Isolation an identification of rotenoids in Pachyrhizus tuberosus seeds
Amazonian yam bean (Pachyrhizus tuberosus Spreng., Leguminosae) is a perennial twining plant indigenous to South America used for food and as a fodder. Large tuberous roots, which are eaten fresh or roasted, contain high amount of protein and easily digestible carbohydrates. Leaves, stems, roots, ripe pods, and seeds can be toxic to humans due to the presence of insecticidal and piscicidal compounds of isoflavonoid type called rotenoids . Aqueous/methanolic extract obtained from dried seeds (collected in Peruvian Amazon) was pretreated on an immunoaffinity column (IAC)  and subsequently analyzed by reverse phase HPLC with diode array detector. Immunosorbents for IAC are characterized by high molecular selectivity so that single group of structurally related compounds can be targeted. Certain levels of compounds with immunoreactivity similar to isoflavonoids were identified. The extract was subsequently separated by flash chromatography into fractions and semipreparative HPLC column into individual compounds. Their structures were identified by 1H and 13C NMR and confirmed by HR-MS.
A study of chemical constituents of the seeds of P. tuberosus led to the isolation and identification of one new rotenoid of chemical formula C20H16O7, along with five other known rotenoids (rotenone, pachyrrhizine, neotenone, erosone and 12α-hydroxydolineone) . The new rotenoid was assigned structure of 12α-hydroxyerosone based on the detailed analysis of 1H and 13C NMR spectra. According to previous literary data describing various biological activities of rotenoids, we suppose that future research on this new rotenoid may lead to new findings in the phytochemistry of these bioactive compounds.
Acknowledgement: 1. Czech Science Foundation (Project GA 525/09/0994), 2. Ministry of Education, Youth and Sports (Institutional research plan MSM 6046070901)
References: 1. Sørensen M (1997) Biodivers Conserv 6: 1581–1625, 2. Delaunay N et al. (2000)J Chromatogr B 745: 15–37, 3. Krishnamurti M et al. (1970) Tetrahedron 26: 3023–3027.