Isolation and Chemical Characterization of Components with Biological Activity Extracted from Azadirachta indica and Melia azedarach

In this chapter we review the biological activity of Azadirachta indica A. Juss (neem) (AI) and Melia azedarach L. (chinaberry) (MA), as well as the principal components this activity has been attributed to. We develop analytical methods to elucidate the structure and to quantify the most abundant limonoids contained in seeds of AI and MA and report on their biological properties. The limonoids obtained from AI were azadirachtin A and B, nimbin, salannin and their acetyl derivatives; while from MA we obtained a new triterpenoid, named 3-α-tigloylmelianone, as well as three known limonoids named methyl kulonate, 21-β-acetoxymelianone and melianone. The elucidation of the limonoids’ structures was performed by means of 1D and 2D-NMR and the accuracy of theoretical exact mass values, was deduced by HPLC-Q-TOF analysis. According to our results 21-β-acetoxymelianone and 3-α-tigloylmelianone show both antiproliferative (IC50 = 100 and 91.8 μg/mL) and cytotoxic (CC50 = 90.6 and 64.7 μg/mL) activity on the tumorigenic cell line A549, while melianone exhibited the highest cytotoxic activity with a CC50 calculated at 3.6 μg/mL. Methyl kulonate as well as limonoids isolated from AI were found neither cytotoxic nor antiproliferative. Methanol extract from MA fruits was analysed by GC/MS and found to contain hexadecanoic, acetic, and hexanoic acids as well as furfural and 5-hydroxymethylfurfural. The extract was found nematicidal on Meloidogyne incognita, both in terms of juveniles paralysis (EC50/96h = 0.04 %) and biological cycle arrest (EC50 = 0.91 %). This activity, in the concentration range of 31.2-500 μg/mL, has been attributed to the organic acids and aldehydes present and not to the limonoids. Furfural exhibited the highest nematicidal activity for both immersion in test solutions and exposure to vapours (EC50/1 day = 8.5 and 24.1 μg/mL, respectively).