Cytotoxic effect of betulinic acid and betulinic acid acetate isolated from <i>Melaleuca cajuput</i> on human myeloid leukemia (HL-60) cell line

Abstract

The cytotoxic effect of betulinic acid (BA), isolated from Melaleuca cajuput a Malaysian plant and its four synthetic derivatives were tested for their cytotoxicity in various cell line or peripheral blood mononuclear cells (PBMC) by 3-[4,5-dimethylthizol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay. Betulinic acid acetate (BAAC) was most effective than other betulinic acid derivatives. It had most active cytotoxic activity against human myeloid leukemia (HL-60), human T4-lymphoblastoid (CEM-SS), BALB/c murine myelomonocytic leukemia (WEHI-3B) and human cervical epithelial carcinoma (HeLa) but not on normal human lymphocytes (PBMC), suggesting its action is specific for tumor cells. BA and BAAC inhibit HL-60 cell line at low concentration after 72 h with IC₅₀ values at 2.60 and 1.38 g/mL, respectively. DNA fragmentation analysis showed ladder formation in the 100 - 1500 bp region in HL-60 cell lines after 24 h of treatment with IC₅₀ values. The induction of apoptosis was also confirmed by flow cytometric analysis of cell cycle. BA and BAAC have been shown to induce a time dependant increase in the sub G₁ peak indicating apoptotic phenomenon as obtained from the DNA content histogram analysis. Thus, betulinic acid isolated from Malaysia plant showed good potential as an anti-cancer compound with less toxicity to human normal cells.

Key words: Betulinic acid, HL 60, cytotoxicity, MTT assay, DNA laddering, Cell cycle PI