A new diterpene glycoside from the seeds of Pharbitis nil

Abstract

Pharbitis nil (Convolvulaceae) is an annual climbing herb, and widely distributed throughout Korea, Japan, and China. In China, it has been used as folk medicine for treatment of a variety of digestive problems. The flowers and seeds of P. nil are known for their diversified compounds, particularly for the presence of resin glycosides, gibberellins, flavonoids, and anthocyanins. Its extract showed antitumor and anti-fungal activities. Recently, we reported the isolation from the CHCl3 and EtOAc soluble fraction, of ent-kaurane type diterpenes, lignans, phenolic amides, and allogibberic acid, which showed cytotoxic activities and the ability to inhibit NO production. In our continuing search for bioactive constituents from Korean medicinal plants, we investigated the BuOH fraction of P. nil. Repeated column chromatographic purification resulted in the isolation of one new diterpene glycoside (1), along with three known compounds (2-4). The structure of new one was determined on the basis of 1D and 2D NMR spectroscopic data and chemical means.