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Biosynthesis of antimalarial aryltetralone lignans from Holostylis reniformis
Holostylis reniformis biosynthesizes aryltetralone lignans without 9,9'-oxygenation. Several of these lignans have attracted much interest due to their antiplasmodial activity . To elucidate the biosynthetic pathways for these lignans, the reputed precursors [U-14C]phenylalanine, [9-3H1]coniferyl alcohol, and [9-3H1]isoeugenol were administered to roots of the plant, which led to the incorporation of 3H and 14C into 10 aryltetralone lignans and two 7,7'-epoxylignans. These lignans were identified by comparison of their Rt, ESI-MS, and 1H NMR spectra with those of authentic samples previously isolated from this plant [1–3]. Feeding experiments showed that these lignans are propenylphenol-derived and that H. reniformis can exhibit regioselective control of radical-radical coupling (isoeugenol radical). Regiospecific control over propenylphenol-derived lignan biosynthesis was observed, together with diastereoselective control of C2-C7' bond for aryltetralone lignans (7'R). These experiments provide evidence that isoeugenol is a biosynthetic intermediate of aryltetralone and furan lignans.
Acknowledgements: Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq).
References: 1. Andrade-Neto, V.F. et al. (2007) Antimicrob. Agents Chemother. 51: 2346–2350
2. da Silva, T., Lopes, L.M.X. (2004) Phytochemistry 65: 751–759.
3. da Silva, T., Lopes, L.M.X. (2006) Phytochemistry 67: 929–937.