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ARS Home » Pacific West Area » Logan, Utah » Poisonous Plant Research » Research » Publications at this Location » Publication #331663
Title: In vitro cytotoxicity of various dehydropyrrolizidine ester alkaloids

Author
item Field, Reuel
item Stegelmeier, Bryan
item Colegate, Steven
item BROWN, AMMON - Environmental Laboratory, Us Army Engineer Research And Development Center, Waterways Experiment St
item McCollum, Isabelle - Anita
item Knoppel, Edward

Submitted to: International Symposium on Poisonous Plants
Publication Type: Proceedings
Publication Acceptance Date: 5/30/2015
Publication Date: 6/5/2015
Citation: Field, R.A., Stegelmeier, B.L., Colegate, S.M., Brown, A., Mccollum, I.J., Knoppel, E.L. 2015. In vitro cytotoxicity of various dehydropyrrolizidine ester alkaloids. International Symposium on Poisonous Plants. 9:281-286.

Interpretive Summary: Dehydropyrrolizidine alkaloids (DHPAs) are plant-derived poisons. Because of the difficulty in isolating sufficient DHPA for toxicological studies, there are few direct comparisons of toxicity. The objectives of study was to develop an in vitro cell cultures model to allow comparison of lycopsamine (retronecine monoester), intermedine (retronecine monoester), heliotrine (heliotridine monoester), senecionine (retronecine 12-membered macrocyclic diester), senecionine N-oxide, seneciphylline (retronecine 12-membered macrocyclic diester), riddelliine (retronecine 12-membered macrocyclic diester), riddelliine N-oxide, monocrotaline (retronecine 11-membered macrocyclic diester), lasiocarpine (retronecine open chain diester), and lasiocarpine N-oxide. Various transformed cells lines were evaluated and LMH/2A (ATCC, CRL-2118) chicken hepatocellular carcinoma cells were found to be the most sensitive to DHPA toxicity. Historical comparisons suggested that macrocyclic diester DHPAs such as riddelliine, retrorsine and monocrotaline are more biologically active than the monoester heliotrine. Riddelliine and retrorsine, which are 12-membered macrocyclic diesters with an a,ß-unsaturated double bond linked to the ester group at the C-7 position of the necine base, were considered more toxic than 11-membered macrocyclic diesters, such as monocrotaline, and other macrocyclic DHPAs that lack the a,ß-unsaturated double bond. In this study, however, the open chain heliotridine-based diester lasiocarpine was among the most cytotoxic DHPAs as assessed by both MTT and LDH-release assays. Furthermore, even the heliotridine-based monoester heliotrine had a greater tendency to affect cell viability (MTT assay), on a par with the three consistently cytotoxic DHPAs senecionine, seneciphylline, and lasiocarpine. All were significantly more cytotoxic than the 12-membered macrocyclic diester riddelliine. Since the mechanism of cytotoxicity may be the same as for DHPA-related genotoxicity and carcinogenicity the data suggest that several of the DHPAs evaluated in this study may be more carcinogenic than riddelliine, the only one that is currently listed as a potential human carcinogen.

Technical Abstract: Dehydropyrrolizidine alkaloids (DHPAs) are plant-derived hepato-, pneumo- and geno-toxins that are carcinogenic in several species. Because of the difficulty in isolating sufficient DHPA for toxicological studies, there are few direct comparisons of toxicity. The objectives of this study was to develop an in vitro cell cultures model to allow comparison of lycopsamine (retronecine monoester), intermedine (retronecine monoester), heliotrine (heliotridine monoester), senecionine (retronecine 12-membered macrocyclic diester), senecionine N-oxide, seneciphylline (retronecine 12-membered macrocyclic diester), riddelliine (retronecine 12-membered macrocyclic diester), riddelliine N-oxide, monocrotaline (retronecine 11-membered macrocyclic diester), lasiocarpine (retronecine open chain diester), and lasiocarpine N-oxide. Various transformed cells lines were evaluated and LMH/2A (ATCC, CRL-2118) chicken hepatocellular carcinoma cells were found to be the most sensitive to direct DHPA toxicity. Historical comparisons suggested that macrocyclic diester DHPAs such as riddelliine, retrorsine and monocrotaline are more biologically active than the monoester heliotrine. Riddelliine and retrorsine, which are 12-membered macrocyclic diesters with an a,ß-unsaturated double bond linked to the ester group at the C-7 position of the necine base, were considered more toxic than 11-membered macrocyclic diesters, such as monocrotaline, and other macrocyclic DHPAs that lack the a,ß-unsaturated double bond. In this study the open chain heliotridine-based diester lasiocarpine was among the most cytotoxic DHPAs as assessed by both MTT and LDH-release assays. Furthermore, even the heliotridine-based monoester heliotrine had a greater tendency to affect cell viability (MTT assay), on a par with the three consistently cytotoxic DHPAs senecionine, seneciphylline, and lasiocarpine. All were significantly more cytotoxic than the 12-membered macrocyclic diester riddelliine. Since the mechanism of cytotoxicity may be the same as for DHPA-related genotoxicity and carcinogenicity the data suggest that several of the DHPAs evaluated in this study may be more carcinogenic than riddelliine, the only one that is currently listed as a potential human carcinogen.