Sexual hybrids of Tanacetum: biochemical, cytological and pharmacological characterization

Abstract

crude F 1 leaf extract displaying significant (>5%) inhibition of PMNL activity, provides further evidence Novel sexual hybrids have been produced between that parthenolide is not the sole determinant of the medicinally-important species T. parthenium (L.) pharmacological activity in the genus Tanacetum. Schultz-Bip. (feverfew) and T. vulgare (L.) Schultz-Bip. (tansy). Morphologically, the F 1 hybrids were more Key words: Feverfew, tansy, sexual hybridization, parthenclosely aligned to feverfew than to tansy, although olide, novel compounds. notable differences were observed in floral and leaf morphologies of the hybrid plants compared to both parental species. Ultrastructurally, the lower Introduction epidermal leaf surfaces of the F 1 hybrids displayed characteristics from both parents, with glandular The genus Tanacetum (L.), formerly Pyrethrum (Zinn), trichome morphology and density similar to that of is a large, poorly defined classification group in the feverfew, but non-glandular trichome density compar- Asteraceae (Compositae) containing 150‐200 species, able to that of tansy. Diploid F 1 (2n=2x=18) hybrids many of which have applications as herbal medicines. and their parental progenitors were analysed biochem- Two of the more common European species of Tanacetum ically, using chromatographic techniques. The bioac- were selected for sexual hybridization, to determine the tive germacranolide, parthenolide, was present in high impact of this process on biochemical and pharmacoconcentrations [1.72±0.16% dry leaf weight (mean logical characteristics of plant extracts. Previous bio±s.d., n=5)] in leaf extracts from feverfew, but to a chemical studies of sexual hybridization in the genus much lesser extent in both tansy and the F 1 hybrids Helianthus of the Asteraceae (Buschmann and Spring, (<0.03% and <0.01% dry leaf weight, respectively). 1995) have shown that F 1 hybrids are capable of synthesWhilst secondary metabolite accumulation in the izing novel compounds (specifically, sesquiterpene leaves of the F 1 hybrids was largely additive compared lactones), which are absent from both parental species. If to the parental species, novel compounds were also novel secondary products could be synthesized similarly detected in the F 1 hybrids by HPLC, GC and TLC, in Tanacetum F 1 hybrids or their oVspring, in which a indicating the expression of new metabolic pathways number of compounds are known to have pronounced as a result of sexual hybridization. Pharmacologically, pharmacological activity ( Knight, 1995), these hybrid leaf extracts from the F 1 hybrids inhibited human poly- plants could represent a valuable source of novel molecmorphonuclear leucocyte (PMNL) activity in vitro, des- ules of potential biomedical application. Additionally, pite containing only trace amounts of parthenolide, analysis of Tanacetum F 1 hybrid generations could help the principal bioactive moiety from feverfew. This, in elucidate inheritance patterns for specific Tanacetum metabolites/secondary products, which may advance conjunction with the isolation of a fraction from the