Yellow Passionfruit Juice Reduces Cancer in Cell Culture

GAINESVILLE, Fla.--- University of Florida researchers have found an extract prepared from the juice of yellow passion fruit kills cancer in cell cultures.

"We know that eating fruits and vegetables is associated with a reduced risk of cancer," said Susan Percival, professor of Food Science and Human Nutrition in the Institute of Food and Agricultural Science at UF. "That reduced risk is due to plant compounds or phytochemicals, such as carotenoids and polyphenols, both of which are found in abundance in passionfruit juice."

Percival's work was with yellow passion fruit, which is native to Ecuador and Brazil. The plum-sized fruit contains a fleshy pulp and many seeds, and is harvested mainly for its acidic juice. The juice is served fresh in South America, and it is prized for its sweet flavor, a little bit like pear and a little bit like banana. Processed passion fruit juice is one of the base flavors in mixed fruit drinks such as Snapple Sky and Hawaiian Punch. Until now, the passion fruit has been known only as a good-tasting fruit drink.

"Yellow passion fruit juice contains 13 different carotenoids and 8 different polyphenols, in a single whole food," said Steve Talcott, Assistant Professor of Food Science and Human Nutrition. "Most of the research on phytochemicals has been done on one or two compounds, rather than a whole fruit. We wanted to test the effects of the whole passionfruit on cancer cells."

Percival's group created extracts of the passionfruit juice, one that contained only the carotenoids and polyphenols.

The extracts were prepared in several concentrations, to determine the most effective level and to determine at what levels the extract would be toxic to the cell cultures. The extract was administered to mouse cell cultures that had become cancerous after exposure to benzo-alpha-pyrene, a chemical compound known to have carcinogenic effects.

"When a cell culture becomes cancerous, it changes in appearance," said Percival. "Instead of forming a thin layer on top of the medium, the cancerous cells continue to multiply until they form little heaps of cells, called a focus."

"Foci are scored by their appearance," Percival said. "As their interior organization becomes increasingly disorganized, as the cells pill up on each other more densely, and as they invade the layer of non-cancerous cells around them, they are classified as Type I, II, or Type III. Only foci that are Type II and III were counted in this study, and then only if they were one mm across or larger."

"When we examined the cancerous cultures that had been given passionfruit extract, the number of foci or little tumors were smaller and fewer in number than those in the untreated cancerous cultures," said Percival.

"Cancerous cells not only change in appearance, but they change in longevity. Normal cells live and divide, and eventually they undergo an enzymatic breakdown and the cells die," said Percival. "This is a process called apoptosis, and an enzyme called caspace-3 is part of the breakdown process. But cancer cells have somehow managed to disable the cellular death process."

Percival's research indicates the passion fruit juice extract induces the activity of caspase-3, and so those cells treated with the extract become committed to apoptosis, a good thing in the case of cancer cells.

"It's too soon to say that passion fruit juice is an effective cancer preventative when consumed by humans. We can say the juice is loaded with antioxidants, which protect cells from damage caused by free radicals," said Percival.

"Even when you don't think about the carotenoids and polyphenols, a single glass of passion fruit juice contains 50 percent of the daily requirement for vitamin C, 60 percent of the requirement for vitamin A, and 40 percent of the requirement for potassium," Percival said. "Although you could take a pill for your vitamins and minerals, fruits like the passionfruit can provide other benefits for the American public from the antioxidant content."