Table 2 The binding energy and interaction sites of TMPRSS2, ACE2, and SARS-CoV-2 S proteins with eriodictyol and umbelliferone

Eriodictyol

TMPRSS2

− 13.05

Cys 148

Hydrogen bond (2.60 Å)

Asp 482

Hydrogen bond (2.09 Å)

Arg 489

Pi-Cation (3.73 Å)

S protein-ACE2

− 33.478

Arg 403^a

Pi-Cation (2.89 Å)

Glu 406^a

Hydrogen bond (2.03 Å)

Tyr 453^a

Hydrogen bond (2.24 Å)

Ser 494^a

Pi-Lone pair (2.69 Å)

Gly 496^a

Hydrogen bond (2.02 Å)

His 34^b

Pi-Cation (3.47 Å); Hydrogen bond (2.55 Å); Amide-Pi Stacked (4.48 Å)

Glu 35^b

Hydrogen bond (2.03 Å)

Lys 353^b

Hydrogen bond (1.83 Å, 1.93 Å)

Umbelliferone

TMPRSS2

− 14.82

Arg 150

Attractive charge (4.93 Å)

Pro 369

Hydrogen bond (2.41 Å); Pi-Alkyl (4.54 Å)

Asp 482

Pi-Anion (3.99 Å)

S protein-ACE2

− 36.539

Arg 403^a

Pi-Cation (4.03 Å)

Gly 496^a

Hydrogen bond (2.61 Å)

Tyr 505^a

Pi-Pi T shaped (5.97 Å)

Lys 353^b

Salt bridge (1.65 Å)