Free radical scavenging activity of two Hylocereus species (Cactaceae) and their effect on the proliferation of HeLa and MDA-MB-231 cancer cell lines

Hylocereus polyrhizus (red flesh) and Hylocereus undatus (white flesh) are two species of dragon fruit or 'pitaya fruit'. Both of them belong to the cactus family and are grown intensively worldwide. The fruit grows at the tip of the branch and they got their names due to the dragon-like-scales on the skin of the fruit. This study was aimed to determine the total phenolic content, antioxidant activity and antiproliferative effect against cervical cancer (HeLa) and breast cancer (MDA-MB-231) cell lines. Total phenolic content was determined using Folin-Ciocalteu method and the free radical scavenging activity of the crude extracts (aqueous and ethanol) was determined using DPPH free radical scavenging assay. MTT assay was used to investigate the antiproliferative activity of the crude extracts against both cancer cell lines. The total phenolic content of H. polyrhizus and H. undatus were 8.281±0.967 and 6.278±0.317mg GAE/100g of fresh weight, respectively (p<0.05). EC₅₀ values of DPPH free radical scavenging assay was only detected in H. polyrhizus aqueous and ethanol extracts, but not in H. undatus extracts at concentration tested (0–100mg/ml). The antiproliferative study on HeLa revealed that H. polyrhizus component was a stronger inhibitor of the growth of HeLa cell line than H. undatus. No inhibition of MDA-MB-231 breast cancer cell line was observed for both fruits. In conclusion, the results indicated that H. polyrhizus and H. undatus were both rich in polyphenols. However, only H. polyrhizus displayed promising antioxidant and antiproliferative properties.

Acknowledgements: Universiti Putra Malaysia, Ministry of Science, Technology and Innovation of Malaysia and Research University Grant Scheme (RUGS).