Noni juice, obtained from the fruit of the noni tree (Morinda citrifolia L.), is a popular commodity in the market, particularly in the South Pacific. It is widely used by consumers for the prevention of several lifestyle diseases such as cancer, diabetes, high blood pressure, cardiopathy, and cerebral apoplexy caused by arteriosclerosis. Although there is an increasing interest in the potential therapeutic use of noni plants, there are no comparative studies on the various commercialized noni fruit juices available to decipher their phytochemical composition and properties against carcinomas. The present study, therefore, aims to fill this research gap and investigate its anecdotal use as complementary alternative medicine to manage cancer.
Five commercial brands of noni juice were included in this study, namely Tahitian Organic Noni (TON), Cook Island Noni (CIN), Dynamic Health Noni (DHN), Fijian Noni (FN), and Life Health Noni (LHN). The juice samples were vacuum filtered and freeze-dried to obtain crystal products for methanolic extraction. Total phenolic content (TPC) and antioxidant capacity (FRAP-Ferric Reducing Antioxidant Power) were determined on the methanolic extracts. The cytotoxicity of the noni juices was also tested on human epithelial adenocarcinomas (HeLa and HT29 cell lines), by dissolving 2 mg of the crystal product in sterile deionized water and diluting to 1000 ug/mL in the media culture. The final concentration of the extracts in the well plate was 500 ug/mL. The MTS cell viability assay was performed after the cells were incubated with the extracts for 48 hours at 37°C with 5% CO2.
The DHN and FN extracts were found to have the highest TPC of 5523 ± 291 and 5193 ± 29 mg gallic acid equivalent /100 g dry weight (DW), respectively, whereas the highest antioxidant capacity was seen in the CIN extract (5666 ± 973 mg Trolox equivalent /100 g DW). The CIN extract also showed the most promising effect with only 67 ± 5 % cell viability whilst the other extracts showed lower cytotoxic effects (85-93% cell viability) on the HeLa cell line. However, HT29 cells appeared to be the most susceptible to the FN extracts with cell viability of 73 % compared to 77-89% viability in the remaining extracts. It is possible that greater cytotoxicity could be observed over long exposure times. The noni juice samples contain high levels of TP and antioxidant capacity and appear to show some level of cytotoxic activity, although not statistically different from the negative control. Further work is required to verify if this is “true” (i.e., statistically significant) anti-cancer activity.