It can be concluded from the above-mentioned experimental results that a high-fructose diet can cause hyperinsulinaemia, while a high-fat diet can result in impaired pancreatic function of insulin secretion and glucose intolerance, indicating that high-fructose diet and a high-fat diet may exert divergent effects on glucose metabolism in rats.

The DPPH scavenging effect, the inhibition of human low-density lipoprotein oxidation, and antioxidative contents were employed for the activity-guided purification to identify the antioxidant components of lotus leaves (leaves of Nelumbo nucifera Gaertn.). The methanolic extract of lotus leaves (LLM) was separated into ethyl acetate (LLME), n-butanol (LLMB), and water (LLMW) fractions. LLME and LLMB exhibited greater capacity to scavenge DPPH radical, delayed LDL oxidation, and had higher antioxidative contents than LLMW. Seven flavonoids were isolated from both fractions by column chromatography. On the basis of 1D- and 2D-NMR experiments and MS data analyses, these compounds were identified as catechin (1), quercetin (2), quercetin-3-O-glucopyranoside (3), quercetin-3-O-glucuronide (4), quercetin-3-O-galactopyranoside (5), kaempferol-3-O-glucopyranoside (6), and myricetin-3-O-glucopyranoside (7). Quercetin and its glycosides (compounds 2-5) exerted potent inhibition of LDL oxidation, whereas myricetin-3-O-glucopyranoside (7) showed stronger DPPH scavenging activity. These results indicate that the antioxidant capacity of lotus leaves is partially relevant to its flavonoids.

No abstract

No abstract

An activity-directed fractionation and purification process was used to identify the antioxidative components of adlay hulls. Hulls of adlay (Coix lachryma-jobi L. var. ma-yuen Stapf) were extracted with methanol and then separated into water, 1-butanol, ethyl acetate, and hexane fractions. The 1-butanol-soluble fraction exhibited greater capacity to scavenge 2,2'-diphenyl-1-picrylhydrazyl (DPPH) radicals when compared with fractions soluble in water, ethyl acetate, and hexane phases. The 1-butanol fraction was then subjected to separation and purification using Diaion HP-20 chromatography, silica gel chromatography, and HPLC. Six compounds showing strong antioxidant activity were identified by spectroscopic methods ((1)H NMR, (13)C NMR, IR, and MS) and by comparison with authentic samples to be coniferyl alcohol (1), syringic acid (2), ferulic acid (3), syringaresinol (4), 4-ketopinoresinol (5), and a new lignan, mayuenolide (6).