NON-TRADITIONAL PLANT RESOURCES FOR GRAZING RUMINANTS IN APPALACHIA
Title: Anthelmintic effect of plant extracts containing condensed and hydrolyzable tannins on Caenorhabditis elegans and their antioxidant capacity
Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 20, 2012
Publication Date: February 18, 2013
Citation: Katiki, L., Ferreira, J.F., Gonzalez, J.M., Zajac, A., Lindsay, D., Chagas, A., Amarante, A. 2013. Anthelmintic effect of plant extracts containing condensed and hydrolyzable tannins on Caenorhabditis elegans and their antioxidant capacity. Veterinary Parasitology. 192(1-3):218-227.
Interpretive Summary: Although tanniferous forages have been reported as viable sources of protein and deworming compounds for grazing ruminants, most research involves forages that contain condensed tannins (CT). There is little information on the anthelmintic capacity, and no information on the antioxidant capacity, of these naturalized tannin sources. We evaluated the anti-worming and antioxidant activity of plant extracts containing CT, hydrolyzable tannins (HT), or both, in a non-parasitic worm widely accepted as a test model. The plant extracts were used at doses ranging from 1-25 mg/mL and evaluated for their ability to kill adult worms within 24 hours. Plant extracts were quantified for their content of CT and HT, and for their antioxidant capacity. Extracts that contained mostly HT, or both CT and HT successfully killed over 80% of the worm at doses of 10mg/mL or lower, while extracts that contained mostly CT killed 63% or less of the test worms even at the highest dose (25mg/mL). All extracts, regardless of their tannin type had high antioxidant capacity. This study indicates that plants that are naturalized to the Appalachian climate, soil, and topography can be better sources of dewormers for grazing ruminants than forages such as sericea lespedeza (one of the plants tested), which is hard to establish and adapt in central Appalachia. The extracts that killed 80% or more of the test worms were, in decreasing order of effectiveness, white oak (at 1mg/mL and higher), staghorn sumac and red maple (both at 5mg/mL and higher), and multifloral rose (at 10mg/mL and higher). These extracts were rich in HT. From the plant extracts containing CT, black locuts was the most active killing 90% or less of the worms at 10mg/mL and higher, while sericea lespedeza and willow were the leasrt effective extracts, killing 63% of the worm or less, even at 25mg/mL. Our results indicate that plants containing HT are an unexplored source of dewormers for grazing animals in Appalachia, while plants containing both CT and HT are rich sources of antioxidants, with potential to improve animal immune system, balance oxidant-antioxidant ratio in their blood, and to increase host resilience to gastrointestinal parasitic worms. These trees, and the shrub multifloral rose, are naturalized to Appalachian climate, soil, and topography and represent a renewable source of tannins and protein to grazing animals where conventional forages such as lespedeza are hard to establish and adapt.
Although tannin-rich forages are known to increase protein uptake and to reduce gastrointestinal nematode infections in grazing ruminants, most published research involves forages with condensed tannins (CT), while published literature lacks information on the anthelmintic capacity, nutritional benefits, and antioxidant capacity of alternative forages containing hydrolyzable tannins (HT). We evaluated the anthelmintic activity and the antioxidant capacity of plant extracts containing either mostly CT, mostly HT, or both CT and HT. Extracts were prepared with 70% acetone, lyophilized, redissolved to doses ranging from 1.0 mg/mL to 25 mg/mL, and tested against adult Caenorhabditis elegans as a test model. The extract concentrations that killed 50% (LC50) or 90% (LC90) of the nematodes in 24 h were determined and compared to the veterinary anthelmintic levamisole (8 mg/mL). Extracts were quantified for CT by the acid butanol assay, for HT (based on gallic acid and ellagic acid) by high-performance liquid chromatography (HPLC) and total phenolics, and for their antioxidant activity by the oxygen radical absorbance capacity (ORAC) assay. Extracts with mostly CT were Lespedeza cuneata, Salix X sepulcralis, and Robinia pseudoacacia. Extracts rich in HT were Acer rubrum, Rosa multiflora, and Quercus alba, while Rhus typhina had both HT and CT. The extracts with the lowest LC50 and LC90 concentrations, respectively, in the C. elegans assay were Q. alba (0.75 and 1.06 mg/mL), R. typhina collected in 2007 (0.65 and 2.74 mg/mL), A. rubrum (1.03 and 5.54 mg/mL), and R. multiflora (2.14 and 8.70 mg/mL). At the doses of 20 and 25 mg/mL, HT-rich, or both CT- and HT-rich, extracts were significantly more lethal to adult C. elegans than extracts containing only CT. All extracts were high in antioxidant capacity, with ORAC values ranging from 1800 µmoles to 4651 µmoles of trolox equivalents/g, but ORAC did not correlate with anthelmintic activity. The total phenolics test had a positive and highly significant (r = 0.826, p = 0.01) correlation with total hydrolyzable tannins. Plants used in this research are naturalized to the Appalachian edaphoclimatic conditions, but occur in temperate climate areas worldwide. They represent a rich, renewable, and unexplored source of tannins and antioxidants for grazing ruminants, whereas conventional CT-rich forages, such as L. cuneata, may be hard to establish and adapt to areas with temperate climate. Due to their high in vitro anthelmintic activity, antioxidant capacity, and their adaptability to non-arable lands, Q. alba, R. typhina, A. rubrum, and R. multiflora have a high potential to improve the health of grazing animals and must have their anthelmintic effects confirmed in vivo in both sheep and goats.