The aims of this study were to evaluate the
antihypertensive effects of the standardised methanolic extract of Carica papaya, its
angiotensin converting enzyme inhibitory effects in vivo, its effect on the baroreflex and serum
angiotensin converting enzyme activity, and its chemical composition. The chemical composition of the methanolic extract of C. papaya was evaluated by liquid chromatography-mass/mass and mass/mass spectrometry. The
angiotensin converting enzyme inhibitory effect was evaluated in vivo by Ang I administration. The
antihypertensive assay was performed in spontaneously hypertensive rats and Wistar rats that were treated with
enalapril (10 mg/kg), the methanolic extract of C. papaya (100 mg/kg; twice a day), or vehicle for 30 days. The baroreflex was evaluated through the use of
sodium nitroprusside and
phenylephrine.
Angiotensin converting enzyme activity was measured by ELISA, and
cardiac hypertrophy was evaluated by morphometric analysis. The methanolic extract of C. papaya was standardised in
ferulic acid (203.41 ± 0.02 µg/g),
caffeic acid (172.60 ± 0.02 µg/g),
gallic acid (145.70 ± 0.02 µg/g), and
quercetin (47.11 ± 0.03 µg/g). The
flavonoids quercetin,
rutin,
nicotiflorin,
clitorin, and manghaslin were identified in a fraction of the extract. The methanolic extract of C. papaya elicited
angiotensin converting enzyme inhibitory activity. The
antihypertensive effects elicited by the methanolic extract of C. papaya were similar to those of
enalapril, and the baroreflex sensitivity was normalised in treated spontaneously hypertensive rats. Plasma
angiotensin converting enzyme activity and
cardiac hypertrophy were also reduced to levels comparable to the
enalapril-treated group. These results may be associated with the chemical composition of the methanolic extract of C. papaya, and are the first step into the development of a new phytotherapic product which could be used in the treatment of
hypertension.