Neem oil

Neem oil is a vegetable oil pressed from the fruits and seeds of Neem, an evergreen tree which is endemic to the Indian sub-continent and has been introduced to many other areas in the tropics. It is perhaps the most significant of the commercially available products of neem.
Neem oil is typically light to dark brown, bitter and has a rather strong odour that is said to join the odours of peanut and garlic. It comprises mainly triglycerides and large amounts of triterpenoid compounds, which are in charge for the bitter taste. It is hydrophobic in nature and in order to emulisify it in water for application purposes, it must be formulated with suitable surfactants.
Neem oil also contains steroids and a plethora of triterpenoids of which Azadirachtin is the most well known and studied. The Azadirachtin content of Neem Oil varies from 300ppm to over 2000ppm depending on the quality of the neem seeds compressed.