Physicochemical and Chemical Variation in Neem Oils and Some Bioactivity Leads againstSpodoptera lituraF.

Abstract

Forty-two neem ecotypes of India have been found to show a wide variation in the content of oil, and their physicochemical characteristics (color, specific gravity, refractive index, iodine value, acid value, and saponification value), total fatty acid, fatty acid composition (oleic, stearic, palmitic, linoleic, myristic, arachidic, and behenic acids), and the key meliacins (azadirachtin, nimbin, and salannin). The azadirachtin content did not correlate with any of the physicochemical and chemical parameters, but the nimbin and salannin contents correlated significantly with each other. The refractive index (+ve correlation) and iodine value (−ve correlation) showed weak but significant correlation with the contents of nimbin and salannin. Insect growth inhibition of Spodoptera litura revealed a wide variation in the EC50 of the oils. The salannin and azadirachtin contents of the oils correlated the most with bioactivity. The iodine and acid values correlated weakly but significantly with bioactivity. Keywords: Neem; neem oil; physicochemical variation in neem; chemical variation in neem; neem bioactivity

Oil and Azadirachtin contents of neem (<i>Azadirachta indica</i> A. Juss) seed kernels collected from trees growing in different habitats in Sudan

“…Large variations in the Az-content (2895 to 7525 ppm) have also been observed in the NSK of the different ecotypes of Tamil Nadu (Kumar and Parmar, 1996). Very few studies have been carried out so far in the world to detect the existing variability of Az-content in neem trees, and even fewer on oil-content variability.…”

Investigation of the contents of three main bio-active substances in the seed oil of the neem trees planted in Ninh Thuan province, Vietnam.

“…Nh−ng hµm l−îng cña ho¹t chÊt chÝnh azadirachtin n»m chñ yÕu trong b¸nh dÇu, nhiÒu h¬n 6 lÇn trong dÇu Ðp; hµm l−îng cña nimbin cã trong b¸nh dÇu vµ dÇu Ðp t−¬ng ®−¬ng nhau cßn hµm l−îng cña salanin trong dÇu l¹i lín h¬n [11]. DÇu neem cã hiÖu qu ¶ g©y ng¸n ¨n vµ xua ®uaei c«n trïng vµ chÝnh dÇu neem còng cßn cã t¸c dông lµm bÒn ho¹t chÊt chÝnh azadirachtin [10,11]. Nh− vËy, cã thÓ dïng dÇu neem lµm nguyªn liÖu ®Ó s ¶n xuÊt thuèc b ¶o vÖ thùc vËt sinh häc.…”

Natural Pesticides and Future Perspectives

“…(Kavathekar, 2003). Many other compounds are present in smaller quantities in neem seeds (Hallur et al, 2002;Kumar et al 1996aKumar et al , 1996bRagasa et al, 1997;Siddiqui et al, 1986). Therefore, most products from neem oil are usually represented by their azadirachtin content although they also contain other compounds .…”