ABSTRACT
Silk fibroin peptides could be obtained from soluble silk fibroin by enzymatic hydrolysis. Its hydrolyzates produced with Alcalase showed significant inhibitory activity against the angiotensin I-converting enzyme (ACE). One inhibitory peptide from the hydrolyzate at a degree of hydrolysis of 20% (sample A20) was purified and identified. Sample A20 was first isolated by size exclusion chromatography(SEC), eluted with 0.01 mol/L hydrochloric acid solution on a Sephadex G-15 column (1.6 cm i.d. x 100 cm). The peak of No. 5 on the SEC chromatography was further purified by reversed-phase HPLC (mu Bondapak C18 P/N 84176 column, 7.8 mm i.d. x 300 mm), eluted with a linear gradient elution with acetonitrile from 0% to 15% at temperature (30 +/- 2) degrees C. Then the pure peptide with ACE inhibitory activity was obtained, the amino acid sequence of which was identified as Gly-Tyr by mass spectrometry.
Subject(s)
Angiotensin-Converting Enzyme Inhibitors/isolation & purification , Fibroins/isolation & purification , Insect Proteins/chemistry , Peptides/isolation & purification , Angiotensin-Converting Enzyme Inhibitors/analysis , Animals , Bombyx/chemistry , Chromatography, High Pressure Liquid , Dipeptides , Fibroins/analysis , Fibroins/chemistry , Mass Spectrometry , Peptides/analysis , Peptides/chemistry , SilkABSTRACT
With the combination of high performance liquid chromatography-electrospray ionization mass spectrometry (HPLC/ESI-MS) and electron impact mass spectrometry (EI-MS), two steroidal saponins, one compound containing three glycosyls and tigogenin and the other one containing three glycosyls and diosgenin, from the bulbs of Lilium brownii var. calchesteri in China have been screened. In the method, on-line HPLC/ESI-MS allows us to obtain rapidly useful information about the molecular weight and the glycosyl chain of glycoside without the necessity of isolating individual compounds, but little information about steroidal sapogenins. Just with 1 mg to 2 mg of pure sample, off-line EI-MS allows us to acquire useful information about a steroidal sapogenin of saponins, but it is difficult to obtain the molecular ion peak. The combination of HPLC/ESI-MS and EI-MS is well suitable for rapidly screening steroidal saponins from plants.
