Purpose: To examine whether seven species of plants of genus Piper possess anti-cancer effects.

Methods: One normal breast and three breast cancer cell lines were used to test cytotoxic effects over a period of 72 h using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The dried plants were extracted with methanol and dichloromethane, and the effective extract isolated by crystallization, acid/base extraction and column chromatography techniques. Fragmented DNA was purified by phenol/chloroform/isoamyl alcohol.

Results: Methanol and dichloromethane extracts of Piper retrofractum, Piper betle, especially Piper nigrum, exhibited strong effect on MDA-MB-468. When the crude extract of P. nigrum was then separated by column chromatography, fraction D showed activity against both MCF-7 and MDA-MB-468 cells.  Fraction DE that was isolated from D demonstrated a highly cytotoxic effect with IC₅₀ values of 8.33 ± 1.27 and 7.48 ± 0.57 µg/ml on MCF-7 and MDA-MB-468 cells, respectively. Furthermore, fraction DF exhibited a strong cytotoxic effect only on MCF-7 with IC50 value of 6.51 ± 0.39 µg/ml. DNA smears of MCF-7 and MDA-MB-468 cells treated with fraction DE and DF were observed within 7 days.

Conclusions: These results indicate that the compounds isolated from P. nigrum, viz, DE and DF, have cytotoxic effect on breast cancer cell lines. These fractions could be promising agent for breast cancer treatment. Further studies on the isolation, structural and mechanism elucidation of the active compound are still needed being carried out.