There are too many negative effects from arginine for it to be worth taking, such as increased susceptibility to varicella zoster virus (which is in most people's bodies anyway) and risk of heart disease. No, thirty minutes doesn't sound like enough to me unless you're taking it in liquid form as an enema, in which case you'd have to reduce the dose anyway. It would be more a question of taking it on a regular basis, or preferably, including protein sources high in it in your diet. That might, however, increase your risk of heart disease and susceptibility to viral infections, particularly herpes zoster and shingles. There are also a lot of other issues than just that involved in erectile dysfunction, for instance diabetes can make it worse and muscle tension in the groin as well as the usual psychological factors.
Concerning bananas, that would probably be connected with B vitamins.
Fruits high in anthocyanins and flavonoids might help, for instance bilberries, blackcurrants and elderberries.
