Abstract

Natural products have recently become the focus of increased research interest due to their potential pharmacological activities. Therefore, we established a program to screen natural products for cytotoxic activity using the MTT reduction assay system to test HT-29 human colon cancer cells. During the course of screening, we found that the acetone extracts of guava (Psidium guajava L.) branch (GBA) had cytotoxic effects on HT-29 cells. The GBA showed highly cytotoxic effects via the MTT reduction assay, LDH release assay, and colony formation assay. In particular, the GBA of the 250 mg/ml showed 35.5% inhibition against growth of HT-29 cells. As expected, GBA induced characteristic apoptotic effects in HT-29 cells, including chromatin condensation and sharking that occurred 24 h after the cells had been treated at a concentration level of 250mg/ml. To examine the functions on apoptosis, we used a flow cytometric analysis. The apoptotic cells were distributed according to the cell cycle phase shown by sub-G1 DNA content.

Key words: Natural products, HT-29 cells, cytotoxicity, guava branch, anticancer.