Six new withanolides (1-6) were isolated from the aerial parts of Jaborosa bergii plants and characterized by spectroscopic methods (1D and 2D NMR, MS). Five of the new compounds presented a novel norbornane-type structure in ring D of the steroid nucleus (1-5), resulting from a carbon-carbon bond between C-15 and C-21. The sixth withanolide isolated was the 5alpha-chloro-6beta-hydroxy analogue (6) of 2,3-dehydrojaborosalactol M (7), previously isolated from this plant. Compound 1 showed selective phytotoxicity toward monocotiledoneous and dicotiledoneous species.
Antifeedant activity of the 4-deoxi-27-hydroxi-withanolides (1, 2 y 3) isolated from Jaborosa integrifolia (Solanaceae) was investigated in caterpillar Spodoptera littoralis on Leaf Disk Choice Bioassay. Results indicate that the best feed inhibition effect is due to Jaborosalactone A.
Several terpenoids and clerod-14-ene-3alpha, 4beta,13xi-triol (1), the main compound of V. tucumanensis, were isolated and bioassayed. The clerodane 1 showed higher antifeedant activity than other related compounds. Structure-activity relationships are also discussed.
The extracts and sesquiterpene lactones of S.argentinum were assayed to determine their biological activity on Artemia salina. The most active compound was costunolide (1) with LD 50 = 62 ppm.
Phytotoxic Activity of the 6-acetyl-5-hydroxy-2isopropenyl-2,3-dihydrobenzofurane (1) isolated from Trichocline reptans (Asteraceae) was investigated in two weed species. Results indicate that the best growth inhibition effect ocurres on Chenopodium album weed. Phythotoxic effect of the T. reptans chloroformic extract and of the benzofurane are discussed and compared in the two weed species.
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