EFSA Says Saponins are Undesirable in Animal Feed

EU - Saponins are a diverse group of low molecular-weight secondary plant metabolites that are widely distributed in the plant kingdom, says the European Food Standards Agency (EFSA).

27 February 2009

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The chemical structure of saponins consists of an aglycone of either steroidal or a triterpenoid nature and one or more sugar chains (glycosides).

Saponins can form stable foam in aqueous solutions, hence the name “saponin” from the Latin word for soap (sapo). Traditionally, they have been used as detergents, piscicides and molluscicides in addition to industrial applications as foaming and surface active agents.

Madhuca longifolia and other Madhuca species are large evergreen or semi-evergreen trees with a dense spreading crown extensively cultivated in warm climates for their oil-containing seeds. The present opinion deals with saponins in Madhuca longifolia and other Madhuca species as potentially undesirable compounds in feed. Possible occurrence of saponins and also cyanogenic glycosides in “unhusked beech mast” from Fagus silvatica with regard to its listing as an undesirable substance in animal feed was also included in the request. However, since it does not contain saponins or cyanogenic glycosides in significant amounts and its reported toxicity in cattle and horses can most likely be attributed to its high content of oxalates, beech mast is not further discussed in this opinion.

In food and feed, saponins can have an “anti-nutritional” effect and cause toxic effects, but have also been claimed to cause beneficial health effects. Many saponins have a general action on lipid membranes and cause haemolysis in vitro or when injected intra-venously. In general, saponins, as glycosides, have low oral bioavailability, but may be hydrolysed in the intestinal tract and cause systemic toxicity dependent on the structure and absorption of the aglycone. No individual saponin isolated from any of the Madhuca spp.

has been tested in any in vivo toxicity assay. Toxicity studies and observations of toxic effects in feeding studies have been reported using crude total saponins or defatted seed meal from various Madhuca species. The oral LD50 in mice of crude Madhuca saponins (exact botanical source not given) was about 1.0 g/kg body weight. In mice and rats Madhuca saponins caused local gastro-intestinal toxicity as well as liver and kidney toxicity. At lower doses, Madhuca saponins can cause feed refusal and starvation with reduced body weight gain and increased mortality.

The Panel confirmed that although Mahua oil (oil from Madhuca longifolia) caused bilateral testicular atrophy with degenerative changes in the seminiferous tubules in rats; saponins are the substances mainly responsible for the toxicity of Madhuca longifolia in animal feed. No studies on mutagenicity, genotoxicity and carcinogenicity of saponins from Madhuca species have been identified. Studies on other saponins do not indicate a genotoxic or carcinogenic potential. Because of the limited data available, EFSA says that no health-based guidance value (ADI, TDI) can be established for Madhuca saponins.