Sesquiterpene lactones and other bioactive constituents from Schkuhria pinnata var. wislizeni (Asteraceae)

The genus Schkuhria is known as a source of sesquiterpene lactones of different skeletons, some of which display cytotoxic activity [1]. Due to botanical revision, some Schkuhria species from North America (i.e.: S. anthemoidea, S. virgata) have been reclassified and identified as S. pinnata var. wislizeni [2]. Our current investigation on the aerial parts of this species led to the isolation of the sesquiterpene lactones 1–3 and the phenyl propanoids 4 and 5. 2 represents a Diels Alder adduct derived from a guaia-1(2),4(5)-dienolide as diene and the 11,13-olefin of 1 as dienophile, and the theoretical study of the reactants predicted the product. The spectroscopic analysis of 3 allowed the structural reassignment of a compound previously isolated from S. anthemoidea [3]. The antioxidant assay using a rat pancreas homogenate model indicated that 4 and 5 displayed activity and also DPPH radical scavenger capacity.

Acknowledgement: To Dirección General de Asuntos de Personal Académico, UNAM, Chávez M.I., Cogordán J.A., Velasco L., Patiño R. (Instituto de Química, UNAM).

References: 1. Delgado, G. et al. (1998)J. Nat Prod. 61:1082–1085. 2. Turner, BL. (1995) Phytologia 79:364–368. 3. Stewart, E., Mabry, T. J. (1985) Phytochemistry 24:2731–2732.