PHYSICOCHEMICAL AND CHEMICAL VARIATION IN NEEM OILS AND SOME BIOACTIVITY LEADS AGAINST SPODOPTERA-LITURA F

Forty-two neem ecotypes of India have been found to show a wide variat ion in the content of oil, and their physicochemical characteristics ( color, specific gravity, refractive index, iodine value, acid value, a nd saponification value), total fatty acid, fatty acid composition (ol eic, stearic, palmitic, linoleic, myristic, arachidic, and behenic aci ds), and the key meliacins (azadirachtin, nimbin, and salannin). The a zadirachtin content did not correlate with any of the physicochemical and chemical parameters, but the nimbin and salannin contents correlat ed significantly with each other. The refractive index (+ve correlatio n) and iodine value (-ve correlation) showed weak but significant corr elation with the contents of nimbin and salannin. Insect growth inhibi tion of Spodoptera litura revealed a wide variation in the EC(50) of t he oils. The salannin and azadirachtin contents of the oils correlated the most with bioactivity. The iodine and acid values correlated weak ly but significantly with bioactivity.