From Phyllanthus amarus

On the basis of the studies concerning the activity of the hydrolysable tannins from Phyllanthus amarus (Euphorbiaceae), it seems that their effectiveness against common protein kinases is lower than that of condensed tannins. In fact, IC50 values ranged from 0.2 to 1.7 pM for the rat liver PKA-catalytic subunit, and was 26 pM for geraniin (11) and other closely-related compounds against rat brain PKC. Other tannins of the same plant inhibited PKC at the high fixed dose of 167 pM [38]. 

Phyllanthin and hypophyllanthin from Phyllanthus amarus had no cytotoxic activity against different cultured mammalian cells, but both enhanced the cytotoxic response mediated by vinblastine with multidrug-resistant KB cells, and phyllanthin displaced the binding of vinblastine to membrane vesicles derived from this cell line, probably by an interaction with the P-glycoprotein [124],... 

Each dehydrohexahydrodiphenoyl residue is capable of tautomerism to the alternative dibenzofuranoid acetal, giving a total of four equilibrating tautomers. Tannin isol. from Phyllanthus amarus. Yellow amorph. powder. [a]j, -131 (c, 0.12 in MeOH). 

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