Excessive iron accumulation can lead to liver damage in captive black rhinoceros (Diceros bicornis), thus dietary iron absorption must be regulated. A potential method of controlling iron absorption is to use foods that contain compounds that chelate metals. Carolina willow (Salix caroliniana) contains phenolic glycosides and condensed tannins, both of which chelate metals. Thus, we analyzed leaf samples for these compounds. Leaf sample solutions were analyzed by a tannin depolymerization reaction (butanol-HCl assay). Quantities of the phenolic glycosides, salicin and tremulacin, were determined via HPLC; EPI-MS was used to verify the peak identities. Tannin levels in 19 samples ranged from 1.0 to 6.0 mg/g dry weight. Eighty samples of plant material were analyzed and no Salicin or Tremulacin was detected in any of these samples (detection limits are ppt). S. caroliniana leaves have some tannins that could potentially chelate iron and thus make the dietary iron less bio-available.

What to feed the rhinoceros: Quantification of tannins and phenolic glycosides in Carolina willow leaves

245th National Meeting (2013)

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