22 Oat saponins: Structures, properties, and improved isolation techniques for the avenacosides.

A. B. Sarr (1), F. W. COLLINS (1), and D. A. Fielder (2). (1) Agriculture & Agri-Food Canada, Eastern Cereals and Oilseeds Research Centre, Central Experimental Farm, Ottawa, ON, K1A 0C6; (2) CEAPRO Inc., Suite 2830, Manulife Building, 10180-101 St., Edmonton, AB, T5J 3S4.

Oats are unique amongst the north-temperate monocot cereals in that the kernel contains at least 2 types of neutral saponins, the Avenacins and the Avenacosides, the latter consisting of a mixture of nuatigenin type triterpene glycosides. As part of an ongoing research effort to develop preparative isolation methods for value-added phytochemicals, the purification, structure and physicochemical properties of the Avenacosides were examined. Oat flour (cult. HINOAT, 6.0 Kg) was extracted 3 times with 80% ethanol (liquid/solid 5/1), centrifuged, and the supernatants combined to give an 80 L extract. The extract was subjected to double ion exchange chromatography to remove anionic and cationic material and the resulting neutral eluate, containing primarily the saponins, neutral polar lipids and sugars, was further group fractionated by patented separation technologies based on hydrophobic interaction chromatography in aqueous ethanol using modified polysaccharide gels. Individual saponins of the Avenacoside type were isolated and their structures elucidated by molecular spectroscopy. The structures and properties of these saponins suggest they may possess unique physicochemical and bioactive functionality adding value to oats for food and non- food uses.