between 1 and 0.015 µg mL-1 and contained abundant proanthocyanidins exceeding 300 mg g-1 . The proanthocyanidins with higher mean degree of polymerization (mDP), higher proportions of procyanidin dimer (A1 or A2) and (epi)afzelechin of extension units and a lower proportion of epicatechin of terminal units displayed high α-glucosidase-inhibitory activities. CONCLUSION: Proanthocyanidins in HWE were viewed as potential natural α-glucosidase inhibitors for decreasing postprandial hyperglycemia. The results indicated that specific structural characteristics of proanthocyanidins would be required for α-glucosidase-inhibitory activity. © 2018 Society of Chemical Industry.

Antihyperglycemic and antioxidant activities of twig extract from Cinnamomum osmophloeum.

This is the first report concerning the α-glucosidase, α-amylase and protein tyrosine phosphatase 1B (PTP1B) inhibitory activities of cinnamon twig extracts. Comparing the antihyperglycemic activity of renewable plant parts, indigenous cinnamon (Cinnamomum osmophloeum; tǔ ròu guì) twig extracts (CoTE) showed better α-glucosidase and α-amylase activities than leaf, 2-cm branch and 5-cm branch extracts. Chemotype of C. osmophloeum has no influence on the antihyperglycemic activities and proanthocyanidin contents of CoTE. Among four soluble fractions obtained from CoTE by following bioactivity-guided fractionation procedure, the n-butanol soluble fraction (BSF) with abundant proanthocyanidins and condensed tannins, exhibited the best antihyperglycemic and PTP1B inhibitory activities. In addition, the BSF displayed the excellent DPPH free-radical scavenging and ferrous ion-chelating activities. The antihyperglycemic and antioxidant activities of all four soluble fractions from CoTE showed high correlation coefficient with their proanthocyanidin and condensed tannin contents. Furthermore, CoTE had no toxicity on 3T3-L1 preadiocytes. Results obtained demonstrated that CoTE has excellent antihyperglycemic, antioxidant and PTP1B inhibitory activities, and thus has great potential as a source for natural health products.

Structural characterization and bioactivity of proanthocyanidins from indigenous cinnamon (Cinnamomum osmophloeum).

BACKGROUND: Barks and twigs of common species of cinnamon with abundant proanthocyanidins are used as a spice, fold medicine or supplement. Cinnamomum osmophloeum is an endemic species in Taiwan and coumarin was not detected in the oil of the C. osmophloeum twig. The present study aimed to evaluate the relationship between the bioactivities and proanthocyanidins of C. osmophloeum twig extracts (CoTE). The n-butanol soluble fraction from CoTE was divided into 10 subfractions (F1-F10) by Sephadex LH-20 gel chromatography. The antihyperglycemic activities were examined by α-glucosidase, α-amylase and protein tyrosine phosphatase 1B inhibitory assays. Total antioxidant activities were examined by 2,2-diphenyl-1-picrylhydrazyl free radical scavenging and ferrous ion-chelating assays. RESULTS: The results revealed that subfractions F6-F10, with high proanthocyanidin contents, showed excellent antihyperglycemic and antioxidant activities. Subfractions F6-F10 were analyzed further by matrix-assisted laser desorption/ionization-time of flight/mass spectrometry and thiolysis-reversed-phase high-performance liquid chromatography/tandem mass spectrometry methods. The results showed that the mean degrees of polymerization of proanthocyanidins in subfractions F6-F10 ranged from 3.5 to 5.1, with the highest degrees of polymerization of proanthocyanidins reaching 8 in subfractions F8-F10. Two compounds in F6 were identified as cinnamtannin B1 and parameritannin A1. These proanthocyanidins contained at least one A-type and major B-type linkages. CONCLUSION: These results demonstrate that proanthocyanidins are associated with their antihyperglycemic and antioxidant activities in CoTE. © 2016 Society of Chemical Industry.