Effects of pomegranate extracts on rat uterine contraction

Pomegranates (Punica granatum L.) have been widely used for their health benefits. They have been found to be effective in reducing heart disease risk factors [1] and may be effective against prostate cancer [2,3] and osteoarthritis [4]. However, the use of promegranates as uterotonic agents is not well understood. The aims of the study were to investigate the effects of pomegranate seed and peel extracts on rat uterine contraction. We particularly examined the effects of the extracts on phasic contraction arising spontaneously and investigated their underlying mechanisms. Pomegranate seed and peel were collected from local gardens and extracted using methanol. The extracts were then analyses by GC/MS. Rats were killed by asphyxiation with CO₂ and longitudinal uterine smooth muscles isolated. Isometric force was measured and the effects of the extracts studied. Several agents, previously reported to increase contraction in other smooth muscles, were found in both peel and seed extracts. When the extracts were applied on the uterus, they significantly increased uterine contraction. Their effects were dose dependent. The maximal effect of the seed and peel extract was observed at the dose of 2.5mg/ml (2.0–2.6mg/ml) and 0.7mg/ml (0.3–0.9mg/ml) respectively. Neither the seed extract nor the peel extract produced contraction in the absence of external calcium. Wortmannin, a specific inhibitor of myosin light chain kinase, significantly inhibited increases in contraction produced by both extracts. In conclusion, pomegranate seed and peel extracts have uterotonic effects. Increases in contraction produced by the extracts depend on external calcium and myosin light chain kinase.

References: [1] Aviram, M. & Dornfeld, L. (2001) Atherosclerosis 158(1): 195–8. [2] Malik, A. et al. (2005) Proc Natl Acad Sci USA 102(41): 14813–8. [3] Adhami, V.M. & Mukhtar, H.B. (2006) Free Radic Res 40(10):1095–104. [4] Ahmed, S. et al. (2005) J Nutr 135(9): 2096–102.