Can I use neem leaf for substitute of hops? Especially it's difficult to manage hops in our region. I found a lot of health benefit in neem leaf.
You can substitute any bitter herb for hops if you wish. Also given the fact it has anti-fungal and anti-bacterial properties, it will likely protect your brew from biological contamination, as hop alpha acids do.
As it is anti-fungal it may interfere with your yeast. Also, I do not know what off flavours yeast may produce when fermenting in the presence of Neem tea compounds. You may be fine, but experience with mead made from eucalyptus honey makes me consider this as a possible adverse affect.
If you do try this please report back.
Before hops a wide range of herbs are recorded as being used to bitter/flavour ale/gruit there are a few modern breweries doing this: https://en.wikipedia.org/wiki/Gruit
Okay, so I actually tried this. I made a simple gruit(Beer with herbs instead of hops), and I just used neem as the herb. It did not interfere with the yeast at all and created an interesting drink. It tastes a lot like neem tea, and is nice and bitter, but also tastes malty like beer. When warm and un-carbonated, it's not great, but when cold and carbonated in a keg, it's great! I feel if gives you a more floaty and euphoric buzz compared to normal beer.