Cardiovascular action of nuatigenosido from Solanum sisymbriifolium

The root of Solanum sisymbriifolium Lam (Solanceae), a perennial herb, has been used as a traditional medicine possessing diuretic and antihypertensive properties in Paraguay. It was reported that extracts from this plant exerted hypotensive effects in rats. Nuatigenosido was isolated from the extract as one of the prospective active compounds. We have investigated its pharmacological actions. The current study demonstrated the following results: (1) Nuatigenosido at 100 mu g/kg and 1 mg/kg i.v. lowered blood pressure in rats, (2) nuatigenosido at 10(-6) and 10(-5) M augmented the contractile force in the right atrium of a bullfrog, and (3) nuatigenosido at 10(-7) M increased the overshoot amplitude in frog atrial myocytes, action potential durations were shortened, the calcium current (I-Ca) was increased, and the delayed outward potassium current was increased. From these results, it is suggested that nuatigenosido may play an important role in the therapeutic effects of this herb.