Saponins absorption

Saponins. Although the hypocholesterolemic activity of saponins has been known since the 1950s, thek low potency and difficult purification sparked Htde interest in natural saponins as hypolipidemic agents. Synthetic steroids (292, 293) that are structurally related to saponins have been shown to lower plasma cholesterol in a variety of different species (252). Steroid (292) is designated CP-88,818 [99759-19-0]. The hypocholesterolemic agent CP-148,623 [150332-35-7] (293) is not absorbed into the systemic ckculation and does not inhibit enzymes involved in cholesterol synthesis, release, or uptake. Rather, (293) specifically inhibits cholesterol absorption into the intestinal mucosa (253). As of late 1996, CP-148,623 is in clinical trials as an agent that lowers blood concentrations of cholesterol (254). 

Odani, T., Tanizawa, H., and Takino, Y. (1983a). Studies on the absorption, distribution, excretion and metabolism of ginseng saponins. 11. The absorption, distribution and excretion of ginsenoside Rgi in the rat. Chem. Pharm. Bull. 31, 292-298. 

Takino Y, Odani T, Tanizawa FI, Flayashi T. (1982). Studies on the absorption, distribution, excretion, and metabolism of ginseng saponins I. Quantitative analysis of ginsenoside Rgl in rats. Chem Pharm Bull (Tokyo). 30(6) 2196-201. 

Legumes Cardiovascular disease Presence of saponin which decreases cholesterol absorption from the gut... 

Yoshikawa M, Murakami T, Ueno T, Kadoya M, Matsuda H, Yamahara J, Murakami N. (1995) Bioactive saponins and glycosides, i. senegae radix. (1) E-senegasaponins a and b and z-senegasaponins a and b, their inhibitory effect on alcohol absorption and hypoglycemic activity. Chem Pharm Bull 43 2115-2122. 

They also form complexes with bile acids and reduce their absorption in vitro. The anticarcinogenic properties of soybean saponins are apparently related to their ability to bind with bile acids. 

Pillion, D.J., et al. 1995. DS-1, a modified Quillaja saponin, enhances ocular and nasal absorption of insulin. J Pharm Sci 84 1276. 

Saponins appear to lower plasma LDL cholesterol concentration by interfering with cholesterol absorption. Studies in rats and monkeys fed naturally occurring saponins exhibited significant reductions in cholesterol absorption efficiency and an increase in fecal cholesterol excretion (Malinow et al., 1981 Nakamura et al., 1999 Sidhu et al., 1987). Decreased bile acid absorption and increased excretion has also been reported in animals fed saponins (Malinow et al., 1981 Nakamura et al., 1999 Stark and Madar, 1993). One possible mechanism of action for decreased cholesterol absorption is the ability of saponins to form insoluble complexes with cholesterol (Gestetner et al., 1972 Malinow et al., 1977). In an effort to isolate the specific properties of saponins, Malinow (1985) prepared a variety of synthetic saponins in which the complex carbohydrate moieties of native plant saponins were replaced with simplified carbohydrates such as glucose or cellobiose. One of these synthetic saponins, tiqueside (Pfizer, Inc.), can effectively precipitate cholesterol from micelle solutions in vitro and inhibit cholesterol absorption in a variety of animals (Harwood et al., 1993) and in humans (Harris et al., 1997). But despite ample data showing the formation of a saponin/cholesterol complex in vitro, there is essentially no definitive evidence that complexation occurs in the intestinal lumen (Morehouse et al., 1999). 

Another possible mechanism involves the effect of saponins on micelle formation. Saponins are known to alter the size or shape of micelles (Oakenfull, 1986 Oakenfull and Sidhu, 1983), an observation that is consistent with decreased bile acid absorption (Stark and Madar, 1993) and increased fecal bile acid excretion (Malinow et al., 1981 Nakamura et al.,1999). Saponins may also directly bind bile acids (Oakenfull and Sidhu, 1989), which would presumably interfere with micelle formation and decrease cholesterol absorption. Other studies have found that saponins decrease the absorption of fat-soluble vitamins (Jenkins and Atwal, 1994) and triglycerides (Han et al., 2002 Okuda and Han, 2001), indicating decreased micelle formation. However, direct evidence showing impaired micelle formation in vivo is lacking. Moreover, Harwood et al. (1993) reported no change in bile acid absorption or interruption of the enterohepatic circulation of bile acids in hamsters fed tiqueside, despite significant reductions in cholesterol absorption. 

The full extent to which saponins reduce cholesterol absorption requires further study. Because of the large number of saponins present in the food supply, it is possible that all of the mechanisms discussed earlier contribute to reduced cholesterol absorption. Unlike plant sterols in which their mode of action is relatively well defined, there are probably multiple effects of saponins within the intestinal tract, including their ability to interact with other dietary constituents and the ability of some saponins to be absorbed systemically. The regulatory effects of saponins on cellular cholesterol transport have not been examined. 

Harwood, H.J., Jr., Chandler, C.E., Pellarin, L.D., Bangerter, F.W., Wilkins, R.W., Long, C.A., Cosgrove, P.G., Malinow, M.R., Marzetta, C.A., Pettini, J.L., Savoy, Y.E., and Mayne, J.T. 1993. Pharmacologic consequences of cholesterol absorption inhibition Alteration in cholesterol metabolism and reduction in plasma cholesterol concentration induced by the synthetic saponin /Migogenin cellobioside (CP-88818 tiqueside). J. Lipid Res. 34, 377-395. 

The nasal delivery of insulin was demonstrated as early as 1922 by Woodyatt [59]. Since then, numerous studies have focused on this methodology. Some of the early studies included absorption of insulin from the nasal mucosa in human diabetics, the use of an insulin sprayer that contained saponin, and insulin in ethylene glycol or trimethylene glycol applied to the nose in the form of drops or sprays the last... 

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