A previous chemical study on Aristolochia giberti led to the isolation of fourteen compounds, including three lignans [1]. Dibenzylbutyrolactone lignans exhibit insect feeding deterrent activity that is strong enough to mediate plant-insect interactions [2]. Lignans with methoxy and/or methylenedioxy substituents are more actives than those with hydroxyl and glucosyl groups [2]. In addition to deterring appetite on insects, lignans can kill or hindrance their life cycles [3]. In general, lepidopteran larvae convert lignoids into its aromatic ring O-demethylated, hydroxylated, and glycosylated derivatives [4]. In this study, Battus polydamas larvae were fed at laboratory with leaves of A. giberti, and the organic extracts of leaves (LE), feaces (FE), and larvae (LVE) were prepared by maceration. From these extracts, a know lignan, kusunokinin (1), was isolated. Whereas, from the FE two new dibenzylbutane lignans, 2-(4',5'-methylenedioxybenzyl)-3-(4'',5''-dimethoxybenzyl)-4-O-β-glucopyranyl-butan-1-oic acid (2) and 2,3-[4',5':4'',5''-bis(methylenedioxybenzyl)]-4-O-β-glucopyranyl-butan-1-oic acid (3), were isolated and their structures determined by spectroscopic analyses. Compound 4 was identified in LE and FE by HPLC-PDA as cubebin. Compounds 1 and 5 were identified in LVE by CG-MS analyses. It is known that kusunokinin (1) causes high mortality in larvae of soybean caterpillars [3], whereas cubebin (4) and hinoquinin (5) are insect feeding deterrents [2]. Therefore, it is reasonable to propose that 2 could be a product from 1, whereas 3 be a biotransformed product from the 4 or 5. Hence, B. polydamas may have their own strategy to overcome chemical barriers imposed by A. giberti.
References:
[1] Lopes, L. M. X. et al. (2009)J. Braz. Chem. Soc. 2: 19 – 108.
[2] Harmatha, J., Nawrot, J. (2002) Entomol. Exp. Appl. 104: 51 – 60.
[3] Messiano, G. B. et al. (2008)J. Agric. Food Chem. 56: 2655 – 2659.
[4] Ramos, C. S. et al. (2008) Phytochemistry 69: 2157 – 2161.
