Purification of a dimethyladenosine compound from silkworm pupae as a vasorelaxation substance

To identify the active substance in the male silkworm pupae that strengthens men's vitality, the vasorelaxation activity was determined by measuring the vascular endothelial nitric oxide (eNO) produced in calf pulmonary artery endothelial (CPAE) cells treated with extracts from the pupae. Dried silkworm male pupae were extracted with ethanol and suspended in water, then partitioned with hexane, chloroform, ethylacetate, and butanol, sequentially. Among these fractions, the aqueous fraction had maximal NO production (156.87 μM/200 μl well, 10 mg/ml) and minimal cytotoxicity (IC50 362.3 mg/ml). The vasorelaxation substances (VAS) from the aqueous fraction were isolated by a combination of gel filtration and anion-exchange chromatography on DEAE Sephadex A-25 and reverse phase-HPLC. Their chemical structures were determined on the basis of their spectroscopic parameters of EI-MS, MALDI-TOF MS, 1H and 13C NMR, 1H-1H COSY, and GC–MS spectral data. The active substance was subsequently identified as a dimethyladenosine and dimethyladenosine-5′-l-arabinose that has phosphodiesterase (PDE) inhibition activity. This compound was shown to inhibit PDE4 activity in a dose-dependent manner. Also, it inhibited the PDE5 activity of cyclic-GMP-specific PDE5 enzyme. These results imply that dimethyladenosine may be a lead compound for the development and improvement of vasculogenic impotence drugs through phosphodiesterase inhibition and NO production in endothelial cells.