A new ethylene glycol triterpenoid from the leaves of Psidium guajava

One new pentacyclic triterpenoid psidiumoic acid (5) along with four known compounds beta-sitosterol (1), obtusol (2), oleanolic acid (3), and ursolic acid (4) have been isolated from the leaves of Psidium guajava. The new constituent 5 has been characterized as 2 alpha-glycolyl-3beta-hydroxyolean-12-en-28-oic acid through 2D NMR techniques. This is the first report of isolation of compound 2 from the genus Psidium.

Triterpenoids from the leaves of Psidium guajava

Two triterpenoids, 20beta-acetoxy-2alpha,3beta-dihydroxyurs-12-en-28-oic acid (guavanoic acid, 3), and 2alpha,3beta-dihydroxy-24-p-z-coumaroyloxyurs-12-en-28-oic acid (guavacoumaric acid, 7), along with six known compounds 2alpha-hydroxyursolic acid (1), jacoumaric acid (2), isoneriucoumaric acid (4), asiatic acid (5), ilelatifol D (6) and beta-sitosterol-3-O-beta-D-glucopyranoside (8), have been isolated from the leaves of Psidium guajava. Their structures were determined through spectroscopic methods. Compound 5 showed dose-dependent (10-500 microg/ml) spasmolytic activity in spontaneously contracting isolated rabbit jejunum preparations.

Guava leaf extract and topical haemostasis

The effects of guava leaf extract on the bleeding time and the three main mechanisms of haemostasis: vasoconstriction, platelet aggregation and blood coagulation, were investigated. The water extract of guava leaves did not shorten bleeding times in rats. Guava leaf extract potentiated the vascular muscle contraction induced in rabbits by phenylephrine, and when given alone it stimulated human platelet aggregation in vitro in a dose-dependent manner. On the other hand, it significantly prolonged blood coagulation; activated partial thromboplastin time (APTT) test (p < 0.05). The higher the concentration of the extract, the longer APTT was observed. Thus, a water extract of guava leaves showed ambiguous effects on the haemostatic system. Guava leaf extract did not affect bleeding times, it stimulated vasoconstriction and platelet aggregation but it inhibited blood coagulation. Therefore, guava leaf extract is not recommended as a haemostatic agent.