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The effects of Piper malacophyllum (C. Pesl) C. DC extracts and its isolated compounds were analysed in a mouse model of primary dysmenorrhoea (PD). Female Swiss mice (6-8 weeks old) on proestrus were intraperitoneally treated with estradiol benzoate for 3 days, to induce PD. Twenty-four hours later, animals were treated 24 h later with vehicle, plant extract, gibbilimbol B, 4,6-dimethoxy-5-E-phenylbutenolide, mixture of 4,6-dimethoxy-5-E-phenylbutenolide and 4,6-dimethoxy-5-Z-phenylbutenolide, or ibuprofen. One hour later, oxytocin was injected and the numbers of abdominal writhing were counted. Then, mice were euthanized and uteri were collected for morphometrical and histological analyses. The effects of P. malacophyllum in inflammation were investigated in mouse peritoneal neutrophils culture stimulated with LPS or fMLP (chemotaxis and mediator release). Finally, uterus contractile and relaxing responses were assessed. Similar to ibuprofen, P. malacophyllum extract and isolated compounds reduced abdominal writhing in mice with PD. Histology indicated a marked neutrophil and mast cell infiltrate in the uterus of PD animals which was attenuated by the extract. The compounds and the extract reduced neutrophil chemotaxis and inflammatory mediator release by these cells. Reduced TNF levels were also observed in uteri of PD mice treated with P. malacophyllum. The extract did not affect spontaneous uterine contractions nor those induced by carbachol or KCl. However, it caused relaxation of oxytocin-induced uterine contraction, an effect blunted by H1 receptor antagonist. Overall the results indicate that P. malacophyllum may represent interesting natural tools for reliving PD symptoms, reducing the triad of pain, inflammation and spasmodic uterus behaviour.

This study aimed to evaluate the effects of the methanol extract of Synadenium grantii Hook f. stems and its main isolated compound Query3,4,12,13-tetraacetylforbol-20-phenylacetate (1) on experimental dysmenorrhea in mice. Female Swiss mice (n = 6–15) of 6–8 weeks old were used, selected according to the period of the estrous cycle. Animals in proestrus were treated intraperitoneally (i.p.) for 3 days with estradiol. They orally received, on the 4th day, S. grantii extract, the compound 1, ibuprofen or hyoscine butylbromide (Buscopan compound®). Then they were injected (i.p.) with oxytocin 1 h later and individually observed regarding the abdominal writhing for 45 min. The uterus was weighed, photographed and fixed in paraffin for histological analysis. The extract inhibited the abdominal writhing and similar results were obtained with compound 1 and the positive control drugs Ibuprofen and hyoscine butylbromide. Reduction of uterus volume and histological inflammatory parameters, such as oedema and leukocyte infiltrate, were observed in animals treated with the extract and compound 1. Our data show promising activity of the extract against dysmenorrhea, indicating important anti-inflammatory activity. Compound 1 appears to be, at least in part, the main responsible for this promising biological effect.