Studies on the bioactive flavonoids isolated from Azadirachta indica.

Two novel natural metabolites, 3-O-butyl-(-)-epicatechin (1) and 3-O-butyl-(-)-epigallocatechin (2), as well as several known substances, (-)-epicatechin (3), (+)-gallocatechin (4), (-)-epigallocatechin (5), azadirachtin A (6), trilinolein (7) and octadecanoic acid-tetrahydrofuran-3,4-diyl ester (8), were isolated from the bark of Azadirachta indica. The structures of all compounds were established by comprehensive and comparative spectroscopic analysis of NMR and ESI-HRMS data. The new metabolites 1 and 2 represent one of the few examples of natural compounds with a butyl ether group moiety. The acaricidal activity of the compounds was tested using a standard Shaw larval immersion assay. All the compounds, except 7, possess a LD₅₀ value less than or equal to 7.2 mM.