P. JaiarjY. WongkrajangS. ThongpraditchoteP. PeungvichaN. BunyapraphatsaraN. OpartkiattikulMahidol University2018-09-072018-09-072000-09-09Phytotherapy Research. Vol.14, No.5 (2000), 388-3910951418X2-s2.0-0033837785https://repository.li.mahidol.ac.th/handle/20.500.14594/26359The 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 haemostasis 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. Copyright (C) 2000 John Wiley and Sons, Ltd.Mahidol UniversityPharmacology, Toxicology and PharmaceuticsArticleSCOPUS10.1002/1099-1573(200008)14:5<388::AID-PTR638>3.0.CO;2-K