Off-line Supercritical Fluid Extraction and Capillary Gas Chromatography of Pyrrolizidine Alkaloids in Senecio Species

Abstract

The pyrrolizidine alkaloid (PA) fraction of two Senecio species (Senecio inaequidenr and Senerio cordatus) was extracted by off-line supercritical fluid extraction (sfe) and analyzed by capillary gas chromatography. Sfe was carried out with a home-assembled apparatus, using MeOH/CO, as extraction medium, at 55" and 15 MPa. Compared to the classical MeOH Soxhlet extraction, this technique requires a smaller sample amount and provides a quicker extraction, a simplified PA fraction clean-up, and a higher recovery.Supercritical fluid extraction (sfe) is a very powerful method for the extraction oforganic compounds from solid matrices, e.g., flavors and fragrances from natural products, toxic organics from resins, polycyclic aromatic hydrocarbons and polychlorinated biphenyls from environmental solids, etc. The supercritical fluid most often applied is CO, because of its low critical temperature ( 3 lo) and pressure (7.3 MPa). Sfe therefore can be performed at relatively low temperatures, avoiding decomposition of thermolabile compounds. Sfe can be coupled either on-line or off-line with capillary gas chromatography (gc) (1-3). Several sfe systems have been described: Sandra, Onuska, and co-workers proposed an effective and easy-to-assemble apparatus for off-line sfe/ capillary gc (4-6).Pyrrolizidine alkaloids (PAS) with known hepatotoxic and allelopathic properties (7-9) occur in several worldwide plant families, e.g., Boraginaceae, Compositae (Senecioneae and Eupatorieae tribes), and Leguminosae (genus Crotalaria).The applicability of off-line sfe/capillary gc for the analysis of the PA fraction in plants of the Senecio genus [in particular Senecio inaequikns DC. and Senecio corhtus Koch ex Senecio alpinus L. (lo)] was investigated and compared to the classical Soxhlet extraction method. Sfe has already been applied to PA extraction by Schaeffer etal. (1 1-13), who investigated in depth the extraction of monocrotaline from the seeds of Crotalaria spectabilis. RESULTS AND DISCUSSIONPAS are classically extracted from a vegetable matrix by MeOH Soxhlet extraction.This operation is relatively time-consuming (4 h) and requires large amounts of solvent and plant material. Sfe can provide very rapid extraction with high recovery using very small sample amounts. Various densities of supercritical CO, were first tried for the extraction of PAS; this was unsuccessful, probably due to the inappropriate polarity or solvent strength of CO,. Polarity can be increased by adding a modifier. MeOH was chosen for two reasons: it is the usual extraction solvent for PAS, and it is one of the most effective polarity modifiers for supercritical CO,, since amounts as high as 20% are miscible with co*.

Pyrrolizidine Alkaloid Profiles of Some Senecio Species from Egypt

“…As the 13 C NMR spectrum of 4 contained 18 resonances, apparently corresponding to 18 carbons (Table III) with those reported for senecionine (Witte et al, 1993;Logie et al, 1994;Jones et al, 1982;Roeder 1990).…”

Supercritical Fluid Extraction of Plant Flavors and Fragrances

“…Even so, water was used in some cases as a co-solvent for the extraction of more polar compounds from aromatic plants. The presence of water as pretreatment of plant material or added to CO 2 at supercritical and subcritical state as a co-solvent has shown to influence the qualitative and quantitative composition of the extract [13][14][15].…”

“…A total of 44 aroma compounds were identified in Zhenjiang aromatic vinegar SFE extract. Acetic acid (15), ethyl acetate (16), furfural (17), phenethyl alcohol (18), tetramethylpyrazine (19), 3-hydroxy-2-butanone (20) and benzaldehyde (21) were the main aroma compounds in the vinegar SFE extract (Figure 3) [46].…”

“…Volatiles of B. tripartita were characterized by the presence of α-pinene (52, Figure 11), p-cymene (63), (E)-β-ocimene (64), β-elemene (65), iso-caryophyllene (66), α-caryophyllene (67), and α-bergamotene (68) (Figure 14) [78]. The volatile oil parts of frankincense (Boswellia carterii) was extracted with SC CO 2 under constant pressure (15,20,or 25 MPa) and fixed temperature (40, 50, or 60 °C) at given times (60, 90, or 120 min) aiming at the acquisition of enriched fractions containing octyl acetate, a compound of pharmaceutical interest. This study demonstrates that SFE is a feasible method for selective acquisition of volatile oil from B. carterii being 20 Mpa, 55 °C and 94 min the best conditions to obtain the target compounds in higher amounts [79].…”

Supercritical fluid extraction and capillary gas chromatography of the rhizomes of Z. zerumbet

“…Fractionation of the extract by preparative SFC yielded 8 mg of needle-like caffeine crystals [32]. Bicchi et al employed SFE with methanol-modified carbon dioxide to extract the pyrrolidizine alkaloid fraction of two Senecio species, and GC to analyze the extract [33]. Compared to Soxhlet extraction with methanol, the SFE method required a smaller sample size, faster extraction time, a higher recovery, and simplified clean-up of the extract.…”