Leukemia ranks as the 10th most frequent type of cancer in Brazil, according to estimates for the 2023–2025 period, with acute lymphoblastic leukemia (ALL) being the most common cancer type among individuals aged 0 to 19 years, according to the Ministry of Health. This hematological neoplasm is characterized by high rates of relapse and resistance to conventional treatments. In this context, the search for therapeutic alternatives derived from natural products has gained prominence due to the potential of bioactive compounds to predominantly target tumor cells. Among these, the species Piper nigrum L. (black pepper) stands out, whose main alkaloid, piperine, has demonstrated anti-inflammatory, antioxidant, and antitumor activities in various cell models. In this context, it is of interest to compare the essential oil and the isolated alkaloid regarding their potential antineoplastic activity against leukemias.

To evaluate the in vitro cytotoxicity of Piper nigrum (black pepper) oil and its isolated alkaloid, piperine, in the Nalm6 cell line derived from acute lymphoblastic leukemia.

Cells were cultured in flasks containing RPMI medium supplemented with 10% fetal bovine serum and 1% penicillin-streptomycin and maintained at 37°C in a 5% CO₂ atmosphere. The MTT assay was performed to evaluate the effect of the substances on Nalm6 cell viability. Cells were seeded in 96-well plates at a concentration of 30,000 cells/well and treated with black pepper oil and isolated piperine, previously dissolved in dimethyl sulfoxide (DMSO) to obtain initial concentrations of 15.4 and 12.2 mg/mL, respectively. A dose-response assay was then carried out with concentrations ranging from 100 to 1.56 μg/mL. After 72 hours of treatment, the supernatant was removed, and an MTT solution at 5 mg/mL was added and incubated for 3 hours in a CO₂ atmosphere. Subsequently, the solution was removed, and DMSO was added to fully dissolve the formazan crystals. Data analysis was performed using GraphPad Prism 9.0 software, with the experiment conducted in triplicate.

The main results were obtained from the evaluation of the mean inhibitory concentrations (IC50) of Piper nigrum compounds on cell growth. Both substances significantly reduced the viability of the Nalm6 cell line, with IC50 values of 21.6 μg/mL for black pepper oil and 14.1 μg/mL for the isolated alkaloid piperine, the latter showing greater cytotoxic effect.

Cell viability assays demonstrate that both Piper nigrum essential oil and its major alkaloid, piperine, have relevant cytotoxic effects against the Nalm6 cell line, representative of ALL. The lower IC50 value for piperine compared to the essential oil suggests that the alkaloid is one of the main constituents responsible for the antineoplastic activity of Piper nigrum. These findings are consistent with recent investigations that address piperine as a potential antineoplastic agent in different types of cancer, particularly gastric cancer (RAMOS et al., 2023). Therefore, it is of great interest to conduct further biological tests comparing the use of the oil and the isolated compound, as well as to evaluate these substances in non-neoplastic hematological cells.