Toxic Furanoeremophilanes from Senecio bonariensis

Abstract

Four toxic 10 ␣H-9-oxofuranoeremophilanes were isolated and identified from the petroleum ether extract of Senecio bonariensis.

Cacalolides from Senecio barba‐johannis

“…The reaction mixture was stirred at room temperature for 5 h, a solution of 10% NaOH (10 ml) was added and the resulting mixture was extracted with CH 2 Cl 2 . The organic layer was washed with 10% NaOH (3 ð 10 ml) and water until neutral pH, dried over anhydrous Na 2 SO 4 , filtered and evaporated to dryness. The residue was chromatographed over neutral alumina.…”

“…2 The toxicity exhibited by these plants has been attributed to their content of pyrrolizidine alkaloids 2,3 and some furoeremophilanes. 4 Recently it has been reported that some cacalolides exhibit antihyperglycemic activity in mice, 5 are active against some phytopathogenic fungi 6 and show antimicrobial and antifeedant activity. 7 Cacalolides are biogenetic Wagner-Meerwein rearrangement products derived from furoeremophilanes, 8 the name of which is derived from cacalol (1), originally isolated from the antihyperglycemic species Cacalia decompositae.…”

Cacalolides from Senecio madagascariensis

“…The toxic metabolites are thought to be pyrrole derivatives of the pyrrolizidine alkaloids. However, recently some furoeremophylanes have also been described as toxic compounds …”

“…However, recently some furoeremophylanes have also been described as toxic compounds. 7 Senecio madagascariensis Poir. (Compositae, Senecioneae), known as fireweed, is a plant of South African origin, 8 and many efforts have been made to control its infestation level in pastures.…”

“…The 1 H NMR spectrum of 3 (Table 1) shows two hydroxyl group protons at δ 13.17 (1-OH) and 2.83 (6-OH), which are exchangeable with D 2 O, while the remaining signals are similar to those of 12 except for the absence of the acetyl group signal. The 1 Hcoupled 13 C NMR spectrum of 3 shows the carbonyl group at δ 178.5 (C-9) as a singlet with no long-range coupling, while the signals at δ 146.8 (C-12) and 120.7 (C-3) are observed as double quartets (J ) 201.9, 6.1 Hz, and J ) 155.0, 5.2 Hz, respectively) due to one-and three-bond 4.09 (q, 7.1) 2.83 (br s, OH) 4.12 (q, 6.9) 3.40 (br s, OH) 4.15 (q, 6.9) 2.10 (s, OAc) 12 7.49 (q, 1.2) 7.46 (q, 1.1) 7.44 (q, 1.2) 7.34 (q, 1.1) 7.38 (q, 1.2) 7.32 (q, 1.2) 7.45 (q, 1.1) 7.49 (q, 1.1) a At 300 MHz, using TMS as the internal reference (δ 0). b 4-OH: 2.98 (br s), 9-OMe: 4.01 (s).…”