Globally, leukemia ranks as the 13th most common cancer and represents the 10th leading cause of cancer-related death, accounting for approximately 500 thousand new cases and around 300 thousand deaths, according to 2022 estimates by the Global Cancer Observatory (GLOBOCAN). Among its subtypes, acute lymphoblastic leukemia (ALL) is characterized by its aggressive clinical progression, high prevalence of high risk cytogenetic alterations associated with chemotherapy resistance and elevated relapse rates. Additionally, patients are also more susceptible to treatment-related toxicity and long-term side effects. In this context, the development of innovative therapeutic strategies is of particular importance. In light of this, the evaluation of the cytotoxic activity of natural products, such as Piper nigrum (black pepper), is shown to be relevant, considering its recognized anti inflammatory and anti neoplastic properties, thus revealing itself as a promising approach in oncological research.

To evaluate the in vitro cytotoxicity of oils derived from Piper nigrum (oil I, II and III) in an ALL cell line.

This study employed the NALM-6 cell line (acute lymphoblastic leukemia) and the non-neoplastic embryonic kidney cell line HEK-293. The cells were cultured in flasks containing RPMI High Glucose medium supplemented with 10% fetal bovine serum and 1% penicillin-streptomycin, and maintained at 37°C in a humidified atmosphere with 5% CO₂. Cell viability was assessed using the MTT assay. For that purpose, cells were seeded in 96-well plates at a density of 30,000 cells/well and treated with oils I, II and III, previously dissolved in dimethyl sulfoxide (DMSO) to obtain initial concentrations of 16.5; 18, and 15 mg/mL, respectively. The dose-response curve was generated using concentrations ranging from 100 to 1.56 μg/mL. After 72h of incubation, the supernatant was discarded, and MTT solution (0.5 mg/mL) was added and incubated for 3h. Subsequently, the solution was discarded and DMSO was added to completely dissolve the formazan crystals. Data analysis was performed using GraphPad Prism 8.0 software and all experiments were conducted in triplicate.

The main findings were derived from the evaluation of mean concentrations of Piper nigrum oils required to achieve 50% of the maximum inhibitory effect (IC50) in cell growth. Oil I exhibited an IC50 of 23.6 μg/mL, while oil II showed an IC50 of 20.6 μg/mL. Oil III displayed the best results with a lower IC50 at 13.5 μg/mL. This analysis suggests that the oils possess distinct chemical compositions, leading to variations in their cytotoxic activity.

Cell viability assays demonstrated the significant antineoplastic activity of the oils. There was variation in the cytotoxic potential between oils, oil I being the least effective while oil III showed the most cytotoxic effect. This research is pioneering in employing oils derived from Piper nigrum in the context of ALL, supporting previous evidence about their antineoplastic properties. In light of these findings, further biological analyses are warranted, comparing the activity of the oils in multiple cell lines.