Induction of salivary kallikreins by the diet containing a sweet-suppressive peptide, gurmarin, in the rat.

Gymnema sylvestre (gymnema) contains gurmarin that selectively inhibits responses to sweet substances in rodents. The present study investigated possible interaction between gurmarin and the submandibular saliva in rats fed diet containing gymnema. Electrophoretic analyses demonstrated that relative amounts of two proteins in the saliva clearly increased in rats fed the gymnema diet. However, rats previously given section of the bilateral glossopharyngeal nerve showed no such salivary protein induction. Analyses of amino acid sequence indicate that two proteins are rat kallikrein 2 (rK2) and rat kallikrein 9 (rK9). rK2 and rK9, a family of serine proteases, have a striking resemblance of cleavage site in the protein substrates. Interestingly, gurmarin possesses comparable residues with those rK2 and rK9 prefer. The kallikreins significantly inhibited immunoreaction between gurmarin and antigurmarin antiserum. These results suggest that rK2 and rK9 increased by chemosensory information for the gymnema diet via the glossopharyngeal nerve might cleave gurmarin or at least cause specific binding with it.

Antitumor activity of compounds isolated from leaves of Eriobotrya japonica.

In a search for possible antitumor agents from natural sources, megastigmane glycosides and polyphenolic constituents isolated from the leaves of Eriobotrya japonica (Rosaceae) were found to inhibit the 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced activation of Epstein-Barr virus early antigen in Raji cells. Roseoside and procyanidin B-2 were among the active compounds found in an in vitro assay; these compounds were further assessed for antitumor activity in vivo in a two-stage carcinogenesis assay on mouse skin. Roseoside significantly delayed carcinogenesis induced by peroxynitrite (initiator) and TPA (promoter), and its potency was comparable to that of a green tea polyphenol, (-)-epigallocatechin 3-O-gallate, in the same assay.

Production of bioactive triterpenes by Eriobotrya japonica calli.

Callus tissue cultures induced from an axenic leaf of Eriobotrya japonica (Rosaceae) produced triterpenes in large amounts (ca. 50 mg/g dry wt). Nine triterpenes were characterized as ursolic acid, oleanolic acid, 2alpha-hydoxyursolic acid, maslinic acid, tormentic acid, 2alpha, 19alpha-dihydroxy-3-oxo-urs-12-en-28-oic acid, hyptadienic acid and a mixture of 3-O-cis-p-coumaroyltormentic acid and 3-O-trans-p-coumaroyltormentic acid. The triterpene composition in the callus tissues was noticeably different from that in intact leaves. The contents of tormentic acid with antidiabetic action, and 2alpha, 19alpha-dihydroxy-3-oxo-urs-12-en-28-oic acid with anti-HIV activity, were much larger than those in the intact leaves. All of the triterpenes isolated from the callus tissues showed an inhibitory effect comparable to (-)-epigallocatechin gallate (EGCG) of green tea on the activation of Epstein-Barr virus early antigen (EBV-EA) induced by 12-O-tetradecanoylphorbol-13-acetate (TPA). 2alpha, 19alpha-Dihydroxy-3-oxo-urs-12-en-28-oic acid was the most potent inhibitor among them and caused a significant delay of two-stage carcinogenesis on mouse skin.