Hi Rakhi,
Your post reminded me of Viagra, how it was discovered for treatment of hypertension and angina but found to be a potent vasodilator. During the trial study they found that more than being helpful for hypertension and angina this drug was helpful in inducing erections in men.
I am guessing from all this is Kaempferia parviflora ethanol also has vasodilatory effects and thus is helpful with erectile dysfunction in middle and old age men; as men age their arteries get clogged and lose the elasticity and these kind of herb/drugs help with vasodilation and eventually with erectile dysfunction.
Thank you.