Lakshman Phal or Graviola or Soursop fruit (Annona muricata)
Soursop fruit (Annona muricata) has been discussed as a cancer-killing fruit by many people and that's how I came to know about this fruit. Soursop belongs to the Annona family which is the same family that Sitaphal belongs to and hence once cut, it more or less appears like Sitaphal too. It is quite difficult to source and hence have never got a chance to try it. It can be consumed both by the patient and otherwise healthy individuals but the entire fruit is supposed to be used completely (not stored) once cut or else it loses it's medicinal properties.
People in African and South American countries have used Soursop to treat infections with viruses or parasites, rheumatism, arthritis, depression and sickness. There are some Soursop extracts that can help to treat these conditions.
In laboratory studies, Soursop extracts can kill some types of liver and breast cancer cells that are resistant to particular chemotherapy drugs. But there haven't been any large scale studies in humans. So, there is no scientific proof yet that confirms whether it can work as a cancer treatment or not. Overall, there is no evidence to show that Soursop works as a cure for cancer but since the treatment for cancer is supported with hope, there are many who have Soursop as a medicinal fruit to treat cancer.
Note: Soursop may cause side-effects to certain people as it can cause nerve changes, causing symptoms similar to Parkinson's disease. Though, this is rare.
Though Soursop is an all-season fruit, in India it is available only is certain seasons (usually around January) in Crawford Market (Mumbai) or Godrej – Nature's Basket and can also be procured from Kerala. In Kerala the fruit is called "Aathakka pazham" or "aatha chakka" and over there I suppose the fruit is available throughout the year.