Streptozotocin 유발 당뇨 쥐에 대한 야콘 괴경 추출물과 그 성분인 Chlorogenic Acid의 혈당강하효과 = Hypoglycemic Effect of Yacon Tuber Extract and Its Constituent, Chlorogenic Acid, in Streptozotocin-Induced Diabetic Rats

다국어 초록 (Multilingual Abstract)

Smallanthus sonchifolius (Yacon, Asteraceae) was originally cultivated in South America and used in traditional medicine by Andean inhabitants. Yacon is known to be potentially beneficial for the management of diabetes. Yacon is composed of fructooligosaccharides, proteins, minerals and phenolic compounds. The aim of study is to investigate hypoglycemic effect of yacon tuber extract (YTE) and its constituent, chlorogenic acid (CGA), in streptozotocin(STZ)-induced diabetic rats. In this study, a HPLC method was developed for simultaneous determination of major active phenolic components, CGA and caffeic acid in YTE. We investigated the hypoglycemic effect of YTE and CGA in STZ-induced diabetic rats and studied glucose tolerance test (GTT). The effect of orally administered multiple dose of YTE and CGA on plasma biochemical parameters was examined using diabetic rats. We also measured free radical scavenging activity by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay and determined nitric oxide (NO) production. The stability test of pharmaceutical formulations (tablet and suspension) of YTE was studied under accelerated condition. The oral administration of YTE (200mg/kg) and CGA (10mg/kg) for 6 weeks produced significant hypoglycemic effect on STZ-induced diabetic rats. YTE and CGA-treated groups showed significant decrease in plasma glucose surge during the GTT. Total cholesterol (TC) and triglyceride (TG) concentrations were significantly decreased by 33 % and 49 %, respectively in YTE-treated rats. TC and TG concentrations were also significantly decreased by 26 % and 41 %, respectively in CGA-treated rats. In the DPPH assay, free radical scavenging activity of CGA was similar to vitamin E, a positive control in the assay. YTE and CGA were found to prevent NO production. CGA concentration in yacon tuber tablet and suspension remained 92 % and 79 %, respectively after 6 months of the accelerated stability test (40 ± 2 ℃, 75 ± 5 % RH). This study suggests that YTE and its constituent, CGA, may be an useful option for management of hyperglycemia and diabetic nephropathy.

국문 초록 (Abstract)

Smallanthus sonchifolius (야콘, Asteraceae)는 남아메리카에서 자생하는 식물로서 지역 원주민에 의해 전통 약물로 이용되어져 왔다. 야콘은 당뇨병에 이로운 식이로서의 알려져 있다. 야콘은 물, 프럭토올리고당, 단백질, 미네랄, 폴리페놀 등으로 이루어져 있다. 이번 연구에서 야콘 괴경 추출물의 주요 활성 폴리페놀 성분으로 chlorogenic acid (CGA)와 caffeic acid 가 있음을 HPLC를 통하여 발견하였다. Streptozotocin (STZ)으로 유발된 당뇨 쥐에서의 야콘 괴경 추출물과 CGA의 혈당강하효과를 연구하였고 내당능 시험도 수행하였다. 야콘 괴경 추출물과 CGA의 반복투여로 인한 당뇨 쥐에서의 생화학적 지표들에 대해서도 조사하였다. 항산화 효과와 nitric oxide (NO) 생성에 미치는 영향을 측정하고 야콘 괴경 추출물의 두 가지 제형에서의 안정성 시험을 수행하였다. 야콘 괴경 추출물 200 mg/kg 과 CGA 10 mg/kg 의 6주간의 투여에서 STZ 유발 당뇨 쥐에서의 유의한 혈당강하효과를 얻을 수 있었다. 내당능 시험에서도 야콘 괴경 추출물과 CGA 모두 내당능이 있었다. 야콘 괴경 추출물 투여군에서 total cholesterol (TC)과 triglyceride (TG)의 농도가 각각 33 % 와 49 % 로 유의성 있게 감소하였다. CGA 투여군에서는 TC와 TG의 농도가 각각 26 % 와 41 % 로 유의성 있게 감소하였다. CGA는 양성대조군인 vitamin E와 비교하여 비슷한 정도의 항산화 효과를 나타내었고 야콘 괴경 추출물과 CGA 모두 NO 생성을 억제하는 효과를 보였다. 안정성 시험을 6개월간 시행한 결과 야콘 괴경 추출물의 정제와 액제에 남아있는 CGA의 양은 각각 92 % 와 79 %로 나타났다. 이번 연구를 통해 CGA를 함유한 야콘 괴경 추출물은 hyperglycemia 와 diabetic nephropathy 등에 유용한 치료 물질로서 생각된다.

목차 (Table of Contents)

• Ⅰ. Introduction 1
• Ⅱ. Materials and Methods 4
• 2-1. Preparaion of yacon tuber extract (YTE) 4
• 2-2. HPLC analysis of phenolic compounds in YTE 4
• 2-3. Animals and induction of diabetes 4
• 2-4. Glucose tolerance test (GTT) 5
• 2-5. Measurement of plasma glucose level, body weight, food and drinking water intake 5
• 2-6. Collection of blood and tissue samples 5
• 2-7. Biochemical estimation of plasma 6
• 2-8. DPPH free radical scavenging activity 6
• 2-9. Determination of NO production 6
• 2-10. Preparation of YTE tablet and suspension for stability test 6
• 2-11. Statistical analysis 7
• Ⅲ. Results and Discussion 8
• 3-1. HPLC analysis of phenolic compounds in YTE 8
• 3-2. Effect of YTE and chlorogenic acid (CGA) on streptozotocin (STZ)-induced diabetic rats 10
• 3-3. Effect of YTE and CGA on GTT 12
• 3-4. Body weight, food intake, drinking water intake and weight of organs 14
• 3-5. Estimation of biochemical parameters in plasma 18
• 3-6. DPPH free radical scavenging activity of YTE and CGA 20
• 3-7. Determination of NO production 22
• 3-8. Stability of YTE formulation 24
• Ⅳ. Conclusion 26
• Ⅴ. References 27
• 국문초록 31