Caco-2 cell permeability of flavonoids and saponins from Gynostemma pentaphyllum : the immortal herb

Gynostemma pentaphyllum (the immortal herb) has been an important component of Chinese Traditional Medicine for millennia. Recent clinical studies have revealed that the plant exhibits numerous beneficial biological activities, making it of interest to the pharmaceutical industry. An extract of the herb contains over 200 individual secondary metabolites including flavonol glycosides and dammarane saponins. To focus attention on the compounds most likely to be responsible for the biological activities, this study predicts the potential oral bioavailability of nine dammarane saponins and five flavonol glycosides from G. pentaphyllum using the Caco-2 cell monolayer permeability model. Two flavonoids, 8 and 9, and four saponins, 10, 11, 12, and 14, exhibited high permeability across the monolayers. The results indicated that a higher degree of glycosylation-facilitated permeability, suggestive of active transport. This study demonstrates the utility of the Caco-2 permeability assay as a method of identifying possible bioavailable compounds from medicinal herbal extracts.