Determination o f Levels of Pyrrolizidine Alkaloids in Symphytum Asperumlepech Growing in Selected Parts of Kenya
Onduso, Shylock Oigara
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Comfrey (Symphytum asperum Lepech) is widely used in Kenya and other countries as a vegetable, herbal medicine and animal feed. It is known to have high nutritional and medicinal value. However, in some countries like the USA and Australia, its usage has been restricted to external application, and in others like Germany, its usage has been banned altogether. This is because the plant contains pyrrolizidine alkaloids (PAs) that are associated with hepatotoxicity, mutagenicity and teratogenicity in both human beings and animals. In Kenya no study has been done to ascertain the levels of these pyrrolizidine alkaloids despite the fact that the plant is widely grown and consumed in central Kenya and other parts. There is need to establish whether these PAs are also present in this species here in Kenya or whether the levels have been affected by genetic drift or epigenetic factors. This study was aimed at determining the levels of the pyrrolizidine alkaloids (PAs) in the roots and leaves of comfrey from two agro-ecological zones in Kenya, Kiambu and Kisii counties during wet(April2012)and the dry (September 2012) seasons. The samples were collected and dried under the shade for four weeks. They were then ground and extraction of the PAs done with different solvent systems. There was no significant difference in the percentage dry weights for both the leaves and the roots from Kisii and Kiambu counties during the wet and dry seasons (p>0.05 at 95 % confidence limit). Gas Chromatography (GC) interphased with Mass spectrometer (MS) was used in the analyses of the samples, characterization and quantification of major components. From the root samples, echimidine (7), 7-acetyllycopsamine (17), 3’-acetyllycopsamine (18), triangularine (19) and heliosupine (24), were identified. 7-Acetyllycopsamine (17) showed significantly higher levels during the wet season than in the dry season (p=0.033, α=0.05, t-test). The other pyrrolizidine alkaloids did not vary significantly between the two seasons (p>0.05, α=0.05, t-test).All the compounds reported in the root samples are associated with toxicity and their values are above the tolerable levels as recommended by relevant regulatory bodies in various countries. Echimidine (7), one of the most toxic PAs, was found in all the root samples. The leaf samples however, had levels of PAs below detectable limits using GC-MS. More research is however required to be done on the leaves at different levels of maturation and from a larger profile of the plant to determine whether the PAs can be found. It is recommended that further research be done to determine the levels of this particular PA and related analogues in a larger profile of the plants growing in other agro-ecological zones in Kenya. Toxicity studies should also be done on heliosupine (24) which was also found in significant amounts as such studies have not been done on this constituent. Preparative isolation of the PAs should be done also so that they can be used as reference standards in other quantification facilities using Gas chromatography, since GC –MS is a rather expensive method.