In vitro and in silico studies on clinically important enzymes inhibitory activities of flavonoids isolated from Euphorbia pulcherrima

Figures & data

Table 1. Enzyme inhibitory screening of compounds 1 and 2 isolated from E. pulcherrima.

Code	IC50 ± S.E.M. (µM) (urease)	IC50 ± S.E. (µM) (tyrosinase)	IC50 ± S.E.M. (phosphodiesterase)	IC50 ± S.E. (µM) (antiglycation)
H16	15.3 ± 2.13	48.7 ± 2.19	148.7 ± 1.09	NA
H5	19.0 ± 2.43	74.8 ± 1.79	95.2 ± 4.14	244.8 ± 1.79
STD	21.0 ± 0.21 (thiourea)	47.6 ± 0.67 (kojic acid)	265 ± 2.24 (EDTA)	295 ± 3.14 (rutin)

S.E.M.: standard error of the mean; IC₅₀: minimum inhibitory concentration; STD: standard.

Figure 1. (a) Chemical structures of isolated compounds from E. pulcherrima. (b) Illustration of predicted docked poses of compounds 1 and 2 (indicated by green colour sticks) in the binding pocket of urease (a), tyrosinase (b), bovine serum albumin (c), and phosphodiesterase-I (d). All predicted conformations were created at the binding site of crystal structures, whereas existing co-crystallized compounds are bonded in the active site.

Figure 2. Interactions of compound 1 with the binding pocket of urease enzyme in 2D (a) and 3D (b). Hydrophobic interactions are depicted as half-moons, whereas dotted green lines with distances in angstrom represent hydrogen bonding.

Table 2. Molecular docking details of isolated compounds 1 and 2 and against urease and tyrosinase enzymes.

Compound		Hydrogen bonding residues and distance		Hydrophobic interacting residues	B. affinity (kcal/mol)
1		His541	3.32 Å	His408, Cys442, Leu488, His491, Ile517 and Tyr543	–8.7
2		Ala439	2.69 Å	Cys405, His408, Thr437, Cys442, Leu488, His491, Ile517, His541 and Tyr543	–8.7
Thiourea (standard)					–3.4
1	No H bonding			Gly62, Phe90, Trp93, Val262, Phe292 and His296	–7.6
2	No H bonding			Phe90, Val262, Phe292, His295 and His296	–7.5
Kojic acid (standard)					–5.1

Table 3. Docking details of BSA and phosphodiesterase-I receptors with compounds 1 and 2.

Compound		Hydrogen bonding residues and distance		Hydrophobic interacting residues	B. affinity (kcal/mol)
1		His145 Glu424 Ser428	3.06 Å 2.84 Å 2.75 Å	Leu189, Thr190, Ala193, Arg196, Lys431, Tyr451 and Arg458	–8.8
2		Arg194 Ser428 Arg458	3.09 Å 2.34 Å 2.99 Å	His145, Val188, Thr190, Ser191, Val425 and Ile455	–8.5
Rutin (standard)					–9.4
1	Tyr378 Thr455 Arg456		3.21 Å 2.90 Å 2.83 Å	Lys184, His309, Leu363, GLu379, Gly380, Pro381, Trp446, Met447 and Thr461	–8.4
2	Lys184, Trp446 His462		3.34 Å 3.01 Å 3.05 Å 3.16 Å	His309, Leu363, Glu379 and Gly380	–8
EDTA (standard)					–4.9

Figure 3. The interactions of the urease enzyme with compound 2 are determined by binding residues. Compound 2 interacts with the active site in 2D (a) and 3D (b).

Figure 4. The interactions of the tyrosinase enzyme with compound 1 are determined by binding residues. Detailed interactions of compound 1 with active sites of the enzyme in 2D (a) and 3D (b).

Figure 5. The interactions of the tyrosinase enzyme with compound 2 are determined by binding residues. Detailed interactions of compound 2 with active sites of the enzyme in 2D (a) and 3D (b).

Figure 6. The interactions of bovine serum albumin with compound 1. Detailed interactions of compound 1 with active sites of the enzyme in 2D (a) and 3D (b).

Figure 7. Detail interactions display of compound 2 with bovine serum albumin. Detailed interaction of compound 2 with the active site in 2D (a) and 3D (b).

Figure 8. Phosphodiesterase-I interactions with compound 1 are mediated by binding residues. Detailed interaction of compound 1 with the active site is shown in 2D (a) and 3D (b).

Figure 9. Phosphodiesterase-I interactions with compound 2 are mediated by binding residues. Detailed interaction of compound 2 with the active site in 2D (a) and 3D (b).

Table 4. Prediction of ADMET properties of compounds 1 and 2.

Compound no.	MlogP	S + logP	S + logD	Rule of 5	MWt	M_NO	TPSA	HBDH
1	–0.415	1.466	–0.652	0	346.295	8	144.52	5
2	–0.327	2.118	0.863	0	358.307	8	137.43	4

Data availability statement

The data based on the results of the current study are obtained from the corresponding authors upon request.