It reminds me of an Asian gourd, especially the inside of the fruit and seeds...but I can't pin it down to which one...look's close to the Coccinia..maybe close to coccinia grandis (ivy gourd) but the leaves are off a bit.
Do you have a picture of the whole fruit?
Keeping your location in mind, South Africa, there is a local Coccinia...Coccinia sessilifolia...It might be the one!