Essential Oil and Major Non-Volatile Secondary Metabolites from the Leaves of Amazonian Piper subscutatum.

The essential oil and the major non-volatile secondary metabolites from the leaves of Piper subscutatum (Miq.) C. DC. (Family Piperaceae), collected in the Ecuadorian Amazon, were analyzed for the first time in the present study. The essential oil was submitted to chemical and enantioselective analyses by GC-MS and GC-FID. (E)-ß-caryophyllene (25.3-25.2%), ß-chamigrene (10.3-7.8%), (E)-nerolidol (8.1-7.7%), ß-selinene (7.2-7.7%), δ-cadinene (2.7-3.9%), bicyclogermacrene (3.7-2.4%), and ß-pinene (2.6-3.4%) were the major components. The enantioselective analysis, carried out on a ß-cyclodextrin-based column, showed four scalemic mixtures in which (1R,5R)-(+)-α-pinene, (1S,5S)-(-)-ß-pinene, (S)-(-)-limonene, and (1R,2S,6S,7S,8S)-(-)-α-copaene were the major enantiomers, with enantiomeric excesses of 28.8%, 77.8%, 18.4%, and 6.0%, respectively. The study was complemented with the chemical analysis of the organic fraction dissolved in the hydrolate, whose major components were 6-methyl-5-hepten-2-one (63.7-64.4%) and linalool (6.5-6.0%). Concerning the non-volatile fraction, five lignans were the major components. (-)-Beilshminol B, (-)-grandisin, (-)-3',4'-methylenedioxy-3,4,5-trimethoxy-7,7'-epoxylignan, (-)-3',4'-methylenedioxy-3,4,5,5'-tetramethoxy-7,7'-epoxylignan, and (-)-3,4,3',4'-dimethylenedioxy-5,5'-dimethoxy-7,7'-epoxylignan were identified by means of NMR spectroscopy, mass spectrometry and X-ray crystallography. The absolute configuration 7S,8S,7'S,8'S was tentatively assigned to all of them.

Limitations of the fasting proinsulin to insulin ratio as a measure of ß-cell health in people with and without impaired glucose tolerance.

BACKGROUND: The fasting proinsulin to insulin ratio is elevated in people with type 2 diabetes and has been suggested as a marker of ß-cell health. However, its utility in discriminating between individuals with varying degrees of ß-cell dysfunction is unclear. Proinsulin has a very different half-life to insulin and unlike insulin does not undergo hepatic extraction prior to reaching the systemic circulation. Given these limitations, we sought to examine the relationship between fasting and postprandial concentrations of ß-cell polypeptides (proinsulin, insulin and C-peptide) in people with normal and impaired glucose tolerance in differing metabolic environments. DESIGN: Subjects were studied on two occasions in random order while undergoing an oral challenge. During one study day, free fatty acids were elevated (to induce insulin resistance) by infusion of Intralipid with heparin. Proinsulin to insulin and proinsulin to C-peptide ratios were calculated for the 0-, 30-, 60- and 240-minute time points. Insulin action (Si) and ß-cell responsivity (Φ) indices were calculated using the oral minimal model. RESULTS: The fasting proinsulin to c-peptide or fasting proinsulin to insulin ratios did not differ between groups and did not predict subsequent ß-cell responsivity to glucose during the glycerol or Intralipid study days in either group. CONCLUSIONS: Among nondiabetic individuals, the fasting proinsulin to insulin ratio is not a useful marker of ß-cell function.