Antiproliferative activity of Psidium guajava essential oil: a preliminary study

Psidium guayava essential oil (EO) from Ecuador was screened for its antiproliferative activity against three human colon carcinoma cell lines: HCT116 a human colon adenocrcinoma grade II, sensitive to 5-fluorouracil and oxaliplatin; CaCO2, a primary adenocarcinoma grade II; SW620, a highly resistant cell line deriving from a lymph-node mestastasis. Peripheral Blood Mononucleated Cells (PBMC) from a healthy donor buffy coat were utilized as healthy control cells. Cells were treated with increasing concentrations of P. guajava EO (40-80  µg/ml) dissolved in 0.25 DMSO and added to growth medium. 24 hours after cells were detached with trypsin and number of viable cells was determined by Tripan blue exclusion and/or or calcein-AM method, thus providing percentage of viable cells and rate of proliferation as well. Dose dependent antiproliferative and cytotoxic effects were observed, with a percentage of growth inhibition ranging from 40 to 80 %. 48h treatment did not increased effectiveness of the EO (probably because of a short half-life) Interestingly treating PBMC with 50µg/ml no anti-proliferative effects were observed, suggesting that this concentration, corresponding to IC 50 of this OE, did not lead evaluable toxicity to healthy cells such as PBMC. Further studies regarding chemical characterization and combination with commonly utilized anticancer drugs may be done as next step.