MS system (LCQDECA, Finigan company, USA),equipped with a Hewlett–Packard 9000 computer system,
was used to determine the molecular weight. Sample (1 mg) was dissolved in 10 ml of methanol. One hundred microliter of sample solution was injected into the MS system.Mass spectroscopy was recorded with a heat capillary voltage of 4.5 kV, a heat capillary temperature of 280 C,sheath gas flow rate of 70 units and auxiliary gas flow rate of 10 units. The scan range of m/z was 200–1200.