SELECTIVE POLARITY-GUIDED AND ADSORPTION-GUIDED EXTRACTION PURIFICATION OF ANNONA SP. POLAR ACETOGENINS AND BIOLOGICAL ASSAY AGAINST AGRICULTURAL PESTS

Annonaceae acetogenins (AG) comprise a family of natural chemical modi fications of long-chain fatty acids (C35-37) bearing one to several hy droxyls (less often ore), middle-chain tetrahydrofuran rings, and a ga mma-lactonized, alpha/beta-unsaturated carboxyl group. Acetogenins' st rong biological activity as larvicides, pesticides, and antitumorals i s dependent on these structural variations. The hydroxylation degree i s particularly important for these etfects. Seeds, albeit rich in fats (mostly triacylglycerols, [TAG]), are a nonpredatory source of these drugs as compared to other botanical parts such as roots and stems. Co nventional lipid extractions lead to quantitative lipid recovery and t hen the unfavorable natural ratio of TAG:AG in the range >90:<0.1 Thes e extracts thus require, for instance, partitions and extensive silica gel column chromatographic steps, in order to enrich or purify the AG fraction(s). Great operational difficulties result from the similar p olarity and mol. wt. range of TAG and AG when carrying out these purif ication steps. An alternative fast two-step procedure to obtain polar acetogenin (pAG)-enriched preparations was developed. The extraction p rocedure for Annona spp. seeds pAG was carried out with acetonitrile ( E degrees = 0.65; log P = -0.33) as a polar organo-solvent, followed b y the adsorption of the solvent-free extract on activated charcoal, th en washed with hexane and/or chloroform (E degrees = 0.0 and 0.40: log P = 3.5 and 2.0) for most of the contaminating TAG removal, and then with acetone (E degrees = 0.56; log P = -0.23) to the desorption of an enriched pAG fraction. An alternative procedure for pAG extraction wa s supercritical fluid extraction (SFE) at moderate thermopressurizatio n conditions (65-82 degrees C; 120-130 atm) using CO2, with 10% aceton itrile as the polarity modifier. The PAG fractions' bioactivity was ev aluated with the brine-shrimp test (BST), and for feed deterrance, gro wth inhibition, and lethality against the high-impact agricultural pes ts Anticarsia gemmatalis and Pseudaletia in sequax caterpillars feedin g on soya or grass leaves sprayed with a 10% alcohol-stabilized emulsi on of pAG.