Late Professor B. Tiagi was a great botanist who taught almost all the people or now teachers  ( or now retired teachers ) who worked all over Rajasthan in the period hailing from 1960s to 1990s or even later on. He was very regular to the Department and always working with simple tools. He was my source of inspiration that time.
He had a plant in his backyard which was famous for cure of asthama. Tylophora indica .
It grew like a climber. People visited his house and he fondly gave some leaves of this plant  The leaves are dried and grounded and taken a bit in some very very small amounts alone or sometimes with root powder.
People reported that it cured asthama
I never tried it myself but as my teacher said it cured I believed it. Most of the oriental medicines are matter of faith as well. However steroids and terpenoids which might be present in the leaves of a plant of family Asclepiadaceae could have some role but it needs to be proved by scientific studies.