Fig 1.
The chemical structure of nine bufadienolides.
Fig 2.
Quenching effect of bufadienolides against human serum albumin (HSA) fluorescence.
Experiments were conducted at 298 K. λex = 280 nm; HSA, 2.0 × 10–6 M; a–g = 0, 10, 20, 40, 80, 160 and 200 × 10–6 M for gamabufotalin (A), arenobufagin (B), bufotalin (C), cinobufagin (D), hellebrigenin (E), telocinobufagin (F), resibufogenin (G) and bufalin (H); and a–g = 0, 6.3, 12.5, 25, 50 and 200×10–6 M for desacety-bufotalin (I).
Table 1.
Stern-Volmer quenching constants (KSV) of the interaction of bufadienolides with HSA at different temperatures.
Fig 3.
Relationship between bufadienolide binding affinities and the number of binding sites for human serum albumin (HSA).
logKa = binding affinity; Ka = binding constant; n = number of binding sites; and R = correlation coefficient.
Table 2.
The binding constants of bufadienolides on HSA fluorescence.
Table 3.
Thermodynamic Parameters between bufadienolides-HSA interaction at pH 7.4.
Table 4.
Structural parameters and binding constants of bufadienolides for HSA at 298 K.
Fig 4.
Relationship between hydrogen (H-) bond acceptor/donor numbers and bufadienolide binding affinities for human serum albumin (HSA).
The H-bond acceptor/donor numbers were taken from the PubChem Public Chemical Database. logKa = binding affinity; Ka = binding constant; and R = correlation coefficient.
Fig 5.
Bufadienolide docking to site I in human serum albumin (HSA).
The detailed binding conformations are shown for (A) gamabufotalin, (B) bufalin, (C) bufotalin, (D) resibufogenin and (E) cinobufagin. In each case, the drug is shown as a stick model. Key interaction amino acid residues (with names) are shown as sticks that are color-coded by atom type, and green dashed lines indicate hydrogen bonds (H-bonds).
Table 5.
Molecular docking of various bufadienolides to HSA.